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Loudness perception of binaural broadband sounds shows larger individual variations for hearing-impaired subjects after narrowband loudness compensation than for normal-hearing subjects. This is not taken into account in prescription rules for hearing aids that are based on the audiogram. The first goal of the present study was to compare the effects of symmetric and asymmetric hearing impairment on binaural broadband loudness perception. A narrowband loudness compensation rule based on audiometric pure tone thresholds was applied to two groups: eleven subjects with asymmetric and ten subjects with symmetric hearing loss. An additional goal was to compare spatial auditory impressions and lateralization perception for the two groups to the results for normal-hearing subjects. On average, the results of loudness scaling with binaural broadband noises indicated higher binaural broadband loudness summation for subjects with asymmetric than for subjects with symmetric hearing loss. With hearing threshold-based amplification, subjects with asymmetric hearing loss often perceived binaural broadband noise as lateralized towards the ear with the worse average hearing thresholds. Large individual differences were observed for asymmetrically hearing-impaired subjects with respect to both lateralization and loudness. Results of loudness scaling with monaural narrowband noises showed similar loudness functions for the left and the right ears, with the hearing-threshold-based amplification rule for subjects with symmetric hearing loss. However, for half of the asymmetrically hearing-impaired subjects, there were large and unexplained differences between the right and left ear loudness functions of more than 10 dB., Die Lautheitswahrnehmung von binaural breitbandigen Signalen weist bei Schwerhörenden nach schmalbandigem Lautheitsausgleich größere individuelle Schwankungen auf als bei Normalhörenden. Dies wird bei den Anpassformeln für Hörgeräte, die auf dem Audiogramm basieren, nicht berücksichtigt. Das erste Ziel der vorliegenden Studie war es, die Auswirkungen von symmetrischen und asymmetrischen Hörverlusten auf die binaural breitbandige Lautheitswahrnehmung zu vergleichen. Eine Methode für schmalbandigen Lautheitsausgleich, die auf den Hörschwellen des Audiogramms basiert, wurde bei zwei Gruppen angewendet: elf Personen mit asymmetrischer und zehn Personen mit symmetrischer Hörminderung. Ein weiteres Ziel war es, die räumlichen Höreindrücke und die Lateralisierung der beiden Gruppen mit den Ergebnissen von Normalhörenden zu vergleichen. Die Ergebnisse der Lautheitsskalierung mit binauralen breitbandigen Signalen zeigten bei Personen mit asymmetrischem Hörverlust im Durchschnitt eine höhere binaural breitbandige Lautheitssummation als bei Personen mit symmetrischem Hörverlust. Bei hörschwellenbasierter Verstärkung nahmen Probanden mit asymmetrischem Hörverlust binaurale breitbandige Signale häufig in Richtung des Ohrs mit der schlechteren mittleren Hörschwelle wahr. Große individuelle Unterschiede wurden bei asymmetrisch schwerhörenden Personen sowohl in Bezug auf die Lateralisierung als auch auf die Lautheit beobachtet. Bei Personen mit symmetrischem Hörverlust, die mit der hörschwellenbasierten Verstärkungsformel versorgt wurden, zeigten die Ergebnisse der Lautheitsskalierung mit monauralen schmalbandigen Signalen ähnliche Lautheitsfunktionen für das linke und rechte Ohr. Bei der Hälfte der asymmetrisch schwerhörenden Personen gab es jedoch große und nicht erklärbare Unterschiede zwischen den Lautheitsfunktionen des rechten und linken Ohrs von mehr als 10 dB.

In the rodent trigeminal principal nucleus (Pr5) the barrelette thalamic-projecting neurons relay information from individual whiskers to corresponding contralateral thalamic barreloids. Here we investigated the presence of lateral asymmetries in the dendritic trees of these neurons, and the morphometric changes resulting from input-dependent plas- ticity in young adult rats. After retrograde labeling with dex- tran amines from the thalamus, neurons were digitally recon- structed with NeurolucidaTM, and metrically and topologically analyzed with NeuroExplorerTM. The most unexpected and remarkable result was the observation of side-to-side asym- metries in the barrelette neurons of control rats. These asym- metries more significantly involved the number of low-grade trees and the total dendritic length, which were greater on the left side. Chronic global input loss resulting from infraorbital nerve (IoN) transection, or loss of active touch resulting from whisker clipping in the right neutralized, or even reversed, the observed lateral differences. While results after IoN tran- section have to be interpreted in the context of partial neuron death in this model, profound bilateral changes were found after haptic loss, which is achieved without inflicting any nerve damage. After whisker trimming, neurons on the left side closely resembled neurons on the right in controls, the natural dendritic length asymmetry being reversed mainly by a shortening of the left trees and a more moderate elongation of the right trees. These results demonstrate that dendritic morphometry is both side- and input-dependent, and that unilateral manipulation of the sensory periphery leads to bilateral morphometric changes in second order neurons of the whisker-barrel system. The presence of anatomical asym- metries in neural structures involved in early stages of so- matosensory processing could help explain the expression of sensory input-dependent behavioral asymmetries, Plan National I+D (España), Depto. de Biodiversidad, Ecología y Evolución, Fac. de Óptica y Optometría, TRUE, pub

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with traits from other contexts, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in, and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness, and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that although the OF may not accurately predict aggressive behavior, the MIS test can be used for large-scale aggression profiling of juvenile salmon

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with traits from other contexts, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in, and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness, and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that although the OF may not accurately predict aggressive behavior, the MIS test can be used for large-scale aggression profiling of juvenile salmon

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with traits from other contexts, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in, and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness, and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that although the OF may not accurately predict aggressive behavior, the MIS test can be used for large-scale aggression profiling of juvenile salmon

