Search

This study compares results from three dichotic listening experiments involving different methods of attention control. In each experiment, participants completed a dichotic listening task requiring two responses to syllables and we noted the order of report for the responses. In Experiment 1, participants reported from a specific ear first in trial blocks. In Experiment 2, an arrow cue indicated the ear of first report. In Experiment 3, a tone was presented to the ear of first report. Free recall in which participants reported the two syllables in any order was also included as a baseline. Results indicated a tendency to report from the right ear first in free recall, producing more reports from that ear, reflecting a right ear advantage (REA). In all cueing conditions, an overall REA emerged but it shifted to a left ear advantage (LEA: more reports from the left ear) when the left ear was cued. Additionally, larger laterality scores ([Right − Left]/[Right + Left]) for the conditions where the right ear was cued, relative to where the left ear was cued, suggests that attention control is limited in overriding the structural auditory asymmetries. We discuss the implications of these results for models of dichotic listening. [ABSTRACT FROM AUTHOR]

Abstract How stress affects functional hemispheric asymmetries is relevant because stress represents a risk factor for the development of mental disorders and various mental disorders are associated with atypical lateralization. Using three lateralization tasks, we investigated whether functional hemispheric asymmetries in the form of hemispheric dominance for language (verbal dichotic listening task), emotion processing (emotional dichotic listening task), and visuo-spatial attention (line bisection task) were affected by acute stress in healthy adults. One hundred twenty right-handed men and women performed these lateralization tasks in randomized order after exposure to a mild online stressor (i.e., an online variant of the Trier Social Stress Test (TSST), TSST-OL) and a non-stressful online control task (friendly TSST-OL, fTSST-OL) in a within-subjects design. Importantly, the verbal and the emotional dichotic listening tasks were presented online whereas the line bisection task was completed in paper–pencil form. During these tasks, we found the expected hemispheric asymmetries, indicating that online versions of both the verbal and the emotional dichotic listening task can be used to measure functional hemispheric asymmetries in language and emotion processing remotely. Even though subjective and physiological markers confirmed the success of the online stress manipulation, replicating previous studies, we found no stress-induced effect on functional hemispheric asymmetries. Thus, in healthy participants, functional hemispheric asymmetries do not seem to change flexibly in response to acute stress.

Introduction: Dichotic listening (DL) is a test where auditory stimuli are presented simultaneously to each ear. DL has clinical applications in assessing APD, schizophrenia, and brain injury. It is sensitive to hemisphere differences and has been used to study language lateralization. The study aimed to develop, validate, and establish norms for a Quadri condition Dichotic Double Word Test (free recall, forced right, forced left, and switch attention) in the Kannada language (DDWT-K). Methods: This study was carried out in two phases. Phase 1 aimed to develop and validate the DDWT-K and phase 2 involved data collection. The developed novel dichotic test was administered on 100 normal-hearing adults in four conditions – free recall, forced right, forced left, and switch attention. Results: The results showed significant ear differences in free recall condition indicating right ear advantage. The switch attention condition showed slightly poorer performance when compared to both the forced attention condition indicating greater task difficulty. The test-retest reliability was above 0.7 for all the conditions indicating good reliability. Conclusions: The findings demonstrated the best preservation of the original dichotic effects and hence ready for clinical use. [ABSTRACT FROM AUTHOR]

How stress affects functional hemispheric asymmetries is relevant because stress represents a risk factor for the development of mental disorders and various mental disorders are associated with atypical lateralization. Using three lateralization tasks, we investigated whether functional hemispheric asymmetries in the form of hemispheric dominance for language (verbal dichotic listening task), emotion processing (emotional dichotic listening task), and visuo-spatial attention (line bisection task) were affected by acute stress in healthy adults. One hundred twenty right-handed men and women performed these lateralization tasks in randomized order after exposure to a mild online stressor (i.e., an online variant of the Trier Social Stress Test (TSST), TSST-OL) and a non-stressful online control task (friendly TSST-OL, fTSST-OL) in a within-subjects design. Importantly, the verbal and the emotional dichotic listening tasks were presented online whereas the line bisection task was completed in paper–pencil form. During these tasks, we found the expected hemispheric asymmetries, indicating that online versions of both the verbal and the emotional dichotic listening task can be used to measure functional hemispheric asymmetries in language and emotion processing remotely. Even though subjective and physiological markers confirmed the success of the online stress manipulation, replicating previous studies, we found no stress-induced effect on functional hemispheric asymmetries. Thus, in healthy participants, functional hemispheric asymmetries do not seem to change flexibly in response to acute stress. [ABSTRACT FROM AUTHOR]

Highlights: The main finding was that the developmental pattern of brain laterality from the ages of 6 to 11 in the Dyslexia group differed both from the pattern of the Typical group and from a frequently seen pattern in dyslexia. During the period in which children learn to read and write, a gradual shift from right to left hemisphere dominance for language is typically seen. However, in children with dyslexia, a deviant pattern is described in the literature. As part of a larger longitudinal study (The Bergen Longitudinal Dyslexia Study), the present study aimed to assess this development from an early age before children learn to read and write. Dichotic listening (DL), which is a non-invasive test, was used to assess the development of brain laterality in a Typical group and a Dyslexia group. The participants received yearly sessions of evidence-based literacy training at ages 5 to 7. The Typical group showed increasing ear scores and a shift from no ear advantage in the Pre-literacy stage (age 6), indicative of no hemisphere dominance, to a right ear advantage, indicative of a left hemisphere dominance, in the Emergent literacy stage (age 8) and the Literacy stage (age 11). The Dyslexia group showed a different pattern, with a significant right ear advantage at age 6, indicative of a right hemisphere dominance, and increasing ear scores at ages 8 and 11; however, no ear dominance was observed in the Literacy stage. The results point to an effect of relevant, evidence-based training affecting both right and left hemispheres in dyslexia, which should form a basis for further research. [ABSTRACT FROM AUTHOR]

Age-related changes pose challenges in speech processing for older adults. However, little is known about the role of auditory perceptual ability in their performance in dichotic listening tasks. The present study investigated how older adults' auditory perceptual abilities affected their correct rates and the right ear advantage (REA) in the dichotic listening tasks in two experiments. In Experiment 1, older adults' performance was assessed using dichotic listening tasks based on consonant–vowel (CV) words varying in consonants, vowels, and lexical tones, each presenting distinct auditory perceptual demands. It was found that older adults exhibited decreased correct rates as auditory perceptual demands increased. Moreover, differences in the REA were observed in older listeners, suggesting increased engagement of the hemisphere responsible for acoustic analysis in processing challenging dichotic stimuli. Experiment 2 examined how older individuals' acoustic processing abilities contributed to their dichotic listening performance. It was shown that older adults with acoustic processing abilities comparable to those of younger individuals demonstrated correct rates and REAs similar to those of younger cohorts. These results revealed the nonnegligible role of acoustic processing in the dichotic listening paradigm and the significance of considering listeners' auditory perceptual abilities in investigating language lateralisation using the dichotic listening paradigm. [ABSTRACT FROM AUTHOR]

