Saccadic reaction times in acute and remitted schizophrenics

Summary Schizophrenics are known to have various disturbances of the visuomotor system. Whereas smooth pursuit eye movement disorders have been repeatedly confirmed, there are relatively few reports regarding possible disturbances of the saccadic system. In this study, the saccadic reaction times of 47 schizophrenic inpatients were investigated upon admission and later in the remitted state; 28 age- and sex-matched normal volunteers were tested as controls. Psychopathology and outcome were evaluated according to the Brief Psychiatric Rating Scale and the Prognostic Scale. Light stimuli were presented at random direction, location (ranging from 0° to 20°) and duration (800, 1000, and 1200 ms). The eye movements were recorded by electro-oculography. Compared with the control group, schizophrenics revealed prolonged saccadic reaction times, which correlated with pronounced negative symptoms and an unfavourable course of the illness. The saccadic reaction times remained prolonged in schizophrenic patients. These findings suggest attentional deficits in schizophrenics.This article was presented in part at the Symposium on Eye Movements and Psychopathology, Berlin, 23–24 June 1988     

Blink reflex abnormalities in children with Tourette syndrome

Tourette syndrome (TS) is a common disorder which typically occurs during childhood or early adolescence. There is no definitive diagnostic test for TS. The objective of this study was to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in children with TS. We enrolled 15 children with TS, diagnosed according to DSM IV Diagnostic Criteria, and 15 controls. The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2. The mean duration of R2 was significantly longer in TS patients than in the controls ( P  < 0.001, Student's t -test). An abnormal pattern of the blink reflex can be, even in childhood, an early neurophysiologic marker of TS, which is not related to the duration of TS or to the age of onset.     

Eyelid movements during blinking in patients with Parkinson's disease.

We examined eyelid movements during spontaneous, voluntary, and trigeminal reflex blinks in 16 patients with mild to moderate Parkinson's disease (PD) off medication and 14 controls. Voluntary and reflex blink amplitudes tended to be smaller than normal for PD patients, whereas eyelid kinematics (amplitude-maximum velocity relationship) for all three blink types were normal. Spontaneous blink rate was less than normal for 10 patients and abnormally high for 6 patients. A significant positive correlation between spontaneous blink amplitude and blink rate was found. These observations suggest that PD modifies the gain of a premotor blink circuit shared by spontaneous, voluntary, and reflex blinks.     

Movement disorders in patients with peripheral facial palsy.

Acute unilateral facial paralysis is usually a benign neurological condition that resolves in a few weeks. However, it can also be the source of a transient or long-lasting severe motor dysfunction, featuring disorders of automatic and voluntary movement. This review is organized according to the two most easily recognizable phases in the evolution of facial paralysis: (1). Just after presentation of facial palsy, patients may exhibit an increase in their spontaneous blinking rate as well as a sustained low-level contraction of the muscles of the nonparalyzed side, occasionally leading to blepharospasm-like muscle activity. This finding may be due to an increase in the excitability of facial motoneurons and brainstem interneurons mediating trigeminofacial reflexes. (2). If axonal damage has occurred, axonal regeneration beginning at approximately 3 months after the lesion leads inevitably to clinically evident or subclinical hyperactivity of the previously paralyzed hemifacial muscles. The full-blown postparalytic facial syndrome consists of synkinesis, myokymia, and unwanted hemifacial mass contractions accompanying normal facial movements. The syndrome has probably multiple pathophysiological mechanisms, including abnormal axonal branching after aberrant axonal regeneration and enhanced facial motoneuronal excitability. Although the syndrome is relieved with local injections of botulinum toxin, fear of such uncomfortable contractions may lead the patients to avoid certain facial movements, with the implications that this behavior might have on their emotional expressions.     

Attentional modulation of the cardiac defense response in humans

How cardiac components of the defense reaction are modulated by attentional factors related to sensory intake versus sensory rejection was examined. Forty-eight men participated in a test of the heart rate response to three presentations of an intense auditory stimulus while performing one of three attentional tasks during the 80 s following stimulus onset: (a) internal (rejection) task, (b) external (intake) task, and (c) no task. Results showed a potentiation of the defense response only under the external attention condition. We concluded that defensive reactions, far from provoking the rejection of the aversive stimulus, require allocation of attention to processing that stimulus in detail.     

