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Multidimensional solitary states (MDSS)—self-sustained wavepackets—have attracted renewed interest in many different fields of physics. They are of particular importance in nonlinear optics, especially for the nonlinear propagation of ultrashort pulses in multimode fibres, which contain rich spatiotemporal intermodal interactions and dynamics, albeit often in an unstable manner. Here, we report the observation of the formation of highly stable multidimensional solitary states in a molecular gas-filled large-core hollow-core fibre. We experimentally and numerically demonstrate the creation of MDSS by multimillijoule, subpicosecond near-infrared pulses and the underlying physics. We find that the MDSS have a broadband redshifted spectra with an uncommon negative quadratic spectral phase at the output of the hollow-core fibre, originating from Raman enhancement due to the strong intermodal nonlinear interactions. The spatial and temporal localization of MDSS enables the compression of the broadened pulses at the output to 10.8?fs by simple linear propagation in a piece of fused silica. The high spatiotemporal quality of MDSS is further verified by high-harmonic generation. Our results present new opportunities for studying multimodal spatiotemporal dynamics in the high-energy regime. This work also presents a route toward a new class of compact, tunable and high-energy spatiotemporally engineered coherent light sources based on picosecond ytterbium technology.

We present a novel, to the best of our knowledge, approach for scaling the peak power of mid-infrared laser pulses with few-cycle duration and carrier-to-envelope phase stabilization. Using frequency domain optical parametric amplification (FOPA), selective amplification is performed on two spectral slices of broadband pulses centered at 1.8 µm wavelength. In addition to amplification, the Fourier plane is used for specific pulse shaping to control both the relative polarization and the phase/delay between the two spectral slices of the input pulses. At the output of the FOPA, intrapulse difference frequency generation provides carrier–envelope phase stabilized two-cycle pulses centered at 9.5 µm wavelength with 25.5 µJ pulse energy. The control of the carrier–envelope phase is demonstrated through the dependence of high-harmonic generation in solids. This architecture is perfectly adapted to be scaled in the future to high average and high peak powers using picosecond ytterbium laser technologies.

In the first part, we discuss the stability of the strong slope and of the subdifferential of a lower semicontinuous function with respect to Wijsman perturbations of the function, i.e., perturbations described via Wijsman convergence. In the second part, we show how subdifferential sum rules can be viewed as special cases of subdifferential stability results.

A specially designed telescope with defocusing lens and off-axis parabolic mirror, which is working as a nonlinear element and producing self-phase modulation, was implemented for intense (3.1 TW/cm2) Fourier Transform Limit femtosecond laser pulses with Gaussian beam profiles. The pulse spectrum was broadened quasi- homogeneously over the beam cross-section due to the change in the lens thickness compensating for the reduction of the beam intensity from its center to periphery. In experimental demonstrations a set of chirped mirrors allowed for the spectral phase correction to a final pulse compression of 20 fs from 40 fs.

We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La_3Ga_5.5Ta_0.5O_14. Tunable wavelengths between 1.4 and 4.7 μm are generated by using femtosecond sources. We also report on the measurements of the optical damage threshold in the femtosecond regime and on the nonlinear refractive index n_2.

