Abnormality in saccadic eye movement in dementia.

In a small (n = 15) clinically heterogeneous group of patients with dementia of the Alzheimer-type or vascular dementia, abnormally high frequency of saccadic intrusions during fixation was significantly correlated to the Mini-Mental-State-Examination (MMSE) scores. In addition, the latency of saccades and hypometric saccades also correlated significantly to MMSE-scores. The results point to the possible use of saccadic eye movement as a physiological marker of cognitive performance.     

Diagnostic value of saccadic pursuit eye movement in screening for organic cerebral dysfunction

Summary In order to validate the results obtained in a preliminary investigation the saccadation of slow pursuit eye movements was examined in 19 patients with unilateral brain damage, in 25 patients with diffuse cerebral disease and in 26 neurotic patients.The diagnostic significance of saccadation was ascertained in detecting general cerebral dysfunction. By means of a discriminant function combining the parameters, number and size, of saccades more than 80% of the brain-damaged patients and controls could be identified correctly, but the side of the cerebral lesion could not be determined.

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Zusammenfassung Zur Validierung der Ergebnisse einer Voruntersuchung wurde die Sakkadierung der Augenfolgebewegungen bei 19 einseitig hirngeschädigten, 25 diffus hirnkranken und 26 neurotischen Patienten untersucht.Die diagnostische Valenz des Merkmals der Sakkadierung für den Nachweis cerebraler Funktionsbeeinträchtigungen wurde bestätigt. Mit Hilfe einer Diskriminanzfunktion, die sowohl die Anzahl als auch die Größe der Sakkaden berücksichtigt, konnten mehr als 80% der Hirnkranken und der neurotischen Kontrollpatienten identifiziert werden. Zur Feststellung der Seite der cerebralen Läsion eignet sich das Merkmal nicht.

     

Motoric response inhibition in finger movement and saccadic eye movement: a comparative study.

OBJECTIVE: To study cortical potentials associated with suppression of intended motoric actions. METHODS: Electro-encephalographic activity was recorded in a Go/NoGo reaction time paradigm. Subjects viewed computer-generated pacing stimuli, which provided information concerning the time at which an imperative Go/NoGo signal occurred. A motoric response was required following Go stimuli while motoric response inhibition was required following NoGo stimuli. To examine whether previously reported 'Go/NoGo effects' on event related potential (ERP) components may be generalized across movement modalities, the present experimental paradigm was performed with either finger movement or saccadic eye movement as required motoric response. RESULTS: For both movement modalities, comparable differences in the morphology, amplitude and scalp topography of ERP components were observed between Go trials, with proper movement execution, and NoGo trials, with complete suppression of motoric activity. In addition, for either movement modality a similar 'error related negativity' (ERN) was found for NoGo trials in which motoric activity was present. CONCLUSIONS: The results of the present study suggest that cortical activity underlying the Go/NoGo differences in ERP components represent general cortical processing associated with detection and/or suppression of inappropriate response behaviour, independent of movement modality.     

Dependence of presaccadic cortical potentials on the type of saccadic eye movement.

Premovement cortical potentials were studied with 4 types of saccadic eye movement: (a) visually triggered saccades of normal reaction time (RT; regular saccades); (b) visually triggered saccades of extremely short RT (express saccades); (c) saccades towards predicted target locations (anticipatory saccades); (d) saccades back towards predicted location of fixation point (refixation saccades). With all 4 saccade types a "presaccadic negativity" with the maximum at the vertex (Cz) was observed. A bilaterally symmetrical component contained in this potential (being smallest with almost unconsciously performed refixation saccades and smaller in trained than in naive subjects) appeared to be related mainly to the subjects' volitional effort. In addition, anticipatory and refixation saccades were preceded by an early, widespread contralateral negativity, which we relate to cortical activities that prepare, in general terms, action within or towards the hemifield containing the saccade goal. During the 60 msec before anticipatory saccades, a negativity occurred over the contralateral central lead, which may reflect neural activation in the frontal eye field (FEF) and premotor cortex. In contrast, regular saccades were preceded 30 msec before onset by a negativity over the contralateral parietal cortex, which probably reflects an activation of parietal visuo-motor neurons. No lateralization of the cortical potentials was observed before express saccades, which suggests that these saccades are generated in a reflex-like way mainly by subcortical mechanisms.     

