Pursuit Of Targets Research Articles

Metabolic Syndrome: A Clinical and Molecular Perspective

The metabolic syndrome is a cluster of interrelated common clinical disorders, including obesity, insulin resistance, glucose intolerance, hypertension, and dyslipidemia (hypertriglyceridemia and low HDL cholesterol levels). According to recently defined criteria, the metabolic syndrome is prevalent and is associated with a greater risk of atherosclerotic cardiovascular disease than any of its individual components. Primary defects in energy balance that produce obesity (and visceral adiposity in particular) are sufficient to drive all aspects of the syndrome. Increased free fatty acids and lipid accumulation in certain organs are mediators of insulin resistance. Obesity also leads to a proinflammatory and prothrombotic state that potentiates atherosclerosis. Pathways leading directly from adiposity to the genesis of dyslipidemia and hypertension have been elucidated. Recent knowledge implies a role for fat-derived "adipokines," including TNF alpha and adiponectin, as pathogenic contributors or protective factors. Current therapies include diet and exercise as well as agents indicated for the treatment of individual components of the syndrome. Future therapies may accrue from the aggressive pursuit of newer molecular drug targets that have the potential to prevent or treat multiple aspects of the metabolic syndrome.

Symmetrical horizontal vergence contributes to the asymmetrical pursuit of targets in depth

When a target travels slowly and smoothly along the line of sight of one eye, the eye that is aligned with the target remains stationary while the other eye adducts. The mechanism that is commonly invoked is that commands signaling conjugate pursuit and symmetrical vergence are combined. The two signals are in the same direction in the adducting eye but are in the opposite direction in the stationary eye and, so, cancel. Recent data have challenged this view and the idea that the two eyes are controlled independently has been resurrected. Pursuit and vergence movements are difficult to separate when they occur together because they have similar latencies and dynamics. We have developed a method where horizontal vergence is “tagged” by training it to have a vertical vergence component that can then be identified in combined pursuit–vergence movements. Four subjects trained eye movements to have a vertical vergence component by fusing vertical disparities that varied in association with horizontal convergence. Following training, the vertical vergence aftereffect was found whenever horizontal vergence was stimulated regardless of whether the horizontal vergence resulted from movement of the target in the midsagittal plane (symmetrical vergence) or from movement of the target along the line of sight of one eye (asymmetrical vergence). The vertical vergence aftereffect was never observed in association with conjugate movements indicating that asymmetrical slow eye movements are not controlled monocularly but contain a vergence component along with symmetrical smooth pursuit.

The motivation and behaviour of hospital Trusts

This paper explores the motivation and behaviour of hospitals, using data from UK hospital Trusts. Managers and consultants (hospital specialists) are identified as the main alternative sources of power within Trusts. It is hypothesised that consultants are interested in production or service (volume and quality) while managers are interested primarily in financial break-even, and that in the long run consultants will dominate. A survey of 1500 consultants and managers and a statistical analysis of the behaviour of 100 Trusts over 3 years yielded the empirical results that were largely but not entirely consistent with these hypotheses. Consultants did indeed consider production goals to be more important than financial breakeven, but within those goals, considered quality to be more important than service volume. While the break-even target was found to be the primary goal of managers on average, they proved to be a heterogeneous group with quality ranking as the main priority among those managers who are closest to service delivery. This is at odds with the apparent objective of Trusts, which both groups perceive as being the single-minded pursuit of financial targets, consistent with the formal, government-set requirements. We find that this strong and unequivocal financial driver is not owned or acted upon by either consultants or managers and it is inferred that, in accordance with the dominant motivation of consultants, the Trust's primary objective is to maintain service quality.

Visual tracking neurons in primate area MST are activated by smooth-pursuit eye movements of an "imaginary" target.

