Nobuyuki Morita

VOLUNTARY CONTROL OF SACCADIC EYE MOVEMENTS IN PATIENTS WITH SCHIZOPHRENIC AND AFFECTIVE DISORDERS

We have examined visually guided saccade and antisaccade tasks in 32 schizophrenics, 13 patients with affective disorders and 36 normal controls. Latencies of saccades were within the normal range in all patients examined. In the antisaccade task, 26/32 schizophrenics showed more errors and/or longer latencies, whereas 11/13 patients with affective disorders showed normal results. One manic patient showed significantly longer latency, and one bipolar patient showed a borderline error rate (15%). These results indicate that the antisaccade abnormalities in schizophrenics were not correlated with age, duration of illness, length of education or quantities of medication. None of the schizophrenics with normal antisaccades showed abnormalities in CT scans, while 73% of the schizophrenics who showed both higher error rate and longer latencies showed atrophy of the frontal cortex. The scores of conceptual disorganization and motor retardation in Brief Psychiatric Rating Scale (BPRS) were significantly higher in schizophrenics with abnormal antisaccades, while acute symptoms such as delusions and hallucinations were not correlated with the abnormalities.

Further analysis of the control of voluntary saccadic eye movements in schizophrenic patients

Many schizophrenic patients reveal abnormalities in the antisaccade task. To better understand the nature of these abnormalities, in the present study we have assigned to schizophrenics the no-saccade task (subjects were required to remain fixated without being disturbed by a reflexive saccade) and memory-saccade task (subjects were required to look at a remembered target) in addition to the antisaccade and saccade tasks used previously. Many schizophrenics revealed higher error rates in the no-saccade task, and latencies of saccades to a memorized target were significantly longer than controls in the memory-saccade task. Peak velocities of saccades of large amplitudes in the memory-saccade and antisaccade tasks (but not in the saccade task) were significantly slower and durations of such saccades were longer than normal controls despite the similarity between the distributions of amplitudes of such saccades between the patients and controls. These results suggest that many schizophrenics have difficulty suppressing reflexive saccades and initiating and executing appropriate volitional saccades when the goal for the movements is known but not visible.

Effects of vitamin B12 on plasma melatonin rhythm in humans: increased light sensitivity phase-advances the circadian clock?

Vitamin B12 (methylcobalamine) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatlonin rhythm was significantly phase-advanced (1.1. h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 traial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.

Seasonality in human sleep.

The timing of sleep and sleep EEG parameters in 10 healthy male subjects were investigated in four seasons under controlled conditions. The phase of nocturnal sleep was delayed about one and a half hours in winter as compared to that in summer. The duration of stage 4 sleep decreased and REM sleep increased significantly in winter compared with summer. The seasonality in the timing of sleep can be explained by photoperiodic time cues, but the changes in sleep EEG parameters are diffucult to explain in terms of photoperiod.

Vitamin B12 enhances the phase-response of circadian melatonin rhythm to a single bright light exposure in humans ☆

Eight young males were subjected to a single blind cross-over test to see the effects of vitamin B12 (methylcobalamin; VB12) on the phase-response of the circadian melatonin rhythm to a single bright light exposure. VB12 (0.5 mg/day) or vehicle was injected intravenously at 1230 h for 11 days, which was followed by oral administration (2 mg x 3/day) for 7 days. A serial blood sampling was performed under dim light condition (less than 200 lx) and plasma melatonin rhythm was determined before and after a single bright light exposure (2500 lx for 3 h) at 0700 h. The melatonin rhythm before the light exposure showed a smaller amplitude in the VB12 trial than in the placebo. The light exposure phase-advanced the melatonin rhythm significantly in the VB12 trail, but not in the placebo. These findings indicate that VB12 enhances the light-induced phase-shift in the human circadian rhythm.

Effects of Menstrual Cycle on Plasma Melatonin Level and Sleep Characteristics

It is well known that some clinical symptoms (e.g. psychotic symptoms and epileptic seizures) often aggravate around the time of menstruation. Moreover, the change of subjective sleep feeling throughout the menstrual cycle was reported. Therefore, the menstrual cycle is presumed to affect sleep characteristics and biological rhythm. We investigated a circadian pattern of plasma melatonin and body temperature, and sleep characteristics in the different phases of the menstrual cycle under controlled environmental conditions. In this paper, a part of the results is discussed.

Depressive disorders preceding temporal lobe epilepsy

In this study, we investigated three female patients given a diagnosis of temporal lobe epilepsy preceded by depression. It is notable that all the patients complained of abnormal sensations, either in the throat or oral. The depression in the three patients showed no improvement with antidepressants, but carbamazepine was effective for both epileptic seizures and depression. EEG should be performed on patients who develop antidepressant treatment-refractory depression accompanied by hypochondriacal complaints.