Atypical and inflexible visual encoding in autism spectrum disorder.

Encoding, which involves translating sensory information into neural representations, is a critical first step in the sensory-perceptual pathway. Using a visual orientation task, a new study found both lower encoding capacity and less flexible adaptation in people with autism spectrum disorder.

Optics and neural adaptation jointly limit human stereovision.

Stereovision is the ability to perceive fine depth variations from small differences in the two eyes' images. Using adaptive optics, we show that even minute optical aberrations that are not clinically correctable, and go unnoticed in everyday vision, can affect stereo acuity. Hence, the human binocular system is capable of using fine details that are not experienced in everyday vision. Interestingly, stereo acuity varied considerably across individuals even when they were provided identical perfect optics. We also found that individuals' stereo acuity is better when viewing with their habitual optics rather than someone else's (better) optics. Together, these findings suggest that the visual system compensates for habitual optical aberrations through neural adaptation and thereby optimizes stereovision uniquely for each individual. Thus, stereovision is limited by small optical aberrations and by neural adaptation to one's own optics.

Poster Session: Neural Correlates of the Visual Expectation of Active and Passive Touch.

The sense of touch is frequently paired with a visual stimulus that provides information on how the sensation will be experienced. This is true for both active touch-when a person moves to touch an object-and passive touch-when an object moves to touch a person. However, limited research has been conducted on how active and passive touch are processed by the cortex, as well as how prediction of the sensory experience influences that processing. Here, we use electroencephalography (EEG) to measure cortical activity while virtual reality creates the visual expectation of touching an object that is paired with vibrotactile feedback. In the active condition, the participant will reach toward and receive tactile input from the virtual object. In the passive condition, the virtual object will move toward and provide tactile input to the participant. This experiment will measure an electrophysiological phenomenon called the mismatch negativity (MMN), a distinct deflection in the EEG waveform shown to index a deviation from an established pattern in sensory stimuli. To elicit an MMN, we will manipulate the duration of the vibrotactile stimuli, with 80% being 100 ms long and 20% being 160 ms long. Our experiment is the first to assess the MMN in an active tactile context. Preliminary data (n=4) show a robust N1 component and MMN in response to active and passive touch. Further data collection is ongoing.

Poster Session: Investigating temporal evolutions of perceptual choice within biological and artificial neural networks.

Perceptual decisions involve a process that evolves over time until it reaches a decision boundary. It's important to understand how this process unfolds. Recent psychophysical data indicates that the visual system extracts motion axis information faster than motion direction information (Kwon et al., 2015, J Vision). To understand the underlying mechanisms, we developed a biophysically realistic cortical network model of decision making. We generalized the two-variable reduced spiking neural network (Wong et al., 2006, J Neuroscience) to four-variable. The network input is based on motion energy (Adelson et al., 1985, Josa a) and the temporal profile of surround influence (Tadin et al., 2006, J Neuroscience). The model reproduces the prior experimental findings, showing the motion axis extraction before direction extraction. It reveals a stronger axis-wise inhibitory connection between the selective neural populations than the direction-wise inhibitory connection. We further designed a recurrent deep neural network to validate the neural population connectivity pattern. Our model provides a quantitative explanation for the temporal evolution of motion direction judgments. The results show that the spatiotemporal filtering for visual motion integration, the center-surround antagonism, and stronger axis-wise inhibitory connection between the selective neural populations can explain how the visual system can extract motion axis orientation before detecting motion direction.

Poster Session: A unifying framework for perceptual decision-making.

Perceptual decision making (PDM) has been studied using two approaches. Threshold measurement is predominant used in psychophysics, while reaction times (RT) with associated models have been used to estimate components of PDM (i.e., drift rate). To test if these two approaches reflect overlapping mechanisms, we conducted 3 experiments: a motion, a static orientation, and a dynamic orientation task. DT is the shortest stimulus presentation time sufficient to make accurate perceptual decisions. RTs and choices were fitted by a drift diffusion model (DDM). We expected a close relationship between DTs and drift rates, allowing us to accurately predict DTs from RT. In the motion task, we found a close relation between the empirical DTs and the DTs predicted by the DDM. Surprisingly, in the static task, there was little correlation between the two; DTs, improved monotonically with higher contrast, but drift rates saturated at 6%. We hypothesize that this mismatch is due to the information being available immediately in the static task, without needing to accumulate new evidence. Thus, we developed a novel dynamic orientation task that mimics the dynamic nature of the motion task and found a similar relation between DTs and drift rates. In summary, we show a close link between DTs and drift rate for the two dynamic tasks. This result supports the conceptualization of drift rate as a proxy for perceptual sensitivity but only for task where new information becomes available over time.