Diffusion tensor imaging (DTI) studies have demonstrated white matter microstructural differences between the left and right hemispheres of the brain. However, the basis of these hemispheric asymmetries is not yet understood in terms of the biophysical properties of white matter microstructure, especially in children. There are reports of altered hemispheric white matter lateralization in ASD; however, this has not been studied in other related neurodevelopmental disorders such as sensory processing disorder (SPD). Firstly, we postulate that biophysical compartment modeling of diffusion MRI (dMRI), such as Neurite Orientation Dispersion and Density Imaging (NODDI), can elucidate the hemispheric microstructural asymmetries observed from DTI in children with neurodevelopmental concerns. Secondly, we hypothesize that sensory over-responsivity (SOR), a common type of SPD, will show altered hemispheric lateralization relative to children without SOR. Eighty-seven children (29 females, 58 males), ages 8-12 years, presenting at a community-based neurodevelopmental clinic were enrolled, 48 with SOR and 39 without. Participants were evaluated using the Sensory Processing 3 Dimensions (SP3D). Whole brain 3 T multi-shell multiband dMRI (b = 0, 1,000, 2,500 s/mm2) was performed. Tract Based Spatial Statistics were used to extract DTI and NODDI metrics from 20 bilateral tracts of the Johns Hopkins University White-Matter Tractography Atlas and the lateralization Index (LI) was calculated for each left-right tract pair. With DTI metrics, 12 of 20 tracts were left lateralized for fractional anisotropy and 17/20 tracts were right lateralized for axial diffusivity. These hemispheric asymmetries could be explained by NODDI metrics, including neurite density index (18/20 tracts left lateralized), orientation dispersion index (15/20 tracts left lateralized) and free water fraction (16/20 tracts lateralized). Children with SOR served as a test case of the utility of studying LI in neuro

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with traits from other contexts, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in, and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness, and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that although the OF may not accurately predict aggressive behavior, the MIS test can be used for large-scale aggression profiling of juvenile salmon

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with traits from other contexts, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in, and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness, and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that although the OF may not accurately predict aggressive behavior, the MIS test can be used for large-scale aggression profiling of juvenile salmon

Grossberg’s classification of adaptive resonance mechanisms includes the cognitive-emotional resonances that support conscious feelings and recognition of them. In this regard, a relevant question concerns the processing of signals deriving from the internal body and their contribution to interpersonal synchronization. This study aims to assess hemodynamic inter-subject coherence in the prefrontal cortex (PFC) through functional near-infrared spectroscopy (fNIRS) hyperscan recording during dyadic synchronization tasks proposed with or without a social frame and performed in two distinct interoceptive conditions: focus and no focus on the breathing condition. Individuals’ hemodynamic data (oxygenated and de-oxygenated hemoglobin (O2Hb and HHb, respectively)) were recorded through fNIRS hyperscanning, and coherence analysis was performed. The findings showed a significantly higher O2Hb coherence in the left PFC when the dyads performed the synchronization tasks with a social frame compared with no social frame in the focus condition. Overall, the evidence suggests that the interoceptive focus and the presence of a social frame favor the manifestation of a left PFC interpersonal tuning during synchronization tasks.

This research explored the influence of interoception and social frame on the coherence of inter-brain electrophysiological (EEG) and hemodynamic (collected by functional Near Infrared Spectroscopy, fNIRS) functional connectivity during a motor synchronization task. Fourteen dyads executed a motor synchronization task with the presence and absence of interoceptive focus. Moreover, the motor task was socially or not-socially framed by enhancing the shared intentionality. During the experiment, delta, theta, alpha, and beta frequency bands, and oxygenated and de-oxygenated hemoglobin (O2Hb and HHb) were collected through an EEG-fNIRS hyperscanning paradigm. Inter-brain coherence indices were computed for the two neurophysiological signals and then they were correlated to explore the reciprocal coherence of the functional connectivity EEG-fNIRS in the dyads. Findings showed significant higher correlational values between delta and O2Hb, theta and O2Hb, and alpha and O2Hb for the left hemisphere in the focus compared to the no focus condition and to the right hemisphere (both during focus and no focus condition). Additionally, greater correlational values between delta and O2Hb, and theta and O2Hb were observed in the left hemisphere for the focus condition when the task was socially compared to non-socially framed. This study showed that the focus on the breath and shared intentionality activate coherently the same left frontal areas in dyads performing a joint motor task.

Neurophysiological studies in humans and nonhuman primates have revealed movement representations in both the contralateral and ipsilateral hemispheres. Inspired by clinical observations, we ask if this bilateral representation differs for the left and right hemispheres. Electrocorticography was recorded in human participants during an instructed-delay reaching task, with movements produced with either the contralateral or ipsilateral arm. Using a cross-validated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere, indicating similar neural representations for right and left arm movements. Notably, these left hemisphere electrodes were centered over premotor and parietal regions. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis.

Modern classifier systems can effectively classify targets that consist of simple patterns. However, they can fail to detect hierarchical patterns of features that exist in many real-world problems, such as understanding speech or recognizing object ontologies. Biological nervous systems have the ability to abstract knowledge from simple and small-scale problems in order to then apply it to resolve more complex problems in similar and related domains. It is thought that lateral asymmetry of biological brains allows modular learning to occur at different levels of abstraction, which can then be transferred between tasks. This work develops a novel evolutionary machine-learning (EML) system that incorporates lateralization and modular learning at different levels of abstraction. The results of analyzable Boolean tasks show that the lateralized system has the ability to encapsulate underlying knowledge patterns in the form of building blocks of knowledge (BBK). Lateralized abstraction transforms complex problems into simple ones by reusing general patterns (e.g., any parity problem becomes a sequence of the 2-bit parity problem). By enabling abstraction in evolutionary computation, the lateralized system is able to identify complex patterns (e.g., in hierarchical multiplexer (HMux) problems) better than existing systems.

In this thesis, I used underwater images to determine patterns in lateralization and group size when beluga calves and juveniles are present. Usually, lateralization is defined by either a left or right preference, but using underwater images (an untested, non-invasive approach) provided an opportunity to analyze position bias from three distinct planes, the sagittal (left or right), coronal (dorsal or ventral), and transverse (anterior or posterior). My research found that the presence of the boat may have affected lateralization as juveniles were most frequently observed on the left. This position bias was possibly due to their mothers, who may have positioned themselves between their young and the less familiar boat. Additionally, while both calves and juveniles preferred to be positioned in ventral positions near their mother, juveniles were most frequently observed at the anterior of the head region, while calves were in the posterior or tail region or infant position. This difference is likely due to juveniles having increased swimming abilities, allowing them to compromise the hydrodynamic benefits of the infant position for the anterior position, as the head or anterior is preferred for social interactions in whales. In my second chapter, I determined if mother and calf/juvenile dyads selected larger groups. My results indicated that groups that contained calves and juveniles had more adults present than groups that contained adults only. In comparison with aerial surveys, I found that group sizes in underwater images were significantly larger across all age classes. This may be an effect of methods used, as boats used to collect camera images may have moved to locations where beluga were aggregating. However, further research is needed to determine the effect of boats on juveniles’ interactions.

