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Biomedical subjects

H Imaoka

Publications and source records attributed to H Imaoka.

13 recordsLinked to original sources
PubMed2003

Transcranial magnetic stimulation over the cerebellum evokes late potential in the soleus muscle.

Transcranial magnetic stimulation (TMS) with a double cone coil placed over the left lateral side of the basal occiput was able to elicit late electromyographic (EMG) responses at the bilateral soleus muscles (SOL) averaged over 30 stimulation events, with a mean latency of approximately 100 ms. These EMG responses were detected using a low frequency bandpass filter with 0.05 Hz magnetic stimulation on ten healthy subjects in standing posture. As magnetic stimulation over the left basal occiput with a double cone coil can stimulate cerebellar structure, this late response seems to be conducted from the cerebellar structure to the SOL via an as yet unknown descending pathway. Here, we report new late EMG responses in relation to cerebellum or cerebellum related structures.

Adult↗
PubMed2001

A complex cell-like receptive field obtained by information maximization.

The energy model (Pollen & Ronner, 1983; Adelson & Bergen, 1985) for a complex cell in the visual cortex is investigated theoretically. The energy model describes the output of a complex cell as the squared sum of outputs of two linear operators. An information-maximization problem to determine the two linear operators is investigated assuming the low signal-to-noise ratio limit and a localization term in the objective function. As a result, two linear operators characterized by a quadrature pair of Gabor functions are obtained as solutions. The result agrees with the energy model, which well describes the shift-invariant and orientation-selective responses of actual complex cells, and thus suggests that complex cells are optimally designed from an information-theoretic viewpoint.

Animals↗
PubMed2000

Skin hemodynamics during change from supine to lateral position.

The purpose of this study was to identify the skin hemodynamics during the position change from supine to lateral in patients with neurodegenerative diseases. The participants were 19 patients with neurodegenerative diseases and 12 healthy volunteers. The alteration in the total concentration of oxyhemoglobin and deoxyhemoglobin, indicative of change in blood volume, was measured in the skin of the left flank by using a portable noninvasive tissue oxygen monitor by near-infrared spectroscopy. The positions were changed from the left and right lateral with a return to the supine between each procedure. In healthy volunteers, total hemoglobin concentration (skin blood volume) increased when the position changed from supine to left lateral and decreased when changed from supine to right lateral. The decreased skin blood volume gradually recovered after a change from the supine to the right lateral position in healthy volunteers. However, it did not recover in three sporadic olivopontocerebellar atrophy (OPCA) patients with marked autonomic dysfunction and one Parkinsonian patient with severe orthostatic hypotension. Our study identified that the intracutaneous blood was changing dynamically during the position change from supine to lateral and was regulated by autonomic nerve function.

Autonomic Pathways↗
PubMed1995

Abnormal evoked potentials of Kearns-Sayre syndrome.

We examined eight patients with Kearns-Sayre syndrome (KSS) to investigate a dysfunction in the central nervous system (CNS) using PTN-SEP, MN-SEP and BAEP. We found a significant increase in the P37 latency of PTN-SEPs and the central conduction time of MN-SEPs, and interpeak latencies of BAEPs. Delayed SEPs or BAEPs were caused by a dysfunction of the somatosensory or lateral lemniscus pathways which could be related to mitochondrial abnormalities in the CNS. Long-term therapy with CoQ showed an improvement of the latencies of SEPs after about half a year from the start of CoQ therapy in our patients. The improvement of the latencies of SEPs were preserved during CoQ therapy. It could be demonstrated that CoQ therapy had the beneficial effects on abnormal functions of the CNS in patients with KSS.

Adult↗
PubMed1992

Improved inching method for the diagnosis and prognosis of carpal tunnel syndrome.

A modified sensory "inching" method for the electrodiagnosis of carpal tunnel syndrome (CTS) is described. The median nerve as stimulated at the cubital portion, with 8 channel recording electrodes placed along the nerve across the carpal tunnel. In most of the CTS cases, there was a conductive abnormality from 3 to 4.5 cm distal to the proximal ending of the flexor retinaculum. Subjects' values, obtained by subtracting the theoretical latency from the measured latency, which were more than 0.6 ms, could not be improved by conservative therapy. As we could determine from subtle change at the short span of nerve conduction, below the electrodes from the proximal to the affected site of the carpal tunnel, this method provides high sensitivity and specificity for the diagnosis of CTS.

Action Potentials↗
PubMed1989

Clinical utility of somatosensory evoked potentials in diabetes mellitus.

