Two distinct layer-specific dynamics of cortical ensembles during learning of a motor task

Abstract

The primary motor cortex (M1) possesses two intermediate layers upstream of the motor-output layer: layer 2/3 (L2/3) and layer 5a (L5a). Although repetitive training often improves motor performance and movement coding by M1 neuronal ensembles, it is unclear how neuronal activities in L2/3 and L5a are reorganized during motor task learning. We conducted two-photon calcium imaging in mouse M1 during 14 training sessions of a self-initiated lever-pull task. In L2/3, the accuracy of neuronal ensemble prediction of lever trajectory remained unchanged globally, with a subset of individual neurons retaining high prediction accuracy throughout the training period. However, in L5a, the ensemble prediction accuracy steadily improved, and one-third of neurons, including subcortical projection neurons, evolved to contribute substantially to ensemble prediction in the late stage of learning. The L2/3 network may represent coordination of signals from other areas throughout learning, whereas L5a may participate in the evolving network representing well-learned movements.

Reward-timing-dependent bidirectional modulation of cortical microcircuits during optical single-neuron operant conditioning

“…To introduce physical operant conditioning before 2pSNOC, head-restrained mice were trained to perform a self-initiated lever-pull task using the right forelimb 13,16,19 . A 4-ml water drop was provided as a reward when the lever was pulled for 0.4 s after being left in the wait position for 43 s (Fig.…”

“…1d). Most reconstructed neurons were assumed to be excitatory neurons because GCaMP expression was under the control of synapsin I promoter, which considerably limits the expression to excitatory neurons 16,24 . One neuron was targeted in the conditioning period.…”

“…The changes in the activity of SR and AR neurons were not due to changes in licking or lever-pull behaviours that might be related to reward prediction. The counterbalance of microcircuit activity may play a role in maintaining a constant overall level of network activity for homeostasis 14,16,29 . Our results suggest that RTBM is possibly one of many processes that underlie rapid reorganization of the L2/3 cortical microcircuit during fast adaptation to environmental changes, which occurs during brain-machine and brain-computer interface learning, motor adaptation and skill learning.…”

“…Two-photon calcium imaging of cortical neurons has been used to identify multineuronal activity within a motor cortical microcircuit in rodents [12][13][14][15][16] . In contrast to SNOC in the primate, SNOC in the rodent 11,17 has not been performed with identification of the relations of individual neurons to physical movement.…”

In vivo two-photon imaging of mouse hippocampal neurons in dentate gyrus using a light source based on a high-peak power gain-switched laser diode

“…Techniques capable of revealing the function and behavior of individual neurons in living tissues have the potential to provide a great deal of information about brain functions [1][2][3]. Recent advances have enabled non-invasive high-definition visualization of neural circuits in the living mouse brain using two-photon fluorescence microscopy [4][5][6][7][8][9].…”