Eye movements of waking subjects with closed eyes. A comparison between normals and chronic schizophrenics

A multi-site, multi-participant magnetoencephalography resting-state dataset to study dementia: The BioFIND dataset

Early detection of Alzheimer's Disease (AD) is vital to reduce the burden of dementia and for developing effective treatments. Neuroimaging can detect early brain changes, such as hippocampal atrophy in Mild Cognitive Impairment (MCI), a prodromal state of AD. However, selecting the most informative imaging features by machine-learning requires many cases. While large publically-available datasets of people with dementia or prodromal disease exist for Magnetic Resonance Imaging (MRI), comparable datasets are missing for Magnetoencephalography (MEG). MEG offers advantages in its millisecond resolution, revealing physiological changes in brain oscillations or connectivity before structural changes are evident with MRI. We introduce a MEG dataset with 324 individuals: patients with MCI and healthy controls. Their brain activity was recorded while resting with eyes closed, using a 306-channel MEG scanner at one of two sites (Madrid or Cambridge), enabling tests of generalization across sites. A T1-weighted MRI is provided to assist source localisation. The MEG and MRI data are formatted according to international BIDS standards and analysed freely on the DPUK platform (https://portal.dementiasplatform.uk/Apply). Here, we describe this dataset in detail, report some example (benchmark) analyses, and consider its limitations and future directions.

Verbal hallucinations and language production processes in schizophrenia

How is it that many schizophrenics identify certain instances of verbal imagery as hallucinatory? Most investigators have assumed that alterations in sensory features of imagery explain this. This approach, however, has not yielded a definitive picture of the nature of verbal hallucinations. An alternative perspective suggests itself if one allows the possibility that the nonself quality of hallucinations is inferred on the basis of the experience of unintendedness that accompanies imagery production. Information-processing models of “intentional” cognitive processes call for abstract planning representations that are linked to goals and beliefs. Unintended actions - and imagery - can reflect planning disruptions whereby cognitive products do not cohere with concurrent goals. A model of schizophrenic speech disorganization is presented that postulates a disturbance of discourse planning. Insofar as verbal imagery can be viewed as inwardly directed speech, a consequence of such planning disturbances could be the production of unintended imagery. This link between the outward disorganization of schizophrenic speech and unintended verbal imagery is statistically supported by comparing the speech behavior of hallucinating and nonhallucinating schizophrenics. Studies of “borderline” hallucinations during normal, “goal-less” relaxation and drowsiness suggest that experiential unintendedness leads to a nonpathological variant of hallucinatory otherness that is correctable upon emerging from such passive cognitive states. This contrasts with the schizophrenic case, where nonconcordance with cognitive goals reinforces the unintendedness of verbal images and sustains the conviction of an external source. This model compares favorably with earlier models of verbal hallucinations and provides further evidence for a language production disorder in many schizophrenics.Short Abstract: How is it that many schizophrenics identify certain instances of verbal imagery as hallucinatory? This paper proposes that the critical feature identifying hallucinations is the experience of unintendedness. This experience is nonpathological during passive conscious states but pathological if occurring during goal-directed cognitive processing. A model of schizophrenic speech disorganization is presented that postulates a disturbance of discourse planning that specifies communicative intentions. These alterations could generate unintended verbal imagery as well. Statistical data are offered to support the model, and relevant empirical studies are reviewed.

Studies on exploratory eye movement

This paper describes the pioneering studies on eye movements by Prof. Takuya Kojima, which clarified the scarcity of adjustability of alertness level in schizophrenia. Shimazono first thought that closed-eye eye movement may provide objective and physiological indicator for brain activities during awake state. Prof. Kojima thought that depressive patients may also have latent inner tension and was also intrigued by the contrast of the scarcity of exploratory eye movement in schizophrenic patients. He found out that depressive patients are tense at rest but that accustomization takes place in them, while accustomization does not take place in schizophrenic patients. Isse researched on closed-eye eye movements in relation with alertness and disturbance of consciousness. Prof. Kojima invented eye camera to measure the exploratory eye movement and created Responsive Search Score (RSS), an indicator of the parts which the subject covers during the responsive search. Prof. Kojima's research on differentiation of schizophrenic patients was carried out as WHO and the result was replicated in different ethnicities. Clinical molecular genetic studies suggest that RSS reflects the disposition of susceptibility for schizophrenia and possible linkage between RSS and chromosome 22q. Brain imaging studies showed correlation between RSS and the volume of the right parietal eye field, right frontal eye field including the right supplementary eye field and the right inferior frontal gyrus. Based on these findings Prof. Kojima invented an apparatus which can monitor eye movements and show diagnostic sensitivity 75% and specificity 80% for schizophrenia. The apparatus is expected to be applied clinically in the future.

