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Biomedical subjects

Nobuhiro Mikuni

Publications and source records attributed to Nobuhiro Mikuni.

26 records · Page 2Linked to original sources
PubMed2004

Endotracheal tube electrodes to map and monitor activities of the vagus nerve intraoperatively. Technical note.

Difficulty swallowing due to damage of the vagus nerve is one of the most devastating complications of surgery in and around the medulla oblongata; therefore, intraoperative anatomical and functional evaluation of this nerve is crucial. The authors applied endotracheal tube surface electrodes to record electromyography (EMG) activity from vocal cords innervated by the vagus nerve. The vagal nucleus or rootlet was electrically stimulated during surgery and vocalis muscle EMG activities were displayed by auditory and visual signals. This technique was used successfully to identify the vagus motor nerve and evaluate its integrity during surgery. The advantages of this method compared with the use of needle electrodes include safe simple electrode placement and stable recording during surgery. In cases involving a pontine cavernoma pressing the nucleus or a jugular foramen tumor encircling the rootlet, this method would be particularly valuable. Additional studies with a larger number of patients are needed to estimate the significance of this method as a means of functional monitoring to predict clinical function.

Adolescent↗
PubMed2003

Distinct cortical areas for motor preparation and execution in human identified by Bereitschaftspotential recording and ECoG-EMG coherence analysis.

OBJECTIVE: To clarify the cortical areas involved in motor preparation and execution by investigating Bereitschaftspotentials (BPs) and electrocorticogram-electromyogram (ECoG-EMG) coherence from subdural electrodes placed around the rolandic area. METHODS: BPs and ECoG-EMG coherence were investigated for presurgical evaluation in a patient with cavernoma in the left frontal lobe. BPs were recorded in association with the tongue, right hand and right foot movements. ECoG-EMG coherence was calculated in association with weak muscle contraction of the right hand. RESULTS: Two cortical areas related to voluntary motor control were identified; one in the primary hand motor area, which generated surface-negative BPs with hand movements and showed significant coherence of ECoG with EMG of the contralateral hand muscle, and the other in the ventral rolandic area posterior to the central sulcus, which generated surface-positive BPs with voluntary movements of multiple sites (hand, tongue and foot) but did not show any ECoG-EMG coherence. CONCLUSIONS: It is postulated that the former area represents the primary motor area involved in both motor preparation and execution, and the latter area represents the non-primary motor area involved in motor preparation. SIGNIFICANCE: BP recording combined with ECoG-EMG coherence analysis could reveal the functional roles of motor cortices and the reorganization induced by structural brain lesion.

Brain Mapping↗
PubMed2003

Conversion of semantic information into phonological representation: a function in left posterior basal temporal area.

A unique feature of Japanese language is that its written sentences consist of both morphograms (kanji) and syllabograms (kana). Despite extensive research by PET, functional MRI and magnetoencephalography, the issues of the difference (or the similarities) between the processing of kanji and kana, and between word reading and object/picture naming have not been resolved as yet. This study investigated the function of the posterior basal temporal area in the language dominant hemisphere in auditory and visual language processing, with special emphasis on semantic and phonological recognition. Subdural electrode grids were placed on the left temporal area of a right-handed woman with intractable temporal lobe epilepsy as part of a pre-surgical evaluation. Her dominant hemisphere for language was shown to be the left on the Wada test. Electric stimulation of 50 Hz was applied to the electrodes during the tasks related to language. Our results showed a clear distinction in the responses and/or performance of the subject depending on the type of characters presented and the tasks employed. Electric stimulation of a localized area in the posterior basal temporal lobe caused neither comprehensive nor productive deficit in the tasks using auditory stimuli. In the tasks using visual stimuli, in contrast, impairments were observed in (i) reading of kanji words and (ii) naming of objects/pictures and geometric designs, but not in (iii) reading of kana, (iv) copying of kanji, kana and geometric designs, and (v) using tools. The subject maintained full comprehension of spoken language, suggesting that the auditory tasks are not processed in the posterior basal temporal area. The fact that the impairment of kanji reading and disturbance of object/picture naming were elicited by electric stimulation of the same area indicates that there is at least one anatomical area that is used commonly for kanji (but not kana) and object processing. The conceptual entity of the test items supposedly was recognized correctly, but the concept failed to be matched to correct phonological representation. The left posterior basal temporal area, therefore, has an important function of connecting visual semantic information into phonological representation.

