Brain Advance Access published online on November 3, 2009
Brain, doi:10.1093/brain/awp272
The psychophysics of visual motion and global form processing in autism
1 Medical Investigation of Neurodevelopmental Disorders (M.I.N.D.) Institute, University of California-Davis, Davis, CA, USA 2 Center for Mind and Brain, University of California-Davis, Davis, CA, USA 3 Department of Psychology, University of California-Davis, Davis, CA, USA
Correspondence to:
Kami Koldewyn, McGovern Institute for Brain Research, 43 Vassar Street, room 46-4141, Cambridge, MA 02139, USA E-mail: kamik{at}mit.edu
Several groups have recently reported that people with autism may suffer from a deficit in visual motion processing and proposed that these deficits may be related to a general dorsal stream dysfunction. In order to test the dorsal stream deficit hypothesis, we investigated coherent and biological motion perception as well as coherent form perception in a group of adolescents with autism and a group of age-matched typically developing controls. If the dorsal stream hypothesis were true, we would expect to document deficits in both coherent and biological motion processing in this group but find no deficit in coherent form perception. Using the method of constant stimuli and standard psychophysical analysis techniques, we measured thresholds for coherent motion, biological motion and coherent form. We found that adolescents with autism showed reduced sensitivity to both coherent and biological motion but performed as well as age-matched controls during coherent form perception. Correlations between intelligence quotient and task performance, however, appear to drive much of the group difference in coherent motion perception. Differences between groups on coherent motion perception did not remain significant when intelligence quotient was controlled for, but group differences in biological motion perception were more robust, remaining significant even when intelligence quotient differences were accounted for. Additionally, aspects of task performance on the biological motion perception task were related to autism symptomatology. These results do not support a general dorsal stream dysfunction in adolescents with autism but provide evidence of a more complex impairment in higher-level dynamic attentional processes.
Key Words: autism; visual motion; biological motion; coherent motion; dorsal stream
Abbreviations: ADHD, Attention-deficit hyperactivity disorder; ADOS, Autism Diagnostic Observation Schedule
Received May 6, 2009. Revised September 4, 2009. Accepted September 11, 2009.