Frequency domain analysis of electrooculogram and its correlation with cardiac sympathetic function

To test the hypothesis that electrooculogram contains information on autonomic functions, correlation analyses of electrooculogram and heart rate variability (HRV) parameters during night sleep and over 24 h were performed on 24 healthy young volunteers (12 women and 12 men). Continuous frequency-domain analysis revealed repeated emergence of electrooculogram low-frequency power (PEOG, 0.05-0.5 Hz) during night sleep. The change in the PEOG, when natural log transformed, was graded rather than all or nothing. The PEOG was not correlated with high-frequency power (HF, 0.15-0.4 Hz) of HRV. In contrast, the PEOG was significantly correlated with R-R interval (r=-0.46+/-0.15; mean+/-SD, P<0.05) and low-frequency power (0.04-0.15 Hz) to HF ratio (LF/HF) of HRV (r=0.49+/-0.10, P<0.05). The correlation coefficient between PEOG and R-R interval and between PEOG and LF/HF became even larger (r=-0.68+/-0.08 and 0.58+/-0.09, respectively) when 24-h recordings were analyzed. There was no significant difference in the correlation between women and men. We concluded that the electrooculogram, as analyzed in the frequency domain, contains information on sympathetic activity not only during night sleep but also throughout day and night in healthy young people.

Vigilance, alertness, or sustained attention: physiological basis and measurement

Vigilance is a term with varied definitions but the most common usage is sustained attention or tonic alertness. This usage of vigilance implies both the degree of arousal on the sleep-wake axis and the level of cognitive performance. There are many interacting neural and neurotransmitter systems that affect vigilance. Most studies of vigilance have relied on states where the sleep-wake state is altered, e.g. drowsiness, sleep-deprivation, and CNS-active drugs, but there are factors ranging from psychophysics to motivation that may impact vigilance. While EEG is the most commonly studied physiologic measure of vigilance, various measures of eye movement and of autonomic nervous system activity have also been used. This review paper discusses the underlying neural basis of vigilance and its assessment using physiologic tools. Since, assessment of vigilance requires assessment of cognitive function this aspect is also discussed.

Relationship between attention and arousal level in schizophrenia

The purpose of the present paper was to clarify the link between the attention and arousal level that supports the basis of the cognitive dysfunction in schizophrenia, by investigating the relationship between the simple reaction time and the closed-eye eye movements in 30 patients with schizophrenia and 20 healthy controls. In terms of closed-eye eye movements during the simple reaction time test, healthy controls showed an increase of s-type (small and slow) eye movements after the end of the preparatory interval (PI) in both regular and irregular series, while the patients with schizophrenia, particularly those in whom the cross-over phenomenon was observed, showed no changes and maintained a hyperarousal level during the regular PI test. These results indicate that the patients with schizophrenia could not maintain appropriate attention during the burden tasks and their hyperarousal level persisted. It is therefore suggested that there is a close relationship between attentional deficit and hyperarousal among patients with schizophrenia.

Effects of low-dose ketamine on neuropathic pain: An electroencephalogram-electrooculogram/behavioral study

The aim of the present study was to clarify the neurophysiological changes associated with analgesic and behavioral effects of low-dose ketamine HCl in patients suffering from chronic neuropathic pain. Ten in-patients with neuropathic pain participated in this single-blind, placebo-controlled study after giving written informed consent. Following intravenous injections of a saline solution (placebo), three bolus injections of 5 mg ketamine HCl were administered at 5 min intervals. Changes in pain perception were assessed using a numerical rating scale for pain. Behavioral changes, including psychotomimetic effects, were assessed using the Brief Psychiatric Rating Scale (BPRS). Electroencephalograms (EEG) and electrooculograms (EOG) were recorded continuously throughout the testing period. One minute EEG and closed-eye eye movements were quantified. The effects of ketamine were evaluated by comparing the neurophysiological and behavioral parameters obtained from the placebo and ketamine trials. Pain reduction was significantly correlated with ketamine-induced changes in hallucinatory behavior and excitement as measured by the BPRS. Ketamine injections caused a significant decrease in the EEGalpha amplitude without an accompanying reduction in EEG frequency. The EEGalpha amplitude reduction at the right central electrode was significantly related to subjective pain relief. Subanesthetic doses of ketamine significantly decreased rapid eye movements, but did not initiate slow eye movements. In conclusion, the present EEG-EOG/behavioral results indicate that ketamine-induced failure of neural integration between cortical-subcortical regions induces psychotic symptoms and alters pain perception on neuropathic pain.

