Mental phenomena induced by stimulation in the limbic system.

Direct electrical stimulation of any limbic sector may evoke a visceral sensation or an emotion, usually fear or anxiety. Vivid formed dream- or memory-like hallucinations, or intense feelings of familiarity, may be evoked from the hippocampal formation and amygdala. Conversely, amnesia may result from stimulation-induced bilateral disruption of the same region. Cingulate gyrus stimulation near the supplementary motor cortex may evoke partially adaptive movement sequences, or may interfere with the performance of movements. In general, those phenomena are not due to epileptic pathology, nor to gross spread of activation. The particular response evoked is not related to the precise electrode location, but rather to the patient's psychological traits and concerns. Thus, there is no direct relationship between specific mental contents and the activation of particular limbic neurons. Limbic stimulation appears to produce deep mental alterations whose manifestation at the surface of awareness, or in specific movements, is defined by the ongoing context.