The shift from a biphasic to a monophasic sleep schedule is a fundamental milestone in early childhood. This transition, however, may result in periods of acute sleep loss as children may nap on some but not all days. Although data indicating the behavioral consequences of nap deprivation in young children are accumulating, little is known about changes to sleep neurophysiology following daytime sleep loss. This study addresses this gap in knowledge by examining the effects of acute nap deprivation on subsequent nighttime sleep electroencephalographic (EEG) parameters in toddlers. Healthy children (n=25; 11 males; ages 30–36 months) followed a strict sleep schedule for ≥5 days before sleep EEG recordings performed on 2 non-consecutive days: one after 13h of prior wakefulness and another at the same clock time but preceded by a daytime nap. Total slow-wave energy (SWE) was computed as cumulative slow-wave activity (SWA; EEG power in 0.75–4.5Hz range) over time. Nap and subsequent night SWE were added and compared to SWE of the night after a missed nap. During the night following a missed nap, children fell asleep faster (11.9±8.7 min versus 37.3±22.1min;d=1.6, p=0.01), slept longer (10.1±0.7 h versus 9.6±0.6h; d=0.7, p<0.01) and exhibited greater SWA (133.3±37.5% versus 93.0±4.7%; d=0.9, p<0.01) compared to a night after a daytime nap. SWE for combined nap and subsequent night sleep did not significantly differ from the night following nap deprivation (12141.1±3872.9 μV²*h versus 11,588±3270.8 μV²*h; d=0.6, p=0.12). However, compared to a night following a missed nap, children experienced greater time in bed (13.0±0.8 h versus 10.9±0.5 h; d=3.1, p<0.01) and total sleep time (11.2±0.8 h versus 10.1±0.7 h; d=1.4, p<0.01). Shorter sleep latency, longer sleep duration, and increased SWA in the night following a missed nap indicate that toddlers experience a physiologically meaningful homeostatic challenge after prolonged wakefulness. Whether toddlers fully recover from missing a daytime nap in the subsequent night necessitates further examination of daytime functioning.

AbstractIt is known that a function fdefined on a convex subset of a vector space is convex provided that all its perturbations f+ u*by linear forms are quasiconvex. We show that, under more restrictive assumptions, the convexity of ffollows from the quasiconvexity of perturbations by just a suitable one-parameter family of linear forms.

Agenesis of the corpus callosum (ACC) is a common brain malformation which can be observed either as an isolated condition or as part of numerous congenital syndromes. Therefore, cognitive and neurological involvements in patients with ACC are variable, from mild linguistic and behavioral impairments to more severe neurological deficits. To date, the underlying genetic causes of isolated ACC remains elusive and causative genes have yet to be identified. We performed exome sequencing on three acallosal siblings from the same non-consanguineous family and identified compound heterozygous variants, p.[Gly94Arg];[Asn1232Ser], in the protein encoded by the CDK5RAP2 gene, also known as MCPH3, a gene previously reported to cause autosomal recessive primary microcephaly. Our findings suggest a novel role for this gene in the pathogenesis of isolated ACC.

A specially designed telescope with defocusing lens and off-axis parabolic mirror, which is working as a nonlinear element and producing self-phase modulation, was implemented for intense (3.1 TW/cm2) Fourier Transform Limit femtosecond laser pulses with Gaussian beam profiles. The pulse spectrum was broadened quasi- homogeneously over the beam cross-section due to the change in the lens thickness compensating for the reduction of the beam intensity from its center to periphery. In experimental demonstrations a set of chirped mirrors allowed for the spectral phase correction to a final pulse compression of 20 fs from 40 fs.

Affectively salient stimuli are capable of capturing attentional resources which allow the brain to change the current course of action in order to respond to potentially advantageous or threatening stimuli. Here, we investigated the behavioral and cerebral impact of peripherally presented affective stimuli on the subsequent processing of foveal information. To this end, we recorded whole-head magnetoencephalograms from 12 participants while they made speeded responses to the direction of left- or right-oriented arrows that were presented foveally at fixation. Each arrow was preceded by a peripherally presented pair of pictures, one emotional (unpleasant or pleasant), and one neutral. Paired pictures were presented at 12° of eccentricity to the left and right of a central fixation cross. We observed that the participants responded more quickly when the orientation of the arrow was congruent with the location of the previously presented emotional scene. Results show that non-predictive emotional information in peripheral vision interferes with subsequent responses to foveally presented targets. Importantly, this behavioral effect was correlated with an early (∼135 msec) increase of left fronto-central activity for the emotionally congruent combination, whose cerebral sources were notably located in the left orbitofrontal cortex. We therefore suggest that the prior spatial distribution of emotional salience, like physical salience, grabs attentional resources and modifies the performance in the center of the visual field. Thus, these data shed light on the neurobehavioral correlates of the emotional coding of visual space.