Studies on the psychosomatic functioning of ill-health according to Eastern and Western medicine 5. Psychosomatic characteristics of anxiety and anxiety-affinitive constitution

In successive studies of the psychosomatic functioning of ill-health according to Oriental and Western medicine in medical students, we established the existence of the psychosomatic characteristics we have provisionally termed the anxiety-affinitve constitution at the core of ill-health. Therefore, we conducted this research because our previous investigation showed this constitution included a high complexity of respiratory movement and eye movement with a significant correlation to the State Trait Anxiety Inventory (STAI). We examined the correlation between the STAI and somatic function of 88 medical students to identify the psychosomatic characteristics of anxiety and the anxiety-affinitive constitution. These tests included STAI, fractal (EEG, EOG, plethysmogram, respiratory curves, and EMG) and non-fractal (accelerated plethysmogram) dimension analyses, and malocclusion (based on Angle's classification). In particular, EOG, plethysmogram, and respiratory curves are known to have close association with trait anxiety. We were able to discover the correlation between (1) trait anxiety and thoracic and abdominal respiratory movements, and malocclusion (Class III), and (2) the correlation of state anxiety with thoracic respiratory movement, horizontal eye movement, a plethysmogram and an EEG-Pz (in males only). In subsequent study the relation between thoracic dominance and state-trait anxiety and between abdominal dominance and state-trait anxiety should be assessed to develop this research regarding the psychosomatic characteristics of anxiety and the anxiety-affinitive constitution. Further, it is essential to create an anxiety-affinitve constitution index based on multi-regression analysis.

A psychophysiological study of the development of delirium in coronary care units

This is a longitudinal investigation of the psychophysiological mechanism for the development of delirium in coronary care units (CCUs). Ten patients satisfying DSM-III-R diagnostic criteria for delirium (group D) and 10 controls (group C) were drawn from patients admitted to CCU. Electroencephalogram (EEG) and eye movement recordings were observed over the days that patients were admitted to CCU and on a control day of admission and compared for each group and between each day. In the D group, slowing of background EEG activity, particularly on day 2, and many R (rapid) group eye movements and RS type (rapid superimposed on slow) eye movements, particularly on day 3, were observed. That is, from days 2 to 3, EEG findings showed an improvement in consciousness, and eye movement recordings manifested signs of anxiety and tension. These psychophysiological findings can be used to explain the transition from prodromal delirium to obvious delirium, and are supported by clinical features.

Horizontal component of electro-oculogram as a parameter of arousal in dementia: relationship between intellectual improvement and increasing arousal under pharmacotherapy

Although nootropics and metabolically active compounds sometimes attenuate intellectual deficits of dementia patients, this mechanism has not been discussed or investigated. The authors hypothesized that these compounds act to enhance attention and/or concentration by increasing the arousal level, and then improve intellectual functions. Based on this hypothesis, the authors investigated the arousal level and the improvement of intellectual functions in ten patients with Alzheimer type dementia and ten patients with multi-infarct dementia before and after 3 months pharmacotherapy using bifemelane hydrochloride. They then analyzed whether the increases in arousal level involves or relates to the improvement of intellectual functions. On the 20 patients, psychological tests were carried out, and the arousal level was evaluated using the frequency of rapid eye movements in the electro-oculogram (EOG) before and after 3 months administration of bifemelane hydrochloride. As a result, a significant positive correlation was observed between the improvement on the Hasegawa's dementia scale and the rate of increase in rapid eye movements in the EOG. The EOG monitoring can be a great help in establishing an objective evaluation method on drug efficacy.

Scanning eye movements in schizophrenic patients. Relationship to clinical symptoms and regional cerebral blood flow using 123I-IMP SPECT

Eye movements during the Benton Visual Retention Test were examined using an eye-mark recorder in 32 schizophrenic patients and 32 normal controls. The patients had significantly fewer eye fixations, longer mean duration of fixation and shorter length of mean scan path than the controls. In the patients, these eye movement parameters were significantly correlated with the negative symptom score but not with the positive symptom score on the Positive and Negative Syndrome Scale. These parameters had a significant correlation with the composite score on the Scale for the Assessment of Negative Symptoms (SANS). In particular, they were highly correlated with avolition-apathy and affective flattening or blunting scores on SANS subscales. Thus, examination of scanning eye movements seemed to be a good objective index of negative symptoms. Secondly, regional cerebral blood flow (rCBF) was examined using N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) and single photon emission computer tomography in 17 of 32 patients. With regard to the relationship between the eye movement parameters and rCBF, the mean duration of fixation was negatively correlated with 123I-IMP uptake in the left superior frontal area and left basal ganglia. The mean length of the scan path was correlated with uptake in the left superior frontal area. These findings suggest that the characteristic eye movements of schizophrenic patients are likely to be related with dysfunction of the frontal-basal ganglia neural circuit.