Because smooth-pursuit eye movements (SPEM) can be executed only in the presence of a moving target, it has been difficult to attribute the neuronal activity observed during the execution of these eye movements to either sensory processing or to motor preparation or execution. Previously, we showed that rhesus monkeys can be trained to perform SPEM directed toward an "imaginary" target defined by visual cues confined to the periphery of the visual field. The pursuit of an "imaginary" target provides the opportunity to elicit SPEM without stimulating visual receptive fields confined to the center of the visual field. Here, we report that a subset of neurons [85 "imaginary" visual tracking (iVT)-neurons] in area MST of 3 rhesus monkeys were identically activated during pursuit of a conventional, foveal dot target and the "imaginary" target. Because iVT-neurons did not respond to the presentation of a moving "imaginary" target during fixation of a stationary dot, we are able to exclude that responses to pursuit of the "imaginary" target were artifacts of stimulation of the visual field periphery. Neurons recorded from the representation of the central parts of the visual field in neighboring area MT, usually vigorously discharging during pursuit of foveal targets, in no case responded to pursuit of the "imaginary" target. This dissociation between MT and MST neurons supports the view that pursuit responses of MT neurons are the result of target image motion, whereas those of iVT-neurons in area MST reflect an eye movement-related signal that is nonretinal in origin. iVT-neurons fell into two groups, depending on the properties of the eye movement-related signal. Whereas most of them (71%) encoded eye velocity, a minority showed responses determined by eye position, irrespective of whether eye position was changed by smooth pursuit or by saccades. Only the former group exhibited responses that led the eye movement, which is a prerequisite for a causal role in the generation of SPEM.

Premotor Neurons Encode Torsional Eye Velocity during Smooth-Pursuit Eye Movements

Responses to horizontal and vertical ocular pursuit and head and body rotation in multiple planes were recorded in eye movement-sensitive neurons in the rostral vestibular nuclei (VN) of two rhesus monkeys. When tested during pursuit through primary eye position, the majority of the cells preferred either horizontal or vertical target motion. During pursuit of targets that moved horizontally at different vertical eccentricities or vertically at different horizontal eccentricities, eye angular velocity has been shown to include a torsional component the amplitude of which is proportional to half the gaze angle ("half-angle rule" of Listing's law). Approximately half of the neurons, the majority of which were characterized as "vertical" during pursuit through primary position, exhibited significant changes in their response gain and/or phase as a function of gaze eccentricity during pursuit, as if they were also sensitive to torsional eye velocity. Multiple linear regression analysis revealed a significant contribution of torsional eye movement sensitivity to the responsiveness of the cells. These findings suggest that many VN neurons encode three-dimensional angular velocity, rather than the two-dimensional derivative of eye position, during smooth-pursuit eye movements. Although no clear clustering of pursuit preferred-direction vectors along the semicircular canal axes was observed, the sensitivity of VN neurons to torsional eye movements might reflect a preservation of similar premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.

Frequency and metrics of square-wave jerks: influences of task-demand characteristics.

Square-wave jerks (SWJs) during visual fixation and pursuit tracking of targets of varying speed and predictability were investigated in the present study. SWJs were measured in 91 subjects as they fixated a target or a remembered target location and tracked targets that varied in velocity and predictability. Percentages of subjects making SWJ and mean SWJ frequency per minute in the high- and low-predictability conditions were 99% and 9.34 and 91% and 2.78, respectively. SWJ rates were significantly lower when observers fixated remembered target locations rather than visual targets and during tracking of faster-moving and less predictable targets. Differences in task conditions cannot be explained by volitional influences to control the first saccade in the SWJ. There was also no influence of age on SWJ rate. Reduced SWJ rates after manipulations that increased task demands on visual pursuit of targets suggest an inverse relationship between current demands imposed by visual tasks and rates of intrusive saccades. These findings suggest that signals from cortical attentional systems may suppress inappropriate saccades that would divert the eyes from objects of interest during conditions imposing high task demands on the visual system.

Commodification of Education and Academic LABOUR—Using the Balanced Scorecard in a University Setting

