Authors :
Presenting Author: Ako Matsuhashi, MD – the University of Tokyo
Naoto Kunii, MD, PhD – Jichi Medical University
Seijiro Shimada, MD, PhD – the University of Tokyo
Takeshi Matsuo, MD, PhD – Tokyo Metropolitan Neurological Hospital
Anna Takeda, MD – the University of Tokyo
Toshiya Aono, MD – the University of Tokyo
Shigeta Fujitani, MD, PhD – Department of Neurosurgery, The University of Tokyo Hospital
Keisuke Nagata, MD, PhD – the University of Tokyo
Makoto Sato, MD, PhD – Jichi Medical University
Yohei Ishishita, MD, PhD – Jichi Medical University
Kenji Ibayashi, MD, PhD – Jichi Medical University
Keisuke Ohtani, MD, PhD – Jichi Medical University
Kensuke Kawai, MD, PhD – Jichi Medical University
Nobuhito Saito, MD, PhD – the University of Tokyo
Rationale:
Patients with temporal lobe epilepsy (TLE) often experience difficulties in daily intellectual activities due to recurrent epileptic seizures and deterioration of memory function. While focal resection can eliminate seizures in 60-70% of the patients, about 40% of patients suffer further memory decline after surgery. Hippocampal theta activity during encoding is known to promote subsequent memory function in humans. (Joensen BH et al. Cerebral Cortex, 2023) We hypothesized that neurofeedback (NF) targeting the non-epileptic hippocampus could promote its functional reorganization, allowing it to compensate for the epileptic side. This may help avoid further deterioration of the memory function of TLE patients.
Methods:
Participants were TLE patients with intracranial electrodes implanted in both hippocampi for diagnostic purposes to identify the epileptic focus. Patients with a Full-Scale Intelligence Quotient (FSIQ) below 60 or a Wechsler Memory Scale-Revised (WMS-R) verbal index below 60 were excluded. After identifying the epileptic focus through video intracranial electroencephalography (iEEG) monitoring, we conducted the memory NF task using the electrode implanted in the non-epileptic hippocampus. The NF task was developed specifically for this project and involved real-time analysis and feedback of hippocampal activity during a word encoding task. While participants encoded words shown on a monitor, theta activity in the non-epileptic hippocampus was analyzed in real time and visually fed back as a circle whose diameter varied according to the level of theta activity. We monitored theta activity in the epileptic hippocampus throughout the task as well.
Results:
Seven TLE patients participated in the memory NF task. The median age at surgery was 30 years, median FSIQ was 73, and median WMS-R verbal index was 78. In five out of seven participants, theta activity significantly increased in the non-epileptic hippocampus during the NF task. A mixed linear model analysis across all sessions showed a significant increase in theta activity in the targeted hippocampus, with no significant change in the contralateral side.
Conclusions:
We successfully developed a memory NF task that enhanced theta activity in the targeted hippocampus. To our knowledge, this is the first study to employ iEEG-based NF to enhance targeted hippocampal activity. This finding supports the potential of NF as an effective method to preserve memory function in TLE patients prior to focal resection.
Funding:
This research is supported by AMED Multidisciplinary Frontier Brain and Neuroscience Discoveries (Brain/MINDS 2.0) Grant Number JP25wm0625207 and JSPS KAKENHI Grant Number JP25KJ0945.