Poster Session: Evidence for preserved conscious orientation discrimination in perimetrically-blind fields early after V1-damage.

Cortically-blind (CB) patients with stroke damage to the primary visual cortex (V1) lose conscious vision but many exhibit blindsight - the ability to unconsciously detect or discriminate moving or flickering targets inside their blind-fields. However, the prevalence of conscious visual abilities in CB is less clear. Having developed a new method to assess vision inside perimetrically-defined blind fields, we found that >50% of subacute CB patients (<6 months post-stroke) can consciously discriminate global motion inside their blind field. Here, we asked if they can also discriminate orientation of static targets, which do not typically elicit blindsight. In 10 subacute patients, we mapped their intact and blind hemifields using static, non-flickering, 1cpd Gabors across a wide range of luminance contrasts. Blind-field locations were labeled "preserved" if performance was >72.5% correct. Considering overall performance, only 1 participant had preserved static orientation perception in the blind-field. However, this increased to 4 participants when only considering performance at high contrasts (>50%), all of whom reported awareness of stimuli. Thus, early after V1 damage, conscious percepts for oriented, high-contrast, static targets can remain inside CB fields, similar in incidence to global motion discriminations. We are now testing additional patients to assess if these abilities persist into the chronic period and to detail their underlying neural substrates.

Functional preservation and enhanced capacity for visual restoration in subacute occipital stroke.

Stroke damage to the primary visual cortex (V1) causes a loss of vision known as hemianopia or cortically-induced blindness. While perimetric visual field improvements can occur spontaneously in the first few months post-stroke, by 6 months post-stroke, the deficit is considered chronic and permanent. Despite evidence from sensorimotor stroke showing that early injury responses heighten neuroplastic potential, to date, visual rehabilitation research has focused on patients with chronic cortically-induced blindness. Consequently, little is known about the functional properties of the post-stroke visual system in the subacute period, nor do we know if these properties can be harnessed to enhance visual recovery. Here, for the first time, we show that 'conscious' visual discrimination abilities are often preserved inside subacute, perimetrically-defined blind fields, but they disappear by ∼6 months post-stroke. Complementing this discovery, we now show that training initiated subacutely can recover global motion discrimination and integration, as well as luminance detection perimetry, just as it does in chronic cortically-induced blindness. However, subacute recovery was attained six times faster; it also generalized to deeper, untrained regions of the blind field, and to other (untrained) aspects of motion perception, preventing their degradation upon reaching the chronic period. In contrast, untrained subacutes exhibited spontaneous improvements in luminance detection perimetry, but spontaneous recovery of motion discriminations was never observed. Thus, in cortically-induced blindness, the early post-stroke period appears characterized by gradual-rather than sudden-loss of visual processing. Subacute training stops this degradation, and is far more efficient at eliciting recovery than identical training in the chronic period. Finally, spontaneous visual improvements in subacutes were restricted to luminance detection; discrimination abilities only recovered following deliberate training. Our findings suggest that after V1 damage, rather than waiting for vision to stabilize, early training interventions may be key to maximize the system's potential for recovery.

Boosting Learning Efficacy with Noninvasive Brain Stimulation in Intact and Brain-Damaged Humans.

Numerous behavioral studies have shown that visual function can improve with training, although perceptual refinements generally require weeks to months of training to attain. This, along with questions about long-term retention of learning, limits practical and clinical applications of many such paradigms. Here, we show for the first time in female and male human participants that just 10 d of visual training coupled with transcranial random noise stimulation (tRNS) over visual areas causes dramatic improvements in visual motion perception. Relative to control conditions and anodal stimulation, tRNS-enhanced learning was at least twice as fast, and, crucially, it persisted for 6 months after the end of training and stimulation. Notably, tRNS also boosted learning in patients with chronic cortical blindness, leading to recovery of motion processing in the blind field after just 10 d of training, a period too short to elicit enhancements with training alone. In sum, our results reveal a remarkable enhancement of the capacity for long-lasting plastic and restorative changes when a neuromodulatory intervention is coupled with visual training.SIGNIFICANCE STATEMENT Our work demonstrates that visual training coupled with brain stimulation can dramatically reduce the training period from months to weeks, and lead to fast improvement in neurotypical subjects and chronic cortically blind patients, indicating the potential of our procedure to help restore damaged visual abilities for currently untreatable visual dysfunctions. Together, these results indicate the critical role of early visual areas in perceptual learning and reveal its capacity for long-lasting plastic changes promoted by neuromodulatory intervention.

