“…One important cognitive behavior that is adversely affected by PD, HD and some of the psychiatric conditions is cognitive flexibility—the ability to disengage from previously learned behavior and adopt a new behavioral response (Lawrence et al, 1999, Buckner, 2004, Lima et al, 2008). Additional experimental support for an involvement of the striatum in mediating cognitive flexibility is provided by animal studies using either MSN lesions, transient pharmacological blockade of MSN activity, or inactivation of dopaminergic and cholinergic signaling in the striatum (Ragozzino et al, 2002, Floresco et al, 2006, Braun and Hauber, 2011, Darvas and Palmiter, 2011, Wang et al, 2013, Darvas et al, 2014). While it has been shown that acute pharmacological blockade of NMDA glutamate receptors in the dorsal striatum impairs one form of cognitive flexibility, i.e., response reversal learning (Palencia and Ragozzino, 2004), it remains unclear whether the effects of transient NMDA receptor blockade also extend to conditions of chronic NMDA receptor signaling loss and whether strategy-shifting, which is another form of cognitive flexibility, also requires NMDA-receptor signaling in the dorsal striatum.…”