NEURAL RESPONSES TO AUDITORY INPUTS IN ALTERED STATES OF CONSCIOUSNESS

Abstract

Altered states of consciousness (ASC) involve changes in perceptual experience or wakefulness. They are accompanied by alterations in brain structure or activity, and therefore provide opportunities to examine neural underpinnings of consciousness. We present three brain imaging studies on neural responses to auditory inputs in ASC of pathological and non-pathological origins. We found: 1) sound induced visual experience alongside early visual cortex activation in a synesthesia case occurred after optic nerve lesion; 2) verbal commands elicited intermittent motor (and other non-auditory) area responses in behaviorally unresponsive patients that suffered from severe brain injuries, even in low arousal state; and 3) sound of varied pitches and AM frequencies activated the auditory cortex, but did not perturb the activation level or pattern in other regions during microsleep. These results show that modality non-specific brain activities can be induced in ASC of pathological origin, but not in naturally occurring ASC.