Sight restoration in congenitally blind humans does not restore visual brain structure.

It is unknown whether impaired brain structure after congenital blindness is reversible if sight is restored later in life. Using structural magnetic resonance imaging, visual cortical surface area and cortical thickness were assessed in a large group of 21 sight-recovery individuals who had been born blind and who months or years later gained sight through cataract removal surgery. As control groups, we included 27 normally sighted individuals, 10 individuals with permanent congenital blindness, and 11 sight-recovery individuals with a late onset of cataracts. Congenital cataract-reversal individuals had a lower visual cortical surface area and a higher visual cortical thickness than normally sighted controls. These results corresponded to those of congenitally permanently blind individuals suggesting that impaired brain structure did not recover. Crucially, structural brain alterations in congenital-cataract reversal individuals were associated with a lower post-surgery visual acuity. No significant changes in visual cortex structure were observed in sight-recovery individuals with late onset cataracts. The results demonstrate that impaired structural brain development due to visual deprivation from birth is not fully reversible and limits functional recovery. Additionally, they highlight the crucial importance of prevention measures in the context of other types of aberrant childhood environments including low socioeconomic status and adversity.

Visual artificial grammar learning across 1 year in 7-year-olds and adults.

Acquiring sequential information is of utmost importance, for example, for language acquisition in children. Yet, the long-term storage of statistical learning in children is poorly understood. To address this question, 27 7-year-olds and 28 young adults completed four sessions of visual sequence learning (Year 1). From this sample, 16 7-year-olds and 20 young adults participated in another four equivalent sessions after a 12-month-delay (Year 2). The first three sessions of each year used Stimulus Set 1, and the last session used Stimulus Set 2 to investigate transfer effects. Each session consisted of alternating learning and test phases in a modified artificial grammar learning task. In Year 1, 7-year-olds and adults learned the regularities and showed transfer to Stimulus Set 2. Both groups retained their final performance level over the 1-year period. In Year 2, children and adults continued to improve with Stimulus Set 1 but did not show additional transfer gains. Adults overall outperformed children, but transfer effects were indistinguishable between both groups. The current results suggest that long-term memory traces are formed from repeated sequence learning that can be used to generalize sequence rules to new visual input. However, the current study did not provide evidence for a childhood advantage in learning and remembering sequence rules.

Child development and the role of visual experience in the use of spatial and non-spatial features in haptic object perception.

Previous work has suggested a different developmental timeline and role of visual experience for the use of spatial and non-spatial features in haptic object recognition. To investigate this conjecture, we used a haptic ambiguous odd-one-out task in which one object needed to be selected as being different from two other objects. The odd-one-out could be selected based on four characteristics: size, shape (spatial), texture, and weight (non-spatial). We tested sighted children from 4 to 12 years of age; congenitally blind, late blind, and adult participants with low vision; and normally sighted adults. Given the protracted developmental time course for spatial perception, we expected a shift from a preference for non-spatial features toward spatial features during typical development. Due to the dominant influence of vision for spatial perception, we expected congenitally blind adults to show a similar preference for non-spatial features as the youngest children. The results confirmed our first hypothesis; the 4-year-olds demonstrated a lower dominance for spatial features for object classification compared with older children and sighted adults. In contrast, our second hypothesis was not confirmed; congenitally blind adults' preferred categorization criteria were indistinguishable from those of sighted controls. These findings suggest an early development, but late maturation, of spatial processing in haptic object recognition independent of visual experience.

Quantifying accuracy and precision from continuous response data in studies of spatial perception and crossmodal recalibration.

