Multisensory-Guided Associative Learning Enhances Multisensory Representation in Primary Auditory Cortex

Sensory cortices, classically considered to represent modality-specific sensory information, are also found to engage in multisensory processing. However, how sensory processing in sensory cortices is cross-modally modulated remains an open question. Specifically, we understand little of cross-modal representation in sensory cortices in perceptual tasks and how perceptual learning modifies this process. Here, we recorded neural responses in primary auditory cortex (A1) both while freely moving rats discriminated stimuli in Go/No-Go tasks and when anesthetized. Our data show that cross-modal representation in auditory cortices varies with task contexts. In the task of an audiovisual cue being the target associating with water reward, a significantly higher proportion of auditory neurons showed a visually evoked response. The vast majority of auditory neurons, if processing auditory-visual interactions, exhibit significant multisensory enhancement. However, when the rats performed tasks with unisensory cues being the target, cross-modal inhibition, rather than enhancement, predominated. In addition, multisensory associational learning appeared to leave a trace of plastic change in A1, as a larger proportion of A1 neurons showed multisensory enhancement in anesthesia. These findings indicate that multisensory processing in principle sensory cortices is not static, and having cross-modal interaction in the task requirement can substantially enhance multisensory processing in sensory cortices.