Although the literature concerning auditory and visual perceptual capabilities in the autism spectrum is growing, our understanding of multisensory integration (MSI) is rather limited. In the present study, we assessed MSI in autism by measuring whether participants benefited from an auditory cue presented in synchrony with the color change of a target during a complex visual search task. The synchronous auditory piptypically increases search efficacy (pip and pop effect), indicative of the beneficial use of sensory input from both modalities. We found that for conditions without auditory information, autistic participants were better at visual search compared to neurotypical participants. Importantly, search efficiency was increased by the presence of auditory pipfor neurotypical participants only. The simultaneous occurrence of superior unimodal performance with altered audio–visual integration in autism suggests autonomous sensory processing in this population.

Background Moderate to severe traumatic brain injuries (TBIs) commonly lead to olfactory dysfunction; it is, however, unclear whether and to what degree mild TBI such as concussions, which are common sports injuries, affect olfactory function. We therefore aimed to evaluate smell function in athletes who sustained one or more sport concussions in a cross-sectional design.Methods Twenty-two University-level football players with one or multiple concussions and 13 control athletes without a history of concussion participated. We measured olfactory function by using the Sniffin’ Sticks test to assess subjects’ ability to discriminate and identify odors as well as their detection thresholds. In addition, we assessed odor intensity and pleasantness.Results We used number of concussions and time since the last concussion as independent variables and measure of olfactory function as dependent variables. Although we did not observe any significant effect of the number of concussions, athletes with a longer delay from time of concussion scored significantly weaker than more recently concussed subjects on the odor identification test and on an aggregate olfactory score. Accordingly, we observed a significant negative linear correlation between the odor identification score and the time elapsed since the last concussion.Conclusion These findings suggest a possible degenerative effect of concussions on olfactory function.

Determining the language dominant hemisphere and the intrahemispheric localization of this function are imperative in the planning of neurosurgical procedures in epileptic patients. New noninvasive diagnostic techniques are being developed to reduce the risks associated with more invasive techniques. The aim of this paper is to review the different protocols for lateralizing and/or localizing language functions using magnetoencephalography (MEG), a noninvasive technique. The reviewed studies include control and patient populations using various protocols which employ different expressive and receptive language tasks. The overall findings reveal high concordance between MEG and the intracarotid amobarbital test (IAT). Moreover, MEG allows intrahemispheric localization of receptive and expressive language functions. However, the different language tasks used with MEG, whether receptive or expressive, appear to activate the left temporal more than frontal areas. The best task to assess language comprehension in both adults and children appears to be a word recognition task. A verbal fluency task could be used to test language production in children and a verb generation task in adults.

The human brain has the remarkable ability to adapt to changes in its environment by benefiting from its ‘plastic’ properties. Following brain injury, the amputation of a limb, or the loss of a sensory input such as peripheral blindness, brain circuitry often seems to be able to reorganize itself in order to compensate for the handicap by being recruited to carry out tasks not associated with their prior ‘default’ functioning. The purpose of this review is to illustrate the brain's remarkable ability to adapt to changes in its environment, particularly when it is faced with a sensory loss. Two excellent models to study this phenomenon are provided by blind and deaf individuals. In both cases, studies have shown that they appear to compensate for the loss of sensory input with enhanced abilities in their remaining senses. These behavioral modifications are often coupled with changes in cerebral processing, generally in the form of crossmodal recruitment of deaffarented primary and secondary sensory areas. We will also discuss the possible mechanisms underlying these changes and whether the functional topography of these regions present in unimpaired individuals is preserved in blindness and deafness. The notion of a critical period for plastic changes will also be discussed and its importance will be shown to be twofold. On the one hand, the functional relevance of crossmodal processing appears to decrease as a function of the age of onset of the deficiency. On the other hand, the more cortical reorganization takes place, the less likely brain areas will be able to process input from its original sensory modality. This is especially important for deaf individuals as auditory input can now be restored thanks to cochlear implants. Copyright © 2010 John Wiley & Sons, Ltd.

