Schizoid and Schizotypal Personality Disorder

P. Roussos , ... L.J. Siever , in Encyclopedia of Man Behavior (Second Edition), 2012

Smooth pursuit centre movement

SPEM measures visual tracking of smoothly moving targets, such equally a pendulum. The psychophysiological study of eye movements, particularly the antisaccade task, has been proposed as a candidate endophenotype for schizophrenia. This is a effect of SPEM deficits being evident in the bulk of patients with chronic schizophrenia when compared with controls. Additionally, SPEM damage is also significantly more marked in relatives of probands with schizophrenia and STPD individuals. Volunteers who were selected on the basis of poor eye-tracking accuracy had a greater prevalence of STPD diagnosis than the control group with loftier eye-tracking accuracy. In addition, deficits during the eye-movements task have been observed in nonclinical populations such every bit adult, healthy volunteers with a high degree of schizotypy. STPD patients with positive-like symptoms are likely to show elevated fault rates on standard antisaccade tasks in comparing to healthy normal controls. Additionally, a recent written report showed that SPEM deficits were predicted solely by the criterion of social isolation, with depression accuracy trackers also reporting reduced want for social contact. These findings support the notion of impaired SPEM in relation to negative-symptom schizotypy. However, other studies have failed to demonstrate differences in antisaccade error rates between STPD with predominantly negative-like symptoms and normal individuals. Based on this, it remains unclear whether dumb SPEM is specific to negative versus positive symptoms or instead reflects the unabridged schizotypal syndrome. All the same, SPEM deficits are found in both STPD and schizophrenia patients, further supporting the notion of impaired SPEM as an endophenotype for schizophrenia-spectrum disorders.

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Pursuit Eye Movements

U.J. Ilg , in Encyclopedia of Neuroscience, 2009

Because smooth pursuit eye movements (SPEMs) can be executed only in the presence of a moving target, they correspond an platonic beliefs for studying the mechanisms of visual movement processing. Position, velocity, and dispatch of the target are extracted from the retinal epitome and robustly used to generate SPEMs. This motility processing is confined to a retinal frame of reference. In dissimilarity, our motion perception during the execution of SPEMs is non based on this reference. We perceive the target moving in an external frame of reference even in the total absence of retinal image motion. Some neurons in the posterior parietal cortex of rhesus monkeys code for the target movement in space during the execution of SPEMs.

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Cerebellar Learning

Suryadeep Nuance , Peter Thier , in Progress in Brain Inquiry, 2014

4 Shine Pursuit Accommodation

Polish pursuit eye movements (SPEMs) are tracking eye movements used to stabilize the image of a moving object of interest on the fovea. But put, SPEMs can be understood as the production of a feedback circuit that translates information on retinal target movement into an appropriate eye move response, reducing retinal image skid ( Rashbass, 1961; Robinson et al., 1986). Still, the first 100–150   ms of the SPEMs are driven by uncompensated retinal target epitome motion due to the long latencies of visual information processing. As a consequence of the lethargy of vision, the eye motility response evoked by the moving target starts simply 100–150   ms after target motion onset (SPEM latency). In other words, the 100–150   ms of SPEMs following the onset of the eye movement are an open-loop response (SPEM initiation) whose size depends solely on the visual target motion signal and a gain parameter that specifies the transformation of the target movement into a pursuit control. How is the gain parameter chosen? The study of smooth pursuit adaptation (SPA) (see below) suggests that the expected eye movement gain governing the early closed-loop behavior is used as a reference for the open-loop gain. This seems reasonable every bit the probability that the motion of a natural pursuit target will substantially modify in this cursory period is low. As a consequence, at that place is a good run a risk that already the initial SPEM has the correct velocity, thereby reducing the need for cosmetic saccades that would otherwise jeopardize the continuous scrutiny of the moving target. SPA refers to the curt-term changes in the proceeds of SPEM initiation brought almost by an experimental manipulation that causes a violation of the aforementioned goal to minimize the pursuit fault at the time airtight-loop beliefs kicks in. This is achieved by exposing the observer to a sequence of trials in which the target moves at an initial constant velocity for around 100–200   ms and so steps to a new predictable velocity, stereotypically at the aforementioned signal in fourth dimension. The pursuit velocity evoked by the initial target velocity is changed such as to brand it more similar to the target velocity later on the velocity pace, thereby minimizing the retinal errors prevailing at the time the loop is closed (Dash et al., 2010; Fukushima et al., 1996; Kahlon and Lisberger, 1996). If the target steps to a higher velocity, subjects learn to upregulate the pursuit proceeds evoked by the initial target velocity (gain-increase SPA). Correspondingly, if the target velocity steps to a lower velocity following the initial target ramp, subjects gradually learn to downregulate their initial pursuit gain (gain-decrease SPA).

