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.     

Relationship between exploratory eye movement, P300, and reaction time in schizophrenia

Aims:  Exploratory eye movement (EEM), P300 and reaction time (RT) tests may relate to the important parts of information processing in the human brain. Therefore the aim of the present study was to compare EEM, P300 and RT test data in schizophrenic and normal control groups to investigate whether schizophrenic patients have information processing abnormalities. In addition, the potential correspondence between the three tests was examined in order to investigate the information processing dysfunctions seen in schizophrenic patients.
Methods:  The EEM, P300 and RT performances were recorded in 34 schizophrenic and 36 normal control subjects. Ten parameters were measured: four from the EEM test (number of eye fixations, total eye scanning length, cognitive search score and responsive search score [RSS]); two from the P300 test (amplitude and latency); and four from the RT test (simple reaction time, index of reaction time crossover [IRT-crossover], set index and coefficient of variation).
Results:  These parameters in the schizophrenic patients differed significantly from those in the control group. Additionally, there was a significant correlation between the RSS and the IRT-crossover in the schizophrenic patients.
Conclusion:  The present group comparisons (schizophrenia vs normal controls) are consistent with previous studies in that the abnormalities in EEM, P300 and RT tests in schizophrenic patients were able to be replicated. Moreover, based on the former psychological theory, it is reasonable to propose that the RSS is associated with the IRT-crossover. The present results may contribute to elucidation of the pathophysiological signature of schizophrenia.     

Smooth pursuit eye movements of patients with schizophrenia and affective disorder during clinical treatment

Background Smooth pursuit eye movement dysfunctions are considered a biological indicator for vulnerability to schizophrenia. This study examines test-retest stability of specific eye movement variables such as velocity gain and different saccadic categories. Methods Smooth pursuit eye movements of 27 schizophrenic patients and 30 patients with major depression were examined three times during clinical treatment using high-resolution infrared oculography. Forty-one normal controls were retested after four weeks. Results Intraclass correlation coefficients as a measure for retest-stability were highly significant in each group for all time-points, except for anticipatory saccades in schizophrenics. No significant correlations were found between psychopathological status, neuroleptic medication and eye movement variables. Conclusions Our results indicate that the most important measures of eye tracking performance in psychiatric patients are not significantly influenced by neuroleptic medication or clinical state and are stable across time. Received: 15 May 2001 / Accepted: 17 December 2001     

Common capacity-limited neural mechanisms of selective attention and spatial working memory encoding

One characteristic feature of visual working memory (WM) is its limited capacity, and selective attention has been implicated as limiting factor. A possible reason why attention constrains the number of items that can be encoded into WM is that the two processes share limited neural resources. Functional magnetic resonance imaging (fMRI) studies have indeed demonstrated commonalities between the neural substrates of WM and attention. Here we investigated whether such overlapping activations reflect interacting neural mechanisms that could result in capacity limitations. To independently manipulate the demands on attention and WM encoding within one single task, we combined visual search and delayed discrimination of spatial locations. Participants were presented with a search array and performed easy or difficult visual search in order to encode one, three or five positions of target items into WM. Our fMRI data revealed colocalised activation for attention-demanding visual search and WM encoding in distributed posterior and frontal regions. However, further analysis yielded two patterns of results. Activity in prefrontal regions increased additively with increased demands on WM and attention, indicating regional overlap without functional interaction. Conversely, the WM load-dependent activation in visual, parietal and premotor regions was severely reduced during high attentional demand. We interpret this interaction as indicating the sites of shared capacity-limited neural resources. Our findings point to differential contributions of prefrontal and posterior regions to the common neural mechanisms that support spatial WM encoding and attention, providing new imaging evidence for attention-based models of WM encoding.     

