Brain stimulation and conscious experience: Electrical stimulation of the cortical surface at a threshold current evokes sustained neuronal activity only after a prolonged latency

Consciousness and Cognition 15 (3):560-565 (2006)
Libet demonstrated that a substantial duration (>0.5-1.0 s) of direct electrical stimulation of the surface of a sensory cortex at a threshold or liminal current is required before a subject can experience a percept. Libet and his co-workers originally proposed that the result could be due either to spatial and temporal facilitation of the underlying neurons or additionally to a prolonged central processing time. However, over the next four decades, Libet chose to attribute the prolonged latency for evoking conscious experience to a prolonged central processing time. In my view, Libet has not provided any convincing evidence, either on the basis of his own past work or in his critique of my paper, for his hypothesis of a central processing time exceeding 0.5s before conscious experience emerges following direct electrical threshold stimulation of the cortical surface. I stand by my original results and conclusion that such prolonged latencies are largely the consequence of a dynamically increasing cortical facilitatory process that begins hundreds of milliseconds before there is a sustained neuronal activation. In some cases, the facilitatory process must overcome an initial stimulus-induced inhibition before neuronal firing commences
Keywords *Brain Stimulation  *Consciousness States  *Motor Processes  *Stimulus Duration  *Visual Cortex  Reaction Time  Self Perception  Visual Perception  Volition
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DOI 10.1016/j.concog.2005.04.003
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Cortical Activation in Conscious and Unconscious Experience.Benjamin Libet - 1965 - Perspectives in Biology and Medicine 9 (1):77-86.
The Neural Time Factor in Conscious and Unconscious Events.Benjamin W. Libet - 1993 - In G. R. Bock & James L. Marsh (eds.), Experimental and Theoretical Studies of Consciousness. (Ciba Foundation Symposium 174). pp. 174--123.
Brain Stimulation and Conscious Experience.Daniel A. Pollen - 2004 - Consciousness and Cognition 13 (3):626-645.

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Inner Light.Daniel Alroy - 1995 - Synthese 104 (1):147-160.
Brain Stimulation and Conscious Experience.Daniel A. Pollen - 2004 - Consciousness and Cognition 13 (3):626-645.


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