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Activity of striatal neurons reflects dynamic encoding and recoding of procedural memories


Learning to perform a behavioural procedure as a well-ingrained habit requires extensive repetition of the behavioural sequence, and learning not to perform such behaviours is notoriously difficult. Yet regaining a habit can occur quickly, with even one or a few exposures to cues previously triggering the behaviour1,2,3. To identify neural mechanisms that might underlie such learning dynamics, we made long-term recordings from multiple neurons in the sensorimotor striatum, a basal ganglia structure implicated in habit formation4,5,6,7,8, in rats successively trained on a reward-based procedural task, given extinction training and then given reacquisition training. The spike activity of striatal output neurons, nodal points in cortico-basal ganglia circuits, changed markedly across multiple dimensions during each of these phases of learning. First, new patterns of task-related ensemble firing successively formed, reversed and then re-emerged. Second, task-irrelevant firing was suppressed, then rebounded, and then was suppressed again. These changing spike activity patterns were highly correlated with changes in behavioural performance. We propose that these changes in task representation in cortico-basal ganglia circuits represent neural equivalents of the explore–exploit behaviour characteristic of habit learning.

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We thank H. F. Hall, P. A. Harlan and C. Thorn for their help. This work was funded by the National Institutes of Health and the Office of Naval Research.

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Correspondence to Ann M. Graybiel.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Methods

Includes references for Supplementary Figure Legends, Supplementary Table 1, (Summary of training schedules and recording yield for the seven rats included in the study) and Supplementary Table 2 (Training sessions included in each learning stage). (DOC 185 kb)

Supplementary Figure 1

Recording sites and unit classification methods. (PDF 1021 kb)

Supplementary Figure 2

Averaged per-neuron spike frequency plots constructed as in Fig. 2. (PDF 2384 kb)

Supplementary Figure 3

Population firing patterns of striatal neurons of the projection neuron class exhibiting task-related activity near the start of the trial runs and those exhibiting task-related activity near the end of the runs. (PDF 854 kb)

Supplementary Figure 4

Extinction-induced reversal of reconfigured striatal activity is not due to increase in running times during extinction. (PDF 1146 kb)

Supplementary Figure 5

Partial and full extinction training procedures yielded similar behavioral and neural changes. (PDF 1947 kb)

Supplementary Figure 6

Multiple changes in striatal projection neuron activity during successive acquisition, extinction and reacquisition training. (PDF 759 kb)

Supplementary Figure 7

Prediction of behavioral accuracy by a composite neural score combining normalized per-neuron firing rate, proportion of different task-responsive sub-populations, and per-phasic response spike proportion. (PDF 640 kb)

Supplementary Figure 8

Late development of restructuring of striatal spike patterns in rats that learned the task at slow rates. (PDF 1065 kb)

Supplementary Figure 9

Averaged per-neuron spike frequency plots for trials with correct and incorrect behavioral responses. (PDF 2309 kb)

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Further reading

Figure 1: T-maze task and behavioural learning.
Figure 2: Plasticity in spike activity patterns of striatal projection neurons.
Figure 3: Multiple changes in projection neuron activity in the sensorimotor striatum during acquisition, extinction and reacquisition training.
Figure 4: Striatal neural activity predictive of behavioural performance.


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