Recent evidence suggests those with autism may be generally impaired in visual motion perception. To examine this, we investigated both coherent and biological motion processing in adolescents with autism employing both psychophysical and fMRI methods. Those with autism performed as well as matched controls during coherent motion perception but had significantly higher thresholds for biological motion perception. The autism group showed reduced posterior Superior Temporal Sulcus (pSTS), parietal and frontal activity during a biological motion task while showing similar levels of activity in MT+/V5 during both coherent and biological motion trials. Activity in MT+/V5 was predictive of individual coherent motion thresholds in both groups. Activity in dorsolateral prefrontal cortex (DLPFC) and pSTS was predictive of biological motion thresholds in control participants but not in those with autism. Notably, however, activity in DLPFC was negatively related to autism symptom severity. These results suggest that impairments in higher-order social or attentional networks may underlie visual motion deficits observed in autism.
Autism spectrum disorder (ASD) has been associated with decreased coherent dot motion (CDM) performance, a task that measures magnocellular sensitivity as well as fronto-parietal attentional integration processing. In order to clarify the role of spatial attention in CDM tasks, we measured the perception of coherently moving dots displayed in the central or peripheral visual field in ASD and typically developing children. A dorsal-stream deficit in children with ASD should predict a generally poorer performance in both conditions. In our study, however, we show that in children with ASD, CDM perception was selectively impaired in the central condition. In addition, in the ASD group, CDM efficiency was correlated to the ability to zoom out the attentional focus. Importantly, autism symptoms severity was related to both the CDM and attentional zooming-out impairment. These findings suggest that a dysfunction in the attentional network might help to explain decreased CDM discrimination as well as the “core” social cognition deficits of ASD.
We used six psychophysical tasks to measure sensitivity to different types of global motion in 45 healthy adults and in 57 stroke patients who had recovered from the initial results of the stroke, but a large subset of them had enduring deficits on selective visual motion perception tasks. The patients were divided into four groups on the basis of the location of their cortical lesion: occipito-temporal, occipito-parietal, rostro-dorsal parietal, or frontal–prefrontal. The six tasks were: direction discrimination, speed discrimination, motion coherence, motion discontinuity, two-dimensional form-from-motion, and motion coherence – radial. We found both qualitative and quantitative differences among the motion impairments in the four groups: patients with frontal lesions or occipito-temporal lesions were not impaired on any task. The other two groups had substantial impairments, most severe in the group with occipito-parietal damage. We also tested eight healthy control subjects on the same tasks while they were scanned by functional magnetic resonance imaging. The BOLD signal provoked by the different tasks correlated well with the locus of the lesions that led to impairments among the different tasks. The results highlight the advantage of using psychophysical/techniques and a variety of visual tasks with neurological patients to tease apart the contribution of different cortical areas to motion processing.
In order to investigate differences in the effects of spatial attention between the left visual field (LVF) and the right visual field (RVF), we employed a full/poor attention paradigm using stimuli presented in the LVF vs. RVF. In addition, to investigate differences in the effects of spatial attention between the Dorsal and Ventral processing streams, we obtained motion thresholds (motion coherence thresholds and fine direction discrimination thresholds) and orientation thresholds, respectively. The results of this study showed negligible effects of attention on the orientation task, in either the LVF or RVF. In contrast, for both motion tasks, there was a significant effect of attention in the LVF, but not in the RVF. These data provide psychophysical evidence for greater effects of spatial attention in the LVF/right hemisphere, specifically, for motion processing in the Dorsal stream.