The ability to detect the absolute location of sensory stimuli can be quantified with either error-based metrics derived from single-trial localization errors or regression-based metrics derived from a linear regression of localization responses on the true stimulus locations. Here we tested the agreement between these two approaches in estimating accuracy and precision in a large sample of 188 subjects who localized auditory stimuli from different azimuthal locations. A subsample of 57 subjects was subsequently exposed to audiovisual stimuli with a consistent spatial disparity before performing the sound localization test again, allowing us to additionally test which of the different metrics best assessed correlations between the amount of crossmodal spatial recalibration and baseline localization performance. First, our findings support a distinction between accuracy and precision. Localization accuracy was mainly reflected in the overall spatial bias and was moderately correlated with precision metrics. However, in our data, the variability of single-trial localization errors (variable error in error-based metrics) and the amount by which the eccentricity of target locations was overestimated (slope in regression-based metrics) were highly correlated, suggesting that intercorrelations between individual metrics need to be carefully considered in spatial perception studies. Secondly, exposure to spatially discrepant audiovisual stimuli resulted in a shift in bias toward the side of the visual stimuli (ventriloquism aftereffect) but did not affect localization precision. The size of the aftereffect shift in bias was at least partly explainable by unspecific test repetition effects, highlighting the need to account for inter-individual baseline differences in studies of spatial learning.

Motor adaptation in deaf and hearing native signers.

Previous studies have suggested that deafness could lead to deficits in motor skills and other body-related abilities. However, the literature regarding motor skills in deaf adults is scarce and existing studies often included participants with heterogeneous language backgrounds and deafness etiologies, thus making it difficult to delineate the effects of deafness. In this study, we investigated motor learning in deaf native signers and hearing nonsigners. To isolate the effects of deafness and those of acquiring a signed language, we additionally tested a group of hearing native signers. Two well-established paradigms of motor learning were employed, in which participants had to adapt their hand movements to a rotation of the visual feedback (Experiment 1) or to the introduction of a force field (Experiment 2). Proprioceptive estimates were assessed before and after adaptation. Like hearing nonsigners, deaf and hearing signers showed robust adaptation in both motor adaptation paradigms. No significant differences in motor adaptation and memory were observed between deaf signers and hearing nonsigners, as well as between hearing signers and hearing nonsigners. Moreover, no discernible group differences in proprioceptive accuracy were observed. These findings challenge the prevalent notion that deafness leads to deficits in motor skills and other body-related abilities.

The development of oscillatory and aperiodic resting state activity is linked to a sensitive period in humans.

Congenital blindness leads to profound changes in electroencephalographic (EEG) resting state activity. A well-known consequence of congenital blindness in humans is the reduction of alpha activity which seems to go together with increased gamma activity during rest. These results have been interpreted as indicating a higher excitatory/inhibitory (E/I) ratio in visual cortex compared to normally sighted controls. Yet it is unknown whether the spectral profile of EEG during rest would recover if sight were restored. To test this question, the present study evaluated periodic and aperiodic components of the EEG resting state power spectrum. Previous research has linked the aperiodic components, which exhibit a power-law distribution and are operationalized as a linear fit of the spectrum in log-log space, to cortical E/I ratio. Moreover, by correcting for the aperiodic components from the power spectrum, a more valid estimate of the periodic activity is possible. Here we analyzed resting state EEG activity from two studies involving (1) 27 permanently congenitally blind adults (CB) and 27 age-matched normally sighted controls (MCB); (2) 38 individuals with reversed blindness due to bilateral, dense, congenital cataracts (CC) and 77 age-matched sighted controls (MCC). Based on a data driven approach, aperiodic components of the spectra were extracted for the low frequency (Lf-Slope 1.5 to 19.5 Hz) and high frequency (Hf-Slope 20 to 45 Hz) range. The Lf-Slope of the aperiodic component was significantly steeper (more negative slope), and the Hf-Slope of the aperiodic component was significantly flatter (less negative slope) in CB and CC participants compared to the typically sighted controls. Alpha power was significantly reduced, and gamma power was higher in the CB and the CC groups. These results suggest a sensitive period for the typical development of the spectral profile during rest and thus likely an irreversible change in the E/I ratio in visual cortex due to congenital blindness. We speculate that these changes are a consequence of impaired inhibitory circuits and imbalanced feedforward and feedback processing in early visual areas of individuals with a history of congenital blindness.

