Here again, the evidence generally suggests that the

striatum is important for control of semantic memory retrieval. Badre et al. (2005) investigated the neural systems supporting the cognitive control of semantic memory retrieval. This study focused on the contribution of left ventrolateral PFC (VLPFC) to different forms of cognitive control of memory retrieval. In a reanalysis conducted for this review, a manipulation of controlled semantic retrieval located activation in the left dorsal caudate (Figure 2). Perhaps consistent with this finding, a recent study from Han et al. (2012) found that VLPFC was preferentially Metformin price engaged during a demanding retrieval task (source memory versus item memory), but only for semantically meaningful items, suggesting that VLPFC was engaged in semantic elaboration to enhance retrieval. The caudate showed a qualitatively identical pattern of activation. Thus, as with the Badre et al. (2005) result noted above, activation in caudate is observed under the same MLN2238 concentration conditions requiring cognitive control of semantic memory that engaged VLPFC. Consistent with the imaging data, at least one study has located interference-induced deficits in semantic retrieval in PD patients. Compared to age-matched controls, PD patients showed an impaired ability to produce a semantically related verb when presented with a noun (Crescentini et al., 2008). The deficit was greatest in a condition where

there was no strongly associated response for the presented stimulus, and instead many weakly associated target verbs. Hence, as with episodic through retrieval, the striatum likely interacts with the PFC to play a causal role in the goal-directed retrieval and selection of semantic information from memory. Importantly, this suggests frontostriatal circuits may play a similar role in the cognitive control of both episodic and semantic retrieval. However, future research will need to test whether this common function in semantic versus episodic memory is instantiated the same or separable frontostriatal circuits. From the preceding review, it seems evident that the striatum plays a necessary

role in optimal declarative retrieval performance, particularly under conditions requiring the cognitive control of memory. In this way, the contribution of striatum appears to mirror that of the frontal cortex during declarative memory tasks (Stuss et al., 1994; Wheeler et al., 1995; Aly et al., 2011; Thompson-Schill et al., 1998). However, research on the neural mechanisms of cognitive control and reinforcement learning, outside of the context of memory, has suggested that striatum and frontal cortex have distinct but complementary roles (Braver and Cohen, 2000; Cools et al., 2004; O’Reilly and Frank, 2006; McNab and Klingberg, 2008; Cools, 2011; Badre and Frank, 2012). In particular, whereas lateral PFC supports cognitive control by sustaining task-relevant information in working memory (i.e.