Similar to STSA, also SPA reflects changes in timing. The major difference between the two is that SPA is based on the control of eye acceleration rather than middle velocity equally in the case of STSA (Fig. 1B). Specifically, during gain-decrease SPA, velocity decreases due to a decrease in acme dispatch not compensated by an increase in the duration of the initial eye acceleration pulse (Dash and Thier, 2013). On the other hand, during proceeds-increase SPA the acceleration profile expands (i.due east., the eyes are accelerated for a longer time) while peak acceleration may increase, decrease, or stay unchanged (Dash and Thier, 2013). In other words, the kinematic changes associated with gain-increase SPA and proceeds-decrease SPA are not mirror symmetric, similar to the asymmetry characterizing proceeds-increase and gain-decrease STSA. Yet another parallel holds for the effects of fatigue. If rhesus monkeys are asked to conduct out long sequences of stereotypical stride-ramp shine pursuit eye movements (Dash and Thier, 2013), they are able to maintain a constant SPEM peak velocity despite constantly declining SPEM elevation acceleration. The decline in peak acceleration is compensated past an expansion of the acceleration contour (i.eastward., an increase in acceleration duration). These changes are analogous to the compensation of the refuse in summit heart velocity past increasing motility duration in the case of a saccade resilience experiment described before. The decrease in elevation acceleration that is observed during gain-subtract SPA may be taken as a manifestation of fatigue. On the other hand, the ability to expand the acceleration pulse in order to realize proceeds-increment SPA is the same 1 that is used to compensate SPEM fatigue (Dash and Thier, 2013) (Fig. aneB).

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Center Movement Enquiry

T.J. Crawford , ... C. Kennard , in Studies in Visual Information Processing, 1995

Abstract

Smoothen pursuit eye movements accept been widely used in clinical research in attempts to analyze the neural machinery underlying various brain diseases. Yet, many of these studies are subject to two major weaknesses: a failure to control for neuropharmacological factors and an inadequately defined visual context confronting which the smooth pursuit tracking is measured. This newspaper addresses both of these issues in patients with schizophrenia or focal cortical lesions. In the commencement written report we compared smooth pursuit eye movements in the dark in medicated and non-medicated patients fulfilling the DSM-IIIR criteria for schizophrenia, and a group of age-matched command subjects. Relative shine pursuit eye velocity (i.east. gain) was reduced in both schizophrenic groups; however the result was significantly greater in the neuroleptically medicated group. In the 2d study smooth pursuit, with and without a structured background, was compared in patients with discrete cortical lesions and normal subjects. The analysis revealed a cohort of patients manifesting a large inhibitory event of a structured groundwork on pursuit middle movements. Exam of CT scans showed that ii regions are of particular importance in this effect: an area of parietal cortex lying within the architectonic boundaries of Brodmann's area xl (Brodmann, 1909); and an area of white thing shut to the lateral ventricles containing cortico-cortical connections. These data signal strongly to the critical importance of neuropharmacological factors and the visual background atmospheric condition in studies of smooth pursuit eye movements.

