Stimulating and Recording Brain Signals in an Olfactory Context: Non-Canonical Brain Structures May Contribute to...

Area of Science:

• Neuroscience
• Sensory Systems
• Biomedical Engineering

Background:

• The sense of smell currently lacks advanced prosthetic solutions, unlike other sensory systems.
• Olfactory implants aim to mimic the olfactory epithelium to translate odors into brain stimulation patterns.
• The role of non-primary olfactory pathway structures in olfactory processing remains underexplored.

Purpose of the Study:

• To investigate the potential of stimulating non-primary olfactory structures for evoking olfactory sensations.
• To explore the role of the amygdala and temporal pole in olfactory processing.
• To inform the development of more effective olfactory implants.

Main Methods:

• A case series of patients with pharmacoresistant epilepsy undergoing stereoencephalography (SEEG) was studied.
• Intracranial electrical stimulation was applied to brain structures.
• Electroencephalographic (EEG) signals were recorded during passive smelling tasks and after stimulation.

Main Results:

• Olfactory sensations were evoked in two patients via stimulation of the amygdala and temporal pole, respectively.
• Post-hoc analysis of SEEG data revealed functional connectivity in these non-primary olfactory structures.
• Findings suggest the amygdala and temporal pole contribute to olfactory processing.

Conclusions:

• Non-primary olfactory structures, particularly the temporal pole, are significant contributors to olfactory processing.
• Future olfactory implants may require stimulation of these association areas, not just primary olfactory pathways.
• The efficacy of olfactory prosthetics may depend on stimulation location, oscillation types, and engagement of associated brain networks.