Temporal course of gene expression during motor memory formation in primary motor cortex of rats

- Motor learning induces a sequential gene regulation with high time-point specificity.
- A shift from initial suppression is followed by a predominant up-regulation.
- The majority of regulated genes can be linked to learning-related plasticity.
- The temporal profile of gene regulation is slower when compared to hippocampus-dependent learning.

Motor learning is associated with plastic reorganization of neural networks in primary motor cortex (M1) that depends on changes in gene expression. Here, we investigate the temporal profile of these changes during motor memory formation in response to a skilled reaching task in rats. mRNA-levels were measured 1 h, 7 h and 24 h after the end of a training session using microarray technique. To assure learning specificity, trained animals were compared to a control group. In response to motor learning, genes are sequentially regulated with high time-point specificity and a shift from initial suppression to later activation. The majority of regulated genes can be linked to learning-related plasticity. In the gene-expression cascade following motor learning, three different steps can be defined: (1) an initial suppression of genes influencing gene transcription. (2) Expression of genes that support translation of mRNA in defined compartments. (3) Expression of genes that immediately mediates plastic changes. Gene expression peaks after 24 h - this is a much slower time-course when compared to hippocampus-dependent learning, where peaks of gene-expression can be observed 6-12 h after training ended.