Despite wide reporting of a right ear (RE) advantage on dichotic listening tasks and a right visual field (RVF) advantage on visual half-field tasks, we know very little about the relationship between these perceptual biases. Previous studies that have investigated perceptual asymmetries for analogous auditory and visual consonant–vowel tasks have indicated a serendipitous finding: a RE advantage and a left visual field (LVF) advantage with poor cross-modal correlations. In this study, we examined the possibility that this LVF advantage for visual processing of consonant–vowel strings may be a consequence of repetition by examining perceptual biases in analogous auditory and visual tasks for both consonant–vowel strings and words. We replicated opposite perceptual biases for consonant–vowel strings (RE and LVF advantages). This did not extend to word stimuli where we found RE and RVF advantages. Furthermore, these perceptual biases did not differ across the three experimental blocks. Thus, we can firmly conclude that this LVF advantage is unique to consonant–vowel strings and is not a consequence of the repetition of a relatively limited number of stimuli. Finally, a test of covariances indicated no cross-modal relationships between laterality indices suggesting that perceptual biases are dissociable within individuals and cluster on mode of presentation. [ABSTRACT FROM AUTHOR]

IntroductionDichotic listening (DL) has been extensively used as a task to investigate auditory processing and hemispheric lateralisation in humans. According to the “callosal relay model,” the typical finding of a right ear advantage (REA) occurs because the information coming from the right ear has direct access to the left dominant hemisphere while the information coming from the left ear has to cross via the corpus callosum. The underlying neuroanatomical correlates and neurophysiological mechanisms have been described using diffusion tensor imaging (DTI) and lagged phase synchronization (LPS) of the interhemispheric auditory pathway. During the non-forced condition of DL, functional connectivity (LPS) of interhemispheric gamma-band coupling has been described as a relevant mechanism related to auditory perception in DL. In this study, we aimed to extend the previous results by exploring the effects of top-down modulation of DL (forced-attention condition) on interhemispheric gamma-band LPS.MethodsRight-handed healthy participants (n = 31; 17 females) performed three blocks of DL with different attention instructions (no-attention, left-ear attention, right-ear attention) during simultaneous EEG recording with 64 channels. Source analysis was done with exact low-resolution brain electromagnetic tomography (eLORETA) and functional connectivity between bilateral auditory areas was assessed as LPS in the gamma-band frequency range.ResultsTwenty-four participants (77%) exhibited a right-ear advantage in the no-attention block. The left- and right-attention conditions significantly decreased and increased right-ear reports, respectively. Similar to the previous studies, functional connectivity analysis (gamma-band LPS) showed significantly increased connectivity between left and right Brodmann areas (BAs) 41 and 42 during left ear reports in contrast with right ear reports. Our new findings notably indicated that the right-attention condition exhibited significantly higher connectivity between BAs 42 compared with the no-attention condition. This enhancement of connectivity was more pronounced during the perception of right ear reports.DiscussionOur results are in line with previous reports describing gamma-band synchronization as a relevant neurophysiological mechanism involved in the interhemispheric connectivity according to the callosal relay model. Moreover, we newly added some evidence of attentional effects on this interhemispheric connectivity, consistent with the attention-executive model. Our results suggest that reciprocal inhibition could be involved in hemispheric lateralization processes.

Abstract Background This study investigated the impact of age on dichotic listening performance by comparing results from the Turkish Dichotic Sentence Mobile Screening Test in young and elderly individuals with normal hearing. A total of 60 adults (30 young, 30 old) underwent otoscopic examination, audiological tests, and, for the elderly group, a mini-mental test. The Turkish Dichotic Sentence Mobile Screening Test was administered, and directed and undirected scores for the right and left ears were compared between age groups. Results In the young group, the directed left ear mean (96.67% ± 8.02%), directed right ear mean (98.33% ± 3.79%), undirected left ear mean (97.67% ± 6.26%), and undirected right ear mean (98.67% ± 5.71%) were obtained. In the elderly group, corresponding values were lower: directed left ear mean (49.00% ± 36.33%), directed right ear mean (54.67% ± 40.66%), undirected left ear mean (64.00% ± 32.86%), and undirected right ear mean (65.00% ± 30.82%). Statistically significant differences were found between the young and elderly groups (p

Abstract Background Bipolar disorder (BD) is often seen as a bridge between schizophrenia and depression in terms of symptomatology and etiology. Interestingly, hemispheric asymmetries as well as behavioral lateralization are shifted towards a tendency of left-side or mixed-side bias in schizophrenia whereas no shift is observed in subjects with depression. Given the role of BD with both, (hypo)manic and depressive episodes, investigating hemispheric asymmetries in subjects with BD is an interesting objective. Method A systematic review of studies including measures of behavioral lateralization in the form of handedness, footedness, eyedness, and language lateralization was performed resulting in 25 suitable studies. Results A broad variety of methods was used to assess behavioral lateralization, especially for eyedness, footedness, and language lateralization hindering the integration of results. Additionally, for hand preference, studies frequently used different cut-off scores and classification systems. Overall, studies do not support alteration in side preference in BD subjects. Studies focusing on differences in handedness demonstrate that subjects show equal rates of right- and non-right-handedness as the general population. Few studies focusing on manic episodes point towards increased left-side bias in ear and eye dominance, but the small sample sizes and conflicting results warrant further investigation. Conclusion The results reinforce that some disorders, such as BD, should not be treated as a homogenous group but sub-groups should be analyzed within the patient’s population. Particularly, clinical implications resulting from neuroimaging studies highlight the need to study hemispheric asymmetries given that they may be important to consider for brain stimulation protocols.

Abstract Background Dichotic listening refers to simultaneously stimulating both ears but with two different stimuli. Dichotic listening tasks were used in the audiological test battery to assess auditory processing abilities in children and adults. Studies have reported the dichotic consonant-vowel syllable test’s test-retest reliability in different attentional manipulation conditions. The objectives are to measure the intra- and inter-test reliability of dichotic consonant vowel tests in young, healthy individuals. Methods Sixty participants aged 18–28 with normal hearing sensitivity were recruited for the study. To measure the intra- and inter-test reliability, the dichotic consonant-vowel test was conducted within and between days. The single correct and double correct scores were calculated. Results The analysis of the study showed good test-retest reliability for the single correct and double correct scores of the dichotic consonant-vowel test based on Cronbach’s alpha values and Friedman’s tests. Conclusion This study’s findings indicate that the dichotic test is a stable measure that can be clinically used for evaluation and can be used for research studies.

During the period in which children learn to read and write, a gradual shift from right to left hemisphere dominance for language is typically seen. However, in children with dyslexia, a deviant pattern is described in the literature. As part of a larger longitudinal study (The Bergen Longitudinal Dyslexia Study), the present study aimed to assess this development from an early age before children learn to read and write. Dichotic listening (DL), which is a non-invasive test, was used to assess the development of brain laterality in a Typical group and a Dyslexia group. The participants received yearly sessions of evidence-based literacy training at ages 5 to 7. The Typical group showed increasing ear scores and a shift from no ear advantage in the Pre-literacy stage (age 6), indicative of no hemisphere dominance, to a right ear advantage, indicative of a left hemisphere dominance, in the Emergent literacy stage (age 8) and the Literacy stage (age 11). The Dyslexia group showed a different pattern, with a significant right ear advantage at age 6, indicative of a right hemisphere dominance, and increasing ear scores at ages 8 and 11; however, no ear dominance was observed in the Literacy stage. The results point to an effect of relevant, evidence-based training affecting both right and left hemispheres in dyslexia, which should form a basis for further research.

