CORTICAL REPRESENTATION OF TOUCH: TRANSFER OF PERCEPTION FROM ARTIFICIAL TO NATURAL STIMULATION

Stimulation of the brain can evoke perception of sensory stimuli. In rodents, artificial stimulation of the primary somatosensory cortex (S1) can replace whisker touch during tactile discrimination tasks. Optogenetics allow to apply precisely defined patterns on the known topography of sensory cortices, mimicking natural spatiotemporal patterns evoked by peripheral stimuli.
In this project, we want to characterize how similar optogenetic and peripheral stimulation are, regarding perception, integration into behavior, and underlying neural activity.
We trained mice to discriminate the position of an optogenetic bar rotating on the barrel cortex. Similarly, mice could learn to discriminate the position of a physical bar rotating across the whiskers.
We further interrogated the ability of mice to transfer such perceptual learning when tactile inputs guide motor learning. We implemented a closed-loop brain-machine interface in which mice learned to control the position of a virtual cursor by modulating the activity of primary motor cortex neurons. Mice were guided by an optogenetic feedback, which was a light bar projected on the barrel cortex. When switching to a peripheral bar feedback, mice managed to control the virtual cursor from the first session.
To understand this transfer, we recorded activity in the barrel cortex of anesthetized mice using voltage-sensitive dye imaging. The rotation of a bar across the whiskers evoked a sequence of blobs, whose location moved on the barrels topography in synchrony with the bar.
Together, these results demonstrate that cortical optogenetic stimulation can reproduce several components of activity caused by natural stimulation, inducing reliable tactile perception.