These findings raise the possibility that dopamine

selleck inhibitor release might subserve multiple functions, conveying different signals to different parts of the brain in order to meet a variety of behavioral demands. Yet a clear delineation of what functions these disparate signals perform has been lacking. In this issue, Matsumoto and Takada (2013) set out to remedy this gap by studying the diversity of dopamine signaling across the midbrain during cognitive performance. To do this, they recorded single neurons from the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) in monkeys performing a visual search task for fluid reward. On most trials, monkeys were first shown a cue indicating whether a large or small reward would be delivered for a correct response. This cue was followed by a sample stimulus (a slanted line). The monkeys were then shown an array of slanted lines (two, four, or six items), selleck products among which they had to search for a match to the sample stimulus. Monkeys indicated a match by visually fixating the matching target. Previous work has shown that dopamine is necessary for maintaining working memory (Li and Mei, 1994, Sawaguchi and Goldman-Rakic, 1991, Sawaguchi and Goldman-Rakic, 1994, Watanabe et al.,

1997 and Williams and Goldman-Rakic, 1995), as well as for facilitating visual perception (Noudoost and Moore, 2011), and thus might be released in response to the display of the target cue. Yet, this should only be necessary when the information in the sample stimulus is needed for the upcoming search. To test this, the authors interleaved blocks of the match-to-sample task with blocks of a second visual search task. In this second task, a slanted line stimulus was again presented, but the search array consisted of unrelated shapes (triangles and squares). The monkey’s

task was then simply to locate the lone triangle, which “popped out” from the array. For this task, the initial stimulus was unnecessary, and no working memory was required. The results of Matsumoto and Takada’s experiment are summarized in Figure 1. As expected, dopamine neurons responded more strongly to Sodium butyrate the cue advertising a large reward than to the cue for a small reward (A). More importantly, cells responded much more strongly to the sample stimulus when it was needed for the upcoming search than when it was irrelevant, suggesting that dopamine release from midbrain neurons contributes to the working memory requirements of the match-to-sample task (B). In addition, dopamine cells fired more strongly to the onset of smaller, easier arrays than to larger, harder ones (C) and responded more strongly when monkeys found targets in large arrays than in small ones (D).