Processing speed and attention training modifies autonomic flexibility: A mechanistic intervention study.

Adaptation capacity is critical for maintaining cognition, yet it is understudied in groups at risk for dementia. Autonomic nervous system (ANS) is critical for neurovisceral integration and is a key contributor to adaptation capacity. To determine the central nervous system's top-down regulation of ANS, we conducted a mechanistic randomized controlled trial study, using a 6-week processing speed and attention (PS/A)-targeted intervention. Eighty-four older adults with amnestic mild cognitive impairment (aMCI) were randomized to a 6-week PS/A-targeted intervention or an active control without PS/A. Utilizing repeated measures (i.e., PS/A test different from the intervention, resting and cognitive task-based ECG, and resting fMRI) at baseline, immediately post-intervention (post-test), and 6-month follow-up, we aimed to test whether PS/A causally influences vagal control of ANS via their shared central neural pathways in aMCI. We indexed vagal control of ANS using high-frequency heart rate variability (HF-HRV) extracted from ECG data. Functional brain connectivity patterns were extracted from fMRI using advanced statistical tools. Compared to the control group, the intervention group showed significant improvement in PS/A, HF-HRV, salience network (SN), central executive network (CEN), and frontal parietal network (FPN) connectivity at post-test; the effect on SN, CEN, and FPN remained at 6-month follow-up. Changes in PS/A and SN connectivity significantly predicted change in HF-HRV from baseline to post-test and/or 6-month-follow-up. Age, neurodegeneration, nor sex did not affect these relationships. This work provides novel support for top-down regulation of PS/A and associated SN on vagal control of ANS. Intervening PS/A may be a viable approach for promoting adaptation capacity in groups at risk for dementia.

Autonomic flexibility reflects learning and associated neuroplasticity in old age.

Effective learning in old age, particularly in those at risk for dementia, is essential for prolonging independent living. Individual variability in learning, however, is remarkable; that is, months of cognitive training to improve learning may be beneficial for some individuals but not others. So far, little is known about which neurophysiological mechanisms account for the observed variability in learning induced by cognitive training in older adults. By combining Lövdén et al.'s (2010, A theoretical framework for the study of adult cognitive plasticity. Psychological Bulletin, 136, 659-676) framework proposing the role of adaptation capacity in neuroplasticity and a neurovisceral integration model of the relationship between autonomic nervous system (ANS) and brain with a novel shapelet analytical approach that allows for accurate and interpretable analysis of time series data, we discovered an acute, ECG-derived ANS segment in response to cognitive training tasks at baseline that predicted learning outcomes from a 6-week cognitive training intervention. The relationship between the ANS segment and learning was robust in both cross-participant and cross-task analyses among a group of older adults with amnestic mild cognitive impairment. Furthermore, the revealed ANS shapelet significantly predicted training-induced neuroplasticity in the dorsal anterior cingulate cortex and select frontal regions during task fMRI. Across outcome measures, individuals were less likely to prospectively benefit from the cognitive training if their ECG data were more similar to this particular ANS segment at baseline. Our findings are among the first empirical evidence to confirm that adaptation capacity, indexed by ANS flexibility, predicts individual differences in learning and associated neuroplasticity beyond individual characteristics (e.g., age, education, neurodegeneration, total training).

Perceptual training profoundly alters binocular rivalry through both sensory and attentional enhancements.

The effects of attention, as well as its functional utility, are particularly prominent when selecting among multiple stimuli that compete for processing resources. However, existing studies have found that binocular rivalry-a phenomenon characterized by perceptual competition between incompatible stimuli presented to the two eyes-is only modestly influenced by selective attention. Here, we demonstrate that the relative resistance of binocular rivalry to selective modulations gradually erodes over the course of extended perceptual training that uses a demanding, feature-based attentional task. The final result was a dramatic alteration in binocular rivalry dynamics, leading to profound predominance of the trained stimulus. In some cases, trained observers saw the trained rival image nearly exclusively throughout 4-min viewing periods. This large change in binocular rivalry predominance was driven by two factors: task-independent, eye-specific changes in visual processing, as well as an enhanced ability of attention to promote predominance of the task-relevant stimulus. Notably, this strengthening of task-driven attention also exhibited eye specificity above and beyond that from observed sensory processing changes. These empirical results, along with simulations from a recently developed model of interocular suppression, reveal that stimulus predominance during binocular rivalry can be realized both through an eye-specific boost in processing of sensory information and through facilitated deployment of attention to task-relevant features in the trained eye. Our findings highlight the interplay of attention and binocular rivalry at multiple visual processing stages and reveal that sustained training can substantially alter early visual mechanisms.