Research on split‐brain individuals started to flourish approximately 70 years ago and has since then significantly contributed to our understanding of hemispheric specialization. This overview aims to capture the essential of its progress. Amongst other things, the disconnection syndrome is exposed through a description of its manifestations on sensory, motor, and cognitive functions. Ground work and recent studies on split‐brain individuals are integrated. Copyright © 2010 John Wiley & Sons, Ltd.

It is now well established that the human brain is endowed with a mechanism that pairs action perception with its execution. This system has been extensively studied using visual stimuli and recent evidence suggests that it is also responsive to the sound of motor actions. Here, we presented action (finger and tongue clicks) and acoustically matched sounds to investigate action-related sound processing in a 12-year-old child undergoing intracranial monitoring of epileptic seizures. Electroencephalography grids were located over a large portion of the right hemisphere, including motor cortex. Wavelet analysis carried out on electrodes overlying the functionally defined hand representation of the motor cortex revealed early (100 ms) and late (250–450 ms) decreases in mu rhythm power (12 and 20 Hz) selective for natural finger-clicks compared with control sounds. These data suggest the presence of a rapid, multimodal resonance mechanism modulating motor cortex activity.

The consequences of febrile seizures (FSs) in infants are still a matter of debate. It is important to develop non‐invasive tools to determine markers of brain function that could have predictive value for the outcome of FSs infants. Pattern visual evoked potentials (pVEPs) were recorded in 18 FS infants (mean age of seizure 15.97 months). Spectral density and coherence analyses were performed in infants evaluated at 1.1 month (n = 4), 5.75 months (n = 4) or 30.33 months (n = 6) following a prolonged FS and compared to age‐matched healthy controls. The impact of severity of seizures was assessed by comparing the children who had prolonged FSs to 4 infants that had experienced a simple FS. Cognitive tests (Bayley, Stanford‐Binet) were administered at the time of testing in FS and control children. Behavioural measures (Achenbach Child Behavior Check List) were administered two years after the FS. pVEP responses and coherence measures failed to yield significant differences between the FS groups and healthy controls. However, spectral density measures showed a significant increase in delta band activity in both FS groups and a reduced high frequency density only in the prolonged FS groups that was seen up to 39 months post‐seizure. Behavioural and cognitive measures revealed cognitive development within average, but lower attentional capacities in the FS infants. The persistent changes in spectral density patterns seen in children with prolonged FS may reflect seizure induced alterations in the developing brain or a result of a complex mode of inheritance. Further studies are needed to determine whether these observations can be used as a marker to predict the vulnerability of the child in developing behavioral deficits or epilepsy.

When seeking comprehensiveness, any collector encounters the rare and the exceptional. Posters and prints are this article’s main theme; many outstanding recent additions of these documents have been made to the Quebec Heritage Collection at Bibliothèque et Archives nationales du Québec since 1992, when new areas of development were added. Various acquisition modes and strategies are described, illustrating original ways to apply legal deposit and documenting varied sources for purchase and donation within each family of publications. Forays made by visual artists into poster production are also outlined. In conclusion, the authors evoke concerns about how to cope with disparate, distant and diversely managed iconographic documents and the strategic value of acquisition data.

It has been proposed that the corpus callosum may play an important role in spectral cue processing that allows vertical auditory movement perception. The purpose of the present study was to assess the contribution of the corpus callosum to this type of auditory processing. Noise bursts were presented to 10 control and two callosal agenesis individuals from different positions located within midsagittal and coronal planes. Although acallosal participants were comparable with controls in their ability to correctly identify the trajectory direction or its length, they showed greater capability in detecting motion per sewhen the task was difficult. These results suggest that in the absence of the corpus callosum, compensatory reorganization of the brain allowed for superior auditory spectral cue processing.

Event-related potentials in the form of mismatch negativity were recorded to investigate auditory scene analysis capabilities in a person with a very circumscribed haemorrhagic lesion at the level of the right inferior colliculus. The results provide the first objective evidence that processing at the level of the inferior colliculus plays an important role in human auditory frequency discrimination. Moreover, the electrophysiological data suggest that following this unilateral lesion, the auditory pathways fail to reorganize efficiently.

