Representational drift influences learning of a sensory cortical microstimulation task

Abstract

Primary sensory cortex is a key locus of plasticity during learning. Exposure to novel stimuli often alters cortical activity, but isolating cortex-specific dynamics is challenging due to extensive pre-cortical processing. Here, we employ optical microstimulation of pyramidal neurons in layer (L) 2/3 of mouse primary vibrissal somatosensory cortex (vS1) to study cortical dynamics as mice learn to discriminate microstimulation intensity. Tracking activity over weeks using two-photon calcium imaging, we observe a rapid sparsification of the photoresponsive population, with the most responsive neurons exhibiting the largest declines in responsiveness. Following sparsification, the photoresponsive population attains a stable rate of neuronal turnover. At the same time, the photoresponsive population increasingly overlaps with populations encoding whisker movement and touch. Finally, we find that mice with larger declines in responsiveness learn the task more slowly than mice with smaller declines. Our results reveal that microstimulation-evoked cortical activity undergoes extensive reorganization during task learning and that the dynamics of this reorganization impact perception.

Microstimulation of sensory cortex engages natural sensory representations

“…Cortical plasticity is often dependent on task engagement: in auditory cortex, enhanced sensitivity to a repeatedly presented tone depends on reward and hence engagement (Kuchibhotla et al, 2017; Weinberger, 2004). In a separate study using a similar paradigm to the one presented here in which mice were trained to discriminate the number of optogenetic pulses delivered to vS1 for a water reward (Pancholi et al, 2022), overall responsiveness declined following training, analogous to our dual-stimulus induction mice but unlike the photostimulus-only induction mice. If photostimulation in a rewarded context is sufficient to drive enhanced overlap, it would suggest an even easier strategy for generating elevated overlap, an approach that could benefit the design of somatosensory feedback prostheses.…”