Neurophysiological studies in humans and nonhuman primates have revealed movement representations in both the contralateral and ipsilateral hemispheres. Inspired by clinical observations, we ask if this bilateral representation differs for the left and right hemispheres. Electrocorticography was recorded in human participants during an instructed-delay reaching task, with movements produced with either the contralateral or ipsilateral arm. Using a cross-validated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere, indicating similar neural representations for right and left arm movements. Notably, these left hemisphere electrodes were centered over premotor and parietal regions. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis.

There is considerable debate about whether additional fMRI-measured activity in the right prefrontal cortex readily observed in older adults represents compensatory activation that enhances cognition or whether maintenance of youthful brain activity best supports cognitive function in late adulthood. To investigate this issue, we tested a large lifespan sample of 461 adults (aged 20-89) and treated degree of left-lateralization in ventrolateral and dorsolateral prefrontal cortex during a semantic judgment fMRI task as an individual differences variable to predict cognition. We found that younger adults were highly left-lateralized, but lateralization did not predict better cognition, whereas higher left-lateralization of prefrontal cortex predicted better cognitive performance in middle-aged adults, providing evidence that left-lateralized, youth-like patterns are optimal in middle age. This relationship was reversed in older adults, with lower laterality scores associated with better cognition. The findings suggest that bilaterality in older adults facilitates cognition, but early manifestation of this pattern during middle age is characteristic of low performers. Implications of these findings for current theories of neurocognitive aging are discussed.

In this thesis, I used underwater images to determine patterns in lateralization and group size when beluga calves and juveniles are present. Usually, lateralization is defined by either a left or right preference, but using underwater images (an untested, non-invasive approach) provided an opportunity to analyze position bias from three distinct planes, the sagittal (left or right), coronal (dorsal or ventral), and transverse (anterior or posterior). My research found that the presence of the boat may have affected lateralization as juveniles were most frequently observed on the left. This position bias was possibly due to their mothers, who may have positioned themselves between their young and the less familiar boat. Additionally, while both calves and juveniles preferred to be positioned in ventral positions near their mother, juveniles were most frequently observed at the anterior of the head region, while calves were in the posterior or tail region or infant position. This difference is likely due to juveniles having increased swimming abilities, allowing them to compromise the hydrodynamic benefits of the infant position for the anterior position, as the head or anterior is preferred for social interactions in whales. In my second chapter, I determined if mother and calf/juvenile dyads selected larger groups. My results indicated that groups that contained calves and juveniles had more adults present than groups that contained adults only. In comparison with aerial surveys, I found that group sizes in underwater images were significantly larger across all age classes. This may be an effect of methods used, as boats used to collect camera images may have moved to locations where beluga were aggregating. However, further research is needed to determine the effect of boats on juveniles’ interactions.

In right-handed adults, face processing is lateralized to the right hemisphere and visual word processing to the left hemisphere. According to the many-to-many account (MTMA) of functional cerebral organization this lateralization pattern is partly dependent on the acquisition of literacy. Hence, the MTMA predicts that: (i) processing of both words and faces should show no or at least less lateralization in individuals with developmental dyslexia compared with controls, and (ii) lateralization in word processing should be normal in individuals with developmental prosopagnosia whereas lateralization in face processing should be absent. To test these hypotheses, 21 right-handed adults with developmental dyslexia and 21 right-handed adults with developmental prosopagnosia performed a divided visual field paradigm with delayed matching of faces, words and cars. Contrary to the predictions, we find that lateralization effects in face processing are within the normal range for both developmental dyslexics and prosopagnosics. Moreover, the group with developmental dyslexia showed right hemisphere lateralization for word processing. We argue that these findings are incompatible with the specific predictions of the MTMA.

Music is often described in the laboratory and in the classroom as a beneficial tool for memory encoding and retention, with a particularly strong effect when words are sung to familiar compared to unfamiliar melodies. However, the neural mechanisms underlying this memory benefit, especially for benefits related to familiar music are not well understood. The current study examined whether neural tracking of the slow syllable rhythms of speech and song is modulated by melody familiarity. Participants became familiar with twelve novel melodies over four days prior to MEG testing. Neural tracking of the same utterances spoken and sung revealed greater cerebro-acoustic phase coherence for sung compared to spoken utterances, but did not show an effect of familiar melody when stimuli were grouped by their assigned (trained) familiarity. However, when participant's subjective ratings of perceived familiarity were used to group stimuli, a large effect of familiarity was observed. This effect was not specific to song, as it was observed in both sung and spoken utterances. Exploratory analyses revealed some in-session learning of unfamiliar and spoken utterances, with increased neural tracking for untrained stimuli by the end of the MEG testing session. Our results indicate that top-down factors like familiarity are strong modulators of neural tracking for music and language. Participants' neural tracking was related to their perception of familiarity, which was likely driven by a combination of effects from repeated listening, stimulus-specific melodic simplicity, and individual differences. Beyond simply the acoustic features of music, top-down factors built into the music listening experience, like repetition and familiarity, play a large role in the way we attend to and encode information presented in a musical context.

In right-handed adults, face processing is lateralized to the right hemisphere and visual word processing to the left hemisphere. According to the many-to-many account (MTMA) of functional cerebral organization this lateralization pattern is partly dependent on the acquisition of literacy. Hence, the MTMA predicts that: (i) processing of both words and faces should show no or at least less lateralization in individuals with developmental dyslexia compared with controls, and (ii) lateralization in word processing should be normal in individuals with developmental prosopagnosia whereas lateralization in face processing should be absent. To test these hypotheses, 21 right-handed adults with developmental dyslexia and 21 right-handed adults with developmental prosopagnosia performed a divided visual field paradigm with delayed matching of faces, words and cars. Contrary to the predictions, we find that lateralization effects in face processing are within the normal range for both developmental dyslexics and prosopagnosics. Moreover, the group with developmental dyslexia showed right hemisphere lateralization for word processing. We argue that these findings are incompatible with the specific predictions of the MTMA.

