Dopamine-behavioral relationships showing changes in DD rate in the left (a) and right (b) GP. A quadratic relationship was found between [11C]-(+)-PHNO Δ%BP and % changes of ln(k) in the bilateral GP (R2=0.74, F2,8=8.17, P<0.01 for left; R2=0.84, F2,8=21.39, P<0.01 for right).