Unifying account of visual motion and position perception.

Despite growing evidence for perceptual interactions between motion and position, no unifying framework exists to account for these two key features of our visual experience. We show that percepts of both object position and motion derive from a common object-tracking system--a system that optimally integrates sensory signals with a realistic model of motion dynamics, effectively inferring their generative causes. The object-tracking model provides an excellent fit to both position and motion judgments in simple stimuli. With no changes in model parameters, the same model also accounts for subjects' novel illusory percepts in more complex moving stimuli. The resulting framework is characterized by a strong bidirectional coupling between position and motion estimates and provides a rational, unifying account of a number of motion and position phenomena that are currently thought to arise from independent mechanisms. This includes motion-induced shifts in perceived position, perceptual slow-speed biases, slowing of motions shown in visual periphery, and the well-known curveball illusion. These results reveal that motion perception cannot be isolated from position signals. Even in the simplest displays with no changes in object position, our perception is driven by the output of an object-tracking system that rationally infers different generative causes of motion signals. Taken together, we show that object tracking plays a fundamental role in perception of visual motion and position.

Cortical thickness is associated with altered autonomic function in cognitively impaired and non-impaired older adults.

KEY POINTS: The parasympathetic nervous system (PNS) is critical for adaptation to environment demands. Alzheimer's disease (AD), via frontal compensatory processes, may affect PNS regulation, thereby compromising older adults' capacity for adaptation, and increasing morbidity and mortality risk. Here we found that AD-associated neurodegeneration accompanied an overactive anterior cingulate cortex, which in turn resulted in a high level of PNS activity at rest, as well as strong PNS activity withdrawal in response to the mental effort. This discovery provides the first line of evidence to suggest that AD-associated neurodegeneration links to altered PNS regulation during mental effort in older adults, and that the compensatory processes accompanying frontal hyperactivation appear to be responsible for these alterations. ABSTRACT: The parasympathetic nervous system (PNS) is critical for adaptation to environment demands. PNS can reflect an individual's regulatory capacity of frontal brain regions and has been linked to cognitive capacity. Yet, the relationship of PNS function to cognitive decline and abnormal frontal function that characterize preclinical progression toward Alzheimer's disease (AD) is unclear. Here, we aimed to elucidate the relationship between PNS function and AD-associated neurodegeneration by testing two competing hypotheses involving frontal regions' activity (neurodegeneration vs. compensation). In 38 older human adults with amnestic mild cognitive impairment (aMCI) or normative cognition, we measured AD-associated neurodegeneration (AD signature cortical thickness; ADSCT), resting-state functional magnetic resonance imaging of frontal regions' spontaneous activation, and an electrocardiography measure of PNS (high frequency heart rate variability; HF-HRV). HF-HRV was assessed at rest and during a cognitive task protocol designed to capture HF-HRV reactivity. Higher HF-HRV at rest was significantly related to both more severe AD-associated neurodegeneration (lower ADSCT scores) and worse cognitive ability. Cognitive impairments were also related to greater suppression of HF-HRV reactivity. High activities of the anterior cingulate cortex significantly mediated relationships between ADSCT and both HF-HRV at rest and HF-HRV reactivity. Notably, these relationships were not affected by the clinical phenotype. We show that AD-associated neurodegeneration is associated with altered PNS regulation and that compensatory processes linked to frontal overactivation might be responsible for those alterations. This finding provides the first line of evidence in a new framework for understanding how early-stage AD-associated neurodegeneration affects autonomic regulation.

Distinct neural mechanisms for body form and body motion discriminations.