In this thesis, I used underwater images to determine patterns in lateralization and group size when beluga calves and juveniles are present. Usually, lateralization is defined by either a left or right preference, but using underwater images (an untested, non-invasive approach) provided an opportunity to analyze position bias from three distinct planes, the sagittal (left or right), coronal (dorsal or ventral), and transverse (anterior or posterior). My research found that the presence of the boat may have affected lateralization as juveniles were most frequently observed on the left. This position bias was possibly due to their mothers, who may have positioned themselves between their young and the less familiar boat. Additionally, while both calves and juveniles preferred to be positioned in ventral positions near their mother, juveniles were most frequently observed at the anterior of the head region, while calves were in the posterior or tail region or infant position. This difference is likely due to juveniles having increased swimming abilities, allowing them to compromise the hydrodynamic benefits of the infant position for the anterior position, as the head or anterior is preferred for social interactions in whales. In my second chapter, I determined if mother and calf/juvenile dyads selected larger groups. My results indicated that groups that contained calves and juveniles had more adults present than groups that contained adults only. In comparison with aerial surveys, I found that group sizes in underwater images were significantly larger across all age classes. This may be an effect of methods used, as boats used to collect camera images may have moved to locations where beluga were aggregating. However, further research is needed to determine the effect of boats on juveniles’ interactions.

In this thesis, I used underwater images to determine patterns in lateralization and group size when beluga calves and juveniles are present. Usually, lateralization is defined by either a left or right preference, but using underwater images (an untested, non-invasive approach) provided an opportunity to analyze position bias from three distinct planes, the sagittal (left or right), coronal (dorsal or ventral), and transverse (anterior or posterior). My research found that the presence of the boat may have affected lateralization as juveniles were most frequently observed on the left. This position bias was possibly due to their mothers, who may have positioned themselves between their young and the less familiar boat. Additionally, while both calves and juveniles preferred to be positioned in ventral positions near their mother, juveniles were most frequently observed at the anterior of the head region, while calves were in the posterior or tail region or infant position. This difference is likely due to juveniles having increased swimming abilities, allowing them to compromise the hydrodynamic benefits of the infant position for the anterior position, as the head or anterior is preferred for social interactions in whales. In my second chapter, I determined if mother and calf/juvenile dyads selected larger groups. My results indicated that groups that contained calves and juveniles had more adults present than groups that contained adults only. In comparison with aerial surveys, I found that group sizes in underwater images were significantly larger across all age classes. This may be an effect of methods used, as boats used to collect camera images may have moved to locations where beluga were aggregating. However, further research is needed to determine the effect of boats on juveniles’ interactions.

Deep learning has achieved a high classification accuracy on image classification tasks, including emotion categorization. However, deep learning models are highly vulnerable to adversarial attacks. Even a small change, imperceptible to a human (e.g. one-pixel attack), can decrease the classification accuracy of deep models. One reason could be their homogeneous representation of knowledge that considers all pixels in an image to be equally important is easily fooled. Enabling multiple representations of the same object, e.g. at the constituent and holistic viewpoints provides robustness against attacking a single view. This heterogeneity is provided by lateralization in biological systems. Lateral asymmetry of biological intelligence suggests heterogeneous learning of objects. This heterogeneity allows information to be learned at different levels of abstraction, i.e. at the constituent and the holistic level, enabling multiple representations of the same object. This work aims to create a novel system that can consider heterogeneous features e.g. mouth, eyes, nose, and jaw in a face image for emotion categorization. The experimental results show that the lateralized system successfully considers constituent and holistic features to exhibit robustness to unimportant and irrelevant changes to emotion in an image, demonstrating performance accuracy better than (or similar) to the deep learning system (VGG19). Overall, the novel lateralized method shows a stronger resistance to changes (10.86–47.72% decrease) than the deep model (25.15–83.43% decrease). The advances arise by allowing heterogeneous features, which enable constituent and holistic representations of image components.

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

Working memory (WM) is a limited-capacity system or set of processes that enables temporary storage and manipulation of information essential for complex cognitive processes. The WM performance is supported by a widespread neural network in which fronto-parietal functional connections have a pivotal role. Transcranial direct current stimulation (tDCS) is rapidly emerging as a promising tool for understanding the role of various cortical areas and their functional networks on cognitive performance. Here we comprehensively evaluated the effects of tDCS on WM by conducting three cross-over counterbalanced sham-controlled experiments in which we contrasted the effects and interactions of the anodal (i.e. facilitatory) tDCS across anterior-posterior (i.e. DLPFC vs PPC) and left-right (i.e. the lateralization) axes, and across online and offline protocols using both verbal and spatial WM (3-back) tasks as outcomes. In the offline protocols, left DLPFC stimulation affected neither verbal nor spatial WM, while left PPC stimulation increased spatial WM. When applied offline over right DLPFC, tDCS improved verbal WM task and marginally enhanced spatial WM; while when tDCS was applied over the right PPC, facilitatory effects were observed on verbal WM. In the online protocol, tDCS did not modulate WM regardless of the task modality or stimulation loci. In summary, the study did not replicate the left DLPFC tDCS effect on WM, found in some of the previous studies, but demonstrated positive effects of stimulation of the right DLPFC as well as PPC bilaterally. The observed effects varied across modality of the 3-back task, and tDCS protocol applied. The results of this study argue for moving towards targeting the lesser-explored stimulation sites within the fronto-parietal network, such as PPC, to gain a better understanding of the usefulness of tDCS for WM neuromodulation.

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

Lateralized behaviour is the most conspicuous manifestation of hemispheric specialization of the brain and has been reported in a variety of taxa. Only a few studies have so far assessed lateralized behaviours in horses. Therefore, I observed ten domestic horses for 16 weeks for an array of spontaneously occurring motor behaviours as well as stimulus-induced behavioural responses to determine if they display side preferences at the individual or population level and to assess possible correlations between lateralized behaviours. Significant side preferences were found for certain behaviours at the individual level, ranging from standing and flexing, to auditory stimuli, and olfactory stimuli. All horses showed task-dependent changes in their side preferences and no significant side preferences were found at the population level for any behaviours. Similarly, no significant correlations were found between behaviours. Taken together, the results of the present study suggest that horses, like all other species studied so far except humans and some great apes, only display lateralized behaviour at the individual, but not at the population level.

