Reinforcement Learning Recruits Somata and Apical Dendrites across Layers of Primary Sensory Cortex

Cell Rep. 2019 Feb 19;26(8):2000-2008.e2. doi: 10.1016/j.celrep.2019.01.093.


The mammalian brain can form associations between behaviorally relevant stimuli in an animal's environment. While such learning is thought to primarily involve high-order association cortex, even primary sensory areas receive long-range connections carrying information that could contribute to high-level representations. Here, we imaged layer 1 apical dendrites in the barrel cortex of mice performing a whisker-based operant behavior. In addition to sensory-motor events, calcium signals in apical dendrites of layers 2/3 and 5 neurons and in layer 2/3 somata track the delivery of rewards, both choice related and randomly administered. Reward-related tuft-wide dendritic spikes emerge gradually with training and are task specific. Learning recruits cells whose intrinsic activity coincides with the time of reinforcement. Layer 4 largely lacked reward-related signals, suggesting a source other than the primary thalamus. Our results demonstrate that a sensory cortex can acquire a set of associations outside its immediate sensory modality and linked to salient behavioral events.

Keywords: GCaMP; apical dendrites; barrel cortex; detection; reward; two-photon; vibrissa; voltage-gated calcium.

Publication types

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

MeSH terms

  • Animals
  • Calcium Signaling
  • Dendrites / metabolism
  • Dendrites / physiology*
  • Female
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Reinforcement, Psychology*
  • Sensory Receptor Cells / metabolism
  • Sensory Receptor Cells / physiology
  • Somatosensory Cortex / cytology
  • Somatosensory Cortex / physiology*
  • Vibrissae / physiology