To stimulate specific brain regions and generate olfactory sensations (phantosmia) to bypass the potential peripheral nerve impairment sufficiently so that it evokes an olfactory sensation.

The study involved 11 patients undergoing stereoencephalography (SEEG, N = 5) and awake brain surgery (ABS, N = 6). Stimulation was applied during SEEG elective procedures and to peritumoral tissue in ABS patients. Interprocedural testing evaluated odor perception, including strength and hedonics. Olfactory performance was assessed preoperatively.

Due to intraoperative speech problems, vomiting and seizure during the procedure, 4 patients were excluded from the study. 4 SEEG and 3 ABS patients were enrolled. During ABS, a single patient reported experiencing a lemon-like olfactory sensation following the direct electrical stimulation of the olfactory tract by the bipolar tweezers. None of the electrical stimulations changed the way the odorants of rose and peppermint were rated. Nevertheless, in a different patient, the application of 6mA electrical stimulation to the gyrus rectus modified his impression of a rose, which he subsequently classified as having a vanilla scent.

The application of stimulus resulted in the emergence of an olfactory percept in 2 SEEG individuals. This was in the right amygdala after stimulation of 1.6mA, 5sec duration, and 50Hz frequency for one patient, which led to a spinach odor perception. In the case of the second patient, an unfamiliar malodorous scent was detected after stimulation in the right temporo-parieto-occipital junction using the specified parameters.: 7mA, 5sec duration and 50Hz frequency. There was no significant impact observed on the perceived ratings of the odorants as a result of any of the administered electrical stimulations.

Overall, the use of central stimulation to circumvent peripheral neuronal damage has shown effectiveness in many sensory systems. We have successfully elicited olfactory sensations by directly stimulating certain areas of the brain, including the right amygdala, left olfactory tract, left temporo-parieto-occipital junction, and left gyrus rectus, despite the small number of patients involved in the study. The findings should be considered as a "proof of concept" and the anatomical locations that had a role in the development of olfactory perception should be examined as potential areas of focus for future research on olfactory stimulation.