spatial attention; laterality; visual field asymmetries; dorsal/ventral; motion; orientation
The sensory abnormalities associated with disorders such as dyslexia, autism and schizophrenia have often been attributed to a generalized deficit in the visual magnocellular–dorsal stream and its auditory homologue. To probe magnocellular function, various psychophysical tasks are often employed that require the processing of rapidly changing stimuli. But is performance on these several tasks supported by a common substrate? To answer this question, we tested a cohort of 1060 individuals on four ‘magnocellular tasks’: detection of low-spatial-frequency gratings reversing in contrast at a high temporal frequency (so-called frequency-doubled gratings); detection of pulsed low-spatial-frequency gratings on a steady luminance pedestal; detection of coherent motion; and auditory discrimination of temporal order. Although all tasks showed test–retest reliability, only one pair shared more than 4 per cent of variance. Correlations within the set of ‘magnocellular tasks’ were similar to the correlations between those tasks and a ‘non-magnocellular task’, and there was little consistency between ‘magnocellular deficit’ groups comprising individuals with the lowest sensitivity for each task. Our results suggest that different ‘magnocellular tasks’ reflect different sources of variance, and thus are not general measures of ‘magnocellular function’.
magnocellular; dorsal stream; psychophysics; vision; hearing; individual differences
Perception of biological motion is linked to the action perception system in the human brain, abnormalities within which have been suggested to underlie impairments in social domains observed in autism spectrum conditions (ASC). However, the literature on biological motion perception in ASC is heterogeneous and it is unclear whether deficits are specific to biological motion, or might generalize to form-from-motion perception.
Methodology and Principal Findings
We compared psychophysical thresholds for both biological and non-biological form-from-motion perception in adults with ASC and controls. Participants viewed point-light displays depicting a walking person (Biological Motion), a translating rectangle (Structured Object) or a translating unfamiliar shape (Unstructured Object). The figures were embedded in noise dots that moved similarly and the task was to determine direction of movement. The number of noise dots varied on each trial and perceptual thresholds were estimated adaptively. We found no evidence for an impairment in biological or non-biological object motion perception in individuals with ASC. Perceptual thresholds in the three conditions were almost identical between the ASC and control groups.
Discussion and Conclusions
Impairments in biological motion and non-biological form-from-motion perception are not across the board in ASC, and are only found for some stimuli and tasks. We discuss our results in relation to other findings in the literature, the heterogeneity of which likely relates to the different tasks performed. It appears that individuals with ASC are unaffected in perceptual processing of form-from-motion, but may exhibit impairments in higher order judgments such as emotion processing. It is important to identify more specifically which processes of motion perception are impacted in ASC before a link can be made between perceptual deficits and the higher-level features of the disorder.
Although the ventral visual stream is understood to be responsible for object recognition, it has been proposed that the dorsal stream may contribute to object recognition by rapidly activating parietal attention mechanisms, prior to ventral stream object processing.
To investigate the relative contribution of the dorsal visual stream to object recognition a group of tertiary students were divided into good and poor motion coherence groups and assessed on tasks classically assumed to rely on ventral stream processing. Participants were required to identify simple line drawings in two tasks, one where objects were presented abruptly for 50 ms followed by a white-noise mask, the other where contrast was linearly ramped on and off over 325 ms and replaced with a mask.
Although both groups only differed in motion coherence performance (a dorsal stream measure), the good motion coherence group showed superior contrast sensitivity for object recognition on the abrupt, but not the ramped presentation tasks.
We propose that abrupt presentation of objects activated attention mechanisms fed by the dorsal stream, whereas the ramped presentation had reduced transience and thus did not activate dorsal attention mechanisms as well. The results suggest that rapid dorsal stream activation may be required to assist with ventral stream object processing.
Background: Schizophrenia patients exhibit deficient processing of perceptual and cognitive information. However, it is not well-understood how basic perceptual deficits contribute to higher level cognitive problems in this mental disorder. Perception of biological motion, a motion-based cognitive recognition task, relies on both basic visual motion processing and social cognitive processing, thus providing a useful paradigm to evaluate the potentially hierarchical relationship between these two levels of information processing.
Methods: In this study, we designed a biological motion paradigm in which basic visual motion signals were manipulated systematically by incorporating different levels of motion noise. We measured the performances of schizophrenia patients (n = 21) and healthy controls (n = 22) in this biological motion perception task, as well as in coherent motion detection, theory of mind, and a widely used biological motion recognition task.
Results: Schizophrenia patients performed the biological motion perception task with significantly lower accuracy than healthy controls when perceptual signals were moderately degraded by noise. A more substantial degradation of perceptual signals, through using additional noise, impaired biological motion perception in both groups. Performance levels on biological motion recognition, coherent motion detection and theory of mind tasks were also reduced in patients.
