This paper summarizes the findings of a pilot study which found a relationship between the post-traumatic symptoms of a) psychic numbing, b) intrusive recollections of traumatic events, and c) hypervigilance and lateralization of electrodermal response (EDR) measurements in six victims of psychological trauma. Hypnotically induced imagery of past traumatic events was often associated with left-sided EDR increases, psychic numbing with left-sided EDR decreases or bilateral EDR unresponsiveness, and revivifications of hypervigilant states with right-sided EDR lateralization. In several cases control of the experience of fear was associated with left-sided or bilaterally decreased EDRThese pilot study findings support previously stated hypotheses: a) EDR obtained from an extremity reflects contralateral cerebral hemisphere functioning; b) left hemisphere functioning is associated with hypervigilance; and c) right hemisphere functioning is associated with emotions and imagery.In addition, the pilot study findings suggest additional hypotheses: a) Post-traumatic symptoms are associated with poorly controlled or integrated cerebral hemisphere functioning; b) psychic numbing and intrusive images, flashbacks, and nightmares are associated with abnormal activation, suppression, or integration of right hemisphere functioning in relationship to the left; c) aggressive behavior, hypervigilance, and character pathology are associated with abnormal activation, suppression, or integration of functioning of the left hemisphere function in relationship to the right; and d) “splitting” as a psychological defense in Vietnam veterans with Borderline Personality Disorders is associated with physiologically impaired interhemispheric integration.