Epilepsy and consciousness.

Seizure activity has long been associated with alterations in consciousness. Philosophical and neurologic debates concerning the definition of consciousness have led to confusion regarding an adequate third person assessment of a subjective experience. In order to avoid these controversies, neurologic evaluation of consciousness has focused on operational definitions that permit an objective assessment of behavioral responses that are constituent functions of consciousness. Clinical experience has demonstrated that ictal and post-ictal alterations in consciousness may be associated with loss of selected behavioral responses depending upon the focus and spread of seizure activity. Ictal electrophysiologic studies and brain stimulation has assisted in determining the anatomic structures involved in specific behavioral alterations. Consciousness-dependent mental activity can be modeled as a series of interactive parallel information channels that can be selectively disrupted at any stage of processing giving rise to ictal behavioral patterns. While such modeling falls to grasp the subjective nature of consciousness, it offers the clinical community an objective measure of those responses believed to be dependent on consciousness.