Conclusion: The results from the motion-noise biological motion paradigm indicate that in the presence of visual motion noise, the processing of biological motion information in schizophrenia is deficient. Combined with the results of poor basic visual motion perception (coherent motion task) and biological motion recognition, the association between basic motion signals and biological motion perception suggests a need to incorporate the improvement of visual motion perception in social cognitive remediation.
biological motion perception; visual motion perception; bottom-up process; social cognition; schizophrenia
Patients with schizophrenia show impairments in motion processing, along with deficits in lower level processing primarily involving the magnocellular visual pathway. The present study investigates potential magnocellular contributions to impaired motion processing in schizophrenia using a combined neurophysiological and behavioral approach. As compared to prior motion studies in schizophrenia, thresholds were determined for both incoherent and coherent visual motion. In this study, velocity discrimination thresholds were measured for schizophrenia patients (n = 14) and age-matched normal control subjects (n = 16) using a staircase procedure. Early visual processing was evaluated using steady-state visual evoked potentials (ssVEP), with stimuli biased toward activation of either the magnocellular or parvocellular visual pathways through luminance contrast manipulation. Patients with schizophrenia showed poor velocity discrimination for both incoherent and coherent motion, with no significant group × task interaction. Further, when coherent motion performance was measured at individually determined incoherent motion thresholds, accuracy levels for patients were similar to controls, also indicating similarity of deficit for incoherent vs. coherent motion discrimination. Impairments in velocity discrimination correlated significantly with reduced amplitude of ssVEP elicited by magnocellular – but not parvocellular – selective stimuli. This study demonstrates that deficits in motion processing in schizophrenia are significantly related to reduced activation of the magnocellular visual system. Further, this study supports and extends prior reports of impaired motion processing in schizophrenia, and indicates significant bottom-up contributions to higher-order cognitive impairments.
Schizophrenia; Motion; Magnocellular; Visual; NMDA
▶ Normal biological motion processing can exist independently from form processing. ▶ Intact ventral stream processing is not necessary for biological form-from-motion. ▶ Proper ventral stream processing is necessary for non-biological form-from-motion. ▶ Normal visual inputs from V5/MT+ can suffice to activate the action perception system. ▶ Biological motion can be processed successfully even with compromised ventral stream.
We explored the extent to which biological motion perception depends on ventral stream integration by studying LG, an unusual case of developmental visual agnosia. LG has significant ventral stream processing deficits but no discernable structural cortical abnormality. LG's intermediate visual areas and object-sensitive regions exhibit abnormal activation during visual object perception, in contrast to area V5/MT+ which responds normally to visual motion (Gilaie-Dotan, Perry, Bonneh, Malach, & Bentin, 2009). Here, in three studies we used point light displays, which require visual integration, in adaptive threshold experiments to examine LG's ability to detect form from biological and non-biological motion cues. LG's ability to detect and discriminate form from biological motion was similar to healthy controls. In contrast, he was significantly deficient in processing form from non-biological motion. Thus, LG can rely on biological motion cues to perceive human forms, but is considerably impaired in extracting form from non-biological motion. Finally, we found that while LG viewed biological motion, activity in a network of brain regions associated with processing biological motion was functionally correlated with his V5/MT+ activity, indicating that normal inputs from V5/MT+ might suffice to activate his action perception system. These results indicate that processing of biologically moving form can dissociate from other form processing in the ventral pathway. Furthermore, the present results indicate that integrative ventral stream processing is necessary for uncompromised processing of non-biological form from motion.