Developmental experiences alter the temporal processing characteristics of the visual cortex: Evidence from deaf and hearing native signers.

To date, the extent to which early experience shapes the functional characteristics of neural circuits is still a matter of debate. In the present study, we tested whether congenital deafness and/or the acquisition of a sign language alter the temporal processing characteristics of the visual system. Moreover, we investigated whether, assuming cross-modal plasticity in deaf individuals, the temporal processing characteristics of possibly reorganised auditory areas resemble those of the visual cortex. Steady-state visual evoked potentials (SSVEPs) were recorded in congenitally deaf native signers, hearing native signers, and hearing nonsigners. The luminance of the visual stimuli was periodically modulated at 12, 21, and 40 Hz. For hearing nonsigners, the optimal driving rate was 12 Hz. By contrast, for the group of hearing signers, the optimal driving rate was 12 and 21 Hz, whereas for the group of deaf signers, the optimal driving rate was 21 Hz. We did not observe evidence for cross-modal recruitment of auditory cortex in the group of deaf signers. These results suggest a higher preferred neural processing rate as a consequence of the acquisition of a sign language.

Balance, gait, and navigation performance are related to physical exercise in blind and visually impaired children and adolescents.

Self-motion perception used for locomotion and navigation requires the integration of visual, vestibular, and proprioceptive input. In the absence of vision, postural stability and locomotor tasks become more difficult. Previous research has suggested that in visually deprived children, postural stability and levels of physical activity are overall lower than in sighted controls. Here we hypothesized that visually impaired and blind children and adolescents differ from sighted controls in postural stability and gait parameters, and that physically active individuals outperform sedentary peers in postural stability and gait parameters as well as in navigation performance. Fourteen blind and visually impaired children and adolescents (8-18 years of age) and 14 matched sighted individuals took part. Assessments included postural sway, single-leg stance time, parameters of gait variability and stability, self-reported physical activity, and navigation performance. Postural sway was larger and single-leg stance time was lower in blind and visually impaired participants than in blindfolded sighted individuals. Physical activity was higher in the sighted group. No differences between the group of blind and visually impaired and blindfolded sighted participants were observed for gait parameters and navigation performance. Higher levels of physical activity were related to lower postural sway, longer single-leg stance time, higher gait stability, and superior navigation performance in blind and visually impaired participants. The present data suggest that physical activity may enhance postural stability and gait parameters, and thereby promote navigation performance in blind and visually impaired children and adolescents.

EEG frequency-tagging demonstrates increased left hemispheric involvement and crossmodal plasticity for face processing in congenitally deaf signers.

In humans, face-processing relies on a network of brain regions predominantly in the right occipito-temporal cortex. We tested congenitally deaf (CD) signers and matched hearing controls (HC) to investigate the experience dependence of the cortical organization of face processing. Specifically, we used EEG frequency-tagging to evaluate: (1) Face-Object Categorization, (2) Emotional Facial-Expression Discrimination and (3) Individual Face Discrimination. The EEG was recorded to visual stimuli presented at a rate of 6 Hz, with oddball stimuli at a rate of 1.2 Hz. In all three experiments and in both groups, significant face discriminative responses were found. Face-Object categorization was associated to a relative increased involvement of the left hemisphere in CD individuals compared to HC individuals. A similar trend was observed for Emotional Facial-Expression discrimination but not for Individual Face Discrimination. Source reconstruction suggested a greater activation of the auditory cortices in the CD group for Individual Face Discrimination. These findings suggest that the experience dependence of the relative contribution of the two hemispheres as well as crossmodal plasticity vary with different aspects of face processing.

Differential effects of the temporal and spatial distribution of audiovisual stimuli on cross-modal spatial recalibration.