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Middle Movement Enquiry

M.U. Lekwuwa , ... 1000.A. Grealy , in Studies in Visual Data Processing, 1995

Introduction

Polish pursuit eye movements are effected by two main mechanisms ( Barnes & Asselman, 1991; Barnes, Donnelly & Eason, 1987; Dallos & Jones, 1963; Bahill & McDonald, 1983). There is a basic machinery that uses information about retinal error velocity to drive the pursuit system but has a fairly low gain. It is besides known to contain a substantial time delay of approximately 100   ms (Carl & Gellman, 1987) which would naturally exist expected to requite ascension to a large phase error. The second mechanism functions mainly in the product of predictive activity. The add-on of a predictive component to the pursuit response causes the center movements to become progressively phase advanced, and enhances the proceeds (Barnes & Asselman, 1991; Barnes & Grealy, 1992).

Predictive mechanisms have been postulated to consist of a predictive velocity estimator which samples and holds the gaze velocity information, and a periodicity estimator which controls the anticipatory release of stored waveforms to enhance the gain of smooth pursuit (Barnes, Donnelly & Eason, 1987; Bahill & McDonald, 1983). The neural substrate for prediction in smooth pursuit has not been conspicuously localised. Evidence from recordings in the flocculus of the cerebellum suggests that this might be an important site for the generation of the predictive component of pursuit (Miles & Fuller, 1975; Lisberger & Fuchs, 1978; Noda & Warabi, 1986; Noda & Warabi, 1987). All the same previous studies (Waterston, Barnes, & Grealy, 1992) on patients with various forms of cerebellar disease suggest that prediction is preserved in these patients.

Unlike methods take been used to appraise and written report the predictive component of pursuit. In one method, repeated transient stimulations are used to demonstrate the temporal characteristics of smooth pursuit eye movements (Barnes & Asselman, 1991; Barnes & Grealy, 1992; Boman & Hotson, 1988). Subjects are instructed to follow the move of a abiding velocity target during cursory periods of stimulation that are separated by periods of darkness. The effect of prediction is revealed firstly by the fact that smooth pursuit centre movements become progressively phase advanced with repeated stimulation, and secondly by the observation that anticipatory eye movements occur before the onset of target motion. Prediction has also been assessed by examination of the oculomotor response when, after following a number of cycles of similar stimuli, there is an unexpected change in frequency, management, or amplitude of target motion. Prediction is demonstrated if the eye movement following the unexpected modify has velocity and timing characteristics similar to the preceding eye movements (Keating, 1991; Barnes & Asselman, 1991; Lisberger, Evinger, Johanson, & Fuchs, 1981). The same type of results can also exist obtained if a predictable target is unexpectedly blanked out instead of changing the management, velocity, or amplitude of the target trajectory (Barnes & Grealy, 1992).

In the present study we determined the presence or absenteeism of prediction in cerebellar patients and controls by assessing their ability to build upwards anticipatory eye movements after repeated runs of transiently illuminated predictable stimuli.

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Clinical Examination of the Cranial Nerves

Adam Fisch , in Nerves and Nervus Injuries, 2015

Smoothen Pursuit Eye Movements

Smooth pursuit centre movements allow us to continue a moving target in our fovea and clearly visualize it. Each hemisphere is responsible for ipsilateral smooth pursuit eye movements, meaning the correct hemisphere detects and tracks images as they move to the correct and the left hemisphere detects and tracks images equally they motility to the left. Within the circuitry for smooth pursuit, the contralateral cerebellum and medulla and the ipsilateral pons are involved in a double decussating pathway. M retinal ganglion cells discover the target movement: the visual system is by and large divided into the pathway for detection of move (the magnocellular (or M) pathway, which receives rod photoreceptor stimulation) and the pathway for detection of color (the parvocellar (or P) pathway, which receives cone photoreceptor stimulation). Visual detection of the target'south motility from left to right is projected from the retinae to the right lateral geniculate nucleus and then to the right primary visual cortex (V1). The master visual cortex projects to visual area V5 (the human homologue to the macaque middle temporal area), which then projects to visual area V5a (the human homologue to the macaque medial superior temporal area)—in humans, both V5 and V5a lie at the temporo-occipito-parietal junction. Visual area V5a projects to the posterior parietal cortex, which projects to the frontal heart fields. Note that many nonsequential, bidirectional connections exist within this projection pathway (information technology is non purely sequential and unidirectional).