Biological motion; Form agnosia; Form from motion; Point-light displays; Ventral visual stream
Over the past 25 years, visual processing has been discussed in the context of the dual stream hypothesis consisting of a ventral (“what”) and a dorsal (“where”) visual information processing pathway. Patients with brain damage of the ventral pathway typically present with signs of visual agnosia, the inability to identify and discriminate objects by visual exploration, but show normal perception of motion perception. A dissociation between the perception of biological motion and non-biological motion has been suggested: perception of biological motion might be impaired when “non-biological” motion perception is intact and vice versa. The impact of object recognition on the perception of biological motion remains unclear. We thus investigated this question in a patient with severe visual agnosia, who showed normal perception of non-biological motion. The data suggested that the patient's perception of biological motion remained largely intact. However, when tested with objects constructed of coherently moving dots (“Shape-from-Motion”), recognition was severely impaired. The results are discussed in the context of possible mechanisms of biological motion perception.
vision; agnosia; ventral stream; biological motion; perception
People with schizophrenia (SCZ) are impaired in several domains of visual processing, including the discrimination and detection of biological motion. However, the mechanisms underlying SCZ-related biological motion processing deficits are unknown. Moreover, whether these impairments are specific to biological motion or represent a more widespread visual motion processing deficit is unclear. In the current study, three experiments were conducted to investigate the contribution of global coherent motion processing to biological motion perception among patients with SCZ. In Experiments 1 and 2, participants with SCZ (n = 33) and healthy controls (n = 33) were asked to discriminate the direction of motion from upright and inverted point-light walkers in the presence and absence of a noise mask. Additionally, participants discriminated the direction of non-biological global coherent motion. In Experiment 3, participants discriminated the direction of motion from upright scrambled walkers (which contained only local motion information) and upright random position walkers (which contained only global form information). Consistent with previous research, results from Experiment 1 and 2 showed that people with SCZ exhibited deficits in the direction discrimination of point-light walkers; however, this impairment was accounted for by decreased performance in the coherent motion control task. Furthermore, results from Experiment 3 demonstrated similar performance in the discrimination of scrambled and random position point-light walkers.
biological motion; schizophrenia; paranoid; motion; global mechanisms; local mechanisms; perception
Autistic tendency has been associated with altered visual perception, especially impaired visual motion sensitivity and global/local integration, as well as enhanced visual search and local shape recognition. However, the neurophysiological mechanisms underlying these abnormalities remain poorly defined. The current study recruited 29 young adults displaying low, middle or high autistic trait as measured by Baron-Cohen's Autism spectrum Quotient (AQ), and measured motion coherence thresholds psychophysically, with manipulation of dot lifetime and stimulus contrast, as well as nonlinear cortical visual evoked potentials (VEPs) over a range of temporal luminance contrast levels from 10% to 95%. Contrast response functions extracted from the major first order and second order Wiener kernel peaks of the VEPs showed consistent variation with AQ group, and Naka-Rushton fits enabled contrast gain and semi-saturation contrasts to be elicited for each peak. A short latency second order response (previously associated with magnocellular processing) with high contrast gain and a saturating contrast response function showed higher amplitude for the High AQ (compared with Mid and Low groups) indicating poorer neural recovery after rapid stimulation. A non-linearity evoked at longer interaction times (previously associated with parvocellular processing) with no evidence of contrast saturation and lower contrast gain showed no difference between autism quotient groups across the full range of stimulus contrasts. In addition, the short latency first order response and a small, early second order second slice response showed gain and semi-saturation parameters indicative of magnocellular origin, while the longer latency first order response probably reflects a mixture of inputs (including feedback from higher cortical areas). Significant motion coherence (AQ group) * (dot lifetime) interactions with higher coherence threshold for limited dot lifetime stimuli is consistent with atypical magnocellular functioning, however psychophysical performance for those with High AQ is not explained fully, suggesting that other factors may be involved.