Visual input constantly recalibrates auditory spatial representations. Exposure to isochronous audiovisual stimuli with a fixed spatial disparity typically results in a subsequent auditory localization bias (ventriloquism aftereffect, VAE), whereas exposure to spatially congruent audiovisual stimuli improves subsequent auditory localization (multisensory enhancement, ME). Here, we tested whether cross-modal recalibration is affected by the stimulation rate and/or the distribution of audiovisual spatial disparities during training. Auditory localization was tested before and after participants were exposed either to audiovisual stimuli with a constant spatial disparity of 13.5° (VAE) or to spatially congruent audiovisual stimulation (ME). In a between-subjects design, audiovisual stimuli were presented either at a low frequency of 2 Hz, as used in previous studies of VAE and ME, or intermittently at a high frequency of 10 Hz, which mimics long-term potentiation (LTP) protocols and which was found superior in eliciting unisensory perceptual learning. Compared to low-frequency stimulation, VAE was reduced after high-frequency stimulation, whereas ME occurred regardless of the stimulation protocol. In two additional groups, we manipulated the spatial distribution of audiovisual stimuli in the low-frequency condition. Stimuli were presented with varying audiovisual disparities centered around 13.5° (VAE) or 0° (ME). Both VAE and ME were equally strong compared to a fixed spatial relationship of 13.5° or 0°, respectively. Taken together, our results suggest (a) that VAE and ME represent partly dissociable forms of learning and (b) that auditory representations adjust to the overall stimulus statistics rather than to a specific audiovisual spatial relationship.

Successful visually guided eye movements following sight restoration after congenital cataracts.

Sensitive periods have previously been identified for several human visual system functions. Yet, it is unknown to what degree the development of visually guided oculomotor control depends on early visual experience-for example, whether and to what degree humans whose sight was restored after a transient period of congenital visual deprivation are able to conduct visually guided eye movements. In the present study, we developed new calibration and analysis techniques for eye tracking data contaminated with pervasive nystagmus, which is typical for this population. We investigated visually guided eye movements in sight recovery individuals with long periods of visual pattern deprivation (3-36 years) following birth due to congenital, dense, total, bilateral cataracts. As controls we assessed (1) individuals with nystagmus due to causes other than cataracts, (2) individuals with developmental cataracts after cataract removal, and (3) individuals with normal vision. Congenital cataract reversal individuals were able to perform visually guided gaze shifts, even when their blindness had lasted for decades. The typical extensive nystagmus of this group distorted eye movement trajectories, but measures of latency and accuracy were as expected from their prevailing nystagmus-that is, not worse than in the nystagmus control group. To the best of our knowledge, the present quantitative study is the first to investigate the characteristics of oculomotor control in congenital cataract reversal individuals, and it indicates a remarkable effectiveness of visually guided eye movements despite long-lasting periods of visual deprivation.

Working memory training integrates visual cortex into beta-band networks in congenitally blind individuals.

Congenitally blind individuals have been shown to activate the visual cortex during non-visual tasks. The neuronal mechanisms of such cross-modal activation are not fully understood. Here, we used an auditory working memory training paradigm in congenitally blind and in sighted adults. We hypothesized that the visual cortex gets integrated into auditory working memory networks, after these networks have been challenged by training. The spectral profile of functional networks was investigated which mediate cross-modal reorganization following visual deprivation. A training induced integration of visual cortex into task-related networks in congenitally blind individuals was expected to result in changes in long-range functional connectivity in the theta-, beta- and gamma band (imaginary coherency) between visual cortex and working memory networks. Magnetoencephalographic data were recorded in congenitally blind and sighted individuals during resting state as well as during a voice-based working memory task; the task was performed before and after working memory training with either auditory or tactile stimuli, or a control condition. Auditory working memory training strengthened theta-band (2.5-5 Hz) connectivity in the sighted and beta-band (17.5-22.5 Hz) connectivity in the blind. In sighted participants, theta-band connectivity increased between brain areas typically involved in auditory working memory (inferior frontal, superior temporal, insular cortex). In blind participants, beta-band networks largely emerged during the training, and connectivity increased between brain areas involved in auditory working memory and as predicted, the visual cortex. Our findings highlight long-range connectivity as a key mechanism of functional reorganization following congenital blindness, and provide new insights into the spectral characteristics of functional network connectivity.

