Perception of Shapes Targeting Local and Global Processes in Autism Spectrum Disorders

Grinter, E. J., Maybery, M. T., Pellicano, E., Badcock, J. C., & Badcock, D. R. (2010). Perception of shapes targeting local and global processes in autism spectrum disorders. Journal of Child Psychology & Psychiatry, 51(6), 717-724. doi:10.1111/j.1469-7610.2009.02203.x

I chose this article due to our extensive discussion in class of dorsal and ventral visual streams from Chapter 9 in the textbook and my interest in Autism Spectrum Disorders (ASDs).  Research shows that ASDs are characterized by difficulties in complex information processing, with ASDs being associated with higher thresholds on global dorsal stream processing and with evidence of intact local dorsal stream processing that requires identifying the direction or presence of motion.  The purpose of this study was to examine both local and global visual functioning in the ventral stream by using shapes to minimize the differences between local and global.  Radial frequency patterns (RF) are closed contour shape stimuli that vary the radius of a circle by polar angles in order to create deformity.  High frequency RF patterns can discriminate a whole shape from a circle and are achieved by locally oriented cells in the primary visual cortex (V1).  The researchers used RF3 patterns to assess the global ventral stream processing and RF24 patterns to assess the local ventral stream processing.  Their hypothesis was that ASDs would show higher thresholds on a RF3 task due to poor global processing in the ventral stream.  Thirty-eight high-functioning children ages 8 to 16 were recruited with those having an ASD being recruited through an autism register.  The RF patterns were displayed on a touch screen computer where the child had to choose if the shape, which was either a circle or a RF3/RF24 pattern, looked like a squashed egg or had bumps on it.  Results showed that the researchers’ hypothesis was correct in that the RF3 pattern had a higher threshold in ASDs compared to children without ASDs.  However, there were no significant differences found between the circle and the RF24 pattern.  These results indicate that individuals with ASDs experience problems in global processing within the ventral visual stream, which means that ASDs are associated with difficulty in recognizing the orientation, size, color, and texture of objects.  This study was important in that it may have sparked a discussion among psychologists to begin to use RF patterns as a tool for examining visual function in ASDs.