Eye movements, visual attention, and autism: A saccadic reaction time study using the gap and overlap paradigm

Background: On the basis of the literature on autism, it was hypothesized t hat children with autism have deficits in attentional (dis-)engagement mech anisms. Methods: A saccadic gap- overlap task was used to study visual engagement a nd disengagement in 16 high-functioning autistic children of about 10 years of age and 15 age- and IQ-matched normal control children. Subjects were a sked to make saccadic eye movements from a fixation point to a suddenly app earing target as fast as possible. The saccadic reaction time was compared in two conditions: 1) the overlap condition, in which the fixation point wa s continuously visible, and 2) the gap condition, in which the fixation poi nt was turned off 200 msec before the target appeared. Results: Although no differences between the groups in either condition was observed, the gap effect (i.e., the difference in saccadic reaction time b etween the overlap condition and the gap condition) was smaller in the auti stic group than in the control group. Conclusions: We concluded that autistic children show a lower level of atte ntional engagement. (C) 2001 Society of Biological Psychiatry.