S1). Cells recorded from wires located outside the core and shell, or on the border between the structures were excluded from the analysis. The present data provide an important insight into the specific roles of NAc subregions during PIT. In all groups tested, MLN0128 datasheet there was a selective behavioral enhancement in lever pressing in the presence of the CS+ cue that was not seen in the presence of the CS− cue. However, rats with a history of cocaine self-administration showed transfer that was significantly more robust than either control group. At the neural level, evidence was found that both the core and shell contributed important facets of encoding critical to supporting successful transfer. In all groups, core neurons
were reliably biased BGB324 order in encoding
information about cues, rewards and operant task performance compared with the shell, and cue-related encoding in the core was correlated with the degree of behavioral transfer. In contrast, in naive rats, only shell neurons showed cue-modulated responses during lever press (PIT-modulated neurons) that were correlated with task performance. However, following chronic cocaine taking, shell but not core neurons showed enhanced encoding for all task-related events compared with controls, whereas both core and shell showed a dramatic increase in the percentage of PIT-modulated neural activity to the press. In contrast, the analysis of foodcup entries and neural activity that encoded these responses highlights the specificity of the instrumental transfer feature of the PIT task. Although cocaine experience resulted in a significant potentiation of the PIT effect for lever pressing, it did not translate into more general behaviors in the task such as foodcup activity. These findings indicate that psychostimulant experience did not simply increase hyperactivity in the box, nor did it lead to a differential
response conflict between the instrumental and Pavlovian responses during transfer. Instead, Galeterone cocaine experience selectively enhanced the instrumental response in the presence of the CS+, a feature that was reflected in both the behavior and neural response. In the present study, encoding information about Pavlovian cues in naive animals was largely a function of the NAc core, although a few shell neurons encoded this associative information. This pattern of encoding has been demonstrated reliably in previous studies, whether the cues predict natural rewards such as sucrose (Setlow et al., 2003; Day et al., 2006; Jones et al., 2008) or drugs of abuse such as cocaine (Hollander & Carelli, 2007). These neural representations encode not only the identity of these cues, but also the motivational significance and predictive value of the associated outcome. For example, studies from this laboratory have repeatedly demonstrated that NAc core neurons show little overlap between cues predictive of cocaine and cues predictive of natural reward (Carelli et al., 2000; Carelli & Wondolowski, 2003).
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