Electrical stimulation of the medial orbitofrontal cortex in humans elicits pleasant olfactory perceptions

BackgroundOlfactory hallucinations can be part of epileptic seizures orbitofrontal origin. Olfactory hallucinations, however, are rare and therefore the semiology, localization lateralization characteristics underdetermined. In addition, many discrepancies found in literature regarding olfactory processing (OF) functions function. Particularly, questions laterality affective component coding odors OF cortex remain controversial.AimsThis study explored whether cortical electrical stimulation mesiotemporal brain trigger with special focus on percepts terms hedonics.Materials methodsEight patients temporal lobe epilepsy participated study, at time invasive exploration their epilepsy. The most distal contact anterior hippocampus depth electrodes were stimulated (50 Hz, 0.2 ms biphasic pulse; maximal 4 mA). Patients instructed to report any kind sensation they might experience. Intracranial localized (iElectrodes): subject-specific mask, subcortical segmentation parcellation based Destrieux atlas (FreeSurfer) superposed coregistered T1-weighted MRI CT images (SPM). center mass each electrode-artifact cluster determined electrode localization. labeling was done patient space. To obtain coordinates Montreal Neurological Institute (MNI) space, obtained previously space first segmented normalized Then, procedure (iElectrodes) run again these new MNI space.ResultsNo hallucination evoked by stimulation, neither right nor left (8/8 patients). Pleasant 5/8 either hemisphere. named percept as smell lemon or coffee for example. Among those 5 patients, sulcus, medial orbital sulcus gyrus. Increasing amplitude changed identification 3 out patients. No judgement change perceived odor intensity reported white matter 3/8 independently hemisphere stimulated.ConclusionsThis demonstrated that not its elicits specific pleasant stimulated, supporting one symmetrical human.