The weak central coherence hypothesis represents one of the current explanatory models in Autism Spectrum Disorders (ASD). Several experimental paradigms based on hierarchical figures have been used to test this controversial account. We addressed this hypothesis by testing central coherence in ASD (n = 19 with intellectual disability and n = 20 without intellectual disability), Williams syndrome (WS, n = 18), matched controls with intellectual disability (n = 20) and chronological age-matched controls (n = 20). We predicted that central coherence should be most impaired in ASD for the weak central coherence account to hold true. An alternative account includes dorsal stream dysfunction which dominates in WS. Central coherence was first measured by requiring subjects to perform local/global preference judgments using hierarchical figures under 6 different experimental settings (memory and perception tasks with 3 distinct geometries with and without local/global manipulations). We replicated these experiments under 4 additional conditions (memory/perception*local/global) in which subjects reported the correct local or global configurations. Finally, we used a visuoconstructive task to measure local/global perceptual interference. WS participants were the most impaired in central coherence whereas ASD participants showed a pattern of coherence loss found in other studies only in four task conditions favoring local analysis but it tended to disappear when matching for intellectual disability. We conclude that abnormal central coherence does not provide a comprehensive explanation of ASD deficits and is more prominent in populations, namely WS, characterized by strongly impaired dorsal stream functioning and other phenotypic traits that contrast with the autistic phenotype. Taken together these findings suggest that other mechanisms such as dorsal stream deficits (largest in WS) may underlie impaired central coherence.
Visual processing of color starts at the cones in the retina and continues through ventral stream visual areas, called the parvocellular pathway. Motion processing also starts in the retina but continues through dorsal stream visual areas, called the magnocellular system. Color and motion processing are functionally and anatomically discrete. Previously, motion processing areas MT and MST have been shown to have no color selectivity to a moving stimulus; the neurons were colorblind whenever color was presented along with motion. This occurs when the stimuli are luminance-defined versus the background and is considered achromatic motion processing. Is motion processing independent of color processing? We find that motion processing is intrinsically modulated by color. Color modulated smooth pursuit eye movements produced upon saccading to an aperture containing a surface of coherently moving dots upon a black background. Furthermore, when two surfaces that differed in color were present, one surface was automatically selected based upon a color hierarchy. The strength of that selection depended upon the distance between the two colors in color space. A quantifiable color hierarchy for automatic target selection has wide-ranging implications from sports to advertising to human-computer interfaces.
To explore the relative development of the dorsal and ventral extrastriate processing streams, we studied the development of sensitivity to form and motion in macaque monkeys (Macaca nemestrina). We used Glass patterns and random dot kinematograms (RDK) to assay ventral and dorsal stream function, respectively. We tested 24 animals, longitudinally or cross-sectionally, between the ages of 5 weeks and 3 years. Each animal was tested with Glass patterns and RDK stimuli with each of two pattern types – circular and linear – at each age using a two alternative forced-choice task. We measured coherence threshold for discrimination of the global form or motion pattern from an incoherent control stimulus. Sensitivity to global motion appeared earlier than to global form and was higher at all ages, but performance approached adult levels at similar ages. Infants were most sensitive to large spatial scale (Δx) and fast speeds; sensitivity to fine scale and slow speeds developed more slowly independently of pattern type. Within the motion domain, pattern type had little effect on overall performance. However, within the form domain, sensitivity for linear Glass patterns was substantially poorer than that for concentric patterns. Our data show comparatively early onset for global motion integration ability, perhaps reflecting early development of the dorsal stream. However, both pathways mature over long time courses reaching adult levels between two and three years after birth.
Visual development; Glass pattern; global motion; global form; extrastriate pathways; macaque monkey
Visual motion perception and pursuit eye movement deficits have been reported in autism. However, it is unclear whether these impairments are related to each other or toclinical symptoms of the disorder. High-functioning individuals with autism (41 with and 36 without delayed language acquisition) and 46 control subjects participated in the present study. All three subject groups were matched on chronological age and Full-Scale IQ. The autism group with delayed language acquisition had bilateral impairments on visual motion discrimination tasks, while the autism group without delay showed marginal impairments only in the left hemifield. Both autism groups showed difficulty tracking visual targets, but only the autism group without delayed language acquisition showed increased pursuit latencies and a failure to show the typical rightward directional advantage in pursuit. We observed correlations between performance on the visual perception and pursuit tasks in both autism groups. However, pursuit performance was correlated with manual motor skills only in the autism group with delayed language, suggesting that general sensorimotor or motor disturbances are a significant additional factor related to pursuit deficits in this subgroup. These findings suggest that there may be distinct neurocognitive phenotypes in autism associated with patterns of early language development.
