Visual Integration of Direction and Orientation Information in Autistic Children

Background: Theoretical accounts propose that autistic visual perception is characterised by a focus on details, and a disinclination or reduced ability to integrate information across parts of the scene in order to perceive the overall whole. In contrast to these theories, we recently demonstrated enhanced integration of visual motion signals in autistic children compared to typically developing children (Manning et al., 2015, J Neurosci, 35(18), 6979-6986).

Objectives: Here, we had two main aims: 1) to investigate the robustness of our finding of increased motion integration within a new sample of autistic and typically developing children, and 2) to determine whether increased integration in autistic children would extend to a static, orientation task.

Methods: We presented motion and orientation equivalent noise and coherence tasks to 46 autistic children aged 6 to 14 years and 45 typically developing children matched in age and non-verbal IQ. The equivalent noise tasks consisted of two interleaved conditions: a high-noise condition in which children judged the average direction or orientation of elements while the external noise (standard deviation of direction or orientations) was manipulated, and a no-noise condition in which children were required to judge the direction or orientation of elements sharing the same direction or orientation. The thresholds from this task were subjected to equivalent noise modelling to yield measures of local internal noise and global sampling. In the coherence tasks, the proportion of signal elements sharing the same direction or orientation amidst otherwise random noise elements was manipulated. We assessed group differences using a combination of frequentist and Bayesian statistical approaches.

Results: When combining data from the motion tasks of the original and replication experiments, autistic children had increased integration of direction information compared to typically developing children in the high-noise condition (indexed by higher maximum tolerable noise values), yet similar no-noise and coherence thresholds as typically developing children. Equivalent noise modelling revealed increased sampling in autistic children for motion information but no conclusive evidence for atypical levels of internal noise. Yet, analysis of the data in the replication sample alone did not provide sufficient evidence either in favour or against the hypothesis of increased integration in autism. There was no evidence of differences between autistic and typically developing children in the orientation equivalent noise and coherence tasks.

Conclusions: Overall, autistic children integrated motion information better than typically developing children. However, the groups overlapped considerably and there was substantial individual variability. Therefore, the effect may not always be detected in small samples due to sampling error. There was no indication of atypical integration of orientation information in the current study, although larger samples will be required in order to provide conclusive evidence. These results help characterise the nature of sensory processing in autism, which is of high import and relevance given the recent inclusion of sensory symptoms in diagnostic criteria. If increased integration is specific to motion information, domain-specific accounts of autistic perception will be required.