Takumi Mitsuhashi - Academia.edu (original) (raw)

Papers by Takumi Mitsuhashi

As school challenges intensify, they commonly increase in complexity. In tasks involving new visu... more As school challenges intensify, they commonly increase in complexity. In tasks involving new visuospatial information, we rely on working memory, supported by a distributed brain network. We investigated the dynamic interplay between brain regions, including cortical and white matter structures, to understand how neural interactions change with different memory loads and trials, and their subsequent impact on working memory performance. Patients undertook a task of immediate spatial recall during intracranial EEG monitoring. We charted the dynamics of cortical high-gamma activity and associated functional connectivity modulations in white matter tracts. Elevated memory loads were linked to enhanced functional connectivity via occipital longitudinal tracts, yet decreased through arcuate, uncinate, and superior-longitudinal fasciculi. As task familiarity grew, there was increased high-gamma activity in the posterior inferior-frontal gyrus (pIFG) and diminished functional connectivity ...

Clinical Neurophysiology, Mar 1, 2021

Research Square (Research Square), Feb 26, 2024

Several attempts for speech brain-computer interfacing (BCI) have been made to decode phonemes, s... more Several attempts for speech brain-computer interfacing (BCI) have been made to decode phonemes, sub-words, words, or sentences using invasive measurements, such as the electrocorticogram (ECoG), during auditory speech perception, overt speech, or imagined (covert) speech. Decoding sentences from covert speech is a challenging task. Sixteen epilepsy patients with intracranially implanted electrodes participated in this study, and ECoGs were recorded during overt speech, covert speech, and passive listening of eight Japanese sentences, each consisting of three tokens. A Transformer neural network model was applied to decode text sentences from covert speech, which was trained using ECoGs obtained during overt speech. We first examined the proposed Transformer model using the same task for training and testing and then evaluated the model's performance when trained with overt or perception tasks for decoding covert speech. The Transformer model trained on covert speech achieved an average token error rate (TER) of 46.6% for decoding covert speech, whereas the model trained on overt speech achieved a comparable TER of 46.3% (p > 0.05; d = 0.07). Therefore the challenge of collecting training data for covert speech can be addressed using overt speech. The performance of covert speech can improve by using large amounts of overt speech. * (d=1.02) *: p<0.05 Combination of speech for training and text decoding (In-sample evaluation) Combination of speech for training and text decoding (Out-of-sample evaluation) Perception → Perception Overt → Overt Covert → Covert Perception → Covert Overt → Covert n.s. (d=0.07) n.s. (d=0.38) * (d=1.34) 30.5±10.9% 36.0±10.8% 47.0±3.8% 43.2±4.1% 46.6±5.4% 49.5±4.3% 49.8±2.1% 46.3±3.3%

Research Square (Research Square), Apr 14, 2023

Twisted carotid bifurcation (TCB) is a well-known anatomical variation of the carotid bifurcation... more Twisted carotid bifurcation (TCB) is a well-known anatomical variation of the carotid bifurcation in patients undergoing carotid endarterectomy. However, few investigations of TCB have focused on patients without internal carotid artery (ICA) stenosis. This study was performed to analyze the characteristics of TCB in patients with ICA stenosis and other diverse pathologies. All conventional cerebral angiographies performed in our institute for any reason from January 2012 to December 2018 were reviewed. The patients were divided into two groups, the TCB group and the anatomically normal non-TCB group, and the basic characteristics of the groups were analyzed. Both sides of the carotid bifurcation were clearly visualized in 457 patients. TCB was found in 89 of 457 patients (19.5%); among these 89 patients, 74 (83.1%) had TCB only on the right side, 8 (9.0%) only on the left side, and 7 (7.9%) bilaterally. TCB was found more frequently on the right than left [81 (17.7%) and 15 (3.3%),...

Cognitive Neurodynamics

Epilepsy is a chronic disorder caused by excessive electrical discharges. Currently, clinical exp... more Epilepsy is a chronic disorder caused by excessive electrical discharges. Currently, clinical experts identify the seizure onset zone (SOZ) channel through visual judgment based on long-time intracranial electroencephalogram (iEEG), which is a very time-consuming, difficult and experience-based task. Therefore, there is a need for high-accuracy diagnostic aids to reduce the workload of clinical experts. In this article, we propose a method in which, the iEEG is split into the 20-s segment and for each patient, we ask clinical experts to label a part of the data, which is used to train a model and classify the remaining iEEG data. In recent years, machine learning methods have been successfully applied to solve some medical problems. Filtering, entropy and short-time Fourier transform (STFT) are used for extracting features. We compare them to wavelet transform (WT), empirical mode decomposition (EMD) and other traditional methods with the aim of obtaining the best possible discrimin...

Acta Neurochirurgica

Epileptic seizure is the common symptom associated with lipomas in the Sylvian fissure (Sylvian l... more Epileptic seizure is the common symptom associated with lipomas in the Sylvian fissure (Sylvian lipomas). Removal of these lipomas carries risks of hemorrhage and brain damage. We report a surgical strategy of not removing the lipoma in a case of intractable temporal lobe epilepsy associated with Sylvian lipoma. We performed anterior temporal lobectomy with preservation of the pia mater of the Sylvian fissure and achieved seizure freedom. Focal cortical dysplasia type 1 of the epileptic neocortex adjacent to the Sylvian lipoma was pathologically diagnosed. We recommend our surgical procedure in similar cases to avoid complications and achieve adequate seizure control.

