Biomedical subjects

M Kohsaka

Publications and source records attributed to M Kohsaka.

At least 19 recordsLinked to original sources

PubMed2002

Widespread activation of the brainstem preceding the recruiting rhythm in human epilepsies.

The excitability change of the brainstem was investigated before and during the conspicuous epileptic discharge in six patients with generalized convulsive seizures. The discharge consisted of a short duration of recruiting rhythm, which was considered equivalent to the seizure discharge on electroencephalogram. The excitability of the brainstem was measured with the parameters (amplitude and area) of component waves (wave-III and -V) of brainstem auditory evoked potentials. The theoretical background of the analysis is that brainstem auditory evoked potentials are 'far-field' potentials, by which they convey the information on the activity change of the brainstem even during the paroxysmal discharge within the cortex. The excitability of both the ventral (parameters of wave-III) and the dorsal brainstem (parameters of wave-V) exhibited a synchronized change (activation-inactivation). They were enhanced from -2.4+/-0.4 s, reaching the maxima before the onset of the seizure discharge, and decayed corresponding to the emergence of the recruiting rhythm. The results suggest the possibility that the widespread (ventral and dorsal) and synchronized activation of the brainstem triggers the seizure discharge in human generalized epilepsy. During the widespread activation of the brainstem, both the thalamus and the cortex probably undergo a suppressed inhibitory state through the cholinergic activation, precipitating the seizure discharge.

Acoustic Stimulation↗

PubMed2001

Brainstem activates paroxysmal discharge in human generalized epilepsy.

In nine patients with generalized epilepsy of convulsive seizures, the excitability change of the brainstem was evaluated over the course of the interictal paroxysmal discharge (poly spike-and-wave complex, poly SWC). The evaluation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) before and during one sequence of poly SWC. The characteristics of BAEPs, i.e. far-field evoked potentials, allowed the evaluation of the excitability change in the brainstem, which was not influenced by the cortical activity. The excitability in the ventral brainstem, measured with the parameters of wave-III, showed a biphasic fluctuation (deceleration--acceleration) before the onset of poly SWC (minima at -0.7+/-0.4 s). On the other hand, the excitability in the dorsal brainstem, measured with the parameters of wave-V, showed no significant difference over the course of poly SWC. The results suggest that the biphasic excitability change in the ventral brainstem is conveyed to the cortex through the ascending activating system. The excitability acceleration preceded by deceleration in the ventral brainstem probably synchronizes the cortical activity profoundly enough to produce poly SWC through the activation of intralaminar thalamic neurons.

Adolescent↗

PubMed2001

Effects of bright light exposure on heart rate variability during sleep in young women.

To investigate the effects of evening bright light on the autonomic nervous system, heart rate variability (HRV) during sleep was analyzed in dim light (DL) and bright light (BL) conditions. We recorded polysomnography in nine healthy young women aged 20-21 years. Time series of % delta power was calculated in the 0.49-2.20 Hz band. Heart rate variability was analyzed from a 10-min segment of slow wave sleep. The low- to high-frequency ratio and the low-frequency component decreased significantly in the BL conditions compared with the DL conditions. However, the power of the high-frequency component did not change in the two conditions. These results indicate that evening BL affects the autonomic nervous system during slow wave sleep.

Adult↗

PubMed2001

Effects of bright light at lunchtime on sleep of patients in a geriatric hospital I.

The effects of lunchtime bright light exposure in patients of a geriatric hospital were investigated. Ten inpatients (six women and four men; mean age +/- SD: 81.2 +/- 8.8 years) with sleep disturbances were studied for 9 weeks. Nurses performed daily ratings for sleep-wakefulness disturbances. Approximately 8000 lx bright light exposure was performed for 3 weeks in the light therapy room. Before and after exposure, ocular function was evaluated. Clinical ratings of sleep-wakefulness improved in eight patients. The score of difficulty in falling asleep and drowsiness in the morning declined during the light exposure. The score of drowsiness in the afternoon decreased during the post-light exposure. Post-exposure ocular disturbances were not found.

Aged↗

PubMed2001

Effects of bright light at lunchtime on sleep in patients in a geriatric hospital II.

Inpatients with sleep disturbances in a geriatric hospital received 1 h of exposure to approximately 8000 lx bright light per day for 3 weeks. Polysomnogram was recorded for four female patients. Two (aged 68 and 87 years) were non-demented patients with weak cataracts and the other two (aged 92 and 93 years) were demented patients with severe cataracts. Electroencephalogram results showed that light exposure decreased the proportion of Stage W, while increased the proportion of Stage 2, and these effects continued for at least 3 weeks after the cessation of light exposure. These results suggest that exposure to bright light is effective in improving the disturbed sleep of patients.

Aged↗

PubMed2000

Dual control of the brainstem on the spindle oscillation in humans.