Depuis 1979, à l’hôpital Sainte-Justine de Montréal, notre équipe étudie les effets de l’épilepsie sur le développement psycho-moteur et cognitif de l’enfant. Nous avons d’abord exploré l’étendue et tenté de définir les limites de la plasticité cérébrale d’enfants ayant subi une neurochirurgie précoce (callosotomie, hémisphérectomie). Nous avons démontré que les enfants ayant été opérés avant la puberté bénéficient encore de cette plasticité. En revanche, les mécanismes de compensation sont modestes pour ce qui touche les informations dont la complexité exige d’être traitée par ces structures cérébrales. Par la suite, nous avons étudié les répercussions neuropsychologiques des épilepsies focales, particulièrement les épilepsies frontales et temporales. Les résultats ont révélé que les enfants présentent les mêmes déficits localisés que les adultes, infirmant donc l’idée selon laquelle l’épilepsie infantile entraîne des effets indifférenciés. Depuis peu, nous profitons des techniques d’imagerie fonctionnelle (électrophysiologie de haute densité, magnétoencéphalographie, imagerie optique) pour explorer la propagation des effets de l’épilepsie sur la maturation cérébrale.

Qu’advient-il lorsqu’un individu perd la vue et que les informations visuelles ne parviennent plus aux régions cérébrales dédiées à leur traitement ? Ces régions deviennent-elles désuètes ? Arrêtent-elles de contribuer aux processus sensoriels et cognitifs ? Non. Les connaissances actuelles suggèrent que le cerveau se réorganise et rallie ces régions afin de traiter des stimulus non-visuels. Notre laboratoire se consacre depuis plusieurs années à l’étude de la cécité et des conséquences qui lui sont associées, tant sur le plan comportemental que sur celui de la réorganisation cérébrale.

The intracarotid amobarbital test (IAT) is the most widely used procedure for pre‐surgical evaluation of language lateralization in epileptic patients. However, apart from being invasive, this technique is not applicable in young children or patients who present mental retardation and/or language deficits. Functional magnetic resonance imaging (fMRI) is increasingly employed as a non‐invasive alternative. Again, this method is more difficult to use with young children, especially hyperactive ones, since they have to remain motionless during data acquisition. The aim of this study was to determine whether near‐infrared spectroscopy (NIRS) can be used as an alternative technique to investigate language lateralization in children and special populations. Unlike Wada test, NIRS is non‐invasive, and it is more tolerant to movement artefacts than fMRI. In the present study, NIRS data were acquired in four epileptic children, a 12‐year‐old boy with pervasive developmental disorder and a 3‐year‐old, healthy child, as well as three healthy and two epileptic adults, while they performed a verbal fluency task and a control task. When applicable, the results were compared to the subjects' fMRI and/or IAT findings. Clear laterality of speech was obtained in all participants, including the two non‐epileptic children, and NIRS results matched fMRI and IAT findings. These results, if replicable in larger samples, are encouraging and suggest that NIRS has the potential to become a viable, non‐invasive alternative to IAT and fMRI in the determination of speech lateralization in children and clinical populations that cannot be submitted to more invasive techniques.

The cognitive outcome of the surgical removal of an epileptic focus depends on the assessment of the localisation and functional capacity of language and memory areas which need to be spared by the neurosurgeon. Traditionally, presurgical evaluation of epileptic patients has been achieved by means of the intracarotid amobarbital test assisted by neuropsychological measures. However, the advent of neuroimaging techniques has provided new ways of assessing these functions by means of non‐invasive or minimally invasive methods, such as anatomical and functional magnetic resonance imaging, positron emission tomography, single‐photon emission computed tomography, transcranial magnetic stimulation, functional transcranial Doppler monitoring, magnetoencephalography and near infrared spectroscopy. This paper aims at comparing and evaluating the traditional and recent preoperative approaches from a neuropsychological perspective.

