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 fact that gamma-80 power was high overall during early laps compared to later laps is consistent with the idea that representations of reward are involved in flexible decision-making processes engaged during early learning (Johnson et al., 2007; van der Meer and Redish, 2009). While it may seem paradoxical that representations of reward should be activated during early learning, when uncertainty about reward is relatively high, it is possible that this reflects a multiple-systems organization: during early learning, a “flexible” system representing and evaluating possible outcomes may give rise to reward signals in ventral striatum, while with experience, other areas (such as dorsal striatum) may assume control (Daw et al., 2005; Johnson et al., 2007). Further studies manipulating the value of rewards, as well as tests for the behavioral strategy (outcome-dependent or habitual) could address what specific properties of reward or motivation this signal is associated with.
