Trends in cogn sc 2007 11 158 67 12 the libet et al

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Unformatted text preview: l. experiments The Libet experiment brainpotential…………….. voluntary will ……… voluntary action 0 ms 350 ms 550 ms At time 0, a brain potential can be recorded (readiness potential). Only 350 ms later, we are aware we want to perform a certain action. Another 200 ms later, the voluntary action is initiated. Libet: brain activity begins before willed judgement A brain potential is measured before willed judgement: a readiness potential (Bereitschaftspotenzial) As causes necessarily precede effects, conscious intention cannot be the cause of the neural processes that lead to action. Libet, neuropsychologist, 1970, California The Libet et al. experiments “Die freie Wille ist eine Illusion“ Some neurobiological challenges Are we are puppets on a string? (Crevits) 13 The Crevits et al. ‘zombie* experiments’ The Freudian concepts Light stim. When a target has moved during a saccade (the subject being blind in that time), he adjusts the trajectory without consciously having seen the second target. *A zombie: a hypothetical human being without consciousness ATTENTION U N C O N S C I O U S PRE CONSCIOUS CONSCIOUS INATTENTION Unconsciousness subliminal: a condition of information inaccessibility where bottom-up activation is insufficient to become aware preconscious: potentially conscious, but not now because of lack of attention (topdown) SUBLIMINAL Consciousness Trends in Cognitive Sciences, 2006, 10, 204-211 14 Subliminal visual stimuli evoke a strong activation in extrastriate visual cortex, but their intensity quickly decrease in higher visual areas Only conscious stimuli trigger a late surge of activation in a global prefronto-parietal network. PLoS Biology, 2007, 5, 10, e260, 2408-23 2006, 10, 204-11 Proposed distinction between subliminal, preconscious, and conscious processing defined by bottomup stimulus strength (vertical axis) and top-down attention (horizontal axis). Shades of color: the amount of activation in local areas. Small arrows: the interactions among them...
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