Hidemitsu Saito

Saccadic eye movements in tracking, fixation, and rest in schizophrenic and normal subjects.

Horizontal eye movements were recorded electrooculographically during two different eye fixation tasks, during an eyes-closed waking state, and during eye tracking on a sinusoidally moving target in 16 chronic schizophrenics and in 12 normal subjects. The relationship between saccadic eye movements during tracking and in the other experimental situations was investigated. The intensities of eye fixation were successively decreased from Experiment I (eye fixation on a stationary target) through Experiment II (eye fixation on an imagined spot in the dark) to Experiment III (eyes closed in the dark, no cue for eye fixation), in that order. The frequency of saccades increased as the intensities of fixation decreased from Experiment I to Experiment III in both schizophrenic and normal groups. It was demonstrated that the frequency of saccades was higher in schizophrenics than in normal subjects in all of the experimental conditions. Some correlations were found between the increased frequency of saccades seen during eye tracking and the similar increases seen in eyes-fixated or eyes-closed states in schizophrenic subjects. It is suggested that the increased saccades seen during eye tracking and in other experimental conditions in schizophrenics are related to a deficit of nonvoluntary attention, due to a failure of an inhibitory mechanism.

Smooth pursuit eye movements and express saccades in schizophrenic patients

Abnormalities of saccades such as disinhibition have been hypothesized as one cause of smooth pursuit eye movement (SPEM) dysfunctions in schizophrenia. Thus, we studied saccadic eye movements in schizophrenics with SPEM dysfunction. Subjects were divided into three groups: 10 normal control subjects, 10 schizophrenic subjects without SPEM dysfunction and 10 schizophrenic subjects with SPEM dysfunction characterized by a cogwheel appearance. Visually guided saccades in gap and overlap paradigms (Saslow, 1967) were examined and saccadic reaction times (SRTs) were measured in all subjects. Only schizophrenics with SPEM dysfunctions tended to manifest excessive reflexive saccades, named express saccades (Fischer, 1987), in the gap paradigm. Moreover, most of them were also found to have express saccades in the overlap paradigm, whereas normal subjects and schizophrenic subjects without SPEM dysfunction did not show such phenomena under the same conditions. In particular, most express saccades in the overlap paradigm in schizophrenics with SPEM dysfunction, were found in movements to the right.

Smooth Pursuit Eye Movements and Voluntary Control of Saccades in the Antisaccade Task in Schizophrenic Patients

Abstract: It has been hypothesized that a saccade control dysfunction is one cause of a smooth pursuit eye movement (SPEM) dysfunction in schizophrenia. We studied the voluntary control of saccades in schizophrenic patients with the SPEM dysfunction using an antisaccade task. The mean error rate in the antisaccade task was significantly higher in the two schizophrenic groups with and without a SPEM dysfunction than in the normal control group. Furthermore, the schizophrenic group with the SPEM dysfunction showed significantly more errors than the schizophrenic group without the SPEM dysfunction. These findings seem to suggest a close relationship between the SPEM dysfunction and the appearance of errors which indicates an inability to inhibit reflexive saccades voluntarily in the antisaccade task. However, 4 of 10 subjects with the SPEM dysfunction showed an error rate less than the mean error rate of the schizophrenic group without the SPEM dysfunction. So, a voluntary control disorder of saccades as the main cause of the SPEM dysfunction appeared to be unlikely. An interesting finding of this study was that many schizophrenic subjects with the SPEM dysfunction showed errors with the latencies similar to those in express saccades2, particularly in the rightward direction. This finding may suggest a close relationship between the SPEM dysfunction in schizophrenic patients and some pathological conditions of express saccades such as disinhibition of express saccades.

Visual event‐related potential in mild dementia of the Alzheimer's type

Abstract Visual event‐related potentials (ERP) and behavioral measures were recorded during a geometrical‐figure discrimination task to examine sensory processing in 10 patients with mild dementia of the Alzheimers type (DAT) and 10 age‐matched controls. No difference existed between the groups in P1, N1, and P2 potentials, which reflects the early stage of sensory processing, as well as in NA potential, which reflects pattern recognition. The patients showed reduced amplitude of P3 potential, retarded reaction time, and increased behavioral errors compared to controls. These findings suggest that the patients with mild DAT were intact in early sensory processing including pattern recognition but were selectively compromised in higher‐level processing, including integration of information and memory matching, which may influence behavioral deviation.

Lack of repetition priming effect on visual event-related potentials in schizophrenia.

BACKGROUND The present study was designed to assess, using event-related potentials, whether aberrant semantic processing reported in schizophrenia results from primary semantic overactivation or contextual dysregulation. METHODS The visual event-related brain potentials were compared between 9 schizophrenic subjects and 16 normal control subjects performing two kinds of semantic categorization tasks with different nontarget stimuli: 1) nontargets comprising words, pseudowords, and unpronounceable foreign letters and 2) nontargets comprising initial presenting words, immediate repetition words, and delayed repetition words. RESULTS Schizophrenic subjects showed no evidence suggestive of a greater negative potential associated with words and pseudowords, but they did show a lack of amplitude change associated with immediately repeated words relative to that in control subjects. CONCLUSIONS These results suggest that aberrant semantic activation in schizophrenia results mainly from a failure to utilize information from preceding words or context, and could explain the increased N400 to the congruent or related words recently reported in this disease.

