Multisensory Integration in Pyramidal Cell Dendrites in Parietal Cortex of Awake Behaving Mice
1 RWTH Aachen University
2 Forschungszentrum Jülich
Sensory perception arises in the cortex by integrating external information from the environment. These information arise from different modalities like vision, hearing, touch and smell. The principles by which our brain processes and integrates this multisensory information are still poorly understood. To study how visual and tactile signals are integrated in the brain, we have developed a multisensory evidence accumulation task in head-fixed mice. We found that mice display a higher performance in the multisensory condition compared to unisensory trials. To investigate the neural basis of this effect we used two-photon calcium imaging (2P) in the primary visual cortex (V1) and rostrolateral visual area (RL) in awake behaving mice. Here, we found that multisensory stimuli evoked higher neuronal activity compared to unisensory stimuli. This effect might be due to local network effects or supralinear integration within neuronal dendrites. To study multisensory integration and the changes occurring over the course of learning of the task, 2P imaging was used at dendritic and somatic sites of layer 2/3 pyramidal neurons in V1 and RL. Preliminary results showed that dendrites respond to both modalities expressing reliable Ca2+ signals. Comparing somatic to dendritic activation during multisensory trials revealed a higher activity at the dendritic site. All in all, the results indicated that the improvement in task performance during multisensory stimulation might result from an increase in neuronal activation. This effect is suggested by superadditive multisensory integration. These findings outline specific mechanism by which unisensory and multisensory information is integrated in the brain to guide decision making.