autism phenotypes; visual motion perception; visual pursuit; population heterogeneity; language development; autism subtypes
Vision in Autism Spectrum Conditions (ASC) is characterized by enhanced perception of local elements, but impaired perception of global percepts. Deficits in coherent motion perception seem to support this characterization, but the roots and robustness of such deficits remain unclear. We aimed to investigate the dynamics of the perceptual decision-making network known to support coherent motion perception. In a series of forced-choice coherent motion perception tests, we parametrically varied a single stimulus dimension, viewing duration, to test whether the rate at which evidence is accumulated towards a global decision is atypical in ASC. 40 adult participants (20 ASC) performed a classic motion discrimination task, manually indicating the global direction of motion in a random-dot kinematogram across a range of coherence levels (2–75%) and stimulus-viewing durations (200–1500 ms). We report a deficit in global motion perception at short viewing durations in ASC. Critically, however, we found that increasing the amount of time over which motion signals could be integrated reduced the magnitude of the deficit, such that at the longest duration there was no difference between the ASC and control groups. Further, the deficit in motion integration at the shortest duration was significantly associated with the severity of autistic symptoms in our clinical population, and was independent from measures of intelligence. These results point to atypical integration of motion signals during the construction of a global percept in ASC. Based on the neural correlates of decision-making in global motion perception our findings suggest the global motion deficit observed in ASC could reflect a slower or more variable response from the primary motion area of the brain or longer accumulation of evidence towards a decision-bound in parietal areas.
Studies have reported that a selective deficit in visual motion processing is present in certain developmental disorders, including Williams syndrome and autism. More recent evidence suggests a visual motion impairment is also present in adults with fragile X syndrome (FXS), the most common form of inherited mental retardation. The goal of the current study was to examine low-level cortical visual processing in infants diagnosed with FXS in order to explore the developmental origin of this putative deficit. We measured contrast detection of first-order (luminance-defined) and second-order (contrast-defined) gratings at two levels of temporal frequency, 0 Hz (static) and 4 Hz (moving). Results indicate that infants with FXS display significantly higher detection thresholds only for the second-order, moving stimuli compared to mental age-matched typically-developing controls.
fragile X syndrome; contrast detection; second-order; motion; threshold; forced-choice preferential looking
The magnocellular (M) pathway hypothesis proposes that impaired visual motion perception observed in individuals with Autism Spectrum Disorders (ASD) might be mediated by atypical functioning of the subcortical M pathway, as this pathway provides the bulk of visual input to cortical motion detectors. To test this hypothesis, we measured luminance and chromatic contrast sensitivity, thought to tap M and Parvocellular (P) pathway processing respectively. We also tested the hypothesis that motion processing is impaired in ASD using a novel paradigm that measures motion processing while controlling for detectabilty. Specifically, this paradigm compares contrast sensitivity for detection of a moving grating with contrast sensitivity for direction-of-motion discrimination of that same moving grating. Contrast sensitivities from adolescents with ASD were compared to typically-developing adolescents, and also unaffected siblings of individuals with ASD (SIBS). The results revealed significant group differences on P, but not M, pathway processing, with SIBS showing higher chromatic contrast sensitivity than both participants with ASD and TD participants. This atypicality, unique to SIBS, suggests the possible existence of a protective factor in these individuals against developing ASD. The results also revealed impairments in motion perception in both participants with ASD and SIBS, which may be an endophenotype of ASD. This impairment may be driven by impairments in motion detectors and/or by reduced input from neural areas that project to motion detectors, the latter possibility being consistent with the notion of reduced connectivity between neural areas in ASD.