Neural correlates of semantic and syntactic processing in German Sign Language.

The study of deaf and hearing native users of signed languages can offer unique insights into how biological constraints and environmental input interact to shape the neural bases of language processing. Here, we use functional magnetic resonance imaging (fMRI) to address two questions: (1) Do semantic and syntactic processing in a signed language rely on anatomically and functionally distinct neural substrates as it has been shown for spoken languages? and (2) Does hearing status affect the neural correlates of these two types of linguistic processing? Deaf and hearing native signers performed a sentence judgement task on German Sign Language (Deutsche Gebärdensprache: DGS) sentences which were correct or contained either syntactic or semantic violations. We hypothesized that processing of semantic and syntactic violations in DGS relies on distinct neural substrates as it has been shown for spoken languages. Moreover, we hypothesized that effects of hearing status are observed within auditory regions, as deaf native signers have been shown to activate auditory areas to a greater extent than hearing native signers when processing a signed language. Semantic processing activated low-level visual areas and the left inferior frontal gyrus (IFG), suggesting both modality-dependent and independent processing mechanisms. Syntactic processing elicited increased activation in the right supramarginal gyrus (SMG). Moreover, psychophysiological interaction (PPI) analyses revealed a cluster in left middle occipital regions showing increased functional coupling with the right SMG during syntactic relative to semantic processing, possibly indicating spatial processing mechanisms that are specific to signed syntax. Effects of hearing status were observed in the right superior temporal cortex (STC): deaf but not hearing native signers showed greater activation for semantic violations than for syntactic violations in this region. Taken together, the present findings suggest that the neural correlates of language processing are partly determined by biological constraints, but that they may additionally be influenced by the unique processing demands of the language modality and different sensory experiences.

A Protracted Sensitive Period Regulates the Development of Cross-Modal Sound-Shape Associations in Humans.

Humans preferentially match arbitrary words containing higher- and lower-frequency phonemes to angular and smooth shapes, respectively. Here, we investigated the role of visual experience in the development of audiovisual and audiohaptic sound-shape associations (SSAs) using a unique set of five groups: individuals who had suffered a transient period of congenital blindness through congenital bilateral dense cataracts before undergoing cataract-reversal surgeries (CC group), individuals with a history of developmental cataracts (DC group), individuals with congenital permanent blindness (CB group), individuals with late permanent blindness (LB group), and controls with typical sight (TS group). Whereas the TS and LB groups showed highly robust SSAs, the CB, CC, and DC groups did not-in any of the modality combinations tested. These results provide evidence for a protracted sensitive period during which aberrant vision prevents SSA acquisition. Moreover, the finding of a systematic SSA in the LB group demonstrates that representations acquired during the sensitive period are resilient to loss despite dramatically changed experience.

Spatial and frequency specificity of the ventriloquism aftereffect revisited.

Exposure to audiovisual stimuli with a consistent spatial misalignment seems to result in a recalibration of unisensory auditory spatial representations. The previous studies have suggested that this so-called ventriloquism aftereffect is confined to the trained region of space, but yielded inconsistent results as to whether or not recalibration generalizes to untrained sound frequencies. Here, we reassessed the spatial and frequency specificity of the ventriloquism aftereffect by testing whether auditory spatial perception can be independently recalibrated for two different sound frequencies and/or at two different spatial locations. Recalibration was confined to locations within the trained hemifield, suggesting that spatial representations were independently adjusted for the two hemifields. The frequency specificity of the ventriloquism aftereffect depended on the presence or the absence of conflicting audiovisual adaptation stimuli within the same hemifield. Moreover, adaptation of two different sound frequencies in opposite directions (leftward vs. rightward) resulted in a selective suppression of leftward recalibration, even when the adapting stimuli were presented in different hemifields. Thus, instead of representing a fixed stimulus-driven process, cross-modal recalibration seems to critically depend on the sensory context and takes into account inconsistencies in the cross-modal input.

