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Introduction Studies have shown considerable evidence of visual dysfunction in Autism Spectrum Disorders (ASD). Motion perception research in ASD reports a superior performance in processing motion information of fine details and neglects global information. However, there are many variabilities in these experimental results, particularly in adults with autism. Several theories have been put forward as the underlying cause(s) of motion deficits in autism. These include: enhanced local domain information processing at early visual area V1; abnormal processing at the higher visual cortical area MST including V5/MT; and/or abnormal functional and structural connectivity between and within cortical networks that are recruited during different motion processing tasks. In this study, we used multiple motion perception tasks in order to activate different visual neural networks that may contribute to perception of specific motion domains in order to understand visual perception abnormalities in autism. The specific aims of each experiment included in this thesis are as follow: - Chapter 3: To investigate the theory of enhanced local details and neglected global picture, using- for the first time- local/global motion coherence stimuli in autism. - Chapter 4: To investigate the neural response biased found in autism in response to radial optic flow. We used optic flow stimuli in self-heading direction discrimination tasks. - Chapter 5: To investigate whether speed parameter is normal in autism-based on the previous outcome- using drifting grating stimuli in a speed discrimination task. Participants and Methods This study recruited two groups of subjects -one with ASD (n = 14), and another with Typical Development (TD) (n= 14), age range (16- 40 years). - Chapter 3 : We used Random Dot Kinatogram (RDK) as global coherence stimuli and employed it in two tasks : (1) Coherent Motion (CM) task, where coherence levels were varied and the subjects had to detect the global direction of the coherent dots, (2) CM with Form From Motion (FfM) stimulus where the FfM consisted of one of four different shapes embedded in the global RDK task. - Chapter 4: We used RDK with optic flow stimuli, which investigated self-direction discrimination in two tasks: angle of eccentricity, and contrast sensitivity. In both tasks we randomized the dot density (15, 80 dots) and speed (4, 10 deg/sec) of the moving stimulus dots. - Chapter 5: We used a pair of drifting gratings with a spatial frequency 2 cycle/ degree, oriented vertically and drifting perpendicular to the direction of orientation, and varied the speed (2, 6 deg/ sec) and the stimuli presentation (250 - 500ms) Results - Chapter 3: Although adults with autism showed comparable performance in reporting global direction similar to the control group, their ability to process global properties, when FfM shape was embedded, declined ( Mean threshold ASD: MC= 13.58, CM-FfM= 30.65) In addition, ASD required more time to respond to global coherence even when their performance was comparable to that of the control group. - Chapter 4: No significant group differences were found for low dot density (15 dots), while high dot (80 dots) density showed low sensitivity to OF motion in the ASD group compared to the TD. Contrast sensitivity task, however, showed lower sensitivity in the ASD group for detecting OF motion when dot density was low (15 dots) and no differences at higher dot density (80 dots) was found. Both tasks showed no group differences in the dot speed changing and no significant differences in response time were observed. - Chapter 5: No group differences (p = 0.226) in sensitivity to speed-discrimination task were found between the ASD and control group in all parameters used in this experiment. The response times were also comparable between both groups (p = 0.855). Conclusions - Chapter 3: Motion perception in ASD found enhanced to local details particularly when motion stimuli involve both local/global information segregation at the same time. We suggest increased internal neural noise and worse external noise filtering as cause of poor global performance in this type of task. - Chapter 4: There were selective impairments in OF processing that may related to altered neural connectivity between the activated visual areas in ASD. Another suggestion might be related to long neural trajectory within higher visual areas, ex. MST. - Chapter 5: Normal motion processing may be found in ASD, however, it this might triggered by task complexity and the visual neural areas that are involved in processing motion information. The overall results suggest selective impairments in visual motion perception in ASD. These impairments would depend upon the task requirements and therefore on the activated visual networks that contribute to different aspects of motion information processing. The present studies provide novel findings in defining deficits in motion perception in autism, which thereby may contribute in understanding disturbed visual function in ASD.
The human body has long been a rich source of inspiration for the arts, and artists have long recognized the body's special status. While the scientific study of body perception also has an important history, recent technological advances have triggered an explosion of research on the visual perception of the human body in motion, or as it is traditionally called, biological motion perception. Now reaching a point of burgeoning inter-disciplinary focus, biological motion perception research is poised to transform our understanding of person construal. Indeed, several factors highlight a privileged role for the human body as one of the most critical classes of stimuli affecting social perception. Human bodies in motion, for example, are among the most frequent moving stimulus in our environment. They can be readily perceived at a physical distance or visual vantage that precludes face perception. Moreover, body motion conveys meaningful psychological information such as social categories, emotion state, intentions, and underlying dispositions. Thus, body perception appears to serve as a first-pass filter for a vast array of social judgments from the routine (e.g., perceived friendliness in interactions) to the grave (e.g., perceived threat by law enforcement). This book provides an exciting integration of theory and findings that clarify how the human body is perceived by observers.
