When vision listens: auditory predictive processing in primary visual cortex of anesthetized rats

Primary visual cortex (V1), traditionally considered a purely visual area, is increasingly recognized for its role in multisensory processing. According to predictive coding theory, cortical circuits generate expectations about sensory inputs (predictions) and signal deviations from them (prediction errors). To test whether V1 encodes auditory prediction errors, we recorded neuronal activity and LFP from layers IV-VI in urethane-anesthetized rats during auditory oddball and no-repetition control sequences. Recorded neurons from layers V-VI in our sample responded to tones, with many showing stronger responses to deviant than standard stimuli. Deviant responses primarily reflected prediction error rather than repetition suppression and were enhanced under temporally uncertain (random) conditions. Layer V neuronal responses were faster and more phasic, while in layer VI were broader and more sustained. These results reveal that infragranular circuits in V1 encode auditory prediction errors and contextual regularities, positioning V1 as a multimodal inference hub within predictive hierarchy.