In human subjects, the excitability change of the brainstem was investigated over the course of the spindle oscillation. The investigation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) with reference to one sequence of spindle oscillation. The method was based on the characteristics of BAEPs, i.e. far-field evoked potential. The brainstem revealed two types of excitability change: one in the lower ventral brainstem (wave-III components), and the other in the upper dorsal brainstem (wave-V components). The excitability in the dorsal brainstem showed an oscillation with one cycle period of about 1.5 s, whereas in the ventral brainstem, the excitability showed a long-range biphasic (decaying-growing) fluctuation. Both excitability changes in the brainstem preceded the spindle oscillation, and the phase was reversed during the emerging period of spindle oscillation. The results suggest a primary triggering mechanism of the brainstem for the spindle oscillation, which is independent of preceding cortical drives (K-complexes) upon the thalamus. The difference of the excitability change between the spindle oscillation and the paroxysmal discharge (spike-and-wave complex) was also discussed.

Adult↗

PubMed2000

Differences in electroencephalogram power densities between genuine narcolepsy and secondary narcolepsy.

Diagnosing narcolepsy is not always simple. Some patients secondarily show narcoleptic tetrad through irregular sleep patterns or psychotic diseases. The power densities of daytime electroencephalograms in genuine narcolepsy and secondary narcolepsy were analysed and compared. Electroencephalogram power densities for a 6.5-h period after waking in genuine narcoleptic patients were lower than those of secondary narcoleptic patients in the 11.0-12.5 Hz bands. Arousal levels may be lower in genuine narcoleptic patients than in secondary narcoleptic patients. Spectral analysis may be useful in clarifying differences between the two groups.

Adolescent↗

PubMed2000

Autonomic nervous function after evening bright light therapy: spectral analysis of heart rate variability.

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20-21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF:HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.

Adult↗

PubMed2000

Effect of short duration morning bright light in elderly men: sleep structure.

Sleep structure was measured in five healthy elderly men in their homes. The subjects were exposed to bright light (6000 lx) for 30 min in the morning or instructed to sit in front of a desktop lighting device without light. Relative to the control conditions, bright light exposure significantly decreased time in bed and the number of awakenings. Rapid eye movement sleep was significantly fragmented by stage 1 sleep in the control condition compared with the bright light condition. These findings indicate that a short duration of morning bright light changes sleep structure and is effective in maintaining sleep.

Aged↗

PubMed2000

Psychotic episodes during zonisamide treatment.

Several articles have appeared over the last years devoted to mental side effects during zonisamide (ZNS) treatment. In this study, we were particularly interested in psychotic episodes. Seventy-four epileptic patients with a history of ZNS treatment were surveyed retrospectively over the period spanning 1 March 1984 to 30 June 1994. They were divided into two groups according to the presence or absence of psychotic episodes during ZNS treatment. We analysed various factors pertaining to psychotic episodes during ZNS treatment. Of the 74 patients 14 had psychotic episodes. We found that the incidence of psychotic episodes during ZNS treatment was several times higher than the previously reported prevalence of epileptic psychosis, and that the risk of psychotic episodes was higher in young patients. In 13 patients, psychotic episodes occurred within a few years of commencement of ZNS. In children, obsessive-compulsive symptoms appeared to be related to psychotic episodes. It is important to terminate ZNS as soon as possible if psychotic episodes develop and never restart, even if seizures become worse. It cannot definitely be proved that ZNS causes psychotic episodes, as information on mental side effects during ZNS monotherapy is scant, but it does appear likely that ZNS contributes to psychotic episodes during polytherapy.

Adult↗

PubMed2000

Disturbance of semantic processing in temporal lobe epilepsy demonstrated with scalp ERPs.

We investigated event-related potentials (N400, LPC and CNV) elicited in temporal lobe epilepsy (TLE) patients and control subjects from scalp electrodes, using a word-pair category matching paradigm. Each prime consisted of a Japanese noun (constructed from 2-4 characters of the Hiragana) followed by a Chinese character (Kanji) as the target, the latter representing one of five semantic categories. There were two equally probable target conditions: match or mismatch. Each target was preceded by a prime, either belonging to, or not belonging to, the same semantic category. The subjects were required to respond with a specified button press to the given target, according to the condition. We found RTs to be longer under the mismatch condition in both subject groups. The N400 amplitude was reduced in TLE subjects under both conditions, although LPC and CNV amplitudes showed no significant differences. These results suggest that scalp N400 is capable of demonstrating disturbance of semantic processing in TLE non-invasively.

Adult↗

PubMed1999

Brainstem triggers absence seizures in human generalized epilepsy.

