Odor Naming-related Activities Recorded from the Human Olfactory Cortices
Abstract number :
2.342
Submission category :
11. Behavior/Neuropsychology/Language / 11A. Adult
Year :
2023
Submission ID :
628
Source :
www.aesnet.org
Presentation date :
12/3/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: Kenji Ibayashi, MD, PhD – Jichi Medical University
Yoshiyuki Onuki, PhD – Department of Neurosurgery – Jichi Medical University; Yohei Ishishita, MD, PhD – Department of Neurosurgery – Jichi Medical University; keisuke Otani, MD, PhD – Department of Neurosurgery – Jichi Medical University; takeshi Nakajima, MD, PhD – Department of Neurosurgery – Jichi Medical University; Naoto Kunii, MD, PhD – Department of Neurosurgery – Jichi Medical University; Kensuke Kawai, MD, PhD – Department of Neurosurgery – Jichi Medical University
Rationale:
Emerging evidences have shown that the human olfactory cortex, especially the piriform cortex plays an important role in the epileptic network of temporal lobe epilepsy patients and its extent of removal predicts the surgical outcome. Despite increasing opportunities for intracranial recordings, neural correlates that underlie human olfactory processing remains understudied.
Methods:
We leveraged the opportunity to record intracranial signals from three patients with intractable epilepsy, who underwent either subdural electrode implantation (S1 and S3) or multiple depth electrode implantation (S2) for the assessment of their surgical candidacy. Odorants were delivered to the subject's nasal cavity either by sniffing from an elastic bottle (SNF) or natural nasal breathing (NNB) through an in-house-manufactured odor delivery system. Data was acquired using a 256-channel NihonKoden EEG recording system at Jichi Medical Univeristy. The signal recorded from each channel was re-referenced to the common average of each electrode array. Signals were subsequently epoched into trials, which were aligned to the timing of odor delivery. Time-frequency decomposition was performed via short time Fourier transform to create event related spectral perturbations. Band specific analysis was performed by the bandpass-Hilbert transformation method via the finite impulse response filter. The correlation between the mean power during the peri-stimulus window and the odorant labels was analyzed. Phase Slope Index (PSI) was calculated to evaluate internodal connectivity between the olfactory cortices.
Results:
Analysis of two subjects who underwent SNF task (S1) and NNB task (S3) revealed a high-frequency response induced in the parahippocampal cortex together with that of the orbital cortex during odor naming. The other subject (S2) who underwent NNB task showed beta entrainment immediately after the odor delivery in the periamygdaloid cortex. This beta response was significant to odor-positive breathing and was positively correlated to trial counts (Spearman's R (72) = 0.3, p=0.01). It also showed no evidence of beta power encoding odorant difference, given the high correlation between beta power trace induced by different odorants. PSI analysis showed a shift of direction and an increase of hippocampal-to-entorhinal theta connectivity following odor delivery that peaked at 940ms after onset.
Conclusions:
Our results showed different entrainment patterns in human olfactory-related cortices during the odor-naming task. Beta entrainment within the periamygdaloid cortex was the most prominent stimulus-induced finding, whereas the delayed hippocampal and parahippocampal high-frequency response was more suggestive of encoding the retrieval-related activity during naming. Further study is warranted to reproduce these findings and to elucidate the neural basis of human olfactory processing. An SEEG technique would greatly benefit the investigation of deeply seated olfactory-related cortices whenever these regions are the candidate for intracranial investigation for intractable epilepsy.
Funding: This research is funded by JSPS KAKEN #22K15628.
Behavior