Neurotransmitters, receptors and neuropeptides in post-mortem brains of chronic schizophrenic patients

In the analysis of post-mortem brains of 14 chronic schizophrenic patients and 10 controls, biochemical evidence of a hyperdopaminergic state was found in the basal ganglia of schizophrenics; tyrosine hydroxylase activity was increased with a concomitant increase of homovanillic acid. Unusually high tyrosine hydroxylase activity was noted in 2 schizophrenic cases. The Bmax value of 3H-spiperone binding for schizophrenics was higher than the controls. We also found increased specific binding of 3H-kainic acid to the prefrontal cortex in schizophrenics. A negative correlation existed between 3H-kainic acid binding in the medial frontal cortex, and glutamic acid content in various brain areas. Increased immunoreactivity of substance P was found in more than ten brain areas. Methionine-enkephalin was also increased in three areas of the prefrontal cortex of schizophrenics. These results suggest that the hyperdopaminergic state co-existed with glutamatergic hypofunction and increased neuropeptides in various brain areas of chronic schizophrenic patients.

Continuous observations of daytime EEG patterns in normal subjects under restrained conditions while sitting in armchair or on stool. Part 2. Awake state

While stabilizing (though not completely) both behavioral and environmental factors as far as possible, observations of continuous awake EEG patterns and corresponding behavioral states were made in order to investigate the level of vigilance for extended periods of time in the daytime. The subjects were requested to maintain a constant posture while sitting in an armchair or on a stool, and continuous polygraphic recordings and simultaneous TV monitoring of the subjects' behavior were carried out. Inspections of the EEG records, the rating of simultaneous behavior shown by the subjects and subsequent data analysis produced the following results: 1) From evaluations of EEGs, EOGs and EMG and ratings of the corresponding behavioral states carried out for every 30-second epoch, six types of awake EEG patterns and four types of behavioral states could be defined. There was a strong correlation between the awake EEG pattern and the behavioral state. 2) Regular 6.0-7.0 c/s theta wave trains predominantly in the frontal area were observed in 16 out of 24 normal subjects (67%) in an awake state. In the theta-appearance group, the relative abundance and mode of appearance of theta wave trains varied greatly both intra- and interindividually. The appearance of the theta wave trains was not related to drowsiness and was presumed to reflect the emotional activity under higher levels of vigilance in the subjects.

Pattern of eyelid motion predictive of decision errors during drowsiness: oculomotor indices of altered states

Sequential patterns of eye and eyelid motion were identified in seven subjects performing a modified serial probe recognition task under drowsy conditions. Using simultaneous EOG and video recordings, eyelid motion was divided into components above, within, and below the pupil and the durations in sequence were recorded. A serial probe recognition task was modified to allow for distinguishing decision errors from attention errors. Decision errors were found to be more frequent following a downward shift in the gaze angle which the eyelid closing sequence was reduced from a five element to a three element sequence. The velocity of the eyelid moving over the pupil during decision errors was slow in the closing and fast in the reopening phase, while on decision correct trials it was fast in closing and slower in reopening. Due to the high variability of eyelid motion under drowsy conditions these findings were only marginally significant. When a five element blink occurred, the velocity of the lid over pupil motion component of these endogenous eye blinks was significantly faster on decision correct than on decision error trials. Furthermore, the highly variable, long duration closings associated with the decision response produced slow eye movements in the horizontal plane (SEM) which were more frequent and significantly longer in duration on decision error versus decision correct responses.

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.

Refixation saccades and attention in schizophrenia

Saccadic refixation eye movements of 20 schizophrenic, 20 hospitalized nonpsychotic, and 20 normal subjects were compared in two repetitive fixation tasks with high and low target information. Although no differences emerged among groups in the overall frequency or size of saccades, the average and peak velocity of saccades was slower for schizophrenics than for normals. The velocity of saccades for the hospitalized nonpsychotic group was between that of schizophrenics and normals. To evaluate this finding further, saccades in the first two stimulus cycles were examined. The average and peak velocity of saccades was found to be significantly slower for schizophrenics than for normals. Again, the velocity of saccades for hospitalized nonpsychotic subjects was between that of schizophrenics and normals. Moreover, the size of saccades during the first two cycles was smaller for the schizophrenic than for other subject groups. Embedded alphanumeric information in the fixation target generally resulted in increased velocity of saccades for all subjects. The results were interpreted as evidence for an attentional deficit in schizophrenia. Specifically, schizophrenic subjects appeared to be less able to utilize peripheral visual information than hospitalized or normal subjects.