Theories disagree as to whether it is the early or the late neural correlate of awareness that plays a critical role in phenomenal awareness. According to recurrent processing theory, early activity in primary sensory areas corresponds closely to phenomenal awareness. In support, research with electroencephalography found that in the visual and somatosensory modality, an early neural correlate of awareness is contralateral to the perceived side of stimulation. Thus, early activity is sensitive to the perceived side of visual and somatosensory stimulation. Critically, it is unresolved whether this is true also for hearing. In the present study (N = 26 students), Bayesian analyses showed that the early neural correlate of awareness (auditory awareness negativity, AAN) was stronger for contralateral than ipsilateral electrodes whereas the late correlate of auditory awareness (late positivity, LP) was not lateralized. These findings demonstrate that the early but not the late neural correlate of auditory awareness reflects lateralized experiences. Thus, these findings imply that AAN is a more suitable NCC than LP because it correlates more closely with lateralized experiences.

It may be difficult to determine whether a dichotic lag-click points to the left or right when preceded by a diotic lead-click. Previous research suggests that this loss of spatial information is most prominent at inter-click intervals (ICIs) <10 ms. However, a study by Nilsson, Tirado, and Szychowska [(2019). J. Acoust. Soc. Am. 145, 512–524] found support for loss of spatial information in lag-clicks at much longer ICIs using a stimulus setup differing from those in previous research. The present study used a setup similar to that of the Nilsson, Tirado, and Szychowska study [(2019). J. Acoust. Soc. Am. 145, 512–524] to measure 13 listeners' ability to lateralize (left versus right) and detect (present versus absent) the lag-click in lead–lag click pairs with ICIs of 6–48 ms. The main finding was distinct individual differences in performance. Some listeners could lateralize lag-clicks all the way down to their detection threshold, whereas others had lateralization thresholds substantially higher than their detection thresholds, i.e., they could not lateralize lag-clicks that they could easily detect. Two such listeners trained for 30 days and managed to improve their lateralization thresholds to reach their detection thresholds, but only at longer ICIs (>20 ms), suggesting different mechanisms underlying lag-click lateralization at short versus long ICIs.

1. Movements of either the contralateral or ipsilateral arm produce changes in neural activity insensorimotor cortex as well as subcortical structures. To better understand what information is encoded by the ipsilateral arm, and if this information could be used in more applied settings (i.e., deep brain stimulation), we conducted two experiments utilizing patients who have intracranial recordings for clinical purposes. In the first study we examined patients with intracranial grids implanted in either the left or the right hemisphere. Implementing a crossvalidated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis. In the second study we examined neural recordings from patients with a deep brain stimulation lead targeting the subthalamic nucleus as well as a cortical strip while they made repetitive hand movements. We fit the continuous EMG to the neural activity using a cross-validated encoding model and found that electrodes in the subthalamic region encode both hands equally well whereas in the sensorimotor cortex we found a strong contralateral bias. In addition, we found that electrodes in the subthalamic region generalize across arms better than the sensorimotor cortex and appear to be more sensitive to context (i.e., whether the other arm is engaged in the task or not). 2. Non-invasive brain stimulation (NIBS) can safely manipulate neural excitability in the human brain, providing neuroscientists with a powerful tool to advance our understanding of brain function and clinicians with novel interventions in the treatment of neurological and psychiatric disord

Handedness has been extensively studied because of its relationship with language and the over-representation of left-handers in some neurodevelopmental disorders. Using data from the UK Biobank, 23andMe and the International Handedness Consortium, we conducted a genome-wide association meta-analysis of handedness (N = 1,766,671). We found 41 loci associated (P <5 x 10(-8)) with left-handedness and 7 associated with ambidexterity. Tissue-enrichment analysis implicated the CNS in the aetiology of handedness. Pathways including regulation of microtubules and brain morphology were also highlighted. We found suggestive positive genetic correlations between left-handedness and neuropsychiatric traits, including schizophrenia and bipolar disorder. Furthermore, the genetic correlation between left-handedness and ambidexterity is low (r(G) = 0.26), which implies that these traits are largely influenced by different genetic mechanisms. Our findings suggest that handedness is highly polygenic and that the genetic variants that predispose to left-handedness may underlie part of the association with some psychiatric disorders.A genome-wide association study of 1.7 million individuals identified 41 genetic variants associated with left-handedness and 7 associated with ambidexterity. The genetic correlation between the traits was low, thereby implying different aetiologies.

Working memory (WM) is a limited-capacity system or set of processes that enables temporary storage and manipulation of information essential for complex cognitive processes. The WM performance is supported by a widespread neural network in which fronto-parietal functional connections have a pivotal role. Transcranial direct current stimulation (tDCS) is rapidly emerging as a promising tool for understanding the role of various cortical areas and their functional networks on cognitive performance. Here we comprehensively evaluated the effects of tDCS on WM by conducting three cross-over counterbalanced sham-controlled experiments in which we contrasted the effects and interactions of the anodal (i.e. facilitatory) tDCS across anterior-posterior (i.e. DLPFC vs PPC) and left-right (i.e. the lateralization) axes, and across online and offline protocols using both verbal and spatial WM (3-back) tasks as outcomes. In the offline protocols, left DLPFC stimulation affected neither verbal nor spatial WM, while left PPC stimulation increased spatial WM. When applied offline over right DLPFC, tDCS improved verbal WM task and marginally enhanced spatial WM; while when tDCS was applied over the right PPC, facilitatory effects were observed on verbal WM. In the online protocol, tDCS did not modulate WM regardless of the task modality or stimulation loci. In summary, the study did not replicate the left DLPFC tDCS effect on WM, found in some of the previous studies, but demonstrated positive effects of stimulation of the right DLPFC as well as PPC bilaterally. The observed effects varied across modality of the 3-back task, and tDCS protocol applied. The results of this study argue for moving towards targeting the lesser-explored stimulation sites within the fronto-parietal network, such as PPC, to gain a better understanding of the usefulness of tDCS for WM neuromodulation.

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

Handedness has been extensively studied because of its relationship with language and the over-representation of left-handers in some neurodevelopmental disorders. Using data from the UK Biobank, 23andMe and the International Handedness Consortium, we conducted a genome-wide association meta-analysis of handedness (N = 1,766,671). We found 41 loci associated (P <5 x 10(-8)) with left-handedness and 7 associated with ambidexterity. Tissue-enrichment analysis implicated the CNS in the aetiology of handedness. Pathways including regulation of microtubules and brain morphology were also highlighted. We found suggestive positive genetic correlations between left-handedness and neuropsychiatric traits, including schizophrenia and bipolar disorder. Furthermore, the genetic correlation between left-handedness and ambidexterity is low (r(G) = 0.26), which implies that these traits are largely influenced by different genetic mechanisms. Our findings suggest that handedness is highly polygenic and that the genetic variants that predispose to left-handedness may underlie part of the association with some psychiatric disorders.A genome-wide association study of 1.7 million individuals identified 41 genetic variants associated with left-handedness and 7 associated with ambidexterity. The genetic correlation between the traits was low, thereby implying different aetiologies.

