Internal noise measures in coarse and fine motion direction discrimination tasks, and the correlation with autism traits

Motion perception is essential for visual guidance of behaviour and is known to be limited by both internal additive noise (arising from random fluctuations in neural activity), and by motion pooling (global integration of local motion signals across space). People with autism spectrum disorder (ASD) display abnormalities in motion processing, which has been linked to both elevated noise and abnormal pooling. However, to date, the impact of a third limit - induced internal noise (internal noise that scales up with increases is external noise) - has not been investigated in motion perception of any group. Here, we describe a new double-pass motion direction discrimination paradigm that quantifies additive noise, induced noise, and motion pooling. We measure the impact of induced noise on direction discrimination, which we ascribe to fluctuations in decision-related variables. We report that internal noise is higher individuals with high ASD traits only on coarse but not fine motion direction discrimination tasks. However, we report no significant correlations between autism traits, and additive noise, induced noise or motion pooling, in either task. We conclude that internal noise may be higher in individuals with many ASD traits, and that the assessment of induced internal noise is a useful way of exploring decision-related limits on motion perception, irrespective of ASD traits.