Horizontal and vertical saccadic eye movement abnormalities in Huntington's chorea

With a newly developed infrared reflection technique, voluntary saccadic eye movements (VOLS), visually evoked saccades (VES) and unsuppressed visually evoked reflex saccades (USVERS) were measured in 11 patients with Huntington's chorea. Abnormalities, including latency increase, peak velocity decrease and undershoot dysmetria with multiple step saccades were found in all types of saccadic eye movements. Peak velocity decrease and undershoot dysmetria can be explained by dysfunction of the brainstem reticular formation in Huntington's chorea. USVERS and square wave jerks occurred abnormally frequently and showed direction-dependent differences. Both were more frequent in horizontal than in vertical direction. Frequency of USVERS and square-wave jerks tended to be correlated. These findings point to disinhibited superior colliculi as a possible common supranuclear origin of USVERS and square-wave jerks in Huntington's chorea.     

The effects of antipsychotic medication on saccadic eye movement abnormalities in Huntington's disease

1. The study was a prospective open trial done to determine the effect of antipsychotic medication on saccadic eye movements in patients with Huntington's disease (HD). The authors tested 16 outpatients with HD, 8 of whom were drug free and 8 of whom were on antipsychotic medication. We also tested 24 healthy control subjects. 2. The antisaccade task was used to investigate the voluntary control of saccadic eye movements. Antisaccade latencies and error rates were used as outcome measures. Both HD patient groups showed significantly more antisaccade abnormalities than controls and the rate of abnormalities was very similar between the drug-free and medicated patient groups. 3. The results suggest that these abnormalities are related to underlying neuropathology rather than effects of medication. Either specific dysfunction of the dorsolateral prefrontal cortex or of the subcortical circuit connecting this cortical area to the superior colliculus via the striatum are likely to be responsible for the generation of such antisaccade eye movement abnormalities.     

Handedness,hemispheric specialization and saccadic eye movement latencies

Several recent studies have shown that normal subjects have shorter eye movement latencies for rightward saccades than for leftward saccades. The present study was designed to investigate, by using handedness as a variable, whether a structural factor or a learning effect is the greater contributing factor in this perceptual-motor asymmetry. Results of the study indicated that dextrals had significantly shorter latencies for rightward saccades and that left handers showed no asymmetry. The results support the notion that there is a structural determinant for asymmetries in saccadic latencies.     

Dependence of presaccadic cortical potentials on the type of saccadic eye movement

Premovement cortical potentials were studied with 4 types of saccadic eye movement: (a) visually triggered saccades of normal reaction time (RT; regular saccades); (b) visually triggered saccades of extremely shor RT (express saccades); (c) saccades towards predicted target locations (anticipatory saccades); (d) saccades back towards predicted location of fixation point (refixation saccades). With all 4 saccade types a “presaccadic negativity” with the maximum at the vertex (Cz) was observed. A bilaterally symmetrical component contained in this potential (being smallest with almost unconsciously performed refixation saccades and smaller in trained than in naive subjects) appeared to be related mainly to the subjects' volitional effort. In addition, anticipatory and refixation saccades were preceded by an early, widespread contralateral negativity, which we relate to cortical activities that prepare, in general terms, action within or towards the hemifield containing the saccade goal. During the 60 msec before anticipatory saccades, a negativity occurred over the contralateral central lead, which may reflect neural activation in the frontal eye field (FEF) and premotor cortex. In contrast, regular saccades were preceded 30 msec before onset by a negativity over the contralateral parietal cortex, which probably reflects an activation of parietal visuo-motor neurons. No lateralization of the cortical potentials was observed before express saccades, which suggests that these saccades are generated in a reflex-like way mainly by subcortical mechanisms.     

Effect of aging on the accuracy of visually guided saccadic eye movement

Changes in oculomotor behaviors with aging were studied in normal young and elderly subjects. Saccadic eye movments induced by presentation of a visual target were analyzed. Elderly subjects commonly showed an elongation of the time to locate the target, accompanied by an increase in reaction times (mean increase, 100 ms) and a decrease in saccadic velocities. The decrease in the velocity was particularly notable when a large-amplitude saccade was executed. In spite of the slowed motor responses, most elderly subjects preserved the function necessary to execute a correct saccade toward the visual target. The saccadic slowing was accompanied by an increase in saccade duration. Although a longer time was necessary for elderly subjects to locate the target, the accuracy of the initial saccades was not different from that of young subjects. One group of elderly subjects showed extremely long reaction times. These subjects, displaying no abnormal neurological symptoms, were not able to locate the visual target with initial saccades. They had to execute multistep saccades typically seen in patients with degenerative neurological diseases.     

