Establishing whether or not the modulatory effects of feature-based expectation on sensory responses, unlike those of feature-based attention, are spatially specific may help to shed light on this much debated issue. However, feature-based attention and expectation have been argued to be dissociable 14, and their neural mechanisms may be distinct 3, 15. Of note, feature-based attention has been shown to have spatially non-specific effects, spreading across the visual field 8, 9, 10, 11, 12, affecting even the processing of fully irrelevant peripheral stimuli 13. That is, whether feature-based expectation can affect processing of stimuli at the location in which the stimulus is expected to occur, without affecting processing of stimuli presented elsewhere in the visual field. It is currently unknown whether these regions operate independently, or whether they can synergistically induce top-down modulations in early visual cortex that are both spatially and feature specific 6, 7. This question is particularly interesting given that the higher-order regions in frontal cortex containing spatial and feature information may be largely separate 5. However, it is unclear whether the neural modulation by feature-based expectation (e.g., expecting the colour red) can be spatially specific. Generally, a suppression of activity is observed when expectations are met by congruent input, and an increase in activity is observed when expectations are invalid 1. Independently of each other, both spatial 1, 2 and feature-based 3, 4 expectation have been shown to affect neural processing in early sensory regions. However, expectations about spatial location and stimulus features have mostly been studied in isolation. Such spatially as well as feature specific expectations are ubiquitous in natural perception. This suggests that an expectation violation at one location in the visual world can lead to a spatially non-specific gain increase across the visual field.Īs you hear the sound of the ice cream van approaching around the corner, you have a strong expectation of what you will see next, as well as where you will see it. The neural consequences of this expectation violation, however, spread to cortical locations processing the stimulus in the opposite hemifield. We found an enhanced sensory response for unexpected stimuli, which was elicited only when there was a violation of expectation at the specific location where participants formed a stimulus expectation. Here, we investigated this by inducing expectations of a specific stimulus feature at a specific location, and probing the effects on sensory processing across the visual field using fMRI. Therefore, establishing whether the effects of feature-based expectation are spatially specific may inform this debate. It is still an open question whether the neural mechanisms underlying feature-based expectation differ from those underlying feature-based attention. Interestingly, feature-based attention automatically spreads to unattended locations. However, expectations about spatial location and stimulus features have mostly been studied in isolation, and it is unclear whether feature-based expectation can be spatially specific. These expectations are usually multifaceted – we expect a particular object at a particular location. During natural perception, we often form expectations about upcoming input.
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