Being Conscious of the Absent Stimuli: 1 - Expectation

Abstract

Studies on EEG correlates of consciousness have revealed relations between the degree of consciousness and many Event Related Activity (ERA), In these studies, un or conscious state is manipulated either by controlling stimulus threshold; priming, masking or omission. Here, we decide to study the EEG correlates of consciousness using a different paradigm. We used a series of clicks presented at 1Hz during 30 seconds (phase R) in order to create an expectation about the stimulus occurrence and then we discontinued the stimulation for another 30 seconds (phase E). ERA technique was used to disclose the possible EEG components associated to conscious perception of real (phase R) and absent (phase E) clicks. Five ERA wave components W_i were identified. W₁ to W₄ for real clicks and W₂ to W₅ for absent (imagined) stimuli. It is proposed where that W₁ and W₅ components distinguish conscious perception of real and absent stimuli.