Emotions induced by intracerebral electrical stimulation of the temporal lobe

Purpose: To assess the quality and frequency ofemotions induced by intracerebral electrical stimulation of thetemporal lobe.Methods: Behavioral responses were obtained by electricalstimulation in 74 patients undergoing presurgical video-stereo-EEG monitoring for drug-resistant epilepsy. Intracerebral electricalstimulationwas performed by delivering trains of electricalstimuli of alternating polarity; the intensity could vary from 0.2to 3 mA. Stimulation frequencywas 1Hz or 50 Hz. Nine hundredthirty-eight stimulation procedures were performed.Results: Seventy-nine emotional responses (ERs) were obtained(8.4%). Of these, 67 were “’fear responses.” Sad feelingswere evoked 3 times, happy-pleasant feelings 9 times. Anger anddisgust were never observed. The following variables affectedthe incidence of ER: (a) Anatomical site of stimulation. ERs (always fear) were maximal at the amygdala (12%) and minimalfor lateral neocortical stimulation (3%, p < 0.01). (b) Pathology.Stimulation of a temporal lobe with hippocampal sclerosiswas associated with a lower frequency of ERs compared withstimulation of a temporal lobe with no evidence of atrophy inthe medial temporal structures. (c) Stimulation frequency. ERswere 12% at 50 Hz versus 6.0% at 1 Hz (p < 0.01). (d) Gender.In women fear responses were 16% compared with 3% in men(p < 0.01). There were no gender differences when analyzingnonemotional responses.Conclusions: These data confirm the role of the medial temporallobe region in the expression of emotions, especiallyfear-related behaviors. Fear was observed more frequently inthe absence of medial temporal sclerosis, supporting the hypothesis that emotional behaviors induced by stimulation arepositive phenomena, strictly related to the physiological functionof these regions. Further investigations should addresswhy women express fear behaviors more frequently than men.