Unimanual tactile anomia consequent to corpus callosotomy: reduction of anomic deficit under hypnosis

The split-brain syndrome

A recurrent theme in psychiatry is the belated and often confused appreciation of advances in other relevant disciplines. An example of this is the “split-brain syndrome”, which provoked a Zeitgeist in the kindred field of neuropsychology and which has shaped notions of mental functioning impinging on the domain of psychiatry as well as philosophy, aesthetics, and education (Benson & Zaidel, 1985). The ‘left brain – right brain story’, while giving rise to much creative scientific enquiry, has also spawned some rather dubious psychophantasy. The purpose of this article is therefore to summarise this vast and growing body of work, to highlight areas of particular relevance, and to steer the reader away from the more wayward regions of speculation.

Geophysical variables and behavior: LV. Predicting the details of visitor experiences and the personality of experients: the temporal lobe factor

The visitor experience, a more intense form of the normal sense of presence, emphasizes the deep belief of personal contact with an extraterrestrial (or religious) entity. Phenomenological details of visitor experiences are expected to reflect the functions of deep temporal lobe structures; common details involve cosmic meaningfulness, vestibular experiences, flickering, complex visual sensations and alimentary references. After intense experiences, interictal-like behaviors similar to religious conversions (widening affect, sense of personal, desire to spread the word, concern about Man's destiny) emerge. Normal people who are prone to these experiences show frequent temporal lobe signs and specific personality characteristics that include enhanced creativity, suggestibility, mild hypomania, anxiety, and emotional lability. Learning histories that encourage the use of right temporal lobe functions for the consolidation of memory, such as compartmentalization of beliefs or repression due to early sexual abuse, predispose to intense visitor experiences. The most frequent precipitants are psychological depression, personal (existential) stress and proximal exposure to the focal tectonic strain fields that accompany luminous phenomena. Possible neuropsychological mechanisms are discussed.

Hypnotic susceptibility: A lateral predisposition and altered cerebral asymmetry under hypnosis

Psychophysiological and behavioural evidence is reported of altered cerebral asymmetry under hypnosis in favour of the right hemisphere. This occurred in Susceptible as distinct from Unsusceptible subjects. Measures included bilateral electrodermal responses to tones and bimanual processing times for sorting letters and numbers with eyes closed. Subjects listened to a tape recording of a procedure for inducing relaxation under hypnosis. Susceptible subjects, unlike Unsusceptibles, showed lateral asymmetries in baseline conditions in favour of the left hemisphere. Electrodermal responses were larger on the left than the right hand and haptic processing times were faster with the right than the left hand. Under hypnosis there was a reduction in electrodermal orienting responses coupled with faster habituation and a reversal in lateral asymmetries. Haptic processing revealed a slowing in right hand processing times whereas left hand times were reduced as was the case with bilateral processing times in both Unsusceptible subjects and controls who experienced no hypnosis. Unlike earlier reports left hemisphere dynamic processes were fundamental to the induction of hypnosis. A neuropsychological model is proposed whereby susceptibility is associated both with a left bias prior to hypnosis and left hemisphere inhibition under hypnosis. Unsusceptibles retain a right hemisphere orientation without undergoing left hemisphere inhibition. Thus hypnosis involves an inhibition of left-sided processes which permits the ascendancy of the right hemisphere through the attenuation of left hemisphere control.