Impairment of an event-related potential correlate of memory in schizophrenia: effects of immediate and delayed word repetition.

OBJECTIVE We investigated the nature of the memory impairment in schizophrenia using an event-related potential (ERP). METHODS Visual ERPs were recorded while 20 schizophrenics and 20 controls performed semantic categorization tasks with incidental word repetitions. Participants responded to occasional target words. Half of the non-target words were repeated immediately after initial presentation (lag 0) or after 5 intervening words (lag 5). RESULTS In both groups, ERPs to words at lag 0 were more positive than those to non-repeated words, though this positive-going effect was attenuated in the schizophrenics, especially around 400-500 ms. The effect at lag 5 was smaller and shorter than that at lag 0 but was comparable between groups. Attenuation of the N400 peak occurred for word repetition at lag 0 in controls but not in schizophrenics, whereas a peak increment in the late positive component induced by word repetition at both lags was observed in both groups. CONCLUSIONS Findings indicate that patients with schizophrenia have a deficit in a brain process modulating ERP correlates of memory, when words are repeated immediately. This deficit might be related to an abnormal N400 priming effect in schizophrenia.

Altered endogenous negativities of the visual event-related potential in remitted schizophrenia

Visual event-related potentials (ERPs) were recorded during a simple response task (SRT) and a discriminative response task (DRT) in remitted schizophrenic outpatients and age-matched controls to examine 2 endogenous negative potentials: NA and N2c. The NA potentials were derived by subtracting the ERPs for SRT from those for non-target stimuli in DRT. Other subtracting wave forms, N2c potentials, were calculated as the difference between ERPs for target and non-target stimuli in DRT. Schizophrenics showed retardation in NA and N2c peaks and degradation in N2c amplitude relative to controls. The NA peak latency increased as much as the latencies of N2c and reaction time for DRT in schizophrenia. The NA peak emerged prior to the N2c peak, while the NA peak latency correlated closely with the N2c latency. These results indicate that the retarded NA peak latency may serve as a physiological marker for neurobiological vulnerability of schizophrenia.

Impairment of Parietal Cortical Functions Associated with Episodic Prolonged Spike-and-Wave Discharges

Summary: A case of a 16‐year‐old girl who showed selective impairment of higher cortical functions and very slight lowering of initiative activity without overt disturbance of consciousness, during prolonged generalized spike‐and‐wave discharges with a parietal predominance, is reported. Neuropsychological investigations during the episode revealed a disturbance of parietal cortical functions, such as constructional apraxia, ideational or ideomotor apraxia, finger agnosia, acalculia, right‐left disorientation, disturbance of visual‐spatial orientation, and agraphia. The transient impairment of parietal cortical functions associated with the parietal‐dominant spike‐and‐wave discharges was suggested as a principal pathophysiology of the clinical picture. Emphasis is placed on the importance of neuropsychological assessment in such a case.

Report on Maternal Anxiety 16 Months After the Great East Japan Earthquake Disaster: Anxiety Over Radioactivity

The Great East Japan Earthquake occurred on March 11, 2011. The tsunami caused extensive damage to the Fukushima Daiichi Nuclear Power Plant, resulting in a level 7 nuclear accident. Among those affected by this combined disaster were many pregnant and parturient women. Sixteen months after the earthquake, we conducted a questionnaire survey on anxiety among 259 women who gave birth around the time of the earthquake in Miyagi Prefecture, one of the affected areas. Participants reported 12 categories of anxiety, including anxiety over radioactivity. This study aimed to determine anxiety over radioactivity among this specific population and to record measures for future study. Anxiety over radiation was classified into seven subcategories: food safety, outdoor safety, effects on the fetuses of pregnant women, effects on children, radiation exposure, economic problems, and distrust of information disclosed. This study confirmed that concrete types of anxiety over radiation were keenly felt by mothers who had experienced the disaster who were currently raising children. The findings suggest the need to provide accurate information to these mothers, who are otherwise inundated with miscellaneous confusing information.

Kanji‐predominant alexia in advanced Alzheimer's disease

Objectives ‐ Oral reading is preserved until the late stage of Alzheimers disease (AD). However, it is unknown whether reading of kanji and kana is differentially impaired in Japanese AD patients. The purpose of this study was to examine alexic pattern in AD as related to two script systems. Material and methods ‐ In 18 severe AD patients, reading performance was compared among kana characters, monographic kanji words, and kana‐transcribed words. Auditory comprehension was also examined. Results ‐ With increased severity of dementia, kanji reading was clearly more impaired than kana reading, which was relatively unaffected. Graphic complexity and frequency of the kanji influenced the performance variously among the patients Dissociation between kanji reading and comprehension was also noted. Conclusion ‐ As a result of multiple cognitive deficits, kanji reading is more impaired than kana reading in AD, but the difference is apparent only in the very late stage. Our findings suggest that kanji can be read correctly without meaning.