May 26, 2008

Electrical Stimulation to Elicitate Deja Experience

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When seizure activity cannot be controlled through medication, surgical removal of brain tissue may be required, and prior to this procedure, efforts are made to identify the tissue that is focal to the seizure. As a by-product of this exploration, a deja vu experience is occasionally elicited. With surface stimulation of the cortex, Mullan and Penfield (1959) elicited deja vu experiences in 10 out of 217 TLEs.

Recent procedures involving deep electrode brain implantation (Bancaud et al., 1994; Gloor, 1990; Gloor, Olivier, Quesney, Andermann, & Horowitz, 1982; Halgren, Walter, Cherlow, & Crandall, 1978) have shown that a deja vu similar to one that occurs in the aura can be elicited with stimulation of the amygdala and hippocampus. Although these experiences were not reported in detail, the deja vu generally consisted of a sudden feeling of unfamiliarity in the hospital environment (Bancaud et al., 1994; Gloor et al., 1982) and was often accompanied by epigastric phenomena and fear (Halgren et al., 1978).

The elicitation of deja vu through electrical stimulation may not be reliable. Halgren et al. (1978) stimulated several dozen brain locations in a group of TLEs on two different occasions (2 weeks apart) and found that a number of sites that elicited a deja vu on one session did not do so on the other. Deja vu experiences also resulted from stimulating the nondiseased hemisphere, suggesting that the experience is not necessarily specific to the tissue in which the seizure originates.

Although it is interesting that deja vu experiences are produced through electrical stimulation of cortical and deeper structures of the brain, is this specific to TLEs or can such experiences be elicited in all individuals? There is also the broader question of whether a deja vu experienced by TLEs is comparable with that experienced by individuals who do not have epilepsy (cf. M. A. Harper, 1969).

Neppe (1983e) suggested that the experience in TLEs lasted longer than in people without epilepsy (minutes rather than seconds), was often duplicated (same deja vu on repeated occasions), and may have been accompanied by substantial changes in thinking and emotions (compared with the brief and transient changes in the groups of participants without epilepsy), as well as a heightened sense of awareness of body and environment.

Complicating this evaluation is that fact that the deja vu experienced immediately prior to the epileptic seizure “is often dulled by slight clouding of consciousness, impaired by apprehension and recalled only with difficulty on close questioning” (M. A. Harper, 1969, p. 70).