Visually guided saccades
ASD subjects and healthy controls did not differ in the latency of visually guided saccades [F(1, 31)=1.22, p=0.29; see ]. Latencies were shorter in the gap than the overlap condition [F(1, 31)=244.60, p<0.001] but there was no group difference in gap and overlap trials [F(1, 31)=0.37, p=0.55].
Performance of autism spectrum disorder (ASD) and healthy subjects on visually guided saccade and antisaccade tasks
ASD subjects made more prosaccade errors than healthy individuals on the ANTI task [F(1, 30)=4.12, p=0.05]. For both groups, a greater number of prosaccade errors occurred on gap than overlap trials [F(1, 30)=11.42, p<0.01] and on trials with smaller target displacement [F(1, 30)=9.66, p=0.001]. No differential effect of gap versus overlap trials was observed between groups [F(1, 30)=0.49, p=0.49], but an interaction between location and group was observed as ASD subjects had disproportionately increased error rates on trials where targets were presented closer to central fixation [F(2, 29)=7.65, p=0.01; ]. Differences between groups in error rates were significant [t(30)=2.54, p=0.03] at 10° of visual angle and approached significance at 20° of visual angle [t(30)=1.77, p=0.08]. Increased age was associated with fewer prosaccade errors (r=−0.45, p<0.001), but no age by group interactions were observed [F(2, 29)=0.73, p=0.49].
Fig. 1 Mean rate of prosaccade errors for autism spectrum disorder (ASD, ●) and healthy participants (○) across various target step amplitudes from center fixation in degrees of visual angle on an antisaccade task. ASD participants made more (more ...)
There were no group differences in response latencies for correctly performed ANTI trials [F(1, 31)=0.01, p=0.94]. Shorter latencies for gap relative to overlap trials were observed across groups [F(1, 31)=13.67, p=0.001] but the interaction of group and condition for latency data was not significant [F(1, 31)=0.20, p=0.66]. To examine whether participants adjusted their response timing following antisaccade errors, response latencies for correct responses following antisaccade errors were compared with response latencies for correct responses following a correct response. Overall, participants did not adjust their response rates following antisaccade errors [F(1, 28)=0.28, p=0.60; see ]. The group by trial type (post-error versus post-correct) latency interaction was not significant [F(1, 28)=0.02, p=0.89].
Relationship between ANTI performance and repetitive behaviors ()
Prosaccade errors were related to higher-order repetitive behaviors both before (r=0.65, p=0.01) and after controlling for age (partial r=0.73, p=0.004). Prosaccade errors were not associated with sensorimotor repetitive behaviors (r=0.11, p=0.62; partial r=0.08, p=0.79). The relationship between prosaccade errors on the ANTI task and social and communication scores from the ADI-R were not significant (r's <0.2). The relationship between ADI-R ratings of repetitive behaviors and age was not significant (r=0.04, p= 0.86).
Fig. 2 Relationship between prosaccade error rates and scores on algorithm items C1 and C2 on the restricted, repetitive behavior domain of the Autism Diagnostic Inventory – Revised (ADI-R) for autism spectrum disorder (ASD) participants. This relationship (more ...)