Global context rapidly shapes sensory responses in V1.

Context modulates sensory processing in the cerebral cortex by suppressing responses to expected stimuli and enhancing responses to unexpected ones. Recent proposals argue that early sensory areas such as primary visual cortex (V1) are shaped only by local context, including recent stimulus history, whereas modulation by global context, such as learned temporal structure, is present exclusively in higher cortical areas. This view is incompatible with predictive coding theories. To directly dissociate local and global contextual influences, we used a global/local oddball paradigm in which mice viewed five-item sequences. Across conditions, sequence structure was held constant while stimulus identity and predictability were selectively manipulated, allowing the isolation of response modulations due to local deviance, global expectation, and stimulus repetition independently. In the canonical sequence (AAAA-B), B is locally deviant but globally predictable. Using two-photon calcium imaging and LFP recordings in mouse V1, we found that global predictability abolished context modulation: responses to B were equivalent to those evoked by a random sequence control (e.g., CDEAB). This effect emerged rapidly, after only <10 sequence repetitions, demonstrating fast learning of global structure. When the stimulus was globally deviant, either by replacing B with a novel stimulus (AAAA-C) or by presenting B unpredictably in a standard oddball paradigm, V1 exhibited robust response enhancement. These effects required feedback from anterior cingulate area (ACa), establishing a causal role for higher cortical circuits in conveying global predictions to V1. Strikingly, when an additional A replaced B (AAAA-A), responses were strongly suppressed despite global deviance, indicating that stimulus-specific adaptation may constrain the expression of global prediction error signals in early sensory cortex.