Face and object visual working memory deficits in first-episode schizophrenia correlate with multiple neurocognitive performances

BackgroundWorking memory (WM) deficit is considered a core feature and cognitive biomarker in patients with schizophrenia. Several studies have reported prominent object WM deficits in patients with schizophrenia, suggesting that visual WM in these patients extends to non-spatial domains. However, whether non-spatial WM is similarly affected remains unclear.AimThis study primarily aimed to identify the processing of visual object WM in patients with first-episode schizophrenia.MethodsThe study included 36 patients with first-episode schizophrenia and 35 healthy controls. Visual object WM capacity, including face and house WM capacity, was assessed by means of delayed matching-to-sample visual WM tasks, in which participants must distribute memory so that they can discriminate a target sample. We specifically examined their anhedonia experience by the Temporal Experience of Pleasure Scale and the Snaith-Hamilton Pleasure Scale. Cognitive performance was measured by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).ResultsBoth face and house WM capacity was significantly impaired in patients with schizophrenia. For both tasks, the performance of all the subjects was worse under the high-load condition than under the low-load condition. We found that WM capacity was highly positively correlated with the performance on RBANS total scores (r=−0.528, p=0.005), RBANS delayed memory scores (r=−0.470, p=0.013), RBANS attention scores (r=−0.584, p=0.001), RBANS language scores (r=−0.448, p=0.019), Trail-Making Test: Part A raw scores (r=0.465, p=0.015) and simple IQ total scores (r=−0.538, p=0.005), and correlated with scores of the vocabulary test (r=−0.490, p=0.011) and scores of the Block Diagram Test (r=−0.426, p=0.027) in schizophrenia. No significant correlations were observed between WM capacity and Positive and Negative Syndrome Scale symptoms.ConclusionsOur research found that visual object WM capacity is dramatically impaired in patients with schizophrenia and is strongly correlated with other measures of cognition, suggesting a mechanism that is critical in explaining a portion of the broad cognitive deficits observed in schizophrenia.     

Relationship between financial competence and cognitive function in patients with schizophrenia

The present study examined financial competence in patients with schizophrenia and the relationship between their financial competence and cognitive function. The subjects consisted of 25 patients with schizophrenia (10 inpatients and 15 outpatients) and 22 normal controls who were community-dwelling people with no psychiatric disorders or cognitive deficit. To assess the subjects' cognitive function and financial competence, they completed the Japanese version of the Neurobehavioral Cognitive Status Examination (COGNISTAT), which has 10 subtests, and the Financial Competency Assessment Tool (FCAT), which has six subordinate domains of financial competence. Patients with schizophrenia performed significantly worse than the controls in all scores on the FCAT. The financial scores that were significantly different between the patients and the normal controls were significantly positively correlated with the scores on several COGNISTAT subtests (e.g. comprehension). These results suggest that patients with schizophrenia have problems with financial competence and that these problems may be accounted for by deficits in several cognitive functions.     

Superior colliculus inactivation alters the relationship between covert visual attention and microsaccades

Microsaccades are tiny saccades that occur during gaze fixation. Whereas these movements have traditionally been viewed as random, it was recently discovered that microsaccade directions can be significantly biased by covertly attended visual stimuli. The detailed mechanisms mediating such a bias are neither known nor immediately obvious, especially because the amplitudes of the movements influenced by attentional cueing could be up to two orders of magnitude smaller than the eccentricity of the attended location. Here, we tested whether activity in the peripheral superior colliculus (SC) is necessary for this correlation between attentional cueing and microsaccades. We reversibly and focally inactivated SC neurons representing peripheral regions of visual space while rhesus monkeys performed a demanding covert visual attention task. The normal bias of microsaccade directions observed in each monkey before SC inactivation was eliminated when a cue was placed in the visual region affected by the inactivation; microsaccades were, instead, biased away from the affected visual space. When the cue was placed at another location unaffected by SC inactivation, the baseline cue‐induced bias of microsaccade directions remained mostly intact, because the cue was in unaffected visual space, and any remaining changes were again explained by a repulsion of microsaccades away from the inactivated region. Our results indicate that peripheral SC activity is required for the link between microsaccades and the cueing of covert visual attention, and that it could do so by altering the probability of triggering microsaccades without necessarily affecting the motor generation of these movements.     