Vision scientists have historically motivated their studies of the perception of human movement by asserting that successful social behavior depends upon it. But does it? Five psychophysical studies were performed to address this question. To the extent that social capabilities are related to visual sensitivity to human motion, observers with deficits in social function should show selective decrements in their visual sensitivity to human movement. Autism Spectrum Disorder (ASD) is characterized by impairments in social function and autistic traits extend into the general population. Thus, the magnitude of observers' autistic traits can serve as a measure of their social skills. The experiments reported here utilized a point-light target detection task in which observers reported whether a display contained coherent human, animal, or object movement. Overall, typical observers were consistently most sensitive to the presence of coherent human movement. In Experiments 1-3, both typically developing children and typically developed adults exhibited this pattern of performance. In contrast, observers with ASD and typical observers with increased autistic traits demonstrated equivalent sensitivity to human and object motion. Experiment 4 examined the specificity of this effect by testing relative sensitivity to animal motion. The results of this study indicated that typical adult observers were better able to detect the presence of coherent human motion relative to animal or object motion. Furthermore, autistic traits only correlated with detection of human motion. Experiment 5 tested whether a previously documented perceptual effect; namely, enhanced sensitivity to angry human motion, was related to social abilities. The results of this study indicated that enhanced detection of potentially threatening, angry, human movement decreased as the magnitude of an observer's autistic traits increased. Overall, the results of these studies support a tight coupling of laboratory studies of visual sensitivity to the presence of coherent human movement and social behavior outside of the laboratory. Furthermore, these studies illustrate the promise of measuring autistic traits along a continuum of typical and atypical observers to study social behavior and its relation to performance on psychophysical tasks.
In everyday experience, visual motion is an extremely important source of information about the world. Motion cues are vital to our perception of where objects are and where they are moving. Biological motion cues give us the information from which to build the fine-grained, almost subconscious understanding of another's emotions and intentions that is so often necessary in social interactions.
Autism Spectrum Disorder (ASD) is currently diagnosed based on a series of behavioral tests. The challenge for researchers is to try to uncover the biological basis for these typical behaviors in order to improve diagnosis and identify potential targets for treatment. A multidisciplinary approach is necessary in order to move forward. This includes analysis of the current animal models for ASD and their suitability, reviewing immunological, immunogenetic and epigenetic research, reassessing clinical diagnostic tools, and surveying radiological, pathological, and serological records for clues. This volume includes research from some of the leading researchers on ASD. We are hopeful that it will stimulate further dialogue and research in this challenging field.
Information about the symptoms, treatment, and research on Autism spectrum disorders including Autism and Asperger syndrome.
The Cambridge Handbook of Applied Perception Research covers core areas of research in perception with an emphasis on its application to real-world environments. Topics include multisensory processing of information, time perception, sustained attention, and signal detection, as well as pedagogical issues surrounding the training of applied perception researchers. In addition to familiar topics, such as perceptual learning, the Handbook focuses on emerging areas of importance, such as human-robot coordination, haptic interfaces, and issues facing societies in the twenty-first century (such as terrorism and threat detection, medical errors, and the broader implications of automation). Organized into sections representing major areas of theoretical and practical importance for the application of perception psychology to human performance and the design and operation of human-technology interdependence, it also addresses the challenges to basic research, including the problem of quantifying information, defining cognitive resources, and theoretical advances in the nature of attention and perceptual processes.
Rich in examples and applications to everyday life, Sensation and Perception, Third Edition is a cutting edge and highly readable account of modern sensation and perception from both a cognitive and neurocognitive perspective.
"A growing number of studies suggest atypical visual processing in autism spectrum disorder (ASD). Given that human behavior heavily relies on visual information, impairments in visual processing may have cascading effects on many other brain functions. Recent proposals in ASD, both domain-specific and -general, hypothesize different mechanisms that may impact visual abilities in this population. However, empirical support for such accounts has been lacking, and it is unclear whether and how these mechanisms can influence visual perception in ASD. The series of studies in this dissertation examine atypical visual processing mechanisms in ASD under three frameworks: larger receptive field size, elevated internal noise, and impaired prediction abilities. We examine each of these hypotheses in children and adolescents with ASD, using a combination of psychophysics, computational modeling, and eye-tracking. In Chapter 2, we tested the integrity of receptive field size using a visual motion discrimination task. The results showed that individuals with ASD have impaired motion sensitivity at smaller stimulus size, which was best explained by the larger receptive field size account. In Chapter 3, we investigated whether internal noise is elevated in ASD, and found evidence that supports this account. Importantly, we found that higher internal noise was associated with more severe behavioral symptoms of ASD. Lastly, in Chapter 4, we examined the prediction abilities in ASD in the context of visual motion extrapolation. The results demonstrate impaired motion prediction in ASD, which was also accompanied by their atypical eye-movement patterns during the task. Taken together, these studies reveal deficits in visual processing in ASD across a wide range of processing stages. The findings not only provide empirical support for existing proposals of ASD, but also shed lights on the specific mechanisms associated with atypical visual abilities in this population."--Pages viii-ix.