Expectations about low-level visual features influence late stages of cortical information processing

Abstract

Two factors play an important role in shaping perception: the allocation of selective attention to behaviorally relevant stimulus features, and prior expectations about regularities in the sensory environment. Traditionally, attention is thought to modulate early sensory processing whereas expectation is thought to only affect decision making by biasing choices. However, recent results suggest that expectation can also enhance sensory encoding and increase the rate of evidence accumulation during decision making. To test these accounts, we recorded electroencephalography (EEG) data from human subjects performing a perceptual decision-making task where expectations about stimulus features (i.e., orientation and color) and motor responses were manipulated independently. We also directly manipulated the amount of available sensory evidence to validate a set of neural markers that index sensory processing and evidence accumulation (the early visual negative potential, or VN, and the centro-parietal positive potential, or CPP, respectively). While increasing the amount of sensory evidence enhanced VN amplitude and the slope of the CPP, expectations about sensory features and motor responses did not. On the other hand, violating expectations significantly impacted posterior alpha and frontal theta oscillations, signals thought to track overall processing time and cognitive conflict. Taken together, these data argue against recent theoretical frameworks and suggest that expectations about sensory and motor regularities have little impact on early visual processing and evidence accumulation. Instead, expectations influence decisions primarily by impacting cognitive control processes.

Meeting abstract presented at VSS 2018