La dominanza dell’emisfero cerebrale sinistro (ES) sul destro (ED) nell’ambito della lettura è ampiamente riconosciuto nell’ambito delle neuroscienze cognitive. Tuttavia, non è ancora chiaro se questa dominanza sia basata sulla completa cecità verbale dell’ED (dominanza assoluta dell’ES), o sulla presenza di rappresentazioni più deboli o minori in numero nell’ED rispetto all’ES (dominanza relativa dell’ES). In linea con la prima ipotesi, leggere dovrebbe essere impossibile se il “sistema delle rappresentazioni visive delle parole” nell’ES è lesionato e sia le connessioni afferenti ed efferenti di quest’area con il resto dell’ES sono interrotte dalla lesione. Inoltre, secondo questa ipotesi, le differenze emisferiche all’interno dei compiti di lettura lateralizzata sono spiegabili in termini di una maggiore sensibilità dell’ED rispetto all’ES a fattori di elaborazione ortografici pre-lessicali. Secondo l’approccio che propone una dominanza relativa dell’ES per la lettura e che suggerisce l’esistenza di abilità lessicali più limitate nell’ED rispetto all’ES, la lettura dovrebbe essere possibile anche in caso di lesione e disconnessione del “sistema delle rappresentazioni visive delle parole” nell’ES, sebbene limitata a parole frequenti e/o concrete. In linea con questo approccio, le differenze emisferiche in compiti di lettura lateralizzata sarebbero spiegabili da variabili semantico-lessicali. Le predizioni di questi modelli sono state testate attraverso uno studio comportamentale e di disconnessione strutturale in una paziente con Alessia Pura, e tramite due studi di lettura con campo visivo diviso (condotti su soggetti destrimani e destrimani e mancini, rispettivamente) in cui fattori lessicali e pre-lessicali sono stati manipolati. La presenza di abilità di lettura residue nel caso di lesione del “sistema delle rappresentazioni visive delle parole” dell’ES e di una sua disconnessione con il resto dell’ES, insieme all’evidenza che un effetto lessicale può, The dominance of the left cerebral hemisphere (LH) over the right one (RH) for reading is widely recognized in the domain of cognitive neuroscience. However, it is still not clear whether such dominance is underlaid by a complete word blindness of the RH (absolute LH dominance) or by poorer/weaker lexical representations in the RH than in the LH (relative dominance). According to the first account, reading should be impossible when the visual word form system of the LH is lesioned and both afferent and efferent connections with the rest of the LH are interrupted by the lesion. Also, according to this account, hemispheric differences in lateralized reading in healthy subjects are explained by greater sensitivity of the RH than the LH to pre-lexical orthographic processing factors. According to the framework advocating a relative LH dominance for reading and suggesting poorer lexical orthographic abilities of the RH than the LH, reading should be possible even in case of lesion and disconnection of the LH reading system, although limited to frequent and/or concrete words. Accordingly, hemispheric differences in lateralized reading in healthy subjects should be explained by lexical-semantic factors. The predictions of these models were tested by means of a behavioral and structural disconnectome study on a patient with Pure Alexia, and two divided visual field reading studies (conducted on healthy right-handed and left-and right-handed subjects, respectively) in which pre-lexical and lexical factors were manipulated. Evidence of residual reading abilities in case of a LH visual word form system lesioned with both afferent and efferent connections with the rest of the LH being interrupted, together with evidence of a lexical effect accounting for visual field/hemisphere differences in lateralized reading supported the view of a relative LH dominance, according to the idea of the existence of a poorer/weaker orthographic lexicon in the RH. A computational modelling study

Lateralized behaviour is the most conspicuous manifestation of hemispheric specialization of the brain and has been reported in a variety of taxa. Only a few studies have so far assessed lateralized behaviours in horses. Therefore, I observed ten domestic horses for 16 weeks for an array of spontaneously occurring motor behaviours as well as stimulus-induced behavioural responses to determine if they display side preferences at the individual or population level and to assess possible correlations between lateralized behaviours. Significant side preferences were found for certain behaviours at the individual level, ranging from standing and flexing, to auditory stimuli, and olfactory stimuli. All horses showed task-dependent changes in their side preferences and no significant side preferences were found at the population level for any behaviours. Similarly, no significant correlations were found between behaviours. Taken together, the results of the present study suggest that horses, like all other species studied so far except humans and some great apes, only display lateralized behaviour at the individual, but not at the population level.

An aided sound-field auditory steady-state response (ASSR) has the potential to be used to objectively validate hearing-aid (HA) fittings in clinics. Each aided ear should ideally be tested independently, but it is suspected that binaural testing may be used by clinics to reduce test time. This study simulates dichotic ASSR sound-field conditions to examine the risk of making false judgments due to unchecked binaural effects. Unaided ASSRs were recorded with a clinical two-channel electroencephalography (EEG) system for 15 normal hearing subjects using a three-band CE-Chirp® stimulus. It was found that the noise corrected power of a response harmonic can be suppressed by up to 10 dB by introducing large interaural time differences equal to half the time period of the stimulus envelope, which may occur in unilateral HA users. These large interaural time differences also changed the expression of ASSR power across the scalp, resulting in dramatically altered topographies. This would lead to considerably lower measured response power and possibly nondetections, evidencing that even well fit HAs are fit poorly (false referral), whereas monaural ASSR tests would pass. No effect was found for simulated lateralizations of the stimulus, which is beneficial for a proposed aided ASSR approach. Full-scalp ASSR recordings match previously found 40 Hz topographies but demonstrate suppression of cortical ASSR sources when using stimuli in interaural envelope antiphase.

