Exploring the cortical evidence of a sensory-discrimination process

Ranulfo Romo, Adrián Hernández, Antonio Zainos, Carlos Brody, Emilio Salinas

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Humans and monkeys have similar abilities to discriminate the difference in frequency between two consecutive mechanical vibrations applied to their fingertips. This task can be conceived as a chain of neural operations: encoding the two consecutive stimuli, maintaining the first stimulus in working memory, comparing the second stimulus with the memory trace left by the first stimulus and communicating the result of the comparison to the motor apparatus. We studied this chain of neural operations by recording and manipulating neurons from different areas of the cerebral cortex while monkeys performed the task. The results indicate that neurons of the primary somatosensory cortex (S1) generate a neural representation of vibrotactile stimuli which correlates closely with psychophysical performance. Discrimination based on microstimulation patterns injected into clusters of S1 neurons is indistinguishable from that produced by natural stimuli. Neurons from the secondary somatosensory cortex (S2), prefrontal cortex and medial premotor cortex (MPC) display at different times the trace of the first stimulus during the working-memory component of the task. Neurons from S2 and MPC appear to show the comparison between the two stimuli and correlate with the behavioural decisions. These neural operations may contribute to the sensory-discrimination process studied here.

Original languageEnglish (US)
Pages (from-to)1039-1051
Number of pages13
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1424
StatePublished - Aug 29 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Agricultural and Biological Sciences
  • General Biochemistry, Genetics and Molecular Biology


  • Behaving monkeys
  • Cerebral cortex
  • Sensory discrimination


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