Background: Bipolar disorder (BD) is often seen as a bridge between schizophrenia and depression in terms of symptomatology and etiology. Interestingly, hemispheric asymmetries as well as behavioral lateralization are shifted towards a tendency of left-side or mixed-side bias in schizophrenia whereas no shift is observed in subjects with depression. Given the role of BD with both, (hypo)manic and depressive episodes, investigating hemispheric asymmetries in subjects with BD is an interesting objective. Method: A systematic review of studies including measures of behavioral lateralization in the form of handedness, footedness, eyedness, and language lateralization was performed resulting in 25 suitable studies. Results: A broad variety of methods was used to assess behavioral lateralization, especially for eyedness, footedness, and language lateralization hindering the integration of results. Additionally, for hand preference, studies frequently used different cut-off scores and classification systems. Overall, studies do not support alteration in side preference in BD subjects. Studies focusing on differences in handedness demonstrate that subjects show equal rates of right- and non-right-handedness as the general population. Few studies focusing on manic episodes point towards increased left-side bias in ear and eye dominance, but the small sample sizes and conflicting results warrant further investigation. Conclusion: The results reinforce that some disorders, such as BD, should not be treated as a homogenous group but sub-groups should be analyzed within the patient's population. Particularly, clinical implications resulting from neuroimaging studies highlight the need to study hemispheric asymmetries given that they may be important to consider for brain stimulation protocols. [ABSTRACT FROM AUTHOR]

Background: Dichotic listening refers to simultaneously stimulating both ears but with two different stimuli. Dichotic listening tasks were used in the audiological test battery to assess auditory processing abilities in children and adults. Studies have reported the dichotic consonant-vowel syllable test's test-retest reliability in different attentional manipulation conditions. The objectives are to measure the intra- and inter-test reliability of dichotic consonant vowel tests in young, healthy individuals. Methods: Sixty participants aged 18–28 with normal hearing sensitivity were recruited for the study. To measure the intra- and inter-test reliability, the dichotic consonant-vowel test was conducted within and between days. The single correct and double correct scores were calculated. Results: The analysis of the study showed good test-retest reliability for the single correct and double correct scores of the dichotic consonant-vowel test based on Cronbach's alpha values and Friedman's tests. Conclusion: This study's findings indicate that the dichotic test is a stable measure that can be clinically used for evaluation and can be used for research studies. [ABSTRACT FROM AUTHOR]

BackgroundHearing loss and dementia are linked, although the roles of peripheral and central auditory dysfunction are not well defined. Many behavioral measures of hearing are confounded by the overlapping cognitive functions required to perform the tests.ObjectiveTo collect pilot data to identify how central auditory function, measured using a dichotic listening test that indexes both auditory and cognitive components under different attentional conditions, differs among people with mild cognitive impairment (MCI), dementia and controls, and how performance relates to neuropsychological results.MethodFifty-eight participants (17 MCI, 11 dementia and 30 controls) undertook hearing screening, the Bergen consonant-vowel dichotic listening paradigm, and a short battery of neuropsychological tests chosen to index attention and executive control. Dichotic listening was assessed under three attentional conditions (non-forced, forced right ear and forced left) amongst older adults with normal cognitive function, MCI and dementia.ResultsWe report two main findings: (a) The expected right ear advantage under non-forced conditions, was seen in controls and patients with dementia but not in people with MCI, who showed equal numbers of correct responses from both ears (i.e., a lack of asymmetry); (b) Performance under forced attentional conditions was significantly associated with disease progression (i.e., control > MCI > dementia) and performance on the cognitive tasks.ConclusionThe reduction in asymmetry on dichotic listening tasks may be a marker of MCI and reflect underlying compensatory mechanisms. Use of this test could aid stratification of patients with memory disorders. Whether abnormalities could predict dementia onset needs longitudinal investigation in a larger sample.

Music has a cross-modal influence on the emotional appraisal of pictures, probably due to a misattribution of emotion from music to the visually perceived images. Moreover, dichotic listening studies have demonstrated a left-ear (right-hemisphere) advantage for processing emotional and/or musical stimuli. The present study investigated the role of laterality in cross-modal affect misattribution: that is, whether visual judgments of emotion would be affected differently depending on which ear was presented with music via the dichotic listening task. Participants rated the emotionality of happy, sad, and neutral faces while listening to happy or sad music in one ear and white noise in the other. Baseline ratings without music were used as a comparison to see whether and how emotionality judgments shifted in the music conditions. As predicted, the results showed that happy music played to the left ear had a stronger cross-modal influence on ratings of sad faces than the same music played to the right ear. Furthermore, sad music affected the ratings of all faces regardless of whether it was played to the left or right ear. These results do not fully align with any given lateralized model of emotion processing, suggesting that other factors such as negativity bias may play a role. [ABSTRACT FROM AUTHOR]

Background and Aim: Music can be a favorite, annoying, or even a distracting noise. It is known that the processing of brain hemispheres is affected by the pleasantness/unpleasantness of music, which could be utilized as a signal or noise in auditory neuroscience. By using the Acceptable Noise Level (ANL) test, which is the quantification of noise tolerance while listening to a running speech, we investigated whether the pleasantness/unpleasantness of music affects the ANL results under monotic-listening and dichotic-listening conditions. Methods: Based on the subjective scale scores, pleasant and unpleasant music (10 songs) were selected as alternatives to babble noise or running speech for testing 50 subjects for seven monotic and dichotic listening conditions. Results: While pleasant music changed the ANL significantly under monotic listening conditions, the higher level of babble noise was tolerated, and both characteristics of music pleasantness and unpleasantness changed ANL significantly for various dichotic conditions. The range of the ANL for dichotic conditions is wider than that for monotic conditions. Conclusion: Music can affect the ANL in terms of pleasantness and unpleasantness for both monotic and dichotic listening conditions, with a greater effect on dichotic conditions, indicating the role of hemispheric specification in emotional music processing. [ABSTRACT FROM AUTHOR]

Background: Diurnal changes can be defined as the time of the day over an individual's performance level for different activities that involve physical and mental tasks. Objective: The current study aimed to evaluate the effect of diurnal changes in scores obtained for the Dichotic Consonant-Vowel paradigm by young adults with normal hearing sensitivity. Method: Based on the ‘Morningness-Eveningness questionnaire’ given by Horne & Ostberg, the subjects were divided into moderately-morning, intermediate and moderately-evening categories. The Dichotic Consonant-Vowel tests were performed during morning and evening, and the right ear, left ear and double correct scores were compared between morning and evening for each category. Results: There was significant diurnal changes noted for moderately morning and evening categories, where morning-type individuals performed better during morning and evening-type individuals performed better during the evening. The scores of intermediate individuals remained unchanged between morning and evening test results. Conclusion: Diurnal change is a phenomenon associated with an individual's biological clock mechanism. Hence, attention and inhibitory controls aid them in carrying out tasks that require sufficient physical and mental efforts. The current study suggests that clinicians and researchers consider diurnal changes as an extraneous variable that could affect the reliability of the Dichotic Consonant-Vowel test results.