Exercise-induced neuroplasticity: Balance training increases cortical thickness in visual and vestibular cortical regions.

Physical exercise has been shown to induce structural plasticity in the human brain and to enhance cognitive functions. While previous studies focused on aerobic exercise, suggesting a link between increased cardiorespiratory fitness and exercise-induced neuroplasticity, recent findings have suggested that whole-body exercise with minor metabolic demands elicits beneficial effects on brain structure as well. In the present study, we tested if balance training, challenging the sensory-motor system and vestibular self-motion perception, induces structural plasticity. Thirty-seven healthy adults aged 19-65 years were randomly assigned to either a balance training or a relaxation training group. All participants exercised twice a week for 12 weeks. Assessments before and after the training included a balance test and the acquisition of high-resolution T1-weighted images to analyze morphological brain changes. Only the balance group significantly improved balance performance after training. Cortical thickness was increased in the superior temporal cortex, in visual association cortices, in the posterior cingulate cortex, in the superior frontal sulcus, and in the precentral gyri in the balance group, compared to the relaxation group. Moreover, there was evidence that the balance training resulted in decreased putamen volume. Improved balance performance correlated with the increase of precentral cortical thickness and the decrease in putamen volume. The results suggest that balance training elicits neuroplasticity in brain regions associated with visual and vestibular self-motion perception. As these regions are known for their role in spatial orienting and memory, stimulating visual-vestibular pathways during self-motion might mediate beneficial effects of physical exercise on cognition.

Motion processing after sight restoration: No competition between visual recovery and auditory compensation.

The present study tested whether or not functional adaptations following congenital blindness are maintained in humans after sight-restoration and whether they interfere with visual recovery. In permanently congenital blind individuals both intramodal plasticity (e.g. changes in auditory cortex) as well as crossmodal plasticity (e.g. an activation of visual cortex by auditory stimuli) have been observed. Both phenomena were hypothesized to contribute to improved auditory functions. For example, it has been shown that early permanently blind individuals outperform sighted controls in auditory motion processing and that auditory motion stimuli elicit activity in typical visual motion areas. Yet it is unknown what happens to these behavioral adaptations and cortical reorganizations when sight is restored, that is, whether compensatory auditory changes are lost and to which degree visual motion processing is reinstalled. Here we employed a combined behavioral-electrophysiological approach in a group of sight-recovery individuals with a history of a transient phase of congenital blindness lasting for several months to several years. They, as well as two control groups, one with visual impairments, one normally sighted, were tested in a visual and an auditory motion discrimination experiment. Task difficulty was manipulated by varying the visual motion coherence and the signal to noise ratio, respectively. The congenital cataract-reversal individuals showed lower performance in the visual global motion task than both control groups. At the same time, they outperformed both control groups in auditory motion processing suggesting that at least some compensatory behavioral adaptation as a consequence of a complete blindness from birth was maintained. Alpha oscillatory activity during the visual task was significantly lower in congenital cataract reversal individuals and they did not show ERPs modulated by visual motion coherence as observed in both control groups. In contrast, beta oscillatory activity in the auditory task, which varied as a function of SNR in all groups, was overall enhanced in congenital cataract reversal individuals. These results suggest that intramodal plasticity elicited by a transient phase of blindness was maintained and might mediate the prevailing auditory processing advantages in congenital cataract reversal individuals. By contrast, auditory and visual motion processing do not seem to compete for the same neural resources. We speculate that incomplete visual recovery is due to impaired neural network turning which seems to depend on early visual input. The present results demonstrate a privilege of the first arriving input for shaping neural circuits mediating both auditory and visual functions.