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

Echolocation is the capacity to detect, localize, discriminate, and, overall, gather spatial information from sound reflections. Since we began studying it in humans, we have learned several things. First, most humans can echolocate to some degree. Second, the capacity to echolocate is related to: the type and size of the object that the individual is trying to echolocate; how well the individual can use self-generated or artificial signals; and the distance to the object. Third, the blind tend to perform better than the sighted, although some sighted individuals can perform as well as the blind. It has been speculated that expert echolocators are capable of unlearning the precedence effect (PE), which is the tendency of our auditory system to prioritize spatial information coming from the first wave front instead of the spatial information from the second wave front. This would allow them to obtain more spatial information from echoes, but there is little research linking the PE to echolocation skills, which is why my thesis research has explored this matter. Another contribution of my thesis research was to introduce two new concepts: echo-detection and echo-localization. Echo-detection is the ability to detect an object using echoes as the main cue (“Is the object there, yes or no?”), whereas echo-localization is the ability both to detect and also localize an object using echoes as the main cue (“Is the object situated to the right or left?”). The reason for dividing echolocation into these two tasks is that detecting an echo does not necessarily entail knowing its location. No previous study has compared these two distinct abilities. Echo-detection and echo-localization, though linked to each other, could be influenced by different mechanisms. The aim of this thesis was to explore individual differences in echo-detection, echo-localization, and other fundamental psychoacoustic abilities (i.e., PE and different types of masking) in inexperienced, sighted indivi

The two halves of the brain are believed to play different roles in emotional processing. In studies involving chimeric faces, emotional expressions in the left visual field are more strongly perceived as emotional than those in the right visual field. Notably, the role of facial mimicry has not been studied in relation to hemispheric lateralization. In the current study, which used a novel stimulus set of chimeric faces, we proposed and found that emotional intensity judgments replicate the left visual field bias for facial expressions of emotions. While a general facial mimicry effect to the chimeric faces occurred for the corrugator muscle, these mimicry effects were not related to the visual field bias. The results suggest that encoding the emotionality of another person’s facial expression might occur independent from the mere mimicry of the facial expression itself.

Behavioural lateralization, the asymmetric expression of cognitive functions, is reported to enhance key fitness-relevant traits such as group coordination, multitasking and predator escape. Therefore, studies reporting negative effects on lateralization in fish due to environmental stressors such as ocean acidification, hypoxia and pollutants are worrisome. However, such studies tend to use a detour test and focus on population level measures, without validating whether lateralization is consistent within individuals across time. We conducted a multispecies, international assessment of the repeatability (R) of lateralization in four previously studied fish species using a detour test (T-maze), a common method for testing lateralization. We also reanalysed a published data set on a fifth species using new statistical methods. We expected the three shoaling species to exhibit greater within-individual consistency in lateralization than their nonshoaling counterparts given previous reports of stronger lateralization in group-living fishes. Absolute and relative lateralization scores were highly nonrepeatable in all five species (0.01

Mechanisms of motor deficits (e.g. hemiparesis and hemiplegia) secondary to stroke and traumatic brain injury remain poorly understood. In early animal studies, a unilateral lesion to the cerebellum produced postural asymmetry with ipsilateral hindlimb flexion that was retained after complete spinal cord transection. Here we demonstrate that hindlimb postural asymmetry in rats is induced by a unilateral injury of the hindlimb sensorimotor cortex, and characterize this phenomenon as a model of spinal neuroplasticity underlying asymmetric motor deficits. After cortical lesion, the asymmetry was developed due to the contralesional hindlimb flexion and persisted after decerebration and complete spinal cord transection. The asymmetry induced by the left-side brain injury was eliminated by bilateral lumbar dorsal rhizotomy, but surprisingly, the asymmetry after the right-side brain lesion was resistant to deafferentation. Pancuronium, a curare-mimetic muscle relaxant, abolished the asymmetry after the right-side lesion suggesting its dependence on the efferent drive. The contra- and ipsilesional hindlimbs displayed different musculo-articular resistance to stretch after the left but not right-side injury. The nociceptive withdrawal reflexes evoked by electrical stimulation and recorded with EMG technique were different between the left and right hindlimbs in the spinalized decerebrate rats. On this asymmetric background, a brain injury resulted in greater reflex activation on the contra- versus ipsilesional side; the difference between the limbs was higher after the right-side brain lesion. The unilateral brain injury modified expression of neuroplasticity genes analysed as readout of plastic changes, as well as robustly impaired coordination of their expression within and between the ipsi- and contralesional halves of lumbar spinal cord; the effects were more pronounced after the left side compared to the right-side injury. Our data suggest that changes in the hindlimb p, De två första författarna delar förstaförfattarskapetDe två sista författarna delar sistaförfattarskapet

Behavioural lateralization, the asymmetric expression of cognitive functions, is reported to enhance key fitness-relevant traits such as group coordination, multitasking and predator escape. Therefore, studies reporting negative effects on lateralization in fish due to environmental stressors such as ocean acidification, hypoxia and pollutants are worrisome. However, such studies tend to use a detour test and focus on population level measures, without validating whether lateralization is consistent within individuals across time. We conducted a multispecies, international assessment of the repeatability (R) of lateralization in four previously studied fish species using a detour test (T-maze), a common method for testing lateralization. We also reanalysed a published data set on a fifth species using new statistical methods. We expected the three shoaling species to exhibit greater within-individual consistency in lateralization than their nonshoaling counterparts given previous reports of stronger lateralization in group-living fishes. Absolute and relative lateralization scores were highly nonrepeatable in all five species (0.01

Behavioural lateralization, the asymmetric expression of cognitive functions, is reported to enhance key fitness-relevant traits such as group coordination, multitasking and predator escape. Therefore, studies reporting negative effects on lateralization in fish due to environmental stressors such as ocean acidification, hypoxia and pollutants are worrisome. However, such studies tend to use a detour test and focus on population level measures, without validating whether lateralization is consistent within individuals across time. We conducted a multispecies, international assessment of the repeatability (R) of lateralization in four previously studied fish species using a detour test (T-maze), a common method for testing lateralization. We also reanalysed a published data set on a fifth species using new statistical methods. We expected the three shoaling species to exhibit greater within-individual consistency in lateralization than their nonshoaling counterparts given previous reports of stronger lateralization in group-living fishes. Absolute and relative lateralization scores were highly nonrepeatable in all five species (0.01