The frontal eye fields (and other cortical visual areas, as well) project to the ipsilateral dorsolateral pontine nuclei (DLPN) in the high pons and the ipsilateral nucleus reticularis tegmenti pontis (NRTP) in the upper pons. The DLPN and NRTP project across midline to the contralateral cerebellum: specifically to the flocculus and paraflocculus of the vestibulocerebellum and likewise to the dorsal vermis. These structures projection to the ipsilateral medial vestibular nucleus in the medulla, which projects to the contralateral abducens nucleus in the mid to low pons, which completes the double decussation. The abducens nucleus initiates the final common pathway.

Y-group vestibular nuclear connections to the oculomotor and trochlear nuclei also exist, which are involved in vertical pursuit movements (Figure 15.ten).

Figure 15.10. Smooth Pursuit.

 Reproduced with permission from Fisch, A. Neuroanatomy: Draw it to Know it, twond ed. (Oxford University Printing, 2012), Cartoon 23–5, pg 421.

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Eye Movements

Charles J. Bruce , Harriet R. Friedman , in Encyclopedia of the Homo Encephalon, 2002

4.E.1 Tracking with Pursuit and Saccades

Smoothen-pursuit eye movements support scrutiny of objects moving in space by matching eye velocity to target velocity in order to both reduce retinal mistiness of the moving object and facilitate its continued foveation. Polish pursuit occurs when the FS selects a moving target or when a previously selected stationary target starts to move. Even so, target selection for pursuit also activates the saccadic system; hence, moving targets are unremarkably tracked with a combination of polish pursuit and saccades, with these two eye movement systems operating independently just synergistically to rails the aforementioned called target (Fig. 2). Their synergy reflects control past separate parameters of the target'southward trajectory. The principal impetus for smooth pursuit is target velocity (i.due east., retinal slip), and the pursuit system continuously endeavors to eliminate retinal skid past matching eye velocity to target velocity. In dissimilarity, the principal concern of the saccade system is target position (i.east., retinal error), and saccades are intermittently generated to eliminate retinal error by foveating the target.

Nevertheless, this division of labor is not accented. Smooth pursuit is modestly affected by positional errors: Ongoing pursuit accelerates in response to pocket-size retinal positional errors, and it is fifty-fifty possible to initiate smooth pursuit with an afterimage placed near the fovea (although eccentric afterimages are ordinarily tracked with a succession of saccades). The pursuit system also responds to the rate of modify in retinal slip (i.e., acceleration). Thus, pursuit is a function of the zero-, beginning-, and second-gild derivatives of the target's retinal epitome.

Conversely, the saccadic system attends to target velocity as well as location. Saccadic latency is shorter for targets moving centrifugally (away from the fixation indicate) and longer for targets moving centripetally. Moreover, saccades are commonly directed to a predicted target location based on its position and velocity equally caused 100–200   msec before the saccadic movement starts.

Pursuit velocity ranges up to ∼100°/sec; however, pursuit gain (defined, like VO and OK gain, as eye velocity/target velocity) is generally poor for target velocities above 25°/sec. When the pursuit proceeds is low, the eye will persistently fall behind the target and frequent, large "catch-up" saccades will be made; withal, if gain is high (∼one.0), and so but a few, small saccades may be needed.

