Modality specificity of multisensory integration and decision-making in frontal cortex and superior colliculus
1 RWTH Aachen
2 Forschungszentrum Jülich
The integration of sensory inputs from different senses is a crucial aspect of sensory perception and behavioral decisions. Whether such multisensory integration occurs at specific stages of neural processing remains unclear. Two brain regions, the anterolateral motor cortex (ALM) and the superior colliculus (SC) are important parts of a cortico-subcortical loop that transforms multisensory inputs into behavioral decisions. To study the role of these areas in multisensory integration and decision-making, we trained mice in a multisensory discrimination task, where animals had to integrate visual and tactile information over time to identify the target stimulus side. We then performed simultaneous neural recordings in ALM and SC, using high-density Neuropixels probes, in task-performing animals. We found robust visual and tactile responses in both ALM and SC, with a clear separation of modalities between superficial and deep SC layers (dSC). Aside from sensory responses and correlated movements, both ALM and dSC showed strong choice-predictive activity during the stimulus and subsequent delay period. Optogenetic inactivation of both ALM and dSC also strongly reduced animals’ choice performance, confirming their respective importance for multisensory decision-making. Interestingly, visual and tactile choices were differently encoded in ALM, with no clear relation between visual and tactile choice neurons. Moreover, neurons encoding multisensory choices were distinct from unisensory choice neurons. In contrast, dSC neurons encoded choice signals independently of the sensory modality. This suggests a hierarchical transformation of multisensory information into modality-specific decisions by ALM that are transmitted to the dSC to create unified behaviors.