Psychophysical Investigations into Cortical Encoding of Vibrotactile Stimuli

  1. Derek J. Chadwick,
  2. Mathew Diamond Organizer and
  3. Jamie Goode
  1. Justin A. Harris

Published Online: 7 OCT 2008

DOI: 10.1002/9780470034989.ch19

Percept, Decision, Action: Bridging the Gaps: Novartis Foundation Symposium 270

Percept, Decision, Action: Bridging the Gaps: Novartis Foundation Symposium 270

How to Cite

Harris, J. A. (2006) Psychophysical Investigations into Cortical Encoding of Vibrotactile Stimuli, in Percept, Decision, Action: Bridging the Gaps: Novartis Foundation Symposium 270 (eds D. J. Chadwick, M. Diamond and J. Goode), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9780470034989.ch19

Author Information

  1. School of Psychology, University of Sydney, New South Wales 2006, Australia

Publication History

  1. Published Online: 7 OCT 2008
  2. Published Print: 13 JAN 2006

Book Series:

  1. Novartis Foundation Symposia

Book Series Editors:

  1. Novartis Foundation

ISBN Information

Print ISBN: 9780470012338

Online ISBN: 9780470034989

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Keywords:

  • cortical encoding of vibrotactile stimuli;
  • transcranial magnetic stimulation (TMS);
  • somatosensory cortex (S1) and low frequency vibrations;
  • S1 contribution to tactile perceptual task;
  • discriminating vibration frequency

Summary

Neurons in primary somatosensory cortex (S1) respond to vibrotactile stimuli by firing in phase with each cycle of the vibration. We have investigated how neural activity in S1 might contribute to people's perception of vibration frequency. The contribution of S1 was confirmed using transcranial magnetic stimulation (TMS): accuracy in comparing the frequency of two sequential vibrations was reduced by a single TMS pulse delivered to S1 in the interval between the two vibrations. More recent experiments have revealed that participants use the velocity (or energy) of the stimulus when judging its frequency. This is consistent with a contribution from S1: electrophysiological recording in S1 cortex of rats shows that neurons in S1 do not explicitly code vibration frequency, but instead code the product of frequency and amplitude (proportional to the mean velocity or energy of the vibration). Further, frequency discrimination is reduced by the addition of even very small amounts of noise to the temporal structure of the vibrations (making them irregular). However, noise has no effect if the two vibrations are presented on opposite fingertips (i.e. beyond the range of receptive field sizes of neurons in S1), or if there is no difference in their velocity. Therefore, when judging vibration frequency, humans utilize information about stimulus velocity as coded by neurons in S1, but this coding is dependent on the temporally regular input of the vibration.