Recent work suggests that once the auditory cortex of deaf persons has been reorganized by cross-modal plasticity, it can no longer respond to signals from a cochlear implant (CI) installed subsequently. To further examine this issue, we compared the evoked potentials involved in the processing of visual stimuli between CI users and hearing controls. The stimuli were concentric circles replaced by a different overlapping shape, inducing a shape transformation, known to activate the ventral visual pathway in human adults. All CI users had their device implanted for >1 year, but obtained different levels of auditory performance following training to establish language comprehension. Seven of the 13 patients showed good capacities for speech recognition with the CI (good performers) while the six others demonstrated poor speech recognition abilities (poor performers). The evoked potentials of all patients showed larger amplitudes, with different distributions of scalp activations between the two groups. The poor performers exhibited broader, anteriorly distributed, high P2 amplitudes over the cortex whereas the good performers showed significantly higher P2 amplitudes over visual occipital areas. These results suggest the existence of a profound cross-modal reorganization in the poor performers and an intramodal reorganization in the good performers. We interpret these data on the basis of enhanced audiovisual coupling as the key to a long-term functional improvement in speech discrimination in CI users.

Multisensory integration can occur at relatively low levels within the central nervous system. Recent evidence suggests that multisensory audio-visual integration for speech may have a subcortical component, as acoustic processing in the human brainstem is influenced by lipreading during speech perception. Here, stimuli depicting the McGurk illusion (a demonstration of auditory–visual integration using speech stimuli) were presented to a 12-year-old child (FX) with a circumscribed unilateral lesion of the right inferior colliculus. When McGurk-type stimuli were presented in the contralesional hemifield, illusory perception reflecting bimodal integration was significantly reduced compared with the ipsilesional hemifield and a group of age-matched controls. These data suggest a functional role for the inferior colliculus in the audio-visual integration of speech stimuli.

The current experiment examined the importance of visual input on the construction of inner spatial representations. Early and late-onset blind and paired control participants performed a tactile spatial orientation task. No significant group differences were observed, indicating that the blind can represent space. More errors, however, were committed by the early blind than by the late blind and sighted individuals in portions of the task that involved mental rotation skills, suggesting a potential facilitating role for vision in the proper development of spatial constructs.

Individuals deprived of vision early in life often demonstrate exceptional abilities in their remaining sensory modalities in order to compensate for their handicap. Recent studies have shown that some of these abilities also extend to those who have lost their sight later in life. It is not clear, however, what mechanisms underlie these abilities. Here, we examined cortical activation using positron emission tomography in late-onset blind participants during a free-field auditory localization task. Even though no behavioral enhancements were observed in this testing condition relative to sighted controls, the results revealed that the occipital cortex was nonetheless activated during task execution. We conclude that late-onset blind individuals do manifest cerebral reorganization, although its functional relevance to the task is less clear.

The visual processing of radially modulated concentric patterns was studied in human participants, aged 3–22 years, by recording event-related potentials. These stimuli are known to activate the fusiform face area as well as area V4 in normal adults. The electrophysiological data showed a P1 latency that reached a maturation asymptote before 3 years of age, whereas that of N1 and P2 became adultlike by 13 years of age. In addition, the distribution of the P2 component over the scalp was focalized in the primary visual cortex before adolescence and became distributed over the entire brain after adolescence. Radially modulated concentric stimuli thus induce brain activation that is not mature until 13 years of age.

The degree of involvement of the right and left hemispheres in the system matching perception and execution of actions remains unclear. Some studies have proposed that action observation involves a bilateral network of brain areas, whereas others have suggested left-hemisphere dominance. We explored hemispheric lateralization associated with action observation using transcranial magnetic stimulation over primary motor cortex devoid of callosal influences. We assessed corticospinal excitability related to observation of finger movements in one split-brain patient and six controls. Results revealed that the left hemisphere of the split-brain patient shows enhanced excitability during action observation, whereas no enhancement was found in the right hemisphere. The controls showed increased excitability in both hemispheres during action observation. Our findings suggest a left-hemisphere dominance for mirror-neuron function in the absence of a corpus callosum.