Mechanisms of motor deficits (e.g. hemiparesis and hemiplegia) secondary to stroke and traumatic brain injury remain poorly understood. In early animal studies, a unilateral lesion to the cerebellum produced postural asymmetry with ipsilateral hindlimb flexion that was retained after complete spinal cord transection. Here we demonstrate that hindlimb postural asymmetry in rats is induced by a unilateral injury of the hindlimb sensorimotor cortex, and characterize this phenomenon as a model of spinal neuroplasticity underlying asymmetric motor deficits. After cortical lesion, the asymmetry was developed due to the contralesional hindlimb flexion and persisted after decerebration and complete spinal cord transection. The asymmetry induced by the left-side brain injury was eliminated by bilateral lumbar dorsal rhizotomy, but surprisingly, the asymmetry after the right-side brain lesion was resistant to deafferentation. Pancuronium, a curare-mimetic muscle relaxant, abolished the asymmetry after the right-side lesion suggesting its dependence on the efferent drive. The contra- and ipsilesional hindlimbs displayed different musculo-articular resistance to stretch after the left but not right-side injury. The nociceptive withdrawal reflexes evoked by electrical stimulation and recorded with EMG technique were different between the left and right hindlimbs in the spinalized decerebrate rats. On this asymmetric background, a brain injury resulted in greater reflex activation on the contra- versus ipsilesional side; the difference between the limbs was higher after the right-side brain lesion. The unilateral brain injury modified expression of neuroplasticity genes analysed as readout of plastic changes, as well as robustly impaired coordination of their expression within and between the ipsi- and contralesional halves of lumbar spinal cord; the effects were more pronounced after the left side compared to the right-side injury. Our data suggest that changes in the hindlimb p, De två första författarna delar förstaförfattarskapetDe två sista författarna delar sistaförfattarskapet

Mechanisms of motor deficits (e.g. hemiparesis and hemiplegia) secondary to stroke and traumatic brain injury remain poorly understood. In early animal studies, a unilateral lesion to the cerebellum produced postural asymmetry with ipsilateral hindlimb flexion that was retained after complete spinal cord transection. Here we demonstrate that hindlimb postural asymmetry in rats is induced by a unilateral injury of the hindlimb sensorimotor cortex, and characterize this phenomenon as a model of spinal neuroplasticity underlying asymmetric motor deficits. After cortical lesion, the asymmetry was developed due to the contralesional hindlimb flexion and persisted after decerebration and complete spinal cord transection. The asymmetry induced by the left-side brain injury was eliminated by bilateral lumbar dorsal rhizotomy, but surprisingly, the asymmetry after the right-side brain lesion was resistant to deafferentation. Pancuronium, a curare-mimetic muscle relaxant, abolished the asymmetry after the right-side lesion suggesting its dependence on the efferent drive. The contra- and ipsilesional hindlimbs displayed different musculo-articular resistance to stretch after the left but not right-side injury. The nociceptive withdrawal reflexes evoked by electrical stimulation and recorded with EMG technique were different between the left and right hindlimbs in the spinalized decerebrate rats. On this asymmetric background, a brain injury resulted in greater reflex activation on the contra- versus ipsilesional side; the difference between the limbs was higher after the right-side brain lesion. The unilateral brain injury modified expression of neuroplasticity genes analysed as readout of plastic changes, as well as robustly impaired coordination of their expression within and between the ipsi- and contralesional halves of lumbar spinal cord; the effects were more pronounced after the left side compared to the right-side injury. Our data suggest that changes in the hindlimb p, De två första författarna delar förstaförfattarskapetDe två sista författarna delar sistaförfattarskapet

Laterality of eye use has been increasingly studied in cetaceans. Research supports that many cetacean species keep prey on the right side while feeding and preferentially view unfamiliar objects with the right eye. In contrast, the left eye has been used more by calves while in close proximity to their mothers. Despite some discrepancies across and within species, laterality of eye use generally indicates functional specialization of brain hemispheres in cetaceans. The present study aimed to examine laterality of eye use in bottlenose dolphins (Tursiops truncatus) and rough-toothed dolphins (Steno bredanensis) under managed care. Subjects were video-recorded through an underwater window while viewing two different stimuli, one predictable and static and the other unpredictable and moving. Bottlenose dolphins displayed an overall right-eye preference, especially while viewing the unpredictable, moving stimulus. Rough-toothed dolphins did not display eye preference while viewing stimuli. No significant correlations between degree of laterality and behavioral interest in the stimuli were found. Only for bottlenose dolphins were the degree of laterality and curiosity ratings correlated. This study extends research on cetacean lateralization to a species not extensively examined and to stimuli that varied in movement and degree of predictability. Further research is needed to make conclusions regarding lateralization in cetaceans.

Biological nervous systems can learn knowledge from simple and small-scale problems and then apply it to resolve more complex and large-scale problems in similar and related domains. However, the rudimentary attempts to apply this transfer learning in artificial intelligence systems have struggled. This is maybe due to the homogeneous nature of their knowledge representation. It is believed that it is the lateral asymmetry of the brain, enabling modular learning at different levels of abstraction, which facilitates transfer between tasks. Learning classifier systems (LCSs) are a rule-based evolutionary computation technique that automatically clusters inputs into environmental niches, which makes it an ideal candidate for implementing lateralization. Recently LCSs based systems have applied lateralization and modular learning at different levels of abstraction to solve complex problems in Boolean, computer vision, and navigation domains. This paper aims to bring these three separate implementations together for the first time to understand the methodology of lateralization and appreciate its benefits. The experimental results demonstrate that the LCSs based lateralized systems outperformed state-of-the-art homogeneous systems in solving complex problems. The advances arise from the ability to consider input at both the constituent level and holistic level simultaneously, such that the most appropriate viewpoint controls the system.

Deep learning is an important field of machine learning. It is playing a critical role in a variety of applications ranging from self-driving cars to security and surveillance. However, deep networks have deep flaws. For example, they are highly vulnerable to adversarial attacks. One reason may be the homogeneous nature of their knowledge representation, which allows a single disruptive pattern to cause miss-classification. Biological intelligence has lateral asymmetry, which allows heterogeneous, modular learning at different levels of abstraction, enabling different representations of the same object. This work aims to incorporate lateralization and modular learning at different levels of abstraction in an evolutionary machine learning system. The results of image classification tasks show that the lateralized system efficiently learns hierarchical distributions of knowledge, demonstrating performance that is similar to (or better than) other state-of-the-art deep systems as it reasons using multiple representations. Crucially, the novel system outperformed all the state-of-the-art deep models for the classification of normal and adversarial images by 0.43% - 2.56% and 2.15% - 25.84%, respectively. Lateralisation enabled the system to exhibit robustness beyond previous work, which advocates for the creation of data sets that enable components of objects and the objects themselves to be learned specifically or in an end-to-end manner.