Smooth pursuit and saccadic eye movement performance in a prefrontal leukotomy patient

The authors wished to examine the role of the prefrontal cortex in oculomotor performance. They assessed smooth pursuit and saccadic performance in a patient with schizophrenia who had undergone a bilateral prefrontal leukotomy. Her performance on neuropsychological test measures sensitive to frontal lobe functioning were also examined. Against a background of intact intellectual and neurological functioning, the patient displayed a dissociation in premotor and prefrontal functioning. Smooth pursuit performance was within normal limits, as were the patient's finger tapping scores. In contrast, the patient performed poorly on the Wisconsin Card Sorting Test, and verbal and design fluency tasks. Similarly, her performance on the antisaccade task was markedly deviant. Despite advanced age and a frontal leukotomy, this patient with schizophrenia displayed intact smooth pursuit, indicating that the frontal cortex is not necessary for normal smooth pursuit performance.     

Study of saccadic eye movement in children with attention deficit/hyperactivity disorder

Recent studies have postulated that impairment of behavior inhibition, leading to executive dysfunction in future, is the fundamental pathophysiology of attention deficit/hyperactivity disorder (AD/HD). To evaluate this, we studied two saccadic eye movement tasks: visual- and memory-guided, in 8 children with AD/HD (combined type;mean age, 9.1 years, range 6 approximately 11 years) and 16 healthy children (mean age, 9.2 years, range 6 approximately 12 years). In the memory-guided saccade task, reflexive anticipatory errors were more frequently observed in AD/HD than in controls. The children with AD/HD showed longer response latency in the memory-guided saccade task, and greater coefficient of variation in both the latency and amplitude in both the tasks. These results suggested that saccade tasks, especially the memory-guided task, may be useful in clarifying pathophysiology of AD/HD.     

Overlapping saccades and glissades are produced by fatigue in the saccadic eye movement system

Saccadic eye movements and their neurological control signals change significantly as the human fatigues. Electronic instrumentation with a band-width extending from DC to 1 kHz enabled the recording of anomalous looking saccadic eye movements that occurred as the subject's physiological state changed. Fatigue can produce: overlapping saccades in which the high-frequency saccadic bursts should show large pauses; glissades in which the high-frequency bursts should be much shorter than appropriate for the size of the intended saccades; and low-velocity, long-duration, non-Main Sequence saccades in which the motoneuronal bursts should be of lower frequency and longer duration than normal. As few as 30 saccades of 50 deg magnitude or a longer sequence of saccades as small as 10 deg can produce these aberrant eye movements and their concomitant neuronal firing pattern variations. The effects of fatigue could explain some of the variations between and spread within published data for velocity vs amplitude of human saccadic eye movements. Measuring the resistance to eye movement fatigue could become either a common clinical tool for diagnosing specific or general disease states, or a research tool for studying dyslexia or fatigue.     

Profile of non-compressive myelopathy in eastern India: a 2-year study

Eighty-two patients with non-compressive myelopathy have been studied from July 1994 to June 1996 in Bangur Institute of Neurology and S.S.K.M. Hospital, Calcutta, of which 48 patients were men and 34 patients were women. Presentation was acute in 40 patients (48.78%), subacute in 7 (8.53%), chronic in 27 (32.92%) and history of relapse and remission in 8 (9.75%) patients. Preceding as well as simultaneous fever was observed in 16 cases (19.5%); vaccination (anti-rabies) in 1 case (1.21%); drug abuse in 1 case (1.21%); arthralgia-myalgia and rash in 2 cases (2.42%) and history of electrocution in 2 cases (2.42%). Only pyramidal tract involvement was present in 24 cases (29.26%) and remaining 58 cases (70.73%) had pyramidal tract affection with other sites of involvement. CSF study carried out in 60 cases, revealed rise of protein in 31 (37.8%); oligoclonal band had been detected in 6 (7.31%), pleocytosis in 18 cases (21.95%) and increased IgG index greater than 6.66 in 2 cases (2.42%). CT myelogram done in 23 cases revealed no abnormality. MRI study carried out in 59 cases showed myelomalacia in 1 (1.21%); demyelination plaque in 14 cases (17.07%); atrophy of cord in 3 (3.65%); infarction of cord in 1 (1.21%) and in 40 cases (48.78%) no abnormality could be detected. Etiological diagnosis could be established in 59 (71.95%) cases such as transverse myelitis or myelopathy (post infectious) in 24 (29.26%); demyelination in 16 (19.51%); vascular and vasculitis in 3 (3.65%); toxic in 1 (1.21%); physical (electrocution) in 2 cases (2.42%). In the remaining 23 cases (28.04%) no aetiological factors could be found.     