Actions can be understood based on form cues (e.g., static body posture) as well as motion cues (e.g., gait patterns). A fundamental debate centers on the question of whether the functional and neural mechanisms processing these two types of cues are dissociable. Here, using fMRI, psychophysics, and transcranial magnetic stimulation (TMS), all within the same human participants, we show that mechanisms underlying body form and body motion processing are functionally and neurally distinct. Multivoxel fMRI activity patterns in the extrastriate body area (EBA), but not in the posterior superior temporal sulcus (pSTS), carried cue invariant information about the body form of an acting human. Conversely, multivoxel patterns in pSTS, but not in EBA, carried information about the body motion of the same actor. In a psychophysical experiment, we selectively impaired body form and body motion discriminations by manipulating different visual cues: misaligning the ellipses that made up a dynamic walker stimulus selectively disrupted body form discriminations, while varying the presentation duration of the walker selectively affected body motion discriminations. Finally, a TMS experiment revealed causal evidence for a double-dissociation between neural mechanisms underlying body form and body motion discriminations: TMS over EBA selectively disrupted body form discrimination, whereas TMS over pSTS selectively disrupted body motion discrimination. Together, these findings reveal complementing but dissociable functions of EBA and pSTS during action perception. They provide constraints for theoretical and computational models of action perception by showing that action perception involves at least two parallel pathways that separately contribute to the understanding of others' behavior.

Beyond blindsight: properties of visual relearning in cortically blind fields.

Damage to the primary visual cortex (V1) or its immediate afferents results in a dense scotoma, termed cortical blindness (CB). CB subjects have residual visual abilities, or blindsight, which allow them to detect and sometimes discriminate stimuli with high temporal and low spatial frequency content. Recent work showed that with training, discriminations in the blind field can become more reliable, and even reach consciousness. However, the narrow spatiotemporal bandwidth of blindsight limits its functional usefulness in everyday vision. Here, we asked whether visual training can induce recovery outside the spatiotemporal bandwidth of blindsight. Specifically, could human CB subjects learn to discriminate static, nonflickering stimuli? Can such learning transfer to untrained stimuli and tasks, and does double training with moving and static stimuli provide additional advantages relative to static training alone? We found CB subjects capable of relearning static orientation discriminations following single as well as double training. However, double training with complex, moving stimuli in a separate location was necessary to recover complex motion thresholds at locations trained with static stimuli. Subjects trained on static stimuli alone could only discriminate simple motion. Finally, both groups had approximately equivalent, incomplete recovery of fine orientation and direction discrimination thresholds, as well as contrast sensitivity. These results support two conclusions: (1) from a practical perspective, complex moving stimuli and double training may be superior training tools for inducing visual recovery in CB, and (2) the cortically blind visual system can relearn to perform a wider range of visual discriminations than predicted by blindsight alone.

Is improved contrast sensitivity a natural consequence of visual training?

Many studies have shown that training and testing conditions modulate specificity of visual learning to trained stimuli and tasks. In visually impaired populations, generalizability of visual learning to untrained stimuli/tasks is almost always reported, with contrast sensitivity (CS) featuring prominently among these collaterally-improved functions. To understand factors underlying this difference, we measured CS for direction and orientation discrimination in the visual periphery of three groups of visually-intact subjects. Group 1 trained on an orientation discrimination task with static Gabors whose luminance contrast was decreased as performance improved. Group 2 trained on a global direction discrimination task using high-contrast random dot stimuli previously used to recover motion perception in cortically blind patients. Group 3 underwent no training. Both forms of training improved CS with some degree of specificity for basic attributes of the trained stimulus/task. Group 1's largest enhancement was in CS around the trained spatial/temporal frequencies; similarly, Group 2's largest improvements occurred in CS for discriminating moving and flickering stimuli. Group 3 saw no significant CS changes. These results indicate that CS improvements may be a natural consequence of multiple forms of visual training in visually intact humans, albeit with some specificity to the trained visual domain(s).

The role of sensory ocular dominance on through-focus visual performance in monovision presbyopia corrections.

Monovision presbyopia interventions exploit the binocular nature of the visual system by independently manipulating the optical properties of the two eyes. It is unclear, however, how individual variations in ocular dominance affect visual function in monovision corrections. Here, we examined the impact of sensory ocular dominance on visual performance in both traditional and modified monovision presbyopic corrections. We recently developed a binocular adaptive optics vision simulator to correct subjects' native aberrations and induce either modified monovision (1.5 D anisometropia, spherical aberration of +0.1 and -0.4 µm in distance and near eyes, respectively, over 4 mm pupils) or traditional monovision (1.5 D anisometropia). To quantify both the sign and the degree of ocular dominance, we utilized binocular rivalry to estimate stimulus contrast ratios that yield balanced dominance durations for the two eyes. Through-focus visual acuity and contrast sensitivity were measured under two conditions: (a) assigning dominant and nondominant eye to distance and near, respectively, and (b) vice versa. The results revealed that through-focus visual acuity was unaffected by ocular dominance. Contrast sensitivity, however, was significantly improved when the dominant eye coincided with superior optical quality. We hypothesize that a potential mechanism behind this observation is an interaction between ocular dominance and binocular contrast summation, and thus, assignment of the dominant eye to distance or near may be an important factor to optimize contrast threshold performance at different object distances in both modified and traditional monovision.

