Abstract
Predictive coding models propose that predictions (stimulus likelihood) reduce sensory signals as early as primary visual cortex (V1), and that attention (stimulus relevance) can modulate these effects. Indeed, both prediction and attention have been shown to modulate V1 activity, albeit with fMRI, which has low temporal resolution. This leaves it unclear whether these effects reflect a modulation of the first feedforward sweep of visual information processing and/or later, feedback-related activity. In two experiments, we used electroencephalography and orthogonally manipulated spatial predictions and attention to address this issue. Although clear top-down biases were found, as reflected in pre-stimulus alpha-band activity, we found no evidence for top-down effects on the earliest visual cortical processing stage (<80 ms post-stimulus), as indexed by the amplitude of the C1 event-related potential component and multivariate pattern analyses. These findings indicate that initial visual afferent activity may be impenetrable to top-down influences by spatial prediction and attention.
Highlights
Influential predictive coding theories postulate that predictions derived from past experience reduce the magnitude of sensory responses, and that attention can modulate these effects by boosting prediction precision (Rao 2005; Friston 2009)
Predictive coding models propose that predictions reduce sensory signals as early as primary visual cortex (V1), and that attention can modulate these effects
These findings indicate that initial visual afferent activity may be impenetrable to top-down influences by spatial prediction and attention
Summary
Influential predictive coding theories postulate that predictions derived from past experience reduce the magnitude of sensory responses, and that attention can modulate these effects by boosting prediction precision (Rao 2005; Friston 2009). Recent fMRI studies show that predictions based on visual regularities in the environment can modulate neural responses already at the lowest level of the cortical hierarchy, in primary visual cortex (V1) (e.g., Alink et al 2010). These effects have been shown to depend on attention (e.g., Kok, Rahnev et al 2012). Based on theories of predictive processing, one would expect predictions to modulate visual processing as 2262 | Cerebral Cortex, 2019, Vol 29, No 5 early as V1 (Clark 2013). No study so far has shown that predictions can modulate initial visual afferent activity
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