Sit, T. P. | Search bioRxiv

bioRxiv2021

Behavioral origin of sound-evoked activity in visual cortex

Sensory cortices can be affected by stimuli of multiple modalities and are thus increasingly thought to be multisensory. For instance, primary visual cortex (V1) is influenced not only by images but also by sounds. Here we show that the activity evoked by sounds in V1 is highly stereotyped across neurons and even across mice. It resembles activity measured elsewhere in the brain and is independent of projections from auditory cortex. Its low-dimensional nature starkly contrasts the high dimensional code that V1 uses to represent images. Furthermore, this sound-evoked activity can be precisely predicted by small body movements that are elicited by each sound and are highly stereotyped across trials and across mice. Thus, neural activity that is apparently multisensory may simply arise from low-dimensional signals associated with changes in internal state and behavior.

neuroscience↗

bioRxiv2021

The role of frontal cortex in multisensory decisions

To make accurate perceptual decisions, the brain often combines information across sensory modalities. For instance, localizing objects by integrating their image and sound. However, the cortical substrates underlying this audiovisual integration remain uncertain. Here, we show that mouse frontal cortex combines auditory and visual evidence; that this combination is additive, mirroring behavior; and that it evolves with learning. Scanning optogenetic inactivation demonstrated that inactivating frontal cortex impaired choices based on either sensory modality. Recordings from >10,000 neurons indicated that after task learning, activity in frontal area MOs (secondary motor cortex) encodes an additive combination of visual and auditory signals, consistent with the mices behavioral strategy. An accumulator model applied to these sensory representations reproduced both the observed choices and reaction times. These results indicate that frontal cortex adapts through learning to combine evidence across sensory cortices, providing a signal that is transformed into a binary decision by a downstream accumulator.

neuroscience↗