Abstract
Difficulties in global motion processing have been reported in autism and interpreted as reduced integration of local motion signals. However, these findings are largely based on the motion coherence paradigm, which is not a pure measure of integration. Elevated motion coherence thresholds could also arise from imprecision in estimating the direction of individual elements, as predicted by accounts of increased neural noise in autism (Simmons et al., 2009). Here, we investigated whether poor global motion processing in children with autism is attributable to increased internal noise and/or reduced sampling. Children with autism aged 6 to 13 years (n=35) and age- and ability-matched typically developing children (n=35) performed an equivalent noise direction disrimination task and a motion coherence task with either slow- (1.5 deg/sec) or fast-moving (6 deg/sec) random dot patterns. In the equivalent noise task, two conditions were interleaved to estimate (i) the finest direction discrimination possible in the absence of noise, and (ii) the maximum amount of noise that can be tolerated whilst making a coarse direction discrimination (±45°). These thresholds were used to fit an equivalent noise function and derive estimates of internal noise and sampling. In the motion coherence task, we measured the minimum proportion of coherently moving dots required for a coarse (±90°) direction discrimination. Unexpectedly, children with autism had comparable motion coherence thresholds and similar levels of internal noise as typically developing children. Even more surprisingly, children with autism were able to pool more dots when estimating global direction than their typically developing peers. Our findings challenge the widespread assumption that children with autism have difficulties with global motion integration. Previously reported difficulties in motion coherence tasks might instead be due to children with autism having difficulties segregating signal from noise.
Meeting abstract presented at VSS 2014