Visual recovery in cortical blindness is limited by high internal noise.

Damage to the primary visual cortex typically causes cortical blindness (CB) in the hemifield contralateral to the damaged hemisphere. Recent evidence indicates that visual training can partially reverse CB at trained locations. Whereas training induces near-complete recovery of coarse direction and orientation discriminations, deficits in fine motion processing remain. Here, we systematically disentangle components of the perceptual inefficiencies present in CB fields before and after coarse direction discrimination training. In seven human CB subjects, we measured threshold versus noise functions before and after coarse direction discrimination training in the blind field and at corresponding intact field locations. Threshold versus noise functions were analyzed within the framework of the linear amplifier model and the perceptual template model. Linear amplifier model analysis identified internal noise as a key factor differentiating motion processing across the tested areas, with visual training reducing internal noise in the blind field. Differences in internal noise also explained residual perceptual deficits at retrained locations. These findings were confirmed with perceptual template model analysis, which further revealed that the major residual deficits between retrained and intact field locations could be explained by differences in internal additive noise. There were no significant differences in multiplicative noise or the ability to process external noise. Together, these results highlight the critical role of altered internal noise processing in mediating training-induced visual recovery in CB fields, and may explain residual perceptual deficits relative to intact regions of the visual field.

Illusory movement of stationary stimuli in the visual periphery: evidence for a strong centrifugal prior in motion processing.

Visual input is remarkably diverse. Certain sensory inputs are more probable than others, mirroring statistical regularities of the visual environment. The visual system exploits many of these regularities, resulting, on average, in better inferences about visual stimuli. However, by incorporating prior knowledge into perceptual decisions, visual processing can also result in perceptions that do not match sensory inputs. Such perceptual biases can often reveal unique insights into underlying mechanisms and computations. For example, a prior assumption that objects move slowly can explain a wide range of motion phenomena. The prior on slow speed is usually rationalized by its match with visual input, which typically includes stationary or slow moving objects. However, this only holds for foveal and parafoveal stimulation. The visual periphery tends to be exposed to faster motions, which are biased toward centrifugal directions. Thus, if prior assumptions derive from experience, peripheral motion processing should be biased toward centrifugal speeds. Here, in experiments with human participants, we support this hypothesis and report a novel visual illusion where stationary objects in the visual periphery are perceived as moving centrifugally, while objects moving as fast as 7°/s toward fovea are perceived as stationary. These behavioral results were quantitatively explained by a Bayesian observer that has a strong centrifugal prior. This prior is consistent with both the prevalence of centrifugal motions in the visual periphery and a centrifugal bias of direction tuning in cortical area MT, supporting the notion that visual processing mirrors its input statistics.

A substantial and unexpected enhancement of motion perception in autism.

Atypical perceptual processing in autism spectrum disorder (ASD) is well documented. In addition, growing evidence supports the hypothesis that an excitatory/inhibitory neurochemical imbalance might underlie ASD. Here we investigated putative behavioral consequences of the excitatory/inhibitory imbalance in the context of visual motion perception. As stimulus size increases, typical observers exhibit marked impairments in perceiving motion of high-contrast stimuli. This result, termed "spatial suppression," is believed to reflect inhibitory motion-processing mechanisms. Motion processing is also affected by gain control, an inhibitory mechanism that underlies saturation of neural responses at high contrast. Motivated by these behavioral correlates of inhibitory function, we investigated motion perception in human children with ASD (n = 20) and typical development (n = 26). At high contrast, both groups exhibited similar impairments in motion perception with increasing stimulus size, revealing no apparent differences in spatial suppression. However, there was a substantial enhancement of motion perception in ASD: children with ASD exhibited a consistent twofold improvement in perceiving motion. Hypothesizing that this enhancement might indicate abnormal weakening of response gain control, we repeated our measurements at low contrast, where the effects of gain control should be negligible. At low contrast, we indeed found no group differences in motion discrimination thresholds. These low-contrast results, however, revealed weaker spatial suppression in ASD, suggesting the possibility that gain control abnormalities in ASD might have masked spatial suppression differences at high contrast. Overall, we report a pattern of motion perception abnormalities in ASD that includes substantial enhancements at high contrast and is consistent with an underlying excitatory/inhibitory imbalance.