Eye movement as an indicator of brain function

The level of consciousness between the alert and drowsy states was classified into four stages (Alert, Resting I, Resting II, Drowsy) by studying three factors of the EEG patterns on 23 normal subjects. The eye movements recorded by electro-oculograph were divided into two groups, i.e. rapid eye movements (R type, r type) and slow eye movements (S type, s type). The occurrence of each type of eye movements was confirmed to change in close correspondence to the stages of consciousness. The eye movement on 43 cases with a disturbance of consciousness by metabolic disease were recorded longitudinally according to clinical states. The S type movements were predominantly observed in a state of clouding of consciousness, while the R type and R-S type were observed in a delirious state.

Differential sensitivity to the effects of psychotropic drugs: psychotics vs normals; Asian vs Western populations

The effects and side-effects of psychotropic drugs are determined by many variables, and the host factor is one of the most important. A lower sensitivity of schizophrenics than normals to the sedative effect of chlorpromazine and a manic depressives to imipramine were demonstrated quantitatively by a higher percent time of waking EEG following medication. The mean therapeutic dose of chlorpromazine for the manic state was found to be much lower in Japanese than in Western populations in a controlled study comparing the antimanic efficacy of carbamazepine and chlorpromazine. A lower therapeutic dose in Asian populations has been reported also on other antipsychotic drugs, lithium, and tricyclic antidepressants. The lower therapeutic dose level was discussed from the standpoint of transcultural psychopharmacology.

Disturbances of ocular movements and blinking in schizophrenia

Neurological examination and electroencephalograms and electro-oculograms, recorded by telemetry, from unmedicated patients with acute and chronic schizophrenia demonstrate a number of abnormalities of extraocular movement including staring, abnormal blink rate, absent glabellar reflex, and increase in horizontal eye movements. As potential clues to the pathophysiology of schizophrenia, these disturbances are analysed in relation to anatomical substrate and dopamine modulation of ocular movement, rapid eye movement sleep, and the neurological disorders in which similar disturbances of ocular movement occur.

Sensitivity to chlorpromazine effects on brain function of schizophrenics and normals. A preliminary report

For the purpose of quantitative demonstration of the sensitivity to chlorpromazine (CPZ) effects on brain functions of schizophrenics and normal subjects, polygraphic recordings of electroencephalogram (EEG) and electrodermal response (EDR) were performed before and 3 h after oral administration of 25 mg of CPZ: percent time waking EEG (per cent W-EEG) and number per minute of EDR were measured during the resting period and the period of calculation. In 10 normal adult subject, both per cent W-EEG and number of EDR showed remarkable decrease after CPZ administration. In 22 schizophrenics, however, per cent W-EEG showed no significant decrease after CPZ administration. Number of EDR in schizophrenics during the period of calculation did not show any significant decrease. The neural mechanism underlying the lower sensitivity to CPZ effects in schizophrenics was discussed.

Eye-movement consistency and relationship to the process-reactive dimension in schizophrenia

Horizontal eye movements of schizophrenics were recorded while they viewed 3 different stimuli in succession and they were administered the Ullmann-Giovannoni process-reactive scale. The schizophrenics' eye movements were consistent across stimulus conditions ( rho = .63, .88, .81) and the eye movements in each condition were related to the process-reactive measure ( rho = .64, .72, .64), reactives having more eye movements.

A paradigm for the study of altered states of consciousness

“When man experiences that certain sequences of mental events lead to behavior which has, as a matter of fact, survival value, he calls such mental facts ‘right’. It would be better, however, if instead of this word some neutral symbol were being used for those particular events; because the word ‘right’ leads to the unfortunate notion that some combinations of mental facts are intrinsically better than others. …”

Rates of saccadic eye movement and size judgments of normals and schizophrenics

Saccadic eye movements during fixation of a target image and size estimations were studied in nonschizophrenic and schizophrenic Ss. The results on rate of saccadic movement were quite different in those who overestimated the sizes of the standard disc. Nonschizophrenics who over-estimated had unusually low rates of saccadic movement; schizophrenic Ss who over-estimated had unusually high rates of saccadic movement, especially when they were older patients who had been hospitalized for 12 to 20 yr. No difference in rates of saccadic movement were found between nonschizophrenic and schizophrenic Ss who under-estimated the standard stimuli. The high rate of saccadic eye movements in over-estimating schizophrenics can be compared to the similar result in normals who have been given LSD-25.