Masakiyo Yamamoto

Chronic repetitive transcranial magnetic stimulation increases hippocampal neurogenesis in rats.

Aim:  While the underlying therapeutic mechanisms of repetitive transcranial magnetic stimulation (rTMS) treatment for depression remain unclear, recent animal studies have suggested that hippocampal neurogenesis might be required for the effects of antidepressant treatments including antidepressant drugs and electroconvulsive therapy. The aim of this study was to examine chronic rTMS effects on hippocampal neurogenesis in rats.

Treatment of typical Charles Bonnet syndrome with donepezil

Charles Bonnet syndrome (CBS) is characterized by the presence of complex visual hallucinations in psychologically normal people. Although visual hallucinations in the elderly are often associated with dementia with Lewy body (DLB), Alzheimers disease and delirium, they are excluded from the diagnosis of typical CBS, as are cognitive or psychiatric disturbances, sleep disorders and focal neurological lesions. Here, we describe a patient with typical CBS, who responded to donepezil, a cholinesterase inhibitor, and has not shown any symptoms suggestive of Alzheimers disease or DLB for approximately the past 40 months. However, follow-up examination of her clinical symptoms is necessary for a definite exclusion of Alzheimers disease and DLB. The effectiveness of donepezil indicates that the patients visual hallucinations might be related to dysfunction of cholinergic neurones, although she did not exhibit any cognitive decline, or morphological and physiological brain pathology. Because donepezil has fewer adverse effects than anticonvulsants and neuroleptic drugs, it may be a safer option for the treatment of CBS in the elderly.

Slow repetitive transcranial magnetic stimulation increases somatosensory high-frequency oscillations in humans

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a possible treatment for psychiatric and neurological disorders characterized by focal brain excitability, such as major depression and action myoclonus. However, the mechanism of modulating excitability by rTMS is unclear. We examined the changes in high frequency oscillations (HFOs) of somatosensory evoked potentials (SEPs) before and after slow rTMS over the right primary somatosensory cortex (0.5 Hz, 50 pulses, 80% motor threshold intensity). The HFOs, which represent a localized activity of intracortical inhibitory interneurons, were significantly increased after slow rTMS, while the SEPs were not changed. Our results suggest that slow rTMS affects cortical excitability by modulating the activity of the intracortical inhibitory interneurons beyond the time of the stimulation and that rTMS may have therapeutic effects on such disorders.

Donepezil in the treatment of musical hallucinations

Abstract  Musical hallucinations (MH) typically occur among elderly individuals and are associated with hearing impairment. The authors describe a patient with features of typical MH who was successfully treated with donepezil, a cholinesterase inhibitor, as a combination therapy and who has not shown any subsequent cognitive decline for approximately 5 years. The efficacy of donepezil in this patient indicates that age‐dependent dysfunction of cholinergic neurons might be related to the development of MH.

Spatially Filtered Magnetoencephalographic Analysis of Cortical Oscillatory Changes in Basic Brain Rhythms during the Japanese ‘Shiritori’ Word Generation Task

Background: ‘Shiritori’ (capping verses) is a traditional Japanese word generation game, and is very familiar to native Japanese speakers. The shiritori task is expected to more strongly activate temporal language-related regions than conventional word generation to letters because of its characteristic way to make cue letters. Objectives: The aim of this study was to examine the cortical oscillatory changes in basic brain rhythms during silently performing a shiritori task. Methods: Using synthetic aperture magnetometry (SAM) analysis of magnetoencephalography, we estimated the tomographic distributions of the statistically significant differences of the power in the alpha and beta frequency bands between the resting and the task periods. Results: Significant event-related desynchronization (ERD) in the 8- to 25-Hz band, thought to reflect neural activation, was localized within task-related cortical regions with left-side dominance. The significant ERDs were estimated in both the frontal and temporal language-related regions encompassing Broca’s and Wernicke’s areas, although previous neuroimaging studies using word generation to letters showed neural activation predominantly in frontal regions. Conclusions: Our results show the potential of SAM analysis for reliable brain mapping of language processing, and suggest that the shiritori task might be more suitable for examining the language-related network in the brain than conventional word generation to letters.

Information Processing Flow and Neural Activations in the Dorsolateral Prefrontal Cortex in the Stroop Task in Schizophrenic Patients A Spatially Filtered MEG Analysis with High Temporal and Spatial Resolution

Using a spatially filtered magnetoencephalography analysis (synthetic aperture magnetometry), we estimated neural activations in the Stroop task in nearly real time for schizophrenic patients with/without auditory hallucinations and for normal control subjects. In addition, auditory hallucinations were examined through the information processing flow of the brain neural network, including the frontal regions. One hundred unaveraged magnetoencephalography signals during the incongruent stimulus responses were analyzed with a time window of 200 ms in steps of 50 ms. In the 25–60-Hz band, cortical regions that showed significant current source density changes were examined for each time window. The three groups showed significantly decreased current source density, corresponding to neural activation, with temporal overlap along the fundamental cognitive information processing flow: sensory input system, executive control system, motor output system. Transient neural activations in the dorsolateral prefrontal cortexwere bilateral with left-side dominancy for normal controls, left-lateralized for nonhallucinators and right-lateralized for hallucinators. Our results suggest that the dysfunction in the left dorsolateral prefrontal cortex was related to auditory hallucinations, while the information processing flow was unaffected in the schizophrenic subjects in the Stroop task.

Desynchronization in the right auditory cortex during musical hallucinations: A MEG study

Desynchronization in the right auditory cortices, including the transverse gyrus of Heschl, planum temporale and supramarginal cortex, occurred during musical hallucinations in a 78‐year‐old woman with hearing impairment and depression. This phenomenon was assessed using a novel, spatially filtered magnetoencephalography (MEG) analysis, termed synthetic aperture magnetometry (SAM). In general, the affected areas are consistent with neuroimaging studies of normal musical perception and imagery, suggesting that musical hallucinations involve abnormal spontaneous activity in the neural substrate dedicated to musical perception and imagery in which false imagery occurs.

P03.6 Neuromagnetic oscillatory response during movement observation in Asperger disorder

clinical noninvasive tests of hemispheric language dominance in candidates for brain surgery. Methods: Healthy subjects (10 strongly right-handed, 10 strongly left-handed, 5 weakly right-handed, and 2 ambidextrous) listened to binaural pairs of tones and pairs of Finnish vowels and decided whether the items in the pair were the same (target probability 20%). Cortical responses were recorded with whole-scalp magnetoencephalography. Results: The laterality index for strengths of the auditory-cortex 100-ms responses (N100m) to vowels vs. tones suggested left-hemispheric dominance in 8 of the 10 strongly right-handed subjects, and right-hemispheric dominance in 7 of the 10 left-handed subjects. Conclusions: Our results demonstrate difference in hemispheric dominance for processing of vowels between righthanded and left-handed subjects. This difference resembles language lateralization suggested by previous invasive studies as well as by anatomical and functional comparisons in leftand right-handed subjects.