ABSTRACTAlpha waves - posterior-dominant rhythms at 8-12 Hz reactive to eye opening and closure -... more ABSTRACTAlpha waves - posterior-dominant rhythms at 8-12 Hz reactive to eye opening and closure - are among the most fundamental EEG findings in clinical practice and research since Hans Berger first documented them in the early 20th century. Yet, the exact network dynamics of alpha waves in regard to eye movements remains unknown. High-gamma activity at 70-110 Hz is also reactive to eye movements and a summary measure of local cortical activation supporting sensorimotor or cognitive function. We aimed to build the first-ever brain atlases directly visualizing the network dynamics of eye movement-related alpha and high-gamma modulations, at cortical and white matter levels. We studied 28 patients (age: 5-20 years) who underwent intracranial EEG and electrooculography recordings. We measured alpha and high-gamma modulations at 2,170 electrode sites outside the seizure onset zone, interictal spike-generating areas, and MRI-visible structural lesions. Dynamic tractography animated whit...

Japanese Journal of Neurosurgery

Recently, intracranial electrode implantation using a stereotactic robotic device has been gainin... more Recently, intracranial electrode implantation using a stereotactic robotic device has been gaining universal popularity in the field of stereotactic neurosurgery. Robot-assisted implantation has advantages of accuracy, decreased procedure time, and a low complication rate. However, to perform the procedure safely, it is necessary to be skilled in surgical planning and technique. Here we present a case of intracranial stereo-electroencephalography(SEEG)using ROSA-guided robotic surgery. A 19-year-old male presented with intractable focal seizures with impaired consciousness. Brain MRI showed ischemic ulegyria in the medial right occipital lobe；FDG-PET was suggestive of extensive abnormalities from the medial/lateral right temporal lobe to the occipital lobe. In this case, we hypothesized that the ischemic ulegyria in the medial occipital lobe was the epileptic focus. We decided to implant intracranial electrodes extensively from the occipital lobe to the temporal lobe and record SEEG to localize the epileptic focus. After loading the patient's imaging datasets into the ROSA software, seven stereotactic trajectories were selected for the electrode insertion route. To avoid hemorrhagic complications, ROSA software was used to map the optimal surgical paths for each electrode insertion. By incorporating the preoperative simulation, we efficiently performed implantation and confirmed electrode locations using ROSA software. Finally, we detected the habitual seizure and ictal discharges originating from the hippocampus on SEEG. To perform the procedure safely and quickly, it is important to accumulate tips and pitfalls to avoid complications.

ICASSP 2022 - 2022 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Invasive brain-machine interfaces (BMIs) are a promising neurotechnological venture for achieving... more Invasive brain-machine interfaces (BMIs) are a promising neurotechnological venture for achieving direct speech communication from a human brain, but it faces many challenges. In this paper, we measured the invasive electrocorticogram (ECoG) signals from seven participating epilepsy patients as they spoke a sentence consisting of multiple phrases. A Transformer encoder was incorporated into a "sequence-to-sequence" model to decode spoken sentences from the ECoG. The decoding test revealed that the use of the Transformer model achieved a minimum phrase error rate (PER) of 16.4%, and the median (± standard deviation) across seven participants was 31.3% (±10.0%). Moreover, the proposed model with the Transformer achieved significantly better decoding accuracy than a conventional long short-term memory model.

Journal of Neuroscience Research

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Brain and Development

We describe a case of severe encephalopathy with reversible splenial lesion associated with parec... more We describe a case of severe encephalopathy with reversible splenial lesion associated with parechovirus, followed by intractable temporal lobe epilepsy (TLE), which was improved by epilepsy surgery. A 3-year-old girl was admitted because of fever, consciousness disturbance and generalized tonic clonic seizure. Her seizure lasted for four hours. Fluid-attenuated inversion recovery (FLAIR) showed a hyperintensity in the splenium of the corpus callosum. Electroencephalogram (EEG) demonstarated continuous diffuse epileptic activity represented by synchronous and rhythmic high-amplitude spikes and waves, which led to the diagnosis of status epilepticus. Her consciousness was improved with fosphenytoin, midazolam and methylprednisolone pulse after 3 days. Seven days later, FLAIR hyperintensity in the splenium of the corpus callosum was disappeared; however, a hyperintensity in the right hippocampus was detected. Since the stool examination was positive for parechovirus, her final diagnosis was reversible splenial lesion syndrome (RESLES) associated with parechovirus. At age 8, she experienced epigastric sensation and consciousness disturbance once a week. Based on the scalp EEG and radiological findings, she was diagnosed with intractable right TLE. We performed a right selective amygdalohippocampectomy and anterior temporal disconnection at 10 years of age. One year and 3 months after surgery, she was seizure free. To our knowledge, this is the first report of severe febrile epilepticus status. with RESLES associated with parechovirus, followed by intractable TLE, which was resolved by epilepsy surgery.

The Chemical Society of Japan, Jan 18, 2021

IEICE Technical Report; IEICE Tech. Rep., Feb 24, 2021