STATIC ENCODING OF DYNAMIC AUDIOVISUAL INTEGRATION IN MOUSE FRONTAL CORTEX

Decision-making is a highly flexible process, that relies on integrating inputs from various senses and adapting to changing environments. In static settings, mice integrate visual and auditory cues linearly using their prefrontal cortex, which encodes task-related variables. However, it is unclear whether and how this code would flexibly adapt to changing task contingencies, for example when one of the senses becomes irrelevant.
To address this question, we trained mice to indicate the left-or-right position of audiovisual cues — which were presented alone, or simultaneously in the same or opposite locations — by turning a wheel. We alternated between auditory-dominant and visual-dominant blocks, in which mice were rewarded for responding to the location of the auditory or visual cue, respectively. We recorded the activity of the mice’s prefrontal cortex (area MOs) with chronic Neuropixels probes.
We observed that mice adjusted their strategy to respond to a single sensory modality in conflict trials, progressively increasing the weight given to one sensory modality while decreasing the other. These behavioural changes were paralleled with changes in neural activity, with populations of MOs neurons apparently encoding more strongly the relevant stimuli. However, these changes were largely explained by choice-related activity that matched the changes in the mouse’s choices. When this was taken into account, the sensory representations were largely unchanged by task demands.
These results suggest a largely static neural code in prefrontal cortex, where sensory representations are not modulated by the relevance of the sensory input.