We show that the slope introduced by DeGiorgi, Marino and Tosques in 1980 is stable (in a sense to be made precise) with respect to the variational convergence introduced by the authors in 2000. Applications to the stability of subdifferentials are derived, including a further characterization of slice-convergence of convex functions in terms of set convergence of enlargements of their subdifferentials.

We conducted a double‐blind placebo study to investigate the claim that hyperbaric oxygen treatment (HBO2) improves the cognitive status of children with cerebral palsy (CP). Of 111 children diagnosed with CP (aged 4 to 12 years), only 75 were suitable for neuropsychological testing, assessing attention, working memory, processing speed, and psychosocial functioning. The children received 40 sessions of HBO2or sham treatment over a 2‐month period. Children in the active treatment group were exposed for 1 hour to 100% oxygen at 1.75 atmospheres absolute (ATA), whereas those in the sham group received only air at 1.3 ATA. Children in both groups showed better self‐control and significant improvements in auditory attention and visual working memory compared with the baseline. However, no statistical difference was found between the two treatments. Furthermore, the sham group improved significantly on eight dimensions of the Conners’Parent Rating Scale, whereas the active treatment group improved only on one dimension. Most of these positive changes persisted for 3 months. No improvements were observed in either group for verbal span, visual attention, or processing speed.

In order to evaluate the callosal involvement in sound localization, the present study examined the response accuracy of acallosal and early callosotomized subjects to monaural and binaural auditory targets presented in three-dimensional space. In these subjects, bilateral localization cues, such as interaural time and level differences, are integrated at the cortical and subcortical levels without the additional support of the callosal commissure. Because acallosal and early-callosotomized subjects have developed with this reduced source of binaural activation of cortical cells, they might have perfected their ability to use monaural sound localization cues. This hypothesis was tested by assessing localization performance under both binaural and monaural listening conditions. Five subjects with callosal agenesis, one callosotomized subject operated early in life and 19 control subjects were asked to localize broad-band noise bursts (BBNBs) of fixed intensity in the horizontal plane in an anechoic chamber. BBNBs were delivered through randomly selected loudspeakers. Two conditions were tested: (i) localization of a stationary sound source; and (ii) localization of a moving sound source. Listeners had to report the apparent stimulus location by pointing to its perceived position on a graduated perimeter. The results indicated that the acallosal subjects were less accurate than controls, but only in the binaural moving sound condition. More interestingly, in the monaural testing conditions, some of the acallosal subjects and the early-callosotomized subject performed significantly better than control subjects. This suggests that, because of the absence of the corpus callosum, these subjects compensate for their reduced access to cortically determined binaural cues by making more efficient use of monaural cues.

In order to evaluate the callosal involvement in sound localization, the present study examined the response accuracy of acallosal and early callosotomized subjects to monaural and binaural auditory targets presented in three‐dimensional space. In these subjects, bilateral localization cues, such as interaural time and level differences, are integrated at the cortical and subcortical levels without the additional support of the callosal commissure. Because acallosal and early‐callosotomized subjects have developed with this reduced source of binaural activation of cortical cells, they might have perfected their ability to use monaural sound localization cues. This hypothesis was tested by assessing localization performance under both binaural and monaural listening conditions. Five subjects with callosal agenesis, one callosotomized subject operated early in life and 19 control subjects were asked to localize broad‐band noise bursts (BBNBs) of fixed intensity in the horizontal plane in an anechoic chamber. BBNBs were delivered through randomly selected loudspeakers. Two conditions were tested: (i) localization of a stationary sound source; and (ii) localization of a moving sound source. Listeners had to report the apparent stimulus location by pointing to its perceived position on a graduated perimeter. The results indicated that the acallosal subjects were less accurate than controls, but only in the binaural moving sound condition. More interestingly, in the monaural testing conditions, some of the acallosal subjects and the early‐callosotomized subject performed significantly better than control subjects. This suggests that, because of the absence of the corpus callosum, these subjects compensate for their reduced access to cortically determined binaural cues by making more efficient use of monaural cues.