Compressed Timeline of Recent Experience in Monkey Lateral Prefrontal Cortex

J Cogn Neurosci. 2018 Jul;30(7):935-950. doi: 10.1162/jocn_a_01273. Epub 2018 Apr 26.


Cognitive theories suggest that working memory maintains not only the identity of recently presented stimuli but also a sense of the elapsed time since the stimuli were presented. Previous studies of the neural underpinnings of working memory have focused on sustained firing, which can account for maintenance of the stimulus identity, but not for representation of the elapsed time. We analyzed single-unit recordings from the lateral prefrontal cortex of macaque monkeys during performance of a delayed match-to-category task. Each sample stimulus triggered a consistent sequence of neurons, with each neuron in the sequence firing during a circumscribed period. These sequences of neurons encoded both stimulus identity and elapsed time. The encoding of elapsed time became less precise as the sample stimulus receded into the past. These findings suggest that working memory includes a compressed timeline of what happened when, consistent with long-standing cognitive theories of human memory.

Publication types

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

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Computer Simulation
  • Concept Formation / physiology*
  • Female
  • Likelihood Functions
  • Macaca mulatta
  • Male
  • Memory, Short-Term / physiology*
  • Models, Neurological
  • Neurons / physiology*
  • Photic Stimulation
  • Prefrontal Cortex / cytology*
  • Prefrontal Cortex / physiology
  • Reaction Time / physiology*