Altitude hypoxia can impair sensory and cognitive functions, from causing slowed responses to sensory hallucinations. In a field study, we tested 12 expeditioners at varied altitudes (low: 1696 m; high: 4556 m) with a simple auditory detection task and a dichotic listening paradigm in which a voice was presented, lateralized, within a binaural white noise stream. Slower reaction times and a reduced right ear advantage might be expected at high (vs. low) altitude, due to hypoxia. The participants' performances on both tasks did not differ between conditions, revealing that these functions are resistant to short-term hypoxia in young healthy adults. [ABSTRACT FROM AUTHOR]

Perceiving and producing English phonemic vowel length contrasts is challenging for non‐native speakers. According to multi‐time resolution models, endogenous slow/fast rhythms contribute, respectively, in the right/left hemispheres, to long/short acoustic cue processing. This study introduced a perceptual training method implementing dichotic stimulation to improve /i:/‐/ɪ/ processing by promoting hemispheric complementarity. Twenty non‐dyslexic and 20 dyslexic French adults received 1 hr‐training over 3 days. Productions were evaluated with pre‐/post‐tests. Training enhanced vowel duration contrast in word production by /i:/ lengthening and /ɪ/ shortening in both groups. Adults with dyslexia compensated fewer /i:/ lengthening by /ɪ/ shortening than did non‐dyslexic adults. Transfer from perceptual training to production seems possible for foreign‐language learning even in dyslexic adults. The extent to which dichotic presentation contributed to training effectiveness cannot be evaluated here, but the triggering of lengthening and shortening mechanisms suggests that lateralized complementary skills have been enhanced by dichotic stimulation. [ABSTRACT FROM AUTHOR]

Introduction: Recent studies have reported poor cognition, such as attention and working memory, in adults with listening difficulties (LiD). However, they do not adequately describe the actual state of poor attention ability in adults with LiD. We examined the state of auditory attention in adults with and without LiD in tasks requiring multiple attention controls. Methods: Twenty-one adults who had normal hearing but complained about LiD encountered during everyday life and 22 healthy controls were included. We presented a target detection task using an odd-ball format for one ear and a sentence repetition task for the other ear. In the target detection task, participants listened to the 1,000-Hz tone served as the standard stimulus, while they had to accept a 2,000-Hz tone presented as the deviant stimulus. In the sentence repetition task, short sentences were presented. The stimuli presented to them were played on a personal computer at the most comfortable level. The participants heard these stimuli through headphones. They were required to press a key for standard stimuli in the target detection task and repeat what they heard immediately in the repetition task. We compared the response accuracy for each ear task between adults with and without LiD. Results: Our results showed that there were significant differences between the participant groups in the auditory dual-task under the dichotic listening situation. When examined individually, four adults with LiD had decreased scores in both the sentence repetition and target detection task, while the other nine participants showed a bias toward either task. Furthermore, the analysis of reaction time for pressing button revealed that the standard deviation of reaction time was extended in participants who scored poorly in either of the ear tasks. On the other hand, all adults without LiD were able to conduct the auditory dual-task exactly and promptly. Conclusion: The results suggest that adults with LiD have difficulties in appropriately allocating various cognitive abilities required for each task. We concluded that auditory attention is an important ability to conduct the auditory dual-task, and this is applicable for adults with LiD. Therefore, we believe that it is necessary to use auditory tests that require complex attentional abilities in listening, such as those required in daily life, to assess adults with LiD. [ABSTRACT FROM AUTHOR]

About 95% of right-handers and 70% of left-handers have a left-hemispheric specialization for language. Dichotic listening is often used as an indirect measure of this language asymmetry. However, while it reliably produces a right-ear advantage (REA), corresponding to the left-hemispheric specialization of language, it paradoxically often fails to obtain statistical evidence of mean differences between left- and right-handers. We hypothesized that non-normality of the underlying distributions might be in part responsible for the similarities in means. Here, we compare the mean ear advantage scores, and also contrast the distributions at multiple quantiles, in two large independent samples (Ns = 1,358 and 1,042) of right-handers and left-handers. Right-handers had an increased mean REA, and a larger proportion had an REA than in the left-handers. We also found that more left-handers are represented in the left-eared end of the distribution. These data suggest that subtle shifts in the distributions of DL scores for right- and left-handers may be at least partially responsible for the unreliability of significantly reduced mean REA in left-handers. [ABSTRACT FROM AUTHOR]

Background and Aim: Buffalo model consists of four Central Auditory Processing Disorder (CAPD) categories: decoding, tolerance-fading memory, organization, and integration. Integration is considered as the most complex category. The Dichotic Offset Measure (DOM) provides valuable information about the organization and integration problems. The present study aimed to develop the Persian version of the DOM (P-DOM) and evaluate its psychometric properties in normal-hearing children. Methods: In this study, 25 normal-hearing children (13 girls) aged 7-12 years participated and were divided into six age groups. The face validity was determined based on the opinions of 15 experts, five children with CAPD, and five normal-hearing children. All children were tested with the Persian staggered spondaic word test, Persian phonemic synthesis test, and the Persian randomized dichotic digit test. Results: The results showed the high face validity of the P-DOM. No significant differences were observed between the scores of girls and boys (p=0.394 for the right non-competing, p=0.623 for the right competing, p=0.155 for the left competing, p=0.066 for the left noncompeting, p=0.174 for the total score, and p=0.701 for the reversals). Significant differences were observed in the main scores of P-DOM test among the age groups. The Spearman test showed a high test-retest reliability (r>0.69). Conclusion: As a preliminary study it seems that the P-DOM has good validity and reliability to be used in normal-hearing children, but it needs further research with larger sample size. [ABSTRACT FROM AUTHOR]

Dichotic listening is the high-level auditory process which enables the perception of different verbal stimuli delivered simultaneously to the right and left ears (binaural integration), as well as the perception of a verbal stimulus presented to one ear while ignoring a different stimulus in the other ear (binaural separation). Deficits in central auditory processing have been reported in children with learning disabilities. The present study aimed to compare dichotic listening performances in right-handed impaired readers (IR) and non-impaired readers (non-IR) according to age. For this, a cross-sectional study was conducted in 120 IR (56 males and 64 females) divided into five age groups and 120 non-IR (63 male and 57 female) matched on chronological age (8 to 9 years; 9 to 10 years; 10 to 12 years; 12 to 18 years; adult). They were tested for binaural integration and binaural separation, allowing for the calculation of dichotic aptitude (DA), ear prevalence (EP), and attentional shift index (ASI). A series of ANOVAs showed an effect of age and of the reading group for all the dichotic-related measures, except for EP. Binaural separation scores were lower in IR who also showed more intrusive responses compared to non-IR. These intrusive responses, which were more frequent on the right ear for IR, decreased with age in both groups. Overall, these results suggest that dichotic listening scores improve with age as the central auditory pathways mature. However, whatever the age, performances are lower in IR than in non-IR. This might be explained by an incomplete maturation of the auditory pathways in IR; an early start for long-term follow-up and auditory training is suggested. [ABSTRACT FROM AUTHOR]