The posterior tibial nerve and median nerve somatosensory evoked potentials (PTN-SEPs and MN-SEPs) were investigated in 34 patients with diabetes mellitus (DM). We measured the latency of the first positive cortical potential (the cortical P37) of PTN-SEPs and that of the first negative cortical potential (the cortical N18) and Erb's potential of MN-SEPs. In 18 patients (52.9%), the cortical P37 latency was more than 3 SD longer than normal in the tibial nerve. There were positive correlations between the latency of cortical P37 and the duration of DM and the motor nerve conduction velocity of the posterior tibial nerve. Sensory action potentials of the posterior tibial nerve were not detectable in 21 patients, though cortical P37 potential was unambiguously recorded by stimulating the posterior tibial nerve even in those subjects. Diabetic retinopathy and nephropathy also tended to rise with increasing latency of cortical P37. The latency of cortical P37 is an important parameter in assessing diabetic neuropathy.

Adult↗
PubMed1989

Brainstem auditory and somatosensory evoked potentials in neuro-Behçet's syndrome.

Brainstem auditory evoked potentials (BAEPs) and somatosensory evoked potentials after median nerve stimulation (MN-SEPs) and after posterior tibial nerve stimulation (PTN-SEPs) were studied in 17 patients with neuro-Behçet's syndrome (NB). Eleven patients (64.7%) showed an absence of wave I, III or V or a prolongation of the interpeak latency I-III, or III-V in BAEPs. Six patients (37.4%) showed a prolongation in the latency of cortical P37 of PTN-SEPs and/or the interpeak latency EP-N13 or N13-N18 of MN-SEPs. The BAEP and SEP abnormalities indicated a conduction failure of the acoustic lateral lemniscus pathway and the medial lemniscus pathway in the brainstem of the patients with NB. Abnormal EPs can provide sensitive information which shows the presence of subclinical lesions in the central nervous system.

Adult↗
PubMed1988

Resistance of the peripheral nerve to ischemia in diabetic patients--an electrophysiological study.

We studied the effect of ischemia on the excitability of the sensory fibers of the median nerve in 43 patients with non-insulin-dependent diabetes mellitus (NIDDM) by a double stimulation method. Ischemia caused significantly less reduction of nerve excitability in patients with poor glycemic control and in patients diseased for 5 years or longer than in the normal control group. Hyperexcitability after ischemia was markedly greater than normal among short-term, poorly controlled diabetics, and markedly less pronounced among long-term, poorly controlled diabetics. In many diabetic patients with normal conduction velocity or without sensory disturbance, post-ischemic hyperexcitability was remarkable. A study of nerve excitability may be useful as one means of detecting early-stage disturbance of the diabetic peripheral nerve.

Adult↗
PubMedDate not supplied

Abnormal brainstem evoked potentials in diabetes mellitus. Evoked potential testings and magnetic resonance imaging.

Brainstem auditory evoked potentials (BAEPs) and median nerve somatosensory evoked potentials (MN-SEPs) were measured in 53 diabetic patients. Magnetic resonance imaging (MRI) was performed 12 patients with abnormal BAEPs and/or MN-SEPs in order to confirm the existence of lesions in the central nervous system. Twenty-six percent of the diabetic patients had abnormal BAEPs and three had a prolongation of the central conduction time in the MN-SEPs. MRI findings of ten of the 12 patients with abnormal BAEPs or MN-SEPs showed multiple small lesions in the pons, thalamus, and centrum semiovale etc. Two of them showed small lesion in the pontine basis which could induce prolonged interpeak latencies of BAEPs. Our MRI study might suggest that abnormal brainstem evoked potentials in diabetic patients were induced by diabetic macroangiopathy or microangiopathy.

Adolescent↗
PubMedDate not supplied

Comparative study of evoked potentials in multiple sclerosis and neuro-Behçet's syndrome.

We studied somatosensory evoked potentials (SEPs) and brainstem auditory evoked potentials (BAEPs) in Japanese patients with multiple sclerosis (MS) and those with neuro-Behcet's disease (NB). Abnormal cortical P37 of posterior tibial nerve SEPs or cervical N13 of median nerve SEPs were more frequently found in the MS patients than in the NB patients. On the other hand, prolongation of the central conduction time of median nerve SEPs or abnormal BAEPs were more common in NB than in MS. The present data showed that lesions were mainly present in the spinal cord in MS and in the brainstem in NB. SEPs and BAEPs were considered of great value for detecting the involvement of the central nervous system in MS and NB and distinguishing between these diseases.

Adult↗