Brain stimulation and conscious experience

Consciousness and Cognition
D A Pollen

Abstract

Libet discovered that a substantial duration (> 0.5-1.0 s) of direct electrical stimulation of the surface of the somatosensory cortex at threshold currents is required before human subjects can report that a conscious somatosensory experience had occurred. Using a reaction time method we confirm that a similarly long stimulation duration at threshold currents is required for activation of elementary visual experiences (phosphenes) in human subjects following stimulation of the surface of the striate cortex. However, the reaction times for the subject to respond to the cessation of the visual experience after the end of electrical stimulation could be as brief as 225-242 ms. We also carried out extensive studies in cats under a variety of anesthetic conditions using the same electrodes and parameters of stimulation employed in the human studies to study the patterns of neuronal activity beneath the stimulating surface electrode. Whereas sufficiently strong currents can activate neurons within milliseconds, stimulating currents close to threshold activate sustained neural activity only after at least 350-500 ms. When currents are close to threshold, some neurons are inhibited for several hundreds of millisecond before the balanc...Continue Reading

References

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Citations

May 4, 2010·Bio Systems·I Bókkon, Ram Lakhan Pandey Vimal
Sep 1, 2004·Consciousness and Cognition·Susan Pockett
May 6, 2006·Progress in Neurobiology·Benjamin Libet
Aug 5, 2015·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·Nela Cicmil, Kristine Krug
Dec 1, 2011·Nature Reviews. Neuroscience·Svenja BorchersHans-Otto Karnath
May 15, 2021·Scientific Reports·Damian K F Pang, Stamatis Elntib

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