Interestingly, low polish-pursuit proceeds is the chief symptom of the eye tracking dysfunction (ETD) of schizophrenia. Subsequent research has shown a cluster of oculomotor impairments that covary across the schizophrenic patient population and are often also present in outset-degree relatives of schizophrenic patients. On the basis of the ETD and other cognitive aspects of schizophrenia, information technology has been hypothesized that schizophrenia reflects diminished frontal lobe function in full general, and that the ETD specifically reflects impaired role in both the saccadic and the smoothen-pursuit regions of the FEF.

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Visual and Oculomotor Functions

Stefano Da Pozzo , ... Paolo Perissutti , in Studies in Visual Information Processing, 1994

Introduction

Smooth pursuit centre movements, assuring continuous foveal fixation, allow continuous clear vision of objects moving inside the visual environment ( Leigh & Zee, 1991). Conventionally, pursuit is measured during tracking of a predictable, sinusoidal target movement, while step-ramp stimulations are generally preferred to written report the initiation of the smooth pursuit. A part of the abnormalities of pursuit initiation, smooth pursuit (SP) proceeds (slow eye velocity/target velocity) amending and asymmetry (different gain values for nasal and temporal-directed tracking) are unremarkably studied, ordinarily through sinusoidal stimulation, in a big variety of neurological diseases (Glaser, 1990; Leigh & Zee, 1991). Diverse studies of the effect of ocular misalignment on SP response have been conducted, but nigh of them were related to paralytic strabismus, particularly to abducens nerve palsy. Some studies virtually concomitant strabismus are however present in the literature (Sokol, Peli, Moskowitz, & Reese, 1991; Tychsen, Hurtig, & Scott, 1985; Tychsen & Lisberger, 1986), and all of them report a Smoothen Pursuit Organisation (SPS) damage. From these studies it seems clear that in early-onset strabismus (infantile strabismus, with onset prior to the get-go year of life) an evident asymmetrical gain is present, which is characterized past normal values of nasal-directed and reduced values of temporal-directed pursuit proceeds. Tychsen and Lisberger (1986) attributed this disproportion to a maldevelopment of visual move processing caused by the disruption of binocular vision; in fact, binocular experience is necessary for the normal development of the visual cortex and of the pathways specialized for visual motion processing. Hence, Tychsen et al. (1985) hypothesized that the SPS damage found in early-onset strabismus may represent a static arrest of development at an infantile stage. However, when tardily-onset strabismus (onset after the 2d twelvemonth of life) was considered, conflicting findings were reported. Tychsen et al. (1985) reported that in three subjects with noninfantile strabismus (recorded at ages ranging from seven to 29 years) pursuit proceeds roughshod within the command range of 0.90 or amend and that there was no evidence of a nasal-temporal gain asymmetry. On the other hand, Sokol et al. (1991) reported that half of their xv subjects with belatedly-onset esotropia showed harm of pursuit gain, resulting in reduced but symmetrical nasal-temporal values. The purpose of the present study was to mensurate the SPS response in subjects of pediatric age with late-onset strabismus, through a quantitative evaluation of smooth pursuit gain (SP gain) and a comparison between these values and the corresponding values obtained in orthophoric children of the aforementioned age range. In addition the global pursuit gain (GP gain) was evaluated, because at that place was a lack of data nigh this kind of measurement. The global pursuit results from the cooperation betwixt the smooth pursuit and the saccadic systems. Furthermore, nosotros tried to document the upshot of surgery on GP and SP gains, in the attempt to make up one's mind if their objective quantification could be meaningful and helpful in pre-surgical planning for strabismus or in the evaluation of effectiveness of the postal service-surgical consequence.