Eye movements in patients with schizophrenia: visual stimuli,semantic content and psychiatric symptoms

In order to explore a possible association between psychiatric symptoms and eye movements, 32 patients with schizophrenia were examined using an eye mark recorder in combination with the Positive and Negative Syndrome Scale, and were compared with 32 controls. Four types of figures were presented to the subjects: geometrical figures, drawings, story drawings, and sentences. Mean eye fixation time was significantly longer and mean eye scanning length was significantly shorter for the patients than for controls, not only in response to the geometric figures, but also in response to the story drawings. Eye fixation time and scanning velocity were positively correlated with degrees of thought disturbance. The number of eye fixations, eye fixation time and scanning velocity were negatively correlated with degree of depressive tendency.     

Flickering Light Spot as a Tracking Target for the Study of Smooth Pursuit Eye Movements in Schizophrenics –A New Method–

Abstract: Smooth pursuit eye movements (SPEM) were studied in 26 schizophrenics and 20 normal controls. A light spot on a screen of cathode ray oscilloscope was used as a tracking target. In order to induce SPEM disorder easily, the subjects were required to track a light spot which flickered in various frequencies. This new method devised by the authors has clearly demonstrated that the SPEM in schizophrenics was more profoundly disturbed by the flickering of the tracking target than that in the normal control subjects. It was supposed that poor tracking of a flickering light spot in schizophrenics may be due to the inadequate concentration of attention to visual stimuli, and/or inability to predict the movements of a tracking target.     

Looking you in the mouth: abnormal gaze in autism resulting from impaired top-down modulation of visual attention

People with autism are impaired in their social behavior, includingtheir eye contact with others, but the processes that underliethis impairment remain elusive. We combined high-resolutioneye tracking with computational modeling in a group of 10 high-functioningindividuals with autism to address this issue. The group fixatedthe location of the mouth in facial expressions more than didmatched controls, even when the mouth was not shown, even infaces that were inverted and most noticeably at latencies of200–400 ms. Comparisons with a computational model ofvisual saliency argue that the abnormal bias for fixating themouth in autism is not driven by an exaggerated sensitivityto the bottom-up saliency of the features, but rather by anabnormal top-down strategy for allocating visual attention.     

Exploratory eye movements in schizophrenia

It has been reported that patients with schizophrenia show restricted eye-scanning in comparison with normal controls; however, the precise mechanism underlying the limited eye movement pattern remains unknown. The purpose of this study was to determine the factors affecting restricted eye-scanning in schizophrenic patients by examining exploratory eye movements during demonstration of two different sizes of the S-shaped figure. The second purpose was to determine the effect of the instruction for performance on the restricted viewing pattern in patients with schizophrenia. Eye movements during demonstration of the S-shaped figure of the original or half size were examined in 15 patients with schizophrenia and 15 normal controls using an infrared eye-mark recorder. The patients showed lower search scores than control subjects for both sizes of the figure. The subjects were then instructed to compare a slightly modified figure with the original one. Lower responsive search scores were found for the patients when “fixation point” was defined as a point at which a gaze was held for at least 200 ms, while the patients and control subjects performed equally at the 100-ms setting. Direct instruction to scrutinize the S-shape abolished the difference in the search scores between patients and control subjects at both the 100-ms and 200-ms settings. These findings suggest that the size of the S-figure is not a factor of restricted eye movements, and that the direct instruction improves the visual performance in patients with schizophrenia. Received: 21 February 2000 / Accepted: 15 October 2002 Correspondence to Mié Matsui, Ph. D.     

Impaired modulation of attention and emotion in schizophrenia

Objective: Fronto-limbic interactions facilitate the generation of task-relevant responses while inhibiting interference from emotionally distracting information. Schizophrenia is associated with deficits in both executive attention and affective regulation. This study aims to elucidate the neural correlates of emotion-attention regulation and shifting in schizophrenia. Method: We employed functional magnetic resonance imaging to probe the fronto-limbic regions in 16 adults with schizophrenia and 13 matched adults with no history of psychiatric illness. Subjects performed a forced-choice visual oddball task where they detected infrequent target circles embedded in a series of infrequent nontarget aversive and neutral pictures and frequent squares. Results: In control participants, target events activated a dorsal frontoparietal network, whereas these regions were deactivated by aversive stimuli. Conversely, ventral frontolimbic brain regions were activated by aversive stimuli and deactivated by target events. In the patient group, regional hemodynamic timecourses revealed not only reduced activation to target and aversive events in dorsal executive and ventral limbic regions, respectively, but also reduced deactivation to target and aversive stimuli in ventral and dorsal regions, respectively, relative to the control group. Patients further showed reduced spatial extent of activation in the right inferior frontal gyrus during the target and aversive conditions. Activation of the anterior cingulate to aversive images was inversely related to severity of avolition and anhedonia symptoms in the schizophrenia group. Conclusions: These results suggest both frontal and limbic dysfunction in schizophrenia as well as aberrant reciprocal inhibitions between these regions during attention-emotion modulation in this disorder.     

