Serotonergic neurons signal reward and punishment on multiple timescales

Elife. 2015 Feb 25;4:e06346. doi: 10.7554/eLife.06346.

Abstract

Serotonin's function in the brain is unclear. One challenge in testing the numerous hypotheses about serotonin's function has been observing the activity of identified serotonergic neurons in animals engaged in behavioral tasks. We recorded the activity of dorsal raphe neurons while mice experienced a task in which rewards and punishments varied across blocks of trials. We 'tagged' serotonergic neurons with the light-sensitive protein channelrhodopsin-2 and identified them based on their responses to light. We found three main features of serotonergic neuron activity: (1) a large fraction of serotonergic neurons modulated their tonic firing rates over the course of minutes during reward vs punishment blocks; (2) most were phasically excited by punishments; and (3) a subset was phasically excited by reward-predicting cues. By contrast, dopaminergic neurons did not show firing rate changes across blocks of trials. These results suggest that serotonergic neurons signal information about reward and punishment on multiple timescales.

Keywords: behavior; dorsal raphe; mouse; neurophysiology; neuroscience; punishment; reward; serotonin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Behavior, Animal
  • Conditioning, Psychological
  • Cues
  • Mice, Inbred C57BL
  • Neural Inhibition / physiology
  • Punishment*
  • Reward*
  • Serotonergic Neurons / physiology*
  • Serotonin / metabolism
  • Task Performance and Analysis
  • Time Factors

Substances

  • Serotonin