Masahito Fushimi

K-complex evoked in NREM sleep is accompanied by a slow negative potential related to cognitive process

Evoked cortical responses to two kinds of auditory stimuli (rare and frequent) were analyzed to determine whether or not a K-complex evoked in stage 2 of NREM sleep is accompanied by some endogenous cognitive components of the event-related potential. All the 7 subjects examined in this sleep state failed to provide the correct behavioral response to auditory stimuli, but a K-complex was evoked more frequently by rare stimuli than by frequent stimuli. EEG segments in stage 2 were averaged separately according to the presence or absence of K-complexes emerging just after the stimulation. In cases where K-complexes did not emerge, a long-lasting negative potential of relatively low voltage appeared in the difference wave, which was obtained by subtracting the averaged EEG for frequent stimuli from that for rare stimuli. In cases where K-complexes emerged, a similar long-lasting negative potential of large amplitude appeared in the difference wave. These data may indicate that a K-complex evoked by an external stimulus is accompanied by a potential related to a cognitive process, which appears with greater amplitude in cases where a K-complex is evoked.

Comparison of completed and attempted suicide in Akita, Japan

Abstract  To determine the factors underlying suicide in Akita prefecture, a questionnaire survey was conducted among members of the Akita Prefectural Medical Association (APMA), regarding suicide cases they attended. During the investigation period (1 July 2001–30 June 2002), the total number of suicide cases was 243 (138 completed, 105 attempted). Significant differences were identified between completed and attempted suicide groups in terms of gender, age distribution, and suicidal methods. Specifically, in the completed suicide group, the number of male completers exceeded that of female completers, the number of middle‐aged or elderly completers was high, and the majority of completed suicide cases involved hanging as the suicide method. Conversely, in the attempted suicide group, the number of female attempters exceeded that of male attempters, younger attempters were frequent, hanging was rare, and drug overdose or cutting was common. In addition, the number of cases involving a history of previous suicide attempts was significantly higher in the attempted suicide group than in the completed suicide group. The results of the present study support the concept that the completed and attempted suicide groups are essentially of a different nature. Furthermore, the number of cases involving a history of previous suicide attempts was found to be significantly lower in the completed suicide group than in the attempted suicide group. This result indicates the difficulty in decreasing the number of completed suicides by simply providing intervention and care for individuals who have attempted suicide.

Suicide patterns and characteristics in Akita, Japan

Abstract  Akita Prefecture currently has the highest rate of suicide in Japan. Given this alarming statistic, investigation of the underlying causes of suicide and identification of strategies for suicide prevention are imperative. Members of the Akita Prefectural Medical Association (APMA) see most of the individuals who commit suicides in Akita Prefecture, so data from the APMA would prove advantageous in any investigation of suicides. In this study, members of the APMA who had attended to individuals who had committed suicide were asked to complete a questionnaire about the case to determine the factors underlying suicide in Akita Prefecture. From 1 July 2001 to 30 June 2002, a total of 138 cases (102 males, 36 females) of suicide were reported. Most suicide cases were of 50–69 year olds. Many cases involved relatively lethal methods (such as hanging). Most suicides were performed at home and at a time when the rest of the family was asleep or absent. The most  common  complaint  appeared  to  be  economic‐related  problems.  Depressive  disorder  was the most common psychiatric disorder, and many cases displayed high depressive trait scores. The present results do not exclude the possibility that economic‐related problems are playing a major role in recent increases in suicide numbers. However, strategies for dealing with depression as well as economic‐related problems are considered important.

Benign bilateral independent periodic lateralized epileptiform discharges

Bilateral independent periodic lateralized epileptiform discharges (BIPLEDs) usually appear transiently in patients with severe disturbances of consciousness and are indicative of a poor prognosis. Recurrent BIPLEDs have not previously been reported in the literature. We report a 64‐year‐old patient with bilateral hippocampal lesions (cerebral infarction) who exhibited persistent periodic lateralized epileptiform discharges (PLEDs) (chronic PLEDs) associated with recurrent BIPLEDs. Electroencephalography was recorded for more than 6 months. Left hemispheric PLEDs appeared first. Next, PLEDs shifted to the right hemisphere and BIPLEDs occasionally developed. Brain magnetic resonance imaging and single‐photon emission computed tomography with technetium‐99‐hexamethyl‐propyleneamine oxime was performed before and after the appearance of BIPLEDs. The patient had no remarkable clinical symptoms aside from mild memory impairment for this period of time. This is the first case of recurrent ‘benign’ BIPLEDs, that is, BIPLEDs with a positive prognosis.