Abstract Background Elderly patients frequently suffer from problems in speech discrimination especially in noisy situation, and they also have several problems from using amplifications devices especially binaural amplification. This necessitates the need for central auditory evaluation in association of peripheral auditory evaluation. The aim of the present study was to explore the effects of aging on dichotic listening performance. This was a case-control study conducted at the Audiology Unit, ENT Department. Participant were 46 individuals within the age range of 60 to 89 years with no history of neurological disorder or cognitive impairment, and all the participants were of high social class. Forty-five adult individuals (control group) with the age range 32–57 years, with no history of neurological disorders. Both cases and control groups were subjected to otological examination, immittancemetry, puretone audiometry, speech audiometry, and central auditory processing assessment by the use of central questionnaire for elderly and dichotic digits (version II) test. Results The elderly group scored significantly depressed scores of dichotic digits’ test, especially in the left ear than in the adult group. Conclusion Dichotic listening ability was significantly affected in elderly patients.

Introduction: Our purpose was to investigate binaural integration for spectrally degraded speech in normal-hearing (NH) subjects, single-sided deafness (SSD) cochlear implant (CI) recipients, and bilateral deaf bilateral CI recipients. Methods: We tested ten adult subjects in each group with a modified version of the binaural fusion test according to Matzker. Speech recognition was assessed for monotic listening with the better-hearing ear or CI, monotic listening with the poorer-hearing ear or CI, and dichotic listening. We employed two presentation modes: (1) low pass (LP)-filtered speech to the better ear or CI and high pass (HP)-filtered speech to the poorer ear or CI, and (2) LP-filtered speech to the poorer ear or CI and HP-filtered speech to the better ear or CI. Five magnitudes of LP and HP filtering, i.e., spectral degradation, for each presentation mode were applied yielding two spectrally overlapping and three nonoverlapping presentation conditions. Sentences from the Oldenburg Children's sentence test were applied to assess speech recognition. Results: NH subjects, SSD CI recipients, and bilateral CI recipients were able to understand spectrally degraded speech under both monotic and dichotic listening conditions for both the presentation modes. Speech performance decreased with the increasing loss of spectral information in all the three subject groups. In the NH subjects, speech recognition scores significantly improved for dichotic compared with each monotic listening type under two spectrally nonoverlapping conditions. The SSD CI subjects showed a significant improvement in speech scores for dichotic listening compared with monotic listening with the NH ear under one nonoverlapping condition, i.e., a dichotic benefit in speech recognition with CI. We saw a dichotic benefit in the bilateral CI recipients who achieved significantly better speech scores for dichotic compared with monotic listening with the better CI in three nonoverlapping conditions. Conclusions: All the three groups (NH subjects, SSD CI recipients, and BiCI recipients) showed binaural integration for the side-separated presentation of spectrally degraded speech. Use of strictly side-separated dichotic stimulus presentation avoided the possible occurrence of physical effects such as the head shadow effect and therefore, confirmed the binaural benefit attributable to central binaural processing. [ABSTRACT FROM AUTHOR]

Hearing is multifaceted, and the relative contributions of peripheral and central hearing loss are rarely considered together in the context of dementia. Here, we assessed peripheral (as measured with pure-tone audiometry) and central (as measured with dichotic listening) hearing in 19 patients with typical amnestic Alzheimer's disease (tAD), 10 patients with logopenic variant primary progressive aphasia (lvPPA), 11 patients with nonfluent/agrammatic variant PPA (nfvPPA), 15 patients with semantic variant PPA (svPPA), and 28 healthy age-matched individuals. Participants also underwent neuropsychological assessment and magnetic resonance image scanning, allowing us to use voxel-based morphometry to assess associations between hearing scores and grey matter volume. Dichotic listening was impaired in all patient groups relative to healthy controls. In the combined patient (but not healthy control) cohort, dichotic listening scores were significantly correlated with measures of global cognitive functioning and speech-based neuropsychological tasks. Pure-tone audiometry scores were not significantly elevated in any patient group relative to the healthy control group, and no significant correlations were observed between peripheral hearing and neuropsychological task performance in either the combined patient or healthy control cohorts. Neuroanatomically, dichotic listening performance was associated with grey matter volume in a bilateral fronto-temporoparietal network over the combined patient cohort, but no correlates were identified for pure-tone audiometry. Our findings highlight the importance of speech parsing mechanisms beyond elementary sound detection in driving cognitive test performance, underline the importance of assessing central hearing alongside peripheral hearing in people with dementia, and further delineate the complex auditory profiles of neurodegenerative dementias., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

How do humans excel at tracking the narrative of a particular speaker with a distracting noisy background? This feat places great demands on the collaboration between speech processing and goal-related regulatory functions. Here, we propose that separate subsystems with different cross-task dynamic activity properties and distinct functional purposes support goal-directed speech listening. We adopted a naturalistic dichotic speech listening paradigm in which listeners were instructed to attend to only one narrative from two competing inputs. Using functional magnetic resonance imaging with inter- and intra-subject correlation techniques, we discovered a dissociation in response consistency in temporal, parietal and frontal brain areas as the task demand varied. Specifically, some areas in the bilateral temporal cortex (SomMotB_Aud and TempPar) and lateral prefrontal cortex (DefaultB_PFCl and ContA_PFCl) always showed consistent activation across subjects and across scan runs, regardless of the task demand. In contrast, some areas in the parietal cortex (DefaultA_pCunPCC and ContC_pCun) responded reliably only when the task goal remained the same. These results suggested two dissociated functional neural networks that were independently validated by performing a data-driven clustering analysis of voxelwise functional connectivity patterns. A subsequent meta-analysis revealed distinct functional profiles for these two brain correlation maps. The different-task correlation map was strongly associated with language-related processes (e.g., listening, speech and sentences), whereas the same-task versus different-task correlation map was linked to self-referencing functions (e.g., default mode, theory of mind and autobiographical topics). Altogether, the three-pronged findings revealed two anatomically and functionally dissociated subsystems supporting goal-directed speech listening.