Functional neuroanatomy of sustained attention in schizophrenia: contribution of parietal cortices

Deficits in sustained attention have been frequently described in schizophrenia. The neuroanatomical basis reported previously have included altered levels of activation in cingulate and prefrontal cortex, but the contribution of further regions remains unclear. We explored the full neuroanatomy underlying the sustained attentional deficits observed in naïve schizophrenics compared with controls. Participants included 10 controls and 11 patients. The experimental design included rest, auditory stimulation using clicks, and two counting tasks. Subjects were instructed to mentally count the clicks, and then to count forward at the same frequency they heard previously when listening to the clicks. Relative cerebral blood flow (relCBF) was measured by means of PET ¹⁵O‐water. Differences were observed between both groups at superior temporal cortex, superior parietal gyrus, and cerebellum during tasks requiring listening. During all counting conditions, additionally to supplementary motor area (SMA), dorsolateral prefrontal cortex (DLPCF), precentral gyrus, cingulate, cerebellum, and inferior parietal (IP) gyrus, patients engaged other frontal structures including inferior, medial, and superior frontal areas. When counting with no auditory stimulation (C; requires components of working memory and time estimation), significant differences were observed in the level of activation of frontal and IP regions. Our naïve patients presented abnormal activation of auditory associative pathways. They failed to activate prefrontal and parietal regions at a similar level during tasks requiring increased cognitive effort, and they required a higher activation of inferior frontal regions to properly respond to cognitive demands. Hum. Brain Mapping 17:116–130, 2002. © 2002 Wiley‐Liss, Inc.     

Abnormal exploratory eye movements in schizophrenic patients vs healthy subjects

OBJECTIVE: We examined previously described exploratory eye movements abnormalities as biologic markers in schizophrenic patients in comparison with age-matched healthy subjects. MATERIAL AND METHODS: Using an eye-mark recorder, eye movements were analysed for mean gazing time, total number of gazing points, mean eye scanning length, total eye scanning length, and total gazing times as subjects viewed six simple pictures in preparation for copying them. RESULTS: In-patients, and to a lesser extent, out-patients, with schizophrenia showed a longer gazing time, fewer gazing points, a shorter mean and total eye scanning length. and longer gazing time than healthy subjects. In schizophrenic patients. negative symptom scores were positively correlated with mean gazing time (r = 0.33), and negatively correlated with the total number of gazing points (r = -0.29) as well as, the mean (r = -0.40) and total scanning length (r = -0.46). CONCLUSION: Exploratory eye movements are a biologic marker useful for evaluation of schizophrenia.     

Eye movements during the Rorschach test in schizophrenia

In order to understand relationships between scanning behaviors, characteristics of visual stimuli and the clinical symptoms in schizophrenia, eye movements of 37 schizophrenic patients and 36 controls were recorded using an eye-mark recorder during a free-response period in a Rorschach test. Four cards (I, II, V and VIII) were used. Data were analyzed during 15 s from the presentation of each card. For all cards, the number of eye fixations and the number of eye fixation areas were fewer, and total scanning length and mean scanning length were shorter for schizophrenic patients than for controls. For card II, in the non-popular response group, eye fixation frequency upon area 5 + 6 (red) was higher for schizophrenic patients. For card VIII, in the popular response group, eye fixation frequency upon area 5 + 6 (pink) was lower for schizophrenic patients. For cards II and VIII, the number of eye fixations was inversely correlated with negative symptoms. For card II, total scanning length tended to be inversely correlated with negative symptoms, and mean eye fixation time was correlated with negative symptoms. The number of eye fixation areas was inversely correlated with positive symptoms. For card VIII, eye fixation frequency in a stimulative area tended to be correlated with positive symptoms. Scanning behaviors in schizophrenic patients are affected by characteristics of visual stimuli, and partially by clinical symptoms.     