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The Cerebellum: From Embryology to Diagnostic Investigations

Alexander A. Tarnutzer , ... Michael S. Salman , in Handbook of Clinical Neurology, 2018

Recording the OKR in adults with cerebellar illness

Both SPEM and SEM contribute to the OKR, which is modulated by the cerebellum. Cerebellar structures contributing to the OKR include the ocular motor vermis, the flocculus, and the deep cerebellar nuclei (Dieterich et al., 2000). The OKR may be assessed quantitatively using different devices that provide moving loftier-contrast patterns covering both cardinal and peripheral visual fields. While traditionally studied in a rotating chair with an optokinetic drum, more recently virtual-reality goggles provide the opportunity to modulate the direction and properties of the optokinetic stimulus. Impaired or even abolished OKR has been observed in cerebellar neurodegeneration (Baloh et al., 1975; Zee et al., 1976; Yee et al., 1979). OKR cantankerous-coupling (i.due east., the optokinetic stimulus elicits centre movements dissimilar from the plane of stimulation, e.g., a horizontal optokinetic stimulus elicits vertical heart movements) has besides been described (Walker and Zee, 1999). As for SPEM, vertical OKR gains for upward movements are higher than for downward movements in cerebellar disorders, e.g., in late-onset Tay–Sachs disease (Rucker et al., 2004).

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Visual and Oculomotor Functions

John A. Waterston , ... Madeleine A. Grealy , in Studies in Visual Data Processing, 1994

Introduction

Abnormalities of smooth pursuit (SP) middle movements have been well described in patients with cerebellar ataxia (Baloh, Yee, & Honrubia, 1986; Wennmo, Hindfelt, & Pyykko, 1983; Zee, Yee, Cogan, Robinson, & Engel, 1976), and have also been reported in patients with Parkinson's affliction (PD) (Corin, Elizan, & Bender, 1972; Gibson, Pimlott, & Kennard, 1987; Melville Jones & De Jong, 1976; White, Saint-Cyr, Tomlinson, & Sharpe, 1983). Although the role of the cerebellum in the generation of SP centre movements has been well established in neurophysiological studies (Lisberger & Fuchs, 1978; Miles & Fuller, 1975; Suzuki, Noda, & Kase, 1981; Zee, Yamazaki, Butler, & Gucer, 1981), no such role has been established for the dopaminergic neurons in the substantia nigra which are affected in PD (Kennard & Lueck, 1989), and the exact etiology of the reported pursuit deficits in these patients is unclear.

Optimal SP performance requires the successful interaction of two feedback mechanisms. The closed-loop, visual feedback pathways are able to correct center velocity on the basis of retinal velocity error, but predictive strategies are also necessary to minimize the inherent feedback delays which be in the visuo-motor pathways, and might be expected to influence functioning particularly during high frequency, predictable target motion. In mildly afflicted patients with cerebellar disease, SP abnormalities may only exist axiomatic at higher frequencies of target motion (Zee et al., 1976), suggesting that the predictive mechanisms might be selectively involved in these patients. However, this aspect has not been adequately examined in cerebellar disease. In PD, it has been proposed that prediction is intact on the footing of near normal phase changes during sinusoidal pursuit (Bronstein & Kennard, 1985; Flowers & Downing, 1978; Melville Jones & De Jong, 1976), only functioning during pursuit of unpredictable target movement has received little attention.

To document the frequency-response functioning characteristics in these two patient populations we have examined their pursuit performance during predictable, sinusoidal target motion beyond a wide frequency band in guild to quantify the SP defect.

We have likewise investigated the SP responses with pseudo-random target motility and then as to examine the relationship of the predictive mechanisms to the generalized disturbance of pursuit. In previous studies of normal subjects during pursuit of pseudo-random target movement consisting of the sum of ii or more sinusoids, it has been shown that the boring-stage eye-velocity gains for each of the everyman frequency sinusoids progressively declines as the stimulus is made less predictable by increasing the frequency of the highest frequency component to a higher place a critical level of 0.4 Hz (Barnes & Ruddock, 1989). Further breakup in the SP response tin can too be seen when the velocity of the high-frequency component is increased in relation to the velocity of the other frequency components. This design of response has been attributed to the activity of a predictive velocity estimation mechanism which preferentially enhances the gain at the highest frequency.

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