Hiroyuki Hirose

People with absolute pitch process tones with producing P300

We recorded a P300 component of event-related potentials associated with auditory oddball tasks in nine absolute pitch (AP) possessors and seven non-AP possessors. The previous studies demonstrated that AP possessors did not appear to employ working memory during auditory oddball tasks because they have a fixed tonal template in their memories. However, the present findings showed that the AP possessors exhibited similar P300 as the non-AP possessors and did update the tonal context in the auditory oddball tasks. This result suggests that the AP possessors do not always refer to the fixed tonal template in their memories when executing the oddball tasks and they employ working memory properly according to the difficulty of the auditory tasks.

A magnetoencephalographic study of negative myoclonus in a patient with atypical benign partial epilepsy

PURPOSE To clarify the neurophysiological mechanism of epileptic negative myoclonus (NM) of a patient with atypical benign partial epilepsy whose NM was completely suppressed with ethosuximide. METHODS Polygraphic recordings of whole-head type magnetoencephalography (MEG), EEG and electromyography were made during NM of the bilateral hands. The silent period of 200-400 ms duration in the bilateral biceps muscles was associated with paroxysmal spikes on EEG and MEG. Single equivalent current dipoles (ECD) were calculated for each spike component associated with NM and the estimated generator sources of spikes were superimposed on the patients head MRI. RESULTS The magnetic fields of each peak associated with NM showed clear single dipole pattern and ECDs of each peak were located in the neck and orofacial division of the primary motor cortex. CONCLUSIONS Abnormal firing of the neck and orofacial division of the primary motor cortex was associated with NM generation. Taking the beneficial effect of ethosuximide (a T-type Ca2+ channel blocker in thalamic neurons and the corresponding cortex) and the MEG result together, it is suggested that abnormal interaction of the thalamo-cortical network might be closely related to the pathogenesis of NM.

Patients with benign rolandic epilepsy have a longer duration of somatosensory evoked high-frequency oscillations

Background : High‐frequency oscillations (HFO) ranging between 300–900 Hz have been shown to be superimposed on an early component of somatosensory evoked potentials (SEP) to median nerve stimulation in humans. Although the HFO are speculated to be a localized activity of the GABAergic inhibitory interneurons, the significance in the epileptogenicity remains unclear. The authors of this study analyzed HFO using magnetoencephalography in patients with benign rolandic epilepsy (BRE) to clarify the neurophysio‐logical basis of rolandic discharges (RD).