Simultaneous analysis of brainstem auditory evoked potentials (BAEPs) with reference to electroencephalography (EEG) was designed to examine the brainstem function corresponding to the EEG event. With this method, we investigated the brainstem function pre- and during the paroxysmal discharge in human absence seizures classified as primary generalized epilepsy (PGE). Two types of functional change in the lower brainstem were revealed as parameters of wave-III components (amplitude and area) of BAEPs without significant change in the upper brainstem. One was long-range biphasic fluctuation (acceleration followed by abrupt deceleration with the maximum -6.4+/-3.2 s before the seizure onset), and the other was rhythmic oscillation with 3 Hz. The latter, synchronized with the cortical spike-and-wave complex, imposed on the descending slope of the former. One important point is that both preceded the onset of cortical paroxysmal discharge. The results reappraise the classical hypothesis of "centrencephalic system" on seizure generating mechanism in human PGE. The results prove the primary triggering role of the lower brainstem that is independent of sleep-related synchronizations. The method is applicable to other types of EEG event for the investigation of brainstem involvement.

Adolescent↗

PubMed1999

Estradiol-17beta measurement in women receiving conjugated estrogens. Dissociation between two commercial methods.

To investigate problems associated with measurement of estradiol-17beta (E2) in hormone replacement therapy (HRT), two commercial immunometric methods (Coat-A-Count E2 and Immulyze E2) were used to assay E2 concentrations and the two results were expressed as E2 ratios. Samples were obtained from 97 Japanese women receiving HRT and 168 unmedicated women. The largest differences between methods (P < 0.001) occurred in patients receiving oral conjugated estrogen (CE), while the best concordance was found in unmedicated women; like these controls, patients receiving oral estriol or transdermal E2 showed no significant difference between methods. Defining an E2 ratio > or = 2.0 as an abnormal discordance, the mean E2 ratio and the frequency of abnormal discordance in the CE group were 2.15 +/- 1.18 and 43.6%, respectively. No abnormal discordance for E2 occurred in other groups. In serial serum samples from the control group, no significant difference was seen between the mean E2 ratio at first measurement and those at a subsequent measurement. Similarly, no significant difference in the ratio was seen when two serial samples from CE patients were compared. However, E2 ratios after prescription of CE were significantly higher than before treatment in all patients. In conclusion, although measurement of E2 is important in patients receiving HRT, validity of the test methods must be carefully weighed for patients receiving CE.

Adolescent↗

PubMed1999

Effects of morning bright light in healthy elderly women: effects on wrist activity.

To investigate the effects of 8000 lux morning bright light in the elderly, home-based motor activity on sleep was monitored for 5 days in 10 healthy women (mean age: 59.7 years old, range: 50-69 years old). The activity level and movement index on night 4 were significantly lower in bright light conditions, compared with the controlled condition. The activity level during the day was not significantly different between the two conditions. These results indicate that 8000 lux morning bright light improves sleep quality in healthy elderly women.

Aged↗

PubMed1999

Effects of morning bright light on sleep in healthy elderly women.

Subjective sleep feeling and polysomnography were measured in 10 elderly women to investigate the effects of 8000 lux morning bright light (BL) exposure. The profile of sleep feeling in the BL condition was better than in the control condition. The proportion of awakening time in the first one-third of night sleep decreased, and the amount of awakening time in the last one-third increased in BL condition. Daytime napping reduced in BL condition. These findings suggested the effectiveness of exposure to bright light on the improvement of sleep quality and daytime vigilance of healthy elderly women.

Aged↗

PubMed1999

Analysis of rapid eye movement periodicity in narcoleptics based on maximum entropy method.

We examined REM sleep periodicity in typical narcoleptics and patients who had shown signs of a narcoleptic tetrad without HLA-DRB1*1501/DQB1*0602 or DR2 antigens, using spectral analysis based on the maximum entropy method. The REM sleep period of typical narcoleptics showed two peaks, one at 70-90 min and one at 110-130 min at night, and a single peak at around 70-90 min during the daytime. The nocturnal REM sleep period of typical narcoleptics may be composed of several different periods, one of which corresponds to that of their daytime REM sleep.

Adult↗

PubMed1999

Gender difference of slow wave sleep in middle aged and elderly subjects.

Sleep EEG of eight healthy males and eight females aged 54-72 years were recorded at their homes. The electroencephalograms were visually scored and analyzed by spectral analysis using the FFT method. There were no significant differences in sleep parameters except for a higher percentage of stage 3+4 in females. The spectral power of the delta band EEG was classified into two frequencies: 0.5-2 Hz and 2-4 Hz. The total amount of the delta band spectral power through the night was significantly larger in females. Periodic fluctuation of delta band power was observed in females along with non-rapid eye movement-rapid eye movement cycles.

Aged↗

PubMed1999

Effects of moderately bright light on subjective evaluations in healthy elderly women.

Eight healthy elderly women aged 56-72 years (mean age: 67.4 years) participated in this study. They were exposed to moderately bright light (1000 lux) for 1h in the morning every 6 days in their homes. Moderately bright light improved self evaluations for alertness, mood, motivation, happiness, refreshment, concentration and appetite after the second exposure to the light. Sleep maintenance, anxiety and integrated sleep feeling also improved after the fourth exposure to the light. The phase of rectal temperature rhythm did not change in a moderately bright light condition. These results suggest that bright light influences sleep quality and self evaluations without changing the biological rhythm phase.

Adaptation, Psychological↗