The ramping-up-to-reward effect of ventral striatal gamma-80 power suggests it is primarily related to anticipating aspects of reward, similar to ramping activity observed in ventral striatal units (Lavoie and Mizumori, 1994; Miyazaki et al., 1998; Schultz et al., 1992). It has been suggested that covert representations of reward contribute to flexible, outcome-dependent decision making (Balleine, 2001; Overmier and Lawry, 1979; van der Meer and Redish, 2009); consistent with this idea, there was evidence that high gamma power was increased at the final choice point early in the session, and before turnarounds, suggesting a possible relationship to decision making. This pattern of modulation was reminiscent of the covert representation-of-reward effect reported in van der Meer and Redish (2009); indeed, the peak of increased gamma-80 at the final choice point during early learning matched that of increased reward cell firing in that earlier study, and in both a smaller increase can be seen at other points on the track (e.g., start of maze). This suggests a link between reward-responsive cell activity and gamma-80 that is specific to covert representation of reward. The