不同注意偏移和言语材料对耳优势影响的初步分析

对５５名健康被试在：（１）无注意偏移，（２）注意右偏，（３）注意左偏等三种注意条件下进行了下述３项言语分听测验；１．分离语测验，２。数字测验，３．有鲜明形象意义词汇测验。分析了不同注意偏移和言语材料对耳优优势的影响，认为注意右偏可加强分听言语材料时的右耳优势，左偏可减弱右耳优势，不同言语材料获得耳优势的结果不同。     

Neural control of fast-regular saccades and antisaccades: an investigation using positron emission tomography

 Regional cerebral blood flow changes related to the performance of two oculomotor tasks and a central fixation task were compared in ten healthy human subjects. The tasks were: (a) performance of fast-regular saccades; (b) performance of voluntary antisaccades away from a peripheral cue; (c) passive maintenance of central visual fixation in the presence of irrelevant peripheral stimulation. The saccadic task was associated with a relative increase in activity in a number of occipitotemporal areas. Compared with both the fixation and the saccadic task, the performance of antisaccades activated a set of areas including: the superior and inferior parietal lobules, the precentral and prefrontal cortex, the cingulate cortex, and the supplementary motor area. The results of the present study suggest that: (a) compared with self-determined saccadic responses the performance of fast regular, reflexive saccades produces a limited activation of the frontal eye fields; (b) in the antisaccadic task the inferior parietal lobes subserve operations of sensory-motor integration dealing with attentional disengagement from the initial peripheral cue (appearing at an invalid spatial location) and with the recomputation of the antisaccadic vector on the basis of the wrong (e.g., spatially opposite) information provided by the same cue. Received: 20 May 1996 / Accepted: 28 January 1997     

Emotion and psychopathy: startling new insights

Abnormal affective response in psychopaths is conceptualized within a broad theory of emotion that emphasizes reciprocal appetitive and defensive motivational systems. The startle response is proposed as a specific measure of the directional component of emotional activation. I review the literature that indicates that criminal psychopaths do not show the expected potentiation of the startle reflex that normally occurs during processing of aversive stimuli such as unpleasant photographs or punishment cues. Evidence is presented to demonstrate that this deviant response pattern is specific to individuals who display the classic affective symptoms of psychopathy. The core emotional deviation in psychopathy could be a deficit in fear response, which is defined as a failure of aversive cues to prime normal defensive actions. This emotional deficit may represent an extreme variant of normal temperament.     

Single-equation models for the tear film in a blink cycle: realistic lid motion.

We consider model problems for the tear film over multiple blink cycles that utilize a single equation for the tear film; the single non-linear partial differential equation that governs the film thickness arises from lubrication theory. The two models that we consider arise from considering the absence of naturally occurring surfactant and the case when the surfactant is strongly affecting the surface tension. The film is considered on a time-varying domain length with specified film thickness and volume flux at each end; only one end of the domain is moving, which is analogous to the upper eyelid moving with each blink. Realistic lid motion from observed blinks is included in the model with end fluxes specified to more closely match the blink cycle than those previously reported. Numerical computations show quantitative agreement with in vivo tear film thickness measurements under partial blink conditions. A transition between periodic and non-periodic solutions has been estimated as a function of closure fraction and this may be a criterion for what is effectively a full blink according to fluid dynamics.     

The gap effect and express saccades in the auditory modality

Latencies of eye movements to peripheral targets are reduced when there is a short delay (typically 200 ms) between the offset of a central visual fixation point and the target onset. This has been termed the gap effect. In addition, some subjects, usually with practice, exhibit a separate population of very short latency saccades, called express saccades. Both these phenomena have been attributed to disengagement of visual attention when the fixation point is extinguished. A competing theory of the gap effect attributes it to disengagement of oculomotor fixation during the temporal gap. It is known that auditory targets are effective in eliciting saccadic eye movements, and also that covert attention operates in the auditory modality. If the gap effect and express saccades are due to disengagement of spatial attention, both should persist in the auditory modality. However, fixation of gaze is largely under visual control. If the gap effect results from disengagement of fixation, then at least a reduced effect should be seen in the auditory modality. Human subjects performed the gap task and a control task in the dark, using auditory fixation points and saccadic targets, on five successive days. Despite this practice, express saccades were not observed. There was a reliable gap effect, but the reduction in saccadic latency was only 17 ms, compared with 32 ms for the same subjects in the visual modality. This suggests that about half the gap effect is due to disengagement of visual fixation. The remainder was not due to non-specific warning effects and could be attributed to offset of the auditory fixation stimulus. Received: 1 March 1996 / Accepted: 11 July 1997