Dynamic Reorganization of striatal circuits during the acquisition and consolidation of a skill

• Authors: Yin, Mulcare, Hilario, Clouse, Holloway, Davis, Hansson, Movinger, Costa
• Summary: 
• Region- and pathway specific plasticity sculpts the circuits involved in the performance of the skill as it becomes automatized.
• Background: 
• Dorsomedial (associative; caudate in primates) striatum (DMS) receives input primarily from association cortices such as the prefrontal cortex (PFC). The dorsolateral (sensorimotor; putamen in primates) striatum (DLS) receives input from sensorimotor cortices is critical for the more gradual acquisition of habitual and automatic behavior.
• CPC: 
• What role does the cerebellum play, if any, in the process of "transferring" newly learned skills to some sort of storage? Is it too general to say that DMS is involved in learning causal relationships, whereas DLS is involved in automatic association of these causes and effects?
• Question(s): 
• Can changes in striatal neural activity observed during skill learning be mediated by synaptic plasticity or excitability chagnes in medium spiny projections neurons in the dorsal striatum using an ex vivo (a slice preparation) approach.
• Result(s): 
• "... task-related activity in these striatal regions differed during the acquisition and consolidation of a new skill, with the DMS being engaged during the early phase and the DLS being engaged during the late phase."
• "[in the ex vivo preparation, ] [l]earning was accompanied by long-lasting changes in glutamatergic transmission."
• "These changes evolved dynamically during the different phases of skill learning;
• "Changes in the DMS were predominant early in training, whereas changes in the DLS emerged only after extensive training."
• "Long-lasting changes in the DLS after extensive training were pathway specific and occurred predominantly in DA receptor 2 (D2)-expressing striatopalidal medium spiny neurons."
• Conclusion(s):
• "..., the performance of the skill after extended training became less dependent on the activation of D1-type DA receptors, which are mainly expressed in striatonigral neurons."
• Method(s):
• DMS/DLS Involvement in Early and Late Skill Learning
• Quantified the modulation of activity using the following equation
• In the DMS the rate modulation increased during the early phase of training but returned to naive levels with further training
• In the DLS, the modulation of firing rate increased gradually with training.
• Accompanied by a decrease in baseline firing rate during the intertrial period.
• The authors interpret this as an increase in signal-to-noise ratio after extended training.
• Next question:
• Are the region-specific changes observed in vivo driven by glutamatergic synaptic plasticity or excitability changes in the striatum by training the mice for either 1 day or 8 days on an accelerating rotarod?
• This was followed up by examining ex vivo the changes in DMS and DLS related to the different phases of skill learning.