The Neural Time Factor in Conscious and Unconscious Events

  1. Gregory R. Bock Organizer and
  2. Joan Marsh
  1. Benjamin Libet

Published Online: 28 SEP 2007

DOI: 10.1002/9780470514412.ch7

Ciba Foundation Symposium 174 - Experimental and Theoretical Studies of Consciousness

Ciba Foundation Symposium 174 - Experimental and Theoretical Studies of Consciousness

How to Cite

Libet, B. (2007) The Neural Time Factor in Conscious and Unconscious Events, in Ciba Foundation Symposium 174 - Experimental and Theoretical Studies of Consciousness (eds G. R. Bock and J. Marsh), John Wiley & Sons, Ltd., Chichester, UK. doi: 10.1002/9780470514412.ch7

Author Information

  1. Department of Physiology, University of California at San Francisco, School of Medicine, San Francisco, CA 94143-0444, USA

Publication History

  1. Published Online: 28 SEP 2007

ISBN Information

Print ISBN: 9780471938668

Online ISBN: 9780470514412

SEARCH

Keywords:

  • neural time factor;
  • conscious events;
  • unconscious events;
  • conscious mental function;
  • ‘time-on’ theory

Summary

Our earlier evidence had indicated that a substantial duration of appropriate cerebral activity (up to about 0.5 s) is required for the production of a conscious sensory experience; this means the sensory world is experienced delayed with respect to real time. Subjective timing of the experience can be retroactively referred to the time of the earliest signal arriving at the cortex. Our ‘time-on’ theory states that the transition from an unconscious to a conscious mental function is determined, at least in part, by an increase in the duration of appropriate neural activities. Our experimental finding that conscious intention to act appears only after a delay of about 350ms from the onset of specific cerebral activity that precedes a voluntary act provided indirect evidence for the theory. In a direct experimental test a signal (stimulus to somatosensory thalamus) was correctly detected in a forced-choice test even when the stimulus duration was too short to produce any awareness of the signal; to go from correct detection with no awareness to detection with awareness required an additional 400 ms of the repetitive identical neural volleys ascending to sensory cortex. ‘Time-on’ theory has important implications for a variety of unconscious-conscious interactions.