PPP1R1B and Brain atrophy: R6/2 mice recapitulate several of the neuroanatomical and neurochemical hallmarks observed in HD patients, including robust brain atrophy, a decrease in striatal N-acetyl aspartate (NAA) levels (a marker for neuronal health), a reduced expression of medium spiny neuron marker Ppp1r1b (also known as Darpp-32) and an increase of glial marker myo-inositol [17–19].