Adult↗
PubMed2002

"Supplementary motor area (SMA) seizure" rather than "SMA epilepsy" in optimal surgical candidates: a document of subdural mapping.

PURPOSE: To clarify the relationship between epileptogenic zone and supplementary motor area (SMA) in patients who were regarded as the optimal surgical candidates for their intractable SMA seizures. METHODS: We analyzed the epileptogenic zone at/or adjacent to the SMA in four patients with clinical SMA seizures. All four patients had noninvasive presurgical evaluations (long-term video/EEG monitoring, MRI, and neuroimaging with radioisotopes), which provided convergent results between ictal semiology and the epileptogenic area, and thus, they had chronically implanted subdural electrodes, and finally had focus resection with a follow-up period of more than 2 years. RESULTS: Three patients had lesions shown by MRI outside the SMA, and one patient had a lesion within the SMA. Interictal epileptiform discharges were seen at/or outside the SMA. Ictal EEG pattern originated from the SMA in one patient, from the high lateral frontal area in two patients, and from the precuneus in one patient. In the latter three patients, the ictal EEG pattern immediately spread to the SMA. Those ictal onset zones were consistently localized within/or just adjacent to the lesions revealed by MRI. Only one patient had SMA resection, and three had the resection of epileptogenic zone by preserving the SMA. No neurological deficits developed and good seizure control was achieved. CONCLUSION: Among surgical candidates for intractable SMA seizures, frontal cortex other than SMA or even parietal cortex can be epileptogenic, and thus, the SMA itself may not necessarily have to be resected. This notion is clinically important when selecting surgical candidates as well as when planning presurgical invasive evaluation in patients with intractable SMA seizures.

Adolescent↗
PubMed2002

Low-frequency electric cortical stimulation has an inhibitory effect on epileptic focus in mesial temporal lobe epilepsy.

PURPOSE: This study was conducted to investigate the effect of low-frequency electric cortical stimulation on epileptic focus in humans. METHODS: We stimulated the epileptic focus in a patient with medically intractable mesial temporal lobe epilepsy (MTLE) by means of subdural electrodes and evaluated the change in the number of interictal epileptiform discharges. We used biphasic electric current of 0.3-ms duration presented at 0.9-Hz frequency for 250 s, comparing stimulus intensity of 7.5, 2, and 0.5 mA. RESULTS: Interictal epileptiform discharges at the ictal focus occurred less frequently after the stimulation with the intensity of 0.5 mA. With the intensity of 7.5 mA and 2.0 mA, however, habitual auras were elicited by the stimulation, and afterdischarges were seen on the cortical EEG. CONCLUSIONS: Low-frequency, low-intensity electric cortical stimulation could produce inhibitory effects on epileptic activity. At the same time, however, a caution for possible induction of EEG seizures is needed, even when applying low-frequency electric stimulation.

Adolescent↗
PubMedDate not supplied

Pre- and postnatal expressions of NMDA receptors 1 and 2B subunit proteins in the normal rat cortex.

The NMDA receptor is one of the ionotropic glutamate receptors essential for excitatory neurotransmission and synaptic plasticity. The present study examined the ontogenies of NMDAR1 and NMDAR2B during development (embryonic days: (E) 14, 15, 16, 17 and postnatal days: (P) 0, 5, 10, 20, and 60). The immunoreactivities of both NMDAR1 and NMDAR2B were visualized and semi- quantified simultaneously using batch-matched procedures during the developmental period. In addition, the heteromeric coassembly of NMDAR1 (NR1) and NMDAR2B (NR2B) was analyzed throughout development using immunocoprecipitation blots. Differential developmental expressions were observed between the two NMDA receptor subunits. Although both NR1 and NR2B were already expressed on cortical neurons at E14, NR1 immunoreactivity was lower than NR2B but increased up to P20 then was lower at the last sampling day (P60). By comparison, the high NR2B immunoreactivity at E14 increased until P5, and until the next sample day (P60). Despite the early embryonic protein expressions in prenatal cortex both NR1 and NR2B immunocoprecipitation analyses showed that NR1-NR2B coassembly was not initially detectable until birth (P0), and increased up to P20. This suggests that the physically interactive NMDAR1-2B complex may contribute to the plasticity of early postnatal development characterized by axonal dendritic synaptogenesis.

Analysis of Variance↗