Prevalence of Psychological Distress, as Measured by the Kessler 6 (K6), and Related Factors in Japanese Employees

The aim of this study was to examine the prevalence of and related factors for psychological distress among employees. The employees in Akita prefecture, Japan, were invited to complete the Kessler 6 (K6). A value of 13 or higher on the K6 scale indicated high psychological distress. Furthermore, we identified the relationships among the prevalence of high psychological distress, socio-demographic status, and employment-related variables. The data of 1,709 employees indicated that 10.8% of the employees had high psychological distress; the proportion of psychological distress found in the present study was high compared to that found in previous studies. The identified socio-demographic and occupation-related factors included young age groups associated with a high risk and clerical or administrative tasks associated with a low risk of psychological distress. The data of this study can be used as K6 benchmark values, which enhance the significance of future corporate health risk appraisal surveys.

Progression of P300 in a patient with bilateral hippocampal lesions

OBJECTIVE To evaluate the effects of hippocampal damages on P300 of event-related potentials (ERPs). METHODS ERPs were recorded over about 8 months using the auditory oddball paradigm in a patient with bilateral hippocampal lesions confirmed on brain magnetic resonance imaging. Findings were compared with those from clinical electroencephalography (periodic lateralized epileptiform discharges (PLEDs) or bilateral independent PLEDs (BIPLEDs)). The patient displayed no marked clinical symptoms aside from mild memory impairment during this time, and was able to fully perform the oddball task. RESULTS Clearly identifiable P300 were present in all recordings. Furthermore, increases in the number of right PLEDs were significantly correlated with increases in P300 latency. CONCLUSIONS Two key results were apparent. First, the appearance of P300 in all ERP recordings supports the suggestion that the hippocampus is not indispensable for P300 generation. Second, the correlation between the number of PLEDs and P300 latency supports the suggestion that the hippocampus affect the components of P300 latency. SIGNIFICANCE This case thus offers very suggestive evidence regarding the generation of P300.

PLEDs in Creutzfeldt–Jakob disease following a cadaveric dural graft

INTRODUCTION Periodic synchronous discharges (PSDs) are a well-known electroencephalographic finding associated with Creutzfeldt-Jakob disease (CJD), but only a few reports have documented the appearance of periodic lateralized epileptiform discharges (PLEDs) in CJD and there has been no discussion as to why PLEDs appear with unilateral (right or left) dominance. CASE REPORT AND DISCUSSION We report on a 61-year-old man who received a cadaveric dura mater graft and developed CJD 14 years later. Periodic lateralized epileptiform discharges (PLEDs) were observed predominantly in the right hemisphere, coinciding with the location of the dural graft, the presumed source of the CJD agent and PLEDs seen in this case finally developed into PSDs. A similar case has not been reported in the literature and we believe this case serves to further the understanding of the pathophysiology of CJD.

A negative component on event related potential recorded in the drowsy state

Abstract Behavior of event related potential (ERP) components in the drowsy state was examined in nine subjects using oddball paradigm. A component with peak latency of 300 msec, N300, was superimposed on ERP in the drowsy state. N300 appeared also in stage 1 of NREM sleep and closely resembled vertex sharp wave evoked by sound stimulation in both scalp distribution and peak latency. It was suggested that N300 recorded in the drowsy state and vertex sharp wave recorded in stage 1 of NREM sleep are generated by the identical synchronizing mechanism in the brain.

Marked suppression of cortical auditory evoked response shortly before the onset of REM sleep.

IN 10 of 12 subjects examined, the amplitude of N300, a component of the cortical auditory evoked potential, was evidently smaller in rapid eye movement (REM) sleep than in non-REM sleep. The start of the reduction associated with the onset of the first episode of REM sleep was examined in these 10 subjects. In five of these, a marked reduction of N300 amplitude occurred 0.5–2.5 min before the appearance of muscle atonia of REM sleep. In two subjects, a similarly marked reduction of the N300 amplitude occurred 0.5–1.0 min before the disappearance of sleep spindles or K-complexes. This suggests that a suppression of the synchronizing mechanism in the cerebrum sometimes occurs briefly prior to the occurrence of other physiological phenomena associated with REM sleep.

Cortical activity of REM sleep often occurs earlier than other physiological phenomena

Abstract N300 appearing in response to sound stimulus was used as an index to determine the occurrence of cortical activity characterizing REM sleep. In 5/10 subjects, marked reduction of N300 amplitude occurred even in the period of 0.5‐2.5 min immediately preceding the appearance of muscle atonia characterizing REM sleep. Neither muscle atonia nor rapid eye movements appeared prior to the marked reduction of N300 amplitude in any subject. This suggests that the cortical activity characterizing REM sleep sometimes occurs a few minutes (or less) earlier than other physiological phenomena.