Biomedical subjects

Yasuhiro Haruta

Publications and source records attributed to Yasuhiro Haruta.

6 recordsLinked to original sources

PubMed2004

New method for detecting misrouted retinofugal fibers in humans with albinism by magnetoencephalography.

In humans with albinism, a large percentage of the ganglion cell axons from the temporal retina decussate abnormally in the chiasm and synapse in the contralateral LGN. The aim of this study was to determine whether the misrouting of the optic fibers can be detected by magnetoencephalography (MEG). Visually evoked magnetic fields (VEFs) were recorded from three patients with albinism. After monocular stimulation, the isofield contour maps of the VEFs showed a single current dipole pattern over the contralateral hemisphere in patients with albinism. These results clearly illustrated the reduced uncrossed retinofugal pathway of patients with albinism.

Adolescent↗

PubMed2004

Is there training-dependent reorganization of digit representations in area 3b of string players?

OBJECTIVE: The digit representations in area 3b were studied to examine whether there is training-dependent reorganization in string players. METHODS: Somatosensory evoked magnetic fields were recorded following electrical stimulation of digits 1 (D1), 2 (D2) and 5 (D5) of both hands in 8 string players and of the left hand in 12 control subjects. The N20m and P30m responses, and high-frequency oscillations (HFOs) were separated by 3-300 Hz and 300-900 Hz bandpass filtering. RESULTS: The dipole locations on the coronal plane and strengths of D1, D2 and D5, and D1-D5 cortical distance estimated at the peak of N20m or P30m did not differ between left and right hand in string players or between left hand in string players and controls. On the other hand, the dipole locations of D2 estimated from N20m and P30m and of D1 from N20m were significantly anterior, the D2-D5 distance from P30m longer, and the number of HFO peaks larger for D5 in string players than controls. CONCLUSIONS/SIGNIFICANCE: With strong mutual competition among the fingering digits, the scale of reorganization should be much smaller as compared with the competition-free denervation-induced reorganizations. Taken together, the training-dependent reorganization of somatosensory cortex in string players is manifest not only in the enlarged cortical representation but also in the enhanced HFOs presumably representing activity of the fast-spiking interneurons.

Adolescent↗

PubMed2002

Contribution of primary somatosensory area 3b to somatic cognition: a neuromagnetic study.

Interference effects on somatic cognition were compared with those on primary magnetic N20m responses. During tactile interference to various sets of digits, sensory thresholds for electric middle finger stimulation were measured, and then N20m was elicited with the intensity 4 mA above the sensory threshold measured without interference. After the recording, subjective magnitudes for the test stimuli were reported. Modifications of N20m and above psychophysical measures were dependent on the distance between electrically and mechanically activated areas. The differential N20m attenuation is considered to be generated within the neural circuitry in area 3b consisting of mechanically and electrically activated pyramidal neurons. The result indicates that such circuitry plays a fundamental role in magnitude estimation of somatic stimuli.

Adult↗

PubMed2002

Neural mechanisms for generation of tactile interference effects on somatosensory evoked magnetic fields in humans.

OBJECTIVES: We examined modification of somatosensory evoked fields following electric middle finger stimulation with interference to the same and surrounding digits in 13 subjects. METHODS: During electric middle finger stimulation, concurrent tactile stimulation was applied to the middle finger, to the index and ring fingers, and to the thumb and the little finger, individually. RESULTS: The amplitudes of the N20m and the P30m were significantly reduced by the interference to the middle finger, and to the index and ring fingers. The former interference induced more prominent attenuation than the latter. The amplitudes of the P60m did not show significant changes by any kind of the interference. CONCLUSIONS: The N20m and the P30m were attenuated according to the cortical distance between electrically and mechanically activated 3b areas. Pyramidal neurons are interconnected by intrinsic horizontal collaterals, even if their representations are segregated. The activation of the intrinsic collaterals induces direct excitation and indirect inhibition (via inhibitory interneurons) to the target pyramidal neurons. The result indicates that the activation of the intrinsic collaterals inhibits, on balance, the postsynaptic pyramidal targets, thereby generating the attenuation of the N20m and P30m.

Adult↗

PubMed2002

Movement interference attenuates somatosensory high-frequency oscillations: contribution of local axon collaterals of 3b pyramidal neurons.

OBJECTIVES: We examined the effects of movement interference on high-frequency oscillations (HFOs) and N20m in 10 healthy subjects. METHODS: For the movement interference condition, somatosensory evoked magnetic fields (SEFs) following electric median nerve stimulation were recorded during voluntary movement of the digits. For the control condition, the SEFs were recorded without interference. The N20m and HFOs were separated by 3-300Hz and 300-900Hz bandpass filtering. Then, the peak-to-peak amplitudes were measured. RESULTS: Both interference/control amplitude ratios for the N20m and HFOs were smaller than 100%. In contrast, the HFO/N20m amplitude index, which was calculated by dividing the interference/control amplitude ratio for the HFOs with that for the N20m, was significantly greater in the movement interference condition than in the control condition. CONCLUSIONS: Although the overall amplitude of the HFOs was decreased by movement, enhancement of the HFOs by the movement was revealed by the HFO/N20m amplitude index. Thus, we suggest that the HFOs represent activity of the inhibitory interneurons excited by both thalamocortical afferent impulses and excitatory synaptic inputs from pyramidal neurons in area 3b through their local axon collaterals, thereby reflecting both feed-forward and feedback inhibitory effects onto the post-synaptic pyramidal neurons.

Adult↗

PubMedDate not supplied

Multifocal magnetoencephalogram applied to objective visual field analysis.

PURPOSE: To establish an objective visual field analysis by visual evoked magnetic fields. METHODS: Forty-eight focal areas of the visual field were stimulated by the visual evoked response imaging system (VERIS). The multifocal visual evoked magnetic fields (mfVEFs) of 11 healthy subjects were recorded. The output signals were recorded with VERIS, and the second-order kernel was calculated. The equivalent current dipoles (ECDs) were estimated, and the relative positioning of ECDs was determined by a magnetoencephalography (MEG) system. RESULTS: The mfVEFs consisted of either two- or three-peak waves. Large amplitude mfVEFs were elicited when the stimulus was confined to 6 degrees of the central visual field, but a strong response could not always be obtained between 6 degrees and 12 degrees. All ECDs were estimated to originate in the occipital striate cortex. The ECDs for the upper (lower) field stimulations were estimated to be on the lower (upper) cortex, while those for right (left) field stimulations were on the left (right) cortex. CONCLUSIONS: The locations of mfVEF peak ECDs were correlated with the stimulated visual field and generally matched the cruciform model. In combination with the multifocal technique, MEG can be used for objective visual field analysis.

Adult↗