Haruhiko Naito

Microelectrode study on the subnuclei of the oculomotor nucleus in the cat

Abstract The oculomotor nucleus of the cat was investigated by means of the marking microelectrode technique. By antidromic spike response to stimulation of the respective oculomotor nerve branch, inferior rectus, medial rectus, superior rectus and inferior oblique neurons were identified, and their locations were determined histologically. (1) The antidromic spike latency of 27 inferior rectus units was between 0.4 and 3.0 msec, and the conduction velocity calculated on this group was between 12.0 and 90.0 m/sec. The inferior rectus neurons were predominantly located in the ventro-rostral part of the somatic oculomotor nucleus ipsilateral to the stimulated nerve. (2) The antidromic latency of 39 medial rectus units ranged from 0.5 to 2.1 msec, the conduction velocity along their axons was 14.5 and 64.0 m/sec. The medial rectus neurons were located in the dorsorostral part of the somatic nucleus ipsilateral to the stimulated nerve. (3) The antidromic latency of 17 superior rectus units was between 0.5 and 3.0 msec, and the mean conduction velocity was 27.2 m/sec. The superior rectus neurons were located in the most caudal part of the somatic nucleus contralateral to the stimulated nerve. (4) The antidromic latency of 34 inferior oblique neurons was between 0.4 and 6.6 msec, and the mean conduction velocity was 23.4 m/sec. The inferior oblique neurons were located in the dorsocaudal part of the somatic nucleus ipsilateral to the stimulated nerve.

Intracellular phenomena and spread of epileptic seizure discharges

Abstract The cellular behavior in the course of spreading seizure discharges has been investigated by means of intracellular recordings. These were obtained from cells in the left anterior sigmoid cortex of the cat during and after after-discharges induced by electrical stimulation of the surface of the ipsilateral posterior sigmoid cortex. The responses elicited by single stimuli to the cortical surface of either the anterior or the posterior sigmoid gyrus were also investigated before, during and after epileptiform activation. The intracellular potential changes observed were considered to reflect three different states of cell activity (propagated, projected and depressed seizure state). In a propagated seizure state , a sustained membrane depolarization was generated, in most instances, soon after the cessation of repetitive stimulation. Changes of synaptic potentials elicited by single stimuli were assumed to be similar to those of a cell that was directly induced into a seizure state following local tetanization applied to the cortex involving the cell. In a projected seizure state , little or no sustained depolarization occurred and polarizing waves were seen periodically with concurrent waves in the ECoG. Both excitatory post-synaptic potentials (EPSPs) and inhibitory post-synaptic potentials (IPSPs) could be generated by single stimuli during and after the seizure. In a depressed seizure state , no slow membrane oscillations nor spontaneous spikes could be observed at the resting level of the membrane. The EPSPs and IPSPs by single stimuli were depressed during the seizure, especially in its early stage. Some experimental evidence was obtained concerning a correlation between surface and intracellular potentials in these three seizure situations.

Electroencephalographic Findings of Hereditary Dentatorubral-Pallidoluysian Atrophy (DRPLA)

Abstract: The electroencephalograms (EEGs) of 22 patients suffering from hereditary DRPLA were studied. Epileptoform patterns were observed in 14 patients (63.6%) with epileptic seizures. The epileptoform patterns most frequently observed were those atypical spike‐wave complexes. Slow wave bursts were seen in 18 patients (81.8%). Photosensitivity was revealed in six (27.3%) patients, all of whom presented progressive myoclonus epilepsy (PME) syndrome. Abnormal background activity was evident in 17 (77.3%) patients. These abnormalities in EEG were more severe in patients in the PME type than those of the A (ataxia) and AE (ataxia and epilepsy) types.

Responses of single unit in the caudate nucleus to thalamic stimulation

Abstract Activity of single units was recorded from the caudate nucleus in the cat anesthetized with barbiturate. Single-pulse stimulation of the thalamus induced the responses (either of excitatory or inhibitory response types) in 11.5% of the caudate units tested, and low-frequency stimulation in 47.4%. A different response type was encountered by a small advance of the microelectrode in the same stab. Effective regions for caudate unit responses were the nonspecific thalamic nuclei regardless of whether the stimulation was single or repetitive. When cortical recruiting response was induced by low-frequency stimulation of the nonspecific thalamic nuclei and the nucleus medialis dorsalis, the response of either of the two types was exhibited in 77.6% of caudate units tested. When cortical recruiting response was not induced, the response was observed only in 12.1%. In all caudate units responding to low-frequency stimulation of two different nuclei in the thalamus, the response type of each unit to the stimulation of both nuclei was the same. In all units responding to singlepulse stimulation of both the thalamus and the cortex, the response type was the same. In about two-thirds of caudate units responding both to single-pulse stimulation of the cortex and to low-frequency stimulation of the thalamus, the response type was the same. These results suggest that caudate unit response to low-frequency stimulation of the thalamus is mainly due to activation of the indirect thalamocaudate pathway through the cortex, and that the response type does not depend upon the stimulating site nor the region in which the units existed, but upon the units themselves.

An Overview of Progressive Myoclonus Epilepsy in Japan

Progressive myoclonus epilepsies (PMEs), a group of genetic disorders that are characterized by myoclonus, epileptic seizures, progressive neurological deterioration, dementia, and ataxia,’ are listed as being “symptopmatic generalized epilepsies of specific etiologies ” in the International Classification of Epilepsies, Epileptic Syndromes, and Related Seizure Disorders.’ Various specific diseases may cause the PME syndrome. In Japan three major disease entities account for most PME cases : dentatorubral pallidoluysian atrophy (DRPLA), a MERRF type of mitochondrial en~ephalomyopathy~ and Lafora disease. Each is discussed below. DRPLA is an inherited disease with an autosomal dominant trait that can display a wide variety of clinical symptoms including PME,3 and its onset can range from childhood to senescence. A particular correlation has been found between the age of DRPLA onset and the clinical symptoms, with PME being a characteristic feature of juvenile DRPLA. Along with PME, juvenile DRPLA cases may sometimes also manifest choreoathetosis. The main neuropathologic changes caused by this disease consist of a combined degeneration of the dentatorubra1 and pallidoluysian systems. Although DRPLA cases are extremely rare elsewhere,’ DRPLA is often encountered in Japan, where 19 DRPLA families have been reported. Geographically, most of these DRPLA families live in the middle and northern

A Study on Periodic Abnormal Discharge with Spike Components

Many reports on clinical cases showing periodic abnormal discharge (PAD) in electroencephalogram (EEG ) with periodic synchronous discharge (PSD) are available since Lesse (1956) presented the first cases. On the other hand, Hughes et al. (1965) reported PAD cases with periodically recurring focal discharge (PRFD) . However, no one seems to have performed comparative studies of these two types of PAD cases. We investigated 27 cases (male 15, femaIe 12) of PAD. As they were both of the PSD and PRFD types, we compared their clinical features giving particular attention to the EEG. We divided our cases into two groups based on the localization of spikes; one was the diffuse group, the other was the focal group. Twenty-two cases belonged to the diffuse