Attention and Explicit Knowledge Drive Predictive Sharpening in Early Visual Cortex.

Perception is increasingly understood as an inferential process in which sensory input is interpreted in light of prior knowledge. Although predictive effects are widely documented in sensory cortices and interact with higher cognitive functions such as attention, predictive processes are generally assumed to unfold implicitly. Consequently, research often overlooks the possibility that participants may possess explicit knowledge of task structures, which they might use to guide their predictive processing. In this study, we investigated how the attentional relevance of predicted stimuli and explicit knowledge of predictive associations interact to shape the sensory encoding of visual stimuli. Using a multisensory fMRI paradigm with concurrent but independent visual and auditory probabilistic associations (75% validity), we manipulated endogenous attention across sensory modalities. Consistent with prior work, expected, relative to unexpected, visual stimuli elicited an overall reduction in BOLD activity. Critically, however, representational sharpening-an enhanced encoding fidelity of neural representations for expected inputs-occurred exclusively when visual inputs were attended and concurrently presented auditory inputs were expected. Furthermore, the magnitude of this visual representational sharpening correlated positively with participants' retained explicit knowledge of the predictive associations. These findings highlight the key roles of attention and explicit knowledge in promoting predictive sharpening and underscore the need to study predictive processing in multisensory contexts.