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Kenji Yanashima

Publications and source records attributed to Kenji Yanashima.

6 recordsLinked to original sources
PubMed2004

[Evaluation of time resolution of the primary motor cortex by a single paradigm using a stimulation system].

Many researchers are investigating brain function by using a block paradigm in fMRI measurement. However, time resolution has been limited because the block paradigm employed data collection by consecutive image acquisition after stimulation began. Because of this problem, the evaluation of early brain activity was not adequate. Therefore, a system that was able to take imaging from a high time dependence to stimulation in real time was necessary to evaluate early brain activity. It is necessary to obtain controlled image taking by an MRI device with an external trigger by creating a sequence design in the system controlling stimulation and a sequence designed to achieve the above. The execution of a single paradigm by the originally designed sequence thus becomes possible, and arbitrarily setting all processes from stimulation to image taking is possible. It is thought that the practical use of the single paradigm designed by the control system of stimulation enables real-time imaging for stimulation and provides time-dependent data. From this, evaluation of brain activity of the primary motor cortex is possible in the early stage by event-related data collection. In addition, "sank," a relative decrement in PO(2) was also an initial stage of BOLD, that is, an initial dip occurs as a transitory signal change by using a single paradigm that synchronizes with the control system of stimulation for the evaluation of early brain activity. Moreover, it is thought that taking images by a single paradigm that is synchronized with the control system of stimulation is indispensable for time and spatial elucidation of detailed brain activity, to evaluate hyper brain function. Therefore, the brain activity in the primary visual cortex at the early stage was clarified in this study by using a single paradigm designed to synchronize with the control system of stimulation by single-shot EPI.

Adult↗
PubMed2003

[Electrophysiological and histopathological study on visual toxicity of clioquinol].

OBJECTIVE: To evaluate the effect of clioquinol on the optic nerve and retina of rhesus monkeys by ophthalmoscopy, electrophysiology and histopathology. METHODS: Clioquinol was given orally to 5 monkeys, gradually increasingly from 100 mg/kg/day up to 14 months(total dosage 227 g/kg). Ophthalmoscopy, erectroretinogram(ERG), visual evoked potential(VEP) and histopathological examination of enucleated eyeballs were done periodically up to 10 years. RESULTS: The margin of the optic disc was not clear at the early stage, but the colour became atrophic at the late stage. VEP maximum amplitude decreased quickly at the early stage and the amplitude of ERG a and b waves and oscillatory potential decreased gradually. 37 months after the discontinuation of administration of VEP, ERG amplitude increased gradually. Swelling of axons and disorganization of the myelin sheath were noticed 2.5 months after beginning treatment. Swelling of the peripapillary nerve fiber layer was seen 5.5 months after beginning treatment. Karyorrhexis was seen in the inner layer of the retina after 12.5 months. Axonal swelling disappeared and the myelin sheath became reorganized 9 months after the discontinuation of treatment. CONCLUSIONS: Clioquinol produced an early decrease of electrophysiological function, but recovery of function was seen after discontinuation of treatment. The degeneration of axons and myelin sheath continued during treatment, and interruption of the degeneration was seen after discontinuation of treatment.

Animals↗
PubMedDate not supplied

Multifocal visual evoked potential is dependent on electrode position.

PURPOSE: To investigate whether the multifocal visual evoked potential (mVEP) is dependent on the electrode position, and to confirm the reproducibility of the mVEP. METHODS: The mVEPs were recorded using the Veris III system with two different bipolar electrode settings. In Position 1, electrodes were placed at equal distances in vertical alignment 2 cm above and below the inion. In Position 2, the electrodes were placed in horizontal alignment at equal distances 2 cm to the left and right of the inion. Dartboard pattern stimulation was conducted. The mVEPs were repeatedly recorded from 4 volunteers, and mainly the second-order kernel response components were analyzed. RESULTS: Although the reproducibility of mVEP was good in both Position 1 and Position 2, each waveform of the mVEP was drastically different between the two positions. This difference in the waveforms was clearly shown in the center and at the horizontal meridian. We also investigated the first-order kernel response components of the mVEPs. Several traces of the first-order kernel response components did not reveal flat traces. This point is also worthy of consideration. CONCLUSION: Responses from mVEPs are clearly dependent on the electrode position.

Adult↗
PubMedDate not supplied

Nonlinear component of the electroretinogram recorded from the posterior pole of normal and highly myopic human eyes.

To extract the nonlinear component of the electroretinogram (ERG) from the posterior pole (pp) of the human ocular fundus and to evaluate the possibility of its clinical application, three types of stimulus modes - double-flash, single-flash, and delayed single-flash stimuli - were produced using a conventional electrophysiological system. A large hexagonal element was presented on a CRT monitor, and ppERGs were recorded from 14 normal eyes and 16 eyes of eight highly myopic patients. The nonlinear component of the ppERG was obtained by subtracting the single-flash ERG and delayed single-flash ERG responses from the double flash ERG response. Three peaks were commonly observed in the nonlinear component of ppERG, all of which were significantly depressed in patients with high myopia. ppERGs that can be obtained using a simple algorithm might be useful in clinical applications.

Adolescent↗