Background: Most people have strong left-brain lateralisation for language, with a minority showing right- or bilateral language representation. On some receptive language tasks, however, lateralisation appears to be reduced or absent. This contrasting pattern raises the question of whether and how language laterality may fractionate within individuals. Building on our prior work, we postulated (a) that there can be dissociations in lateralisation of different components of language, and (b) these would be more common in left-handers. A subsidiary hypothesis was that laterality indices will cluster according to two underlying factors corresponding to whether they involve generation of words or sentences, versus receptive language.Methods: We tested these predictions in two stages: At Step 1 an online laterality battery (Dichotic listening, Rhyme Decision and Word Comprehension) was given to 621 individuals (56% left-handers); At Step 2, functional transcranial Doppler ultrasound (fTCD) was used with 230 of these individuals (51% left-handers). 108 left-handers and 101 right-handers gave useable data on a battery of three language generation and three receptive language tasks.Results: Neither the online nor fTCD measures supported the notion of a single language laterality factor. In general, for both online and fTCD measures, tests of language generation were left-lateralised. In contrast, the receptive tasks were at best weakly left-lateralised or, in the case of Word Comprehension, slightly right-lateralised. The online measures were only weakly correlated, if at all, with fTCD measures. Most of the fTCD measures had split-half reliabilities of at least .7, and showed a distinctive pattern of intercorrelation, supporting a modified two-factor model in which Phonological Decision (generation) and Sentence Decision (reception) loaded on both factors. The same factor structure fitted data from left- and right-handers, but mean scores on the two factors were lower (less left-lateralised) in left-handers.Conclusions: There are at least two factors influencing language lateralization in individuals, but they do not correspond neatly to language generation and comprehension. Future fMRI studies could help clarify how far they reflect activity in specific brain regions. [ABSTRACT FROM AUTHOR]

Brain lateralization of lexical tone processing remains a matter of debate. In this study we used a dichotic listening paradigm to examine the influences of the knowledge of Jyutping (a romanization writing system which provides explicit Cantonese tone markers), linguistic-processing demand and tone type on the ear preference pattern of native tone processing in Hong Kong Cantonese speakers. While participants with little knowledge of Jyutping showed a previously reported left-ear advantage (LEA), those with a good level of Jyutping expertise exhibited either a right-ear advantage or bilateral processing during lexical tone identification and contour tone discrimination, respectively. As for the effect of linguisticprocessing demand, while an LEA was found in acoustic/phonetic perception situations, this advantage disappeared and was replaced by a bilateral pattern in conditions that involved a greater extent of linguistic processing, suggesting an increased involvement of the left hemisphere. Regarding the effect of tone type, both groups showed an LEA in level tone discrimination, but only the Jyutping group demonstrated a bilateral pattern in contour tone discrimination. Overall, knowledge of written codes of tones, greater degree of linguistic processing and contour tone processing seem to influence the brain lateralization of lexical tone processing in native listeners of Cantonese by increasing the recruitment of the left-hemisphere language network. [ABSTRACT FROM AUTHOR]

Abstract The quality of the physical language signals to which learners are exposed and which result in neurobiological activity leading to perception constitutes a variable that is rarely, if ever, considered in the context of language learning. It deserves some attention. The current study identifies an optimal audio language input signal for Chinese EFL/ESL learners generated by modifying the physical features of language-bearing audio signals. This is achieved by applying the principles of verbotonalism in a dichotic listening context. Low-pass filtered (320 Hz cut-off) and unfiltered speech signals were dichotically and diotically directed to each hemisphere of the brain through the contralateral ear. Temporal and spatial neural signatures for the processing of the signals were detected in a combined event-related potential (ERP) and functional magnetic resonance imaging (fMRI) experiment. Results showed that the filtered stimuli in the left ear and unfiltered in the right ear (FL-R) configuration provided optimal auditory language input by actively exploiting left-hemispheric dominance for language processing and right-hemispheric dominance for melodic processing, i.e., each hemisphere was fed the signals that it should be best equipped to process—and it actually did so effectively. In addition, the filtered stimuli in the right ear and unfiltered in the left ear (L-FR) configuration was identified as entirely non-optimal for language learners. Other outcomes included significant load reduction through exposure to both-ear-filtered FL-FR signals as well as the confirmation that non-language signals were recognized by the brain as irrelevant to language and did not trigger any language processing. These various outcomes will necessarily entail further research.

Which processes in the human brain lead to the categorical perception of speech sounds? Investigation of this question is hampered by the fact that categorical speech perception is normally confounded by acoustic differences in the stimulus. By using ambiguous sounds, however, it is possible to dissociate acoustic from perceptual stimulus representations. Twenty-seven normally hearing individuals took part in an fMRI study in which they were presented with an ambiguous syllable (intermediate between /da/ and /ga/) in one ear and with disambiguating acoustic feature (third formant, F3) in the other ear. Multi-voxel pattern searchlight analysis was used to identify brain areas that consistently differentiated between response patterns associated with different syllable reports. By comparing responses to different stimuli with identical syllable reports and identical stimuli with different syllable reports, we disambiguated whether these regions primarily differentiated the acoustics of the stimuli or the syllable report. We found that BOLD activity patterns in left perisylvian regions (STG, SMG), left inferior frontal regions (vMC, IFG, AI), left supplementary motor cortex (SMA/pre-SMA), and right motor and somatosensory regions (M1/S1) represent listeners’ syllable report irrespective of stimulus acoustics. Most of these regions are outside of what is traditionally regarded as auditory or phonological processing areas. Our results indicate that the process of speech sound categorization implicates decision-making mechanisms and auditory-motor transformations.

The primary goal of this study was to examine whether degree of bilingualism related to dichotic listening accuracy, a measure of bilateral processing, after controlling for age and income.Participants included 59 children ages 6–11 years (M = 7.86, SD = 1.81) and 61 adults (18–83 years) (M = 34.02, SD = 15.70). Participants completed demographic surveys, vocabulary assessments in English and Spanish, and a dichotic listening test.Multiple linear regressions examined whether the degree of bilingualism predicted bilateral processing.Degree of bilingualism predicted bilateral processing in the whole sample of children and adults.This study is one of the first to examine bilingualism and bilateral processing while including both children and adults. It also importantly controlled for a possible cognate facilitatory effect and participant income differences and measured bilingualism on a continuum.Results highlight the importance of including bilingual groups of different ages when researching bilingualism and laterality. [ABSTRACT FROM AUTHOR]

Several studies have reported the better auditory performance of early-blind subjects over sighted subjects. However, few studies have compared the auditory functions of both hemispheres or evaluated interhemispheric transfer and binaural integration in blind individuals. Therefore, we evaluated whether there are differences in dichotic listening, auditory temporal sequencing ability, or speech perception in noise (all of which have been used to diagnose central auditory processing disorder) between early-blind subjects and sighted subjects. The study included 23 early-blind subjects and 22 age-matched sighted subjects. In the dichotic listening test (three-digit pair), the early-blind subjects achieved higher scores than the sighted subjects in the left ear (p = 0.003, Bonferroni's corrected α = 0.05/6 = 0.008), but not in the right ear, indicating a right ear advantage in sighted subjects (p < 0.001) but not in early-blind subjects. In the frequency patterning test (five tones), the early-blind subjects performed better (both ears in the humming response, but the left ear only in the labeling response) than the sighted subjects (p < 0.008, Bonferroni's corrected α = 0.05/6 = 0.008). Monosyllable perception in noise tended to be better in early-blind subjects than in sighted subjects at a signal-to-noise ratio of –8 (p = 0.054), the results at signal-to-noise ratios of –4, 0, +4, and +8 did not differ. Acoustic change complex responses to/ba/in babble noise, recorded with electroencephalography, showed a greater N1 peak amplitude at only FC5 electrode under a signal-to-noise ratio of –8 and –4 dB in the early-blind subjects than in the sighted subjects (p = 0.004 and p = 0.003, respectively, Bonferroni's corrected α = 0.05/5 = 0.01). The results of this study revealed early-blind subjects exhibited some advantages in dichotic listening, and temporal sequencing ability compared to those shown in sighted subjects. These advantages may be attributable to the enhanced activity of the central auditory nervous system, especially the right hemisphere function, and the transfer of auditory information between the two hemispheres. [ABSTRACT FROM AUTHOR]