Influence of arousal level for functional magnetic resonance imaging (fMRI) study: simultaneous recording of fMRI and electroencephalogram

Simultaneous recording of functional MRI (fMRI) and electroencephalogram (EEG) has been applied to several clinical fields, making it possible to monitor the arousal level of the subject during a cognitive task. The study confirmed that activated cerebral areas were different between high and low arousal levels during the smooth-pursuit eye movement task. When arousal level was high, activations in the parietal eye field, frontal eye field (FEF), supplementary eye field (SMA), visual fields (V1) and occipito-temporal junction (V5) were found. In contrast, when arousal level was low, activations were found only in V1 and FEF. The results indicate that the monitoring of the arousal level of subjects using fMRI and EEG recordings simultaneously is crucial for detecting cortical activations during a cognitive task.     

Saccadic eye movements after extremely short reaction times in the monkey

Monkeys were trained to change their direction of gaze from one point (fixation point) to another (target). If the fixation point was extinguished at the same time when the new target occurred the saccadic reaction times (SRT) were in the order of 200 ms. If the fixation point disappeared 150-250 ms before the new target occurred (gap with no visible stimulus) monkeys made regular saccades after shorter reaction times of about 140 ms. In addition animals in the gap situation made saccades that had reaction times of no more than 70-80 ms measured from the onset of the new target (Express-Saccades). The reaction times of the E-saccades have standard deviations of only +/- 3 ms. E-saccades occurred with a frequency of up to 80% for gaps of 200-240 ms. If the gap was shorter than 180 ms increasingly more regular saccades were made with reaction times of 140-160 ms. With gap duration decreasing from 140 ms to zero all saccades were regular with SRTs increasing linearly to more than 200 ms. In one animal almost all E-saccades fell short and were corrected after less than 250 ms depending on the size of the error: large errors were corrected faster than small ones.     

Behavioral and neuroimaging studies on schizophrenia in Japan

Abstracts Chronic methamphetamine psychotics became a major problem in Japan after World War II. On one hand, the clinical symptoms of chronic methamphetamine psychotics were noted to resemble those of schizophrenics quite closely but, on the other hand, their respective personality profiles appeared to differ. Recent research on exploratory eye movements has also shown such similarities and differences. In long-term remitted chronic methamphetamine psychotics, extremely small doses of drugs, or stress, can be enough to cause a recurrence of symptoms. This phenomenon resembles the recurrence of schizophrenia, and animal experiments and basic research are being actively conducted in order to elucidate the mechanism involved.
Some 20 years ago, unique studies were conducted that objectively looked at the characteristic behavior of severe chronic schizophrenics in a playground situation. Exploratory eye movements can also be regarded as a kind of behavior and, in this paper, eye movement patterns made in response to a maze test are discussed. In addition, much research on brain imaging in schizophrenia is being conducted in Japan and several interesting studies have also been chosen by the authors for presentation in this paper.     

Positive symptoms and duration of illness predict functional laterality and attention modulation in schizophrenia

OBJECTIVE: Dichotic listening (DL) performance in schizophrenia, reflecting hemispheric asymmetry and the functional integrity of the left temporal lobe, can vary with clinical characteristics. Previous studies have not taken the co-linearity of clinical variables into account. The aim of the present study was to evaluate the roles of positive symptoms and duration of illness in DL through Structural Equation Modeling (SEM), thus allowing for complex relationships between the variables. METHOD: We pooled patients from four previous DL studies to create a heterogeneous group of 129 schizophrenic patients, all tested with a consonant-vowel syllables DL procedure that included attentional instructions. RESULTS: A model where positive symptoms predicted a laterality component and duration of illness predicted an attention component in DL was confirmed. CONCLUSION: Positive symptoms predicted reduced functional laterality, suggesting involvement of left temporal lobe language processing. Duration of illness predicted impaired attention modulation, possibly reflecting the involvement of frontotemporal networks.