帕金森病患者眼球扫视与步态适应性的相关性研究

目的 研究早中期帕金森病(PD)患者在复杂步行环境下眼球扫视与步态适应性的相关性,并进一步探讨潜在的影响因素.方法 选取2019年4—11月在北京康复医院帕金森医学中心就诊的早中期PD患者53例作为PD组,并选取25名健康者作为对照组.收集受试者一般临床信息,采用简易智能状态量表(MMSE)、蒙特利尔认知评估量表(Mo...     

The effect of saccadic eye movements on the sensor-level magnetoencephalogram

Objective

We used a combination of simulation and recordings from human subjects to characterize how saccadic eye movements affect the magnetoencephalogram (MEG).

Acute effect of flunarizine on saccadic eye movements.

It has been postulated that flunarizine (FNZ) acts on the brain through a stabilizing effect on membrane electrical activity of neurones. It has been also suggested that neurogenic events characterized by an increased tendency of nerve cells to fire, could be involved in the pathogenesis of migraine and epilepsy. The study was aimed to assess the effect of a single oral dose of FNZ (20 mg) on CNS specific functions by means of computer analysis of saccadic eye movements. The study was performed on six healthy volunteers according to a double-blind, cross-over, placebo controlled design. FNZ produced a significant reduction only of peak saccadic velocity, thus suggesting a rather specific and selective effect on the burst cells of the para-median pontine reticular formation.     

Applying a model of saccadic prediction to patients' saccadic eye movements

A mathematical model of eye tracking of periodic square wave target motion has previously been proposed. In this work the model was further studied with regard to saccadic response time to symmetrical square wave target motion in 6 patients with unilateral parietal lesions following cerebrovascular accidents. Three types of saccadic response time were noted. In patients with type I, saccades contralateral to the damaged hemisphere had similar characteristics to those found in ipsilateral direction, but with longer response time. In those with type II, the saccadic response time was about the same on movement in either direction for repetitive target cycle durations of 1.2 or 2.0 s. In patients with type III, the target motion could not be predicted, in either direction.     

Inhibitory control and spatial working memory: a saccadic eye movement study of negative symptoms in schizophrenia

The negative symptoms of schizophrenia are perhaps the most unremitting and burdensome features of the disorder. Negative symptoms have been associated with distinct motor, cognitive and neuropathological impairments, possibly stemming from prefrontal dysfunction. Eye movement paradigms can be used to investigate basic sensorimotor functions, as well as higher order cognitive aspects of motor control such as inhibition and spatial working memory - functions subserved by the prefrontal cortex. This study investigated inhibitory control and spatial working memory in the saccadic system of 21 patients with schizophrenia (10 with high negative symptoms scores and 11 with low negative symptom scores) and 14 healthy controls. Tasks explored suppression of reflexive saccades during qualitatively different tasks, the generation of express and anticipatory saccades, and the ability to respond to occasional, unpredictable ("oddball") targets that occurred during a sequence of well-learned, reciprocating saccades between horizontal targets. Spatial working memory was assessed using a single and a two-step memory-guided task (involving a visually-guided saccade during the delay period). Results indicated significant increases in response suppression errors, as well as increased response selection impairments, during the oddball task, in schizophrenia patients with prominent negative symptoms. The variability of memory-guided saccade accuracy was also increased in patients with prominent negative symptom scores. Collectively, these findings provide further support for the proposed association between prefrontal dysfunction and negative symptoms.