Background and Aim: Dichotic listening (DL) test is a non-invasive method used to study hemispheric asymmetry, hemispheric dominance for language processing, or brain lateralization. In addition to the type, concurrence, and the intensity of stimuli presented to the ears, other factors exist that may have less effect on the DL test results. This review study aims to find these factors. Recent Findings: The factors that affects the DL included ear advantage, attention, working memory, gender, and top-down and bottom-up factors. These factors were reviewed and discussed in detail so that more precise test results can be obtained. Moreover, due to the significant effects of each factor on the test results, manipulation of these factors was also reviewed. Conclusion: According to the results of previous studies, ear advantage, attention, working memory, gender, and top-down and bottom-up factors play an important role in the interpretation of DL results; their negligence during the test can affect the outcomes and provide incorrect brain lateralization results. [ABSTRACT FROM AUTHOR]

Several studies have reported the better auditory performance of early-blind subjects over sighted subjects. However, few studies have compared the auditory functions of both hemispheres or evaluated interhemispheric transfer and binaural integration in blind individuals. Therefore, we evaluated whether there are differences in dichotic listening, auditory temporal sequencing ability, or speech perception in noise (all of which have been used to diagnose central auditory processing disorder) between early-blind subjects and sighted subjects. The study included 23 early-blind subjects and 22 age-matched sighted subjects. In the dichotic listening test (three-digit pair), the early-blind subjects achieved higher scores than the sighted subjects in the left ear (p = 0.003, Bonferroni’s corrected α = 0.05/6 = 0.008), but not in the right ear, indicating a right ear advantage in sighted subjects (p < 0.001) but not in early-blind subjects. In the frequency patterning test (five tones), the early-blind subjects performed better (both ears in the humming response, but the left ear only in the labeling response) than the sighted subjects (p < 0.008, Bonferroni’s corrected α = 0.05/6 = 0.008). Monosyllable perception in noise tended to be better in early-blind subjects than in sighted subjects at a signal-to-noise ratio of –8 (p = 0.054), the results at signal-to-noise ratios of –4, 0, +4, and +8 did not differ. Acoustic change complex responses to/ba/in babble noise, recorded with electroencephalography, showed a greater N1 peak amplitude at only FC5 electrode under a signal-to-noise ratio of –8 and –4 dB in the early-blind subjects than in the sighted subjects (p = 0.004 and p = 0.003, respectively, Bonferroni’s corrected α = 0.05/5 = 0.01). The results of this study revealed early-blind subjects exhibited some advantages in dichotic listening, and temporal sequencing ability compared to those shown in sighted subjects. These advantages may be attributable to the enhanced activity of the central auditory nervous system, especially the right hemisphere function, and the transfer of auditory information between the two hemispheres.

This study examines patterns of ear advantage and attentional capacity among religious teachers of the Ethiopian Orthodox Church versus adults who are not religious teachers. Religious education, rooted mainly in Christianity and Islam, has a long history in Ethiopia. Most of such education has been practised through recitations and oral presentations, which demand perceptual vigour particularly on the part of the teachers. The present study employed a dichotic listening paradigm, using monosyllabic word and CV-syllables listening tasks, administered in three attentional conditions: non-forced (NF), forced-right (FR) and forced-left (FL). 54 right-handed male adults (27 teachers and 27 non-teachers) served as participants. Percentages of correct responses per ear, as well as Laterality Index (LI) were calculated and analysed using a repeated measures analysis of variance (ANOVA) statistical procedure. Results showed that, on both listening tasks, the religious teachers demonstrated a higher ear advantage in all conditions, indicative of stronger language asymmetry (in non-forced condition) and better ability to focus on one specific ear (in forced conditions). The findings of the present study are very much in support of the theory of neuroplasticity in human cognition (Konorski, 1948). [ABSTRACT FROM AUTHOR]

Most people have a right-ear advantage for the perception of spoken syllables, consistent with left hemisphere dominance for speech processing. However, there is considerable variation, with some people showing left-ear advantage. The extent to which this variation is reflected in brain structure remains unclear. We tested for relations between hemispheric asymmetries of auditory processing and of grey matter in 281 adults, using dichotic listening and voxel-based morphometry. This was the largest study of this issue to date. Per-voxel asymmetry indexes were derived for each participant following registration of brain magnetic resonance images to a template that was symmetrized. The asymmetry index derived from dichotic listening was related to grey matter asymmetry in clusters of voxels corresponding to the amygdala and cerebellum lobule VI. There was also a smaller, non-significant cluster in the posterior superior temporal gyrus, a region of auditory cortex. These findings contribute to the mapping of asymmetrical structure–function links in the human brain and suggest that subcortical structures should be investigated in relation to hemispheric dominance for speech processing, in addition to auditory cortex. [ABSTRACT FROM AUTHOR]

There is considerable individual variability in the reported effectiveness of non-invasive brain stimulation. This variability has often been ascribed to differences in the neuroanatomy and resulting differences in the induced electric field inside the brain. In this study, we addressed the question whether individual differences in the induced electric field can predict the neurophysiological and behavioral consequences of gamma band tACS. In a within-subject experiment, bi-hemispheric gamma band tACS and sham stimulation was applied in alternating blocks to the participants' superior temporal lobe, while task-evoked auditory brain activity was measured with concurrent functional magnetic resonance imaging (fMRI) and a dichotic listening task. Gamma tACS was applied with different interhemispheric phase lags. In a recent study, we could show that anti-phase tACS (180° interhemispheric phase lag), but not in-phase tACS (0° interhemispheric phase lag), selectively modulates interhemispheric brain connectivity. Using a T1 structural image of each participant's brain, an individual simulation of the induced electric field was computed. From these simulations, we derived two predictor variables: maximal strength (average of the 10,000 voxels with largest electric field values) and precision of the electric field (spatial correlation between the electric field and the task evoked brain activity during sham stimulation). We found considerable variability in the individual strength and precision of the electric fields. Importantly, the strength of the electric field over the right hemisphere predicted individual differences of tACS induced brain connectivity changes. Moreover, we found in both hemispheres a statistical trend for the effect of electric field strength on tACS induced BOLD signal changes. In contrast, the precision of the electric field did not predict any neurophysiological measure. Further, neither strength, nor precision predicted interhemispheric integration. In conclusion, we found evidence for the dose-response relationship between individual differences in electric fields and tACS induced activity and connectivity changes in concurrent fMRI. However, the fact that this relationship was stronger in the right hemisphere suggests that the relationship between the electric field parameters, neurophysiology, and behavior may be more complex for bi-hemispheric tACS. [ABSTRACT FROM AUTHOR]

