These results demonstrate that the age-dependent cognitive decline of (Thy1)-h[A30P]αSYN transgenic mice is correlated with a parallel impairment in amygdala and hippocampus synaptic plasticity in vivo, as seen by immunohistological analysis of the immediate-early gene product c-Fos and the neuronal activity responsive kinase Plk2. This evidence concerns the gene FOS and Mental deterioration.