title: Appetitive and aversive information coding in the primate dorsal raphé nucleus.
abstract: Serotonin is known to play a key role in the regulation of emotional behavior. There have been conflicting hypotheses about whether the central serotonergic system is involved in positive or negative emotional information processing. To reveal whether and how such opposing information processing can be achieved by single neurons in the dorsal raphé nucleus (DRN), the major source of serotonin in the forebrain, we recorded the activity of DRN neurons while monkeys were conditioned in a Pavlovian procedure with two distinct contexts: an appetitive block where a reward was available; and an aversive one where an airpuff was delivered. We found that single DRN neurons were involved in several aspects of both appetitive and aversive information processing. First, more than half of the recorded DRN neurons discriminated between appetitive and aversive contexts by tonic changes in their activity. In the appetitive context, they then kept track of the expected reward value indicated by the conditioned stimuli. Some of them also encoded an error between the obtained and expected values. In the aversive context, the same neurons maintained tonic modulation in their activity throughout the block. However, modulation of their responses to aversive task events depending on airpuff probability was less common. Together, these results indicate that single DRN neurons encode both appetitive and aversive information, but over differing time scales: relatively shorter for appetitive, and longer for aversive. Such temporally distinct processes of value coding in the DRN may provide the neural basis of emotional information processing in different contexts.
authors: Department of Physiology, Kansai Medical University, Hirakata, Osaka 570-1010, Japan, and.
authors: Kazuko
authors: K
authors: Hayashi
authors: Department of Physiology, Kansai Medical University, Hirakata, Osaka 570-1010, Japan, and.
authors: Kazuko
authors: K
authors: Nakao
authors: Department of Physiology, Kansai Medical University, Hirakata, Osaka 570-1010, Japan, and Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan nakamkae@hirakata.kmu.ac.jp.
authors: Kae
authors: K
authors: Nakamura
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology*; D001362:Avoidance Learning / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology; D065847:Dorsal Raphe Nucleus / Q000166:cytology* / Q000502:physiology*; D005260:Female; D008252:Macaca fascicularis; D008297:Male; D009474:Neurons / Q000502:physiology*; D012372:ROC Curve; D012201:Reward; D018709:Statistics, Nonparametric
keywords: Pavlovian conditioning; dorsal raphé nucleus; monkey; serotonin; single-unit recording