Neonatal Restriction of Tactile Inputs Leads to Long-Lasting Impairments of Cross-Modal Processing.

Optimal behavior relies on the combination of inputs from multiple senses through complex interactions within neocortical networks. The ontogeny of this multisensory interplay is still unknown. Here, we identify critical factors that control the development of visual-tactile processing by combining in vivo electrophysiology with anatomical/functional assessment of cortico-cortical communication and behavioral investigation of pigmented rats. We demonstrate that the transient reduction of unimodal (tactile) inputs during a short period of neonatal development prior to the first cross-modal experience affects feed-forward subcortico-cortical interactions by attenuating the cross-modal enhancement of evoked responses in the adult primary somatosensory cortex. Moreover, the neonatal manipulation alters cortico-cortical interactions by decreasing the cross-modal synchrony and directionality in line with the sparsification of direct projections between primary somatosensory and visual cortices. At the behavioral level, these functional and structural deficits resulted in lower cross-modal matching abilities. Thus, neonatal unimodal experience during defined developmental stages is necessary for setting up the neuronal networks of multisensory processing.

Evidence of a retinotopic organization of early visual cortex but impaired extrastriate processing in sight recovery individuals.

Numerous studies in visually deprived nonhuman animals have demonstrated sensitive periods for the functional development of the early visual cortex. However, in humans it is yet unknown which visual areas are shaped to which degree based on visual experience. The present study investigated the functional organization and processing capacities of early visual cortex in sight recovery individuals with either a history of congenital cataracts (CC) or late onset cataracts (developmental cataracts, DC). Visual event-related potentials (VERPs) were recorded to grating stimuli which were flashed in one of the four quadrants of the visual field. Participants had to detect rarely occurring grating orientations. The CC individuals showed the expected polarity reversal of the C1 wave between upper and lower visual field stimuli at the typical latency range. Since the C1 has been proposed to originate in the early retinotopic visual cortex, we concluded that one basic feature of the retinotopic organization, upper versus lower visual field organization, is spared in CC individuals. Group differences in the size and topography of the C1 effect, however, suggested a less precise functional tuning. The P1 wave, which has been associated with extrastriate visual cortex processing, was significantly attenuated in CC but not in DC individuals compared to typically sighted controls. The present study thus provides evidence for fundamental aspects of retinotopic processing in humans being independent of developmental vision. We suggest that visual impairments in sight recovery individuals may predominantly arise at higher cortical processing stages.

Early Sign Language Experience Goes Along with an Increased Cross-modal Gain for Affective Prosodic Recognition in Congenitally Deaf CI Users.

It is yet unclear whether congenitally deaf cochlear implant (CD CI) users' visual and multisensory emotion perception is influenced by their history in sign language acquisition. We hypothesized that early-signing CD CI users, relative to late-signing CD CI users and hearing, non-signing controls, show better facial expression recognition and rely more on the facial cues of audio-visual emotional stimuli. Two groups of young adult CD CI users-early signers (ES CI users; n = 11) and late signers (LS CI users; n = 10)-and a group of hearing, non-signing, age-matched controls (n = 12) performed an emotion recognition task with auditory, visual, and cross-modal emotionally congruent and incongruent speech stimuli. On different trials, participants categorized either the facial or the vocal expressions. The ES CI users more accurately recognized affective prosody than the LS CI users in the presence of congruent facial information. Furthermore, the ES CI users, but not the LS CI users, gained more than the controls from congruent visual stimuli when recognizing affective prosody. Both CI groups performed overall worse than the controls in recognizing affective prosody. These results suggest that early sign language experience affects multisensory emotion perception in CD CI users.