Autism endophenotype; Motion perception; Magnocellular; Parvocellular; Visual psychophysics
Schizophrenia subjects’ smooth pursuit abnormalities may reflect a problem with perception of motion, although evidence comes primarily from reports using stimuli that differ from standard smooth pursuit stimuli (i.e moving gratings or coherent dots). This study presented schizophrenia and healthy subjects with a forced choice speed discrimination paradigm using smooth pursuit-like stimuli. The schizophrenia subject’s motion processing was impaired, as evidenced by their significantly higher speed discrimination thresholds (a difference that was 1.7 larger for the patient group). Abnormalities of motion perception in schizophrenia, even for simple stimuli, suggest a problem with motion processing in area MT.
schizophrenia; motion perception; motion discrimination; smooth pursuit; MT
Recent findings of vestibular responses in visual cortex — the dorsal medial superior temporal area (MSTd) — suggest that vestibular signals might contribute to cortical processes mediating self-motion perception. We tested this hypothesis in monkeys trained to perform a fine heading discrimination task based solely on inertial motion cues. Neuronal sensitivity was typically lower than psychophysical sensitivity, and only the most sensitive neurons rivaled behavioral performance. MSTd responses were significantly correlated with perceptual decisions, with correlations being strongest for the most sensitive neurons. These results support a functional link between MSTd and heading perception based on inertial motion cues. These cues are mainly of vestibular origin, since labyrinthectomy produced dramatic elevation of psychophysical thresholds and abolished MSTd responses. This study provides the first evidence that links single-unit activity to spatial perception mediated by vestibular signals, and suggests that the role of MSTd in self-motion perception extends beyond optic flow processing.
monkey; MST; optic flow; heading; visual; vestibular
Typically-developing human infants preferentially attend to biological motion within the first days of life1. This ability is highly conserved across species2,3 and is believed to be critical for filial attachment and for detection of predators4. The neural underpinnings of biological motion perception are overlapping with brain regions involved in perception of basic social signals such as facial expression and gaze direction5, and preferential attention to biological motion is seen as a precursor to the capacity for attributing intentions to others6. However, in a serendipitous observation7, we recently found that an infant with autism failed to recognize point-light displays of biological motion but was instead highly sensitive to the presence of a non-social, physical contingency that occurred within the stimuli by chance. This observation raised the hypothesis that perception of biological motion may be altered in children with autism from a very early age, with cascading consequences for both social development and for the lifelong impairments in social interaction that are a hallmark of autism spectrum disorders8. Here we show that two-year-olds with autism fail to orient towards point-light displays of biological motion, and that their viewing behavior when watching these point-light displays can be explained instead as a response to non-social, physical contingencies physical contingencies that are disregarded by control children. This observation has far-reaching implications for understanding the altered neurodevelopmental trajectory of brain specialization in autism9.
Our visual world is dynamic in nature. The ability to encode, mentally represent, and track an object's identity as it moves across time and space is critical for integrating and maintaining a complete and coherent view of the world. Here we investigated dynamic object processing in typically developing (TD) infants and infants with fragile X syndrome (FXS), a single-gene disorder associated with deficits in dorsal stream functioning. We used the violation of expectation method to assess infants’ visual response to expected versus unexpected outcomes following a brief dynamic (dorsal stream) or static (ventral stream) occlusion event. Consistent with previous reports of deficits in dorsal stream-mediated functioning in individuals with this disorder, these results reveal that, compared to mental age-matched TD infants, infants with FXS could maintain the identity of static, but not dynamic, object information during occlusion. These findings are the first to experimentally evaluate visual object processing skills in infants with FXS, and further support the hypothesis of dorsal stream difficulties in infants with this developmental disorder.
object tracking; occlusion; motion; dorsal/ventral visual streams; attention
A tendency to focus on details at the expense of configural information, 'weak coherence', has been proposed as a cognitive style in autism. In the present study we tested whether weak coherence might be the result of executive dysfunction, by testing clinical groups known to show deficits on tests of executive control. Boys with autism spectrum disorders (ASD) were compared with age- and intelligence quotient (IQ)-matched boys with attention-deficit/hyperactivity disorder (ADHD), and typically developing (TD) boys, on a drawing task requiring planning for the inclusion of a new element. Weak coherence was measured through analysis of drawing style. In line with the predictions made, the ASD group was more detail-focused in their drawings than were either ADHD or TD boys. The ASD and ADHD groups both showed planning impairments, which were more severe in the former group. Poor planning did not, however, predict detail-focus, and scores on the two aspects of the task were unrelated in the clinical groups. These findings indicate that weak coherence may indeed be a cognitive style specific to autism and unrelated to cognitive deficits in frontal functions.