In studies involving V4 of monkeys, tuning properties changed in association with VPL of an orientation discrimination task (Yang & Maunsell 2004). However, no tuning change was observed in V1.In another monkey study (Chowdhury & DeAngelis 2008), inactivation of MT by injection of the gamma-aminobutyric acid agonist muscimol prior to coarse absolute depth discrimination training was shown to impair performance.