Electrode stimulation of the temporal lobes evokes experiences which become part of the subjective stream of consciousness, embedded into the very fabric of the personality, such that the personality, and even sexual orientation may be altered. Moreover, patients may experience profound visual and auditory hallucinations and even feel as if they have left their bodies and are floating in space or soaring across the heavens.
There is no subjective sensations with frontal or parietal or occipital stimulation. In fact, with stimulation to these other brain areas the patient only becomes aware of the stimulation when they attempt to speak or move, or if a finger begins to twitch or if they feel painful tingling or see flashes of light. Although damage to the frontal lobe can produce the “frontal lobe personality” it is the temporal lobe which subserves those aspects of experience which are experienced as personal and subjective, of pertaining to the self and one’s personal and even spiritual identity. Indeed, stimulation of the temporal lobe can give rise to profound personal, emotional, sexual, and even religious feelings which are experienced as personally, spiritually and philosphically meaningful, including even sensations of having the “truth” revealed and of receiving knowledge regarding the meaning of life and death.
LSD. This does not mean, however, that neocortical involvement is not necessary for frequently it is the interpretive interaction of the temporal lobe which gives rise to certain types of hallucinations; i.e. bringing them to a conscious level. That is, although the amygdala (perhaps acting on the hippocampus) may be responsible for the hallucination, the hallucinaton requires an interactions between the amygdala, hippocampus, and the neocortex, for it is only when the “hallucination” envelops the neocortex of the temporal lobe that the individual becomes “conscious of them.”
For example, it is well known that the ingestion of LSD will trigger the formation of vivid and complex auditory and visual hallucinations. Following LSD administration electrophysiological abnormalities are noted in the amyugdala and hippocampus (Chapman et al., 1963). However, if the temporal lobes are surgically removed there is a significant decrease (with unilateral removal, Serafetinides, 1965) or complete abolishion (with bilateral temporal lobe removal) of LSD induced hallucinatory activity (Baldwin et al., 1955)–even when the amygdala and hippocampus are spared. That is, if the overlying neocortex is destroyed the individual will fail to hallucination–or at least to become conscious of the hallucination. Of course, if the overlying temporal lobe is destroyed the amygdala and hippocampus also become disconnected, and cannot help but be injured.
Nevertheless, studies with LSD and temporal lobe neocortical resection suggest that the neocortex is associated with consciousness and the limbic system with the unconscious, and if the pathways between them are destroyed, hallucinations cease to be experienced consciously. Interestingly, the hallucinatory effect of LSD appears to be greatest in the right temporal lobe (Serafetinides, 1965). That is, destruction of the right temporal lobe abolishes LSD-induced hallucinations, where with left temporal destruction, the individual continues to hallucination. Likewise, Penfield and Perot (1963) report that the most vivid hallucination tend to be triggered from the right not the left temporal lobe.
