FOS and Huntington disease: The diminished feed-forward inhibition of PV INs to MSNs may well be linked to the increased MSN activity observed in our HD mice at an early pre-symptomatic stage, but was not anymore associated with an increased c-Fos expression in MSNs at later age (4 months), suggesting further alterations of post-synaptic MSNs activity in symptomatic R6/1 mice.