Figure 3. Potential role of experience and Arc dependent priming of LTD in refinement of neural ensembles with repeated experience or training.

Cao et al, [5] demonstrated that repeated training on a motor task resulted in a sparse neural ensemble of highly active neurons. Motor cortical neurons in M2 induce Arc on day 1 of training (“1”), as imaged with a GFP transcriptional reporter in vivo which may prime these neurons for synaptic plasticity during repeated training days. Neurons with initially weak levels of Arc promoter activity may be primed for LTD which may cause them to be inactive “0” or “dismissed” on subsequent days of training. Neurons with stronger levels of Arc promotor activity on Day 1 may be more likely to undergo LTP and to “retain” their strong neuronal activity during subsequent days of training. (Figure is modified from [5]).