Dichotic listening along with the right-ear advantage (REA) has been a standard method of investigating auditory laterality ever since it was first introduced into neuropsychology in the early 1960s. Beginning in the 1980s, authors reported that it was possible to modulate the bottom-up driven perceptual REA by instructing subjects to selectively attend to and report only from the right or left ear. In the present study, we investigated neuronal correlates of both the bottom-up and top-down modulation of the REA through two fMRI analysis approaches: a traditional region approach and a network connectivity approach. Blood-Oxygenation-Level-Dependent (BOLD) fMRI data were acquired while subjects performed the standard forced-attention paradigm. We asked two questions, could the behavioral REA be replicated in unique brain markers, and second if the profound instruction-induced modulation of the REA found in behavioral data would correspond to a similar modulation of brain activation, both region- and network-specific modulations. The subjects were 70 healthy adult right-handers, about half men and half women. fMRI data were acquired in a 3T MR scanner, and the behavioral results replicated previous findings with a REA in the non-forced (NF) and forced-right (FR) conditions, and a tendency for a left-ear advantage (LEA) in the FL-condition. The fMRI data showed unique activations in the speech perception areas of the left temporal lobe when directly contrasted with activations in the homologous right side. However, there were no remaining unique activations when the FR- and FL-conditions were contrasted against each other, and with the NF-condition, using a conservative significance thresholding. The fMRI results are conceptualized within a network connectivity frame of reference, especially with reference to the extrinsic mode network (EMN). The EMN is a generalized task-positive network that is upregulated whenever the task demands exceed a certain threshold irrespective of the specifics and demands of the task. This could explain the similarity of activations for the FR- and FL-conditions, despite the clear differences in behavior. [ABSTRACT FROM AUTHOR]

Background: Habituation is considered to have protective and filtering mechanisms. The present study is aim to find the casual relationship and mechanisms of excitatory–inhibitory (E/I) dysfunctions in schizophrenia (SCZ) via habituation. Methods: A dichotic listening paradigm was performed with simultaneous EEG recording on 22 schizophrenia patients and 22 gender- and age-matched healthy controls. Source reconstruction and dynamic causal modeling (DCM) analysis were performed to estimate the effective connectivity and casual relationship between frontal and temporal regions before and after habituation. Results: The schizophrenia patients expressed later habituation onset (p < 0.01) and hyper-activity in both lateral frontal–temporal cortices than controls (p = 0.001). The patients also showed decreased top-down and bottom-up connectivity in bilateral frontal–temporal regions (p < 0.01). The contralateral frontal–frontal and temporal–temporal connectivity showed a left to right decreasing (p < 0.01) and right to left strengthening (p < 0.01). Conclusions: The results give causal evidence for E/I imbalance in schizophrenia during dichotic auditory processing. The altered effective connectivity in frontal–temporal circuit could represent the trait bio-marker of schizophrenia with auditory hallucinations. [ABSTRACT FROM AUTHOR]

There is considerable individual variability in the reported effectiveness of non-invasive brain stimulation. This variability has often been ascribed to differences in the neuroanatomy and resulting differences in the induced electric field inside the brain. In this study, we addressed the question whether individual differences in the induced electric field can predict the neurophysiological and behavioral consequences of gamma band tACS. In a within-subject experiment, bi-hemispheric gamma band tACS and sham stimulation was applied in alternating blocks to the participants’ superior temporal lobe, while task-evoked auditory brain activity was measured with concurrent functional magnetic resonance imaging (fMRI) and a dichotic listening task. Gamma tACS was applied with different interhemispheric phase lags. In a recent study, we could show that anti-phase tACS (180° interhemispheric phase lag), but not in-phase tACS (0° interhemispheric phase lag), selectively modulates interhemispheric brain connectivity. Using a T1 structural image of each participant’s brain, an individual simulation of the induced electric field was computed. From these simulations, we derived two predictor variables: maximal strength (average of the 10,000 voxels with largest electric field values) and precision of the electric field (spatial correlation between the electric field and the task evoked brain activity during sham stimulation). We found considerable variability in the individual strength and precision of the electric fields. Importantly, the strength of the electric field over the right hemisphere predicted individual differences of tACS induced brain connectivity changes. Moreover, we found in both hemispheres a statistical trend for the effect of electric field strength on tACS induced BOLD signal changes. In contrast, the precision of the electric field did not predict any neurophysiological measure. Further, neither strength, nor precision predicted interhemispheric integration. In conclusion, we found evidence for the dose-response relationship between individual differences in electric fields and tACS induced activity and connectivity changes in concurrent fMRI. However, the fact that this relationship was stronger in the right hemisphere suggests that the relationship between the electric field parameters, neurophysiology, and behavior may be more complex for bi-hemispheric tACS.

Background: Habituation is considered to have protective and filtering mechanisms. The present study is aim to find the casual relationship and mechanisms of excitatory–inhibitory (E/I) dysfunctions in schizophrenia (SCZ) via habituation.Methods: A dichotic listening paradigm was performed with simultaneous EEG recording on 22 schizophrenia patients and 22 gender- and age-matched healthy controls. Source reconstruction and dynamic causal modeling (DCM) analysis were performed to estimate the effective connectivity and casual relationship between frontal and temporal regions before and after habituation.Results: The schizophrenia patients expressed later habituation onset (p < 0.01) and hyper-activity in both lateral frontal–temporal cortices than controls (p = 0.001). The patients also showed decreased top-down and bottom-up connectivity in bilateral frontal–temporal regions (p < 0.01). The contralateral frontal–frontal and temporal–temporal connectivity showed a left to right decreasing (p < 0.01) and right to left strengthening (p < 0.01).Conclusions: The results give causal evidence for E/I imbalance in schizophrenia during dichotic auditory processing. The altered effective connectivity in frontal–temporal circuit could represent the trait bio-marker of schizophrenia with auditory hallucinations.

Dichotic listening along with the right-ear advantage (REA) has been a standard method of investigating auditory laterality ever since it was first introduced into neuropsychology in the early 1960s. Beginning in the 1980s, authors reported that it was possible to modulate the bottom-up driven perceptual REA by instructing subjects to selectively attend to and report only from the right or left ear. In the present study, we investigated neuronal correlates of both the bottom-up and top-down modulation of the REA through two fMRI analysis approaches: a traditional region approach and a network connectivity approach. Blood-Oxygenation-Level-Dependent (BOLD) fMRI data were acquired while subjects performed the standard forced-attention paradigm. We asked two questions, could the behavioral REA be replicated in unique brain markers, and second if the profound instruction-induced modulation of the REA found in behavioral data would correspond to a similar modulation of brain activation, both region- and network-specific modulations. The subjects were 70 healthy adult right-handers, about half men and half women. fMRI data were acquired in a 3T MR scanner, and the behavioral results replicated previous findings with a REA in the non-forced (NF) and forced-right (FR) conditions, and a tendency for a left-ear advantage (LEA) in the FL-condition. The fMRI data showed unique activations in the speech perception areas of the left temporal lobe when directly contrasted with activations in the homologous right side. However, there were no remaining unique activations when the FR- and FL-conditions were contrasted against each other, and with the NF-condition, using a conservative significance thresholding. The fMRI results are conceptualized within a network connectivity frame of reference, especially with reference to the extrinsic mode network (EMN). The EMN is a generalized task-positive network that is upregulated whenever the task demands exceed a certain threshold irrespective of the specifics and demands of the task. This could explain the similarity of activations for the FR- and FL-conditions, despite the clear differences in behavior.