The dissatisfaction with the financial performance of public enterprises in the 1980s led governments to embrace the rhetoric of free markets, and commercialize many state sector activities. This movement has included universities. In many countries, the state began reducing financial support for higher education, encouraged competition and demanded financial self-dependency. A new managerialism entered universities and ubiquitous management philosophies such as the total quality management (TQM) and the balanced scorecard (BSC) have been tested in some universities, such as the one described in this paper. Pressure upon unit cost has been accompanied and reinforced by the institution of quasi-market funding mechanisms. In the pursuit of business-like efficiency, performance targets and measures have been introduced to measure and evaluate the productivity of individual academics and their departments. The translation of public sector activities into private sector vocabulary calls for managers to re-present the organization in the appropriate economic terms. The BSC and TQM philosophies are central economic vocabularies that have been utilized by some public sector organizations. The paper utilizes Habermas’s critical theory of societal development to evaluate the incidence of TQM and BSC implementation in corporate universities. It argues that although the state presumes that market-based vocabularies like TQM and BSC promotes efficiency and effectiveness in organizations, through their application the very essence of education is jeopardized. The effect of these developments has seen a progressive commodification of students and academic labour. Treating education as a private good, and students as customers, is a constitutive re-ordering of university life, and potential degradation of its function in society.

Pursuit eye movements to second-order motion targets.

We studied smooth-pursuit eye movements elicited by first- and second-order motion stimuli. Stimuli were random dot fields whose contrast was modulated by a Gaussian window with a space constant of 0.5 degrees. For the first-order stimuli, the random dots simply moved across the screen at the same speed as the window; for the second-order stimuli the window moved across stationary or randomly flickering dots. Additional stimuli which combined first- and second-order motion cues were used to determine the degree and type of interaction found between the two types of motion stimuli. Measurements were made at slow (1 degrees/s) and moderate (6 degrees/s) target speeds. At a velocity of 1 degrees/s the initiation, transition, and steady-state phases of smooth pursuit in response to second-order motion targets are severely affected when compared with the smooth pursuit of first-order motion targets. At a velocity of 6 degrees/s there is a small but significant deficit in steady-state pursuit of second-order motion targets but not much effect on pursuit initiation.

Pursuit of Heterospecific Targets by Territorial Amberwing Dragonflies (Perithemis tenera Say): A Case of Mistaken Identity

Although they are defending mating territories, territory residents of a wide variety of insect species have been observed to pursue heterospecifics in addition to the conspecifics that intrude on their territories. One species that has such heterospecific pursuits is the Eastern amberwing dragonfly (Perithemis tenera Say) (Anisoptera: Libellulidae). In this study, we tested five alternative hypotheses for the function of heterospecific pursuits in amberwings: competition for resources, prevention of interference while mating, predator deterrence, foraging, and mistaken identity. Resident males pursued both male and female conspecifics, as well as a species of horse fly (Tabanus spp.) and butterfly (Ancyloxypha numitor). Other intruding odonates, including Epitheca princeps, Erythemis simplicicollis, Libellula luctuosa, Pachydiplax longipennis, and Plathemis lydia, were relatively ignored. Because the horse fly and butterfly were similar to amberwings in body size, color, and flight height, and because they are not predators or prey of amberwings, we concluded that the pursuit of these heterospecifics was due to mistaken identity. The characteristics of the horsefly and butterfly likely correspond to the cues that the male amberwings use to identify conspecifics, and the relative rarity of intrusions by these two species (as well as by female amberwings) probably made it more costly to discriminate and pursue only conspecifics than to make some mistaken pursuits.

Chips Ahoy

Organ-level heart failure can result, most obviously, from the death of cardiac myocytes; such death can occur either acutely (with infarction) or more sporadically (in chronic disease). Both types of death can involve a “cell suicide” pathway known as apoptosis.1 Another key factor for cardiac dysfunction is myocardial fibrosis, which can be, in part, a direct consequence of angiotensin II levels; therefore, a possible benefit of therapy with angiotensin-converting enzyme inhibitors is an improvement in fibrosis. A third generic mechanism for defects in macroscopic or clinically evident cardiac performance arises from changes in the intrinsic mechanical properties of individual cardiac muscle cells.2 This phenomenon is understood to occur, in part, through changes in the expression of cardiac genes, both subtle and overt, which are collectively referred to as the hypertrophic gene “program.”3 Reprogramming cardiac gene expression encompasses, among its other features, alterations in (1) contractile proteins of the sarcomere, (2) regulators of calcium handling and other aspects of ion transport, and (3) secreted growth factors and cytokines. Therefore, in pursuit of potential targets for therapy, 2 important aspects of contemporary heart failure research are to discover the signaling pathways that confer adverse responses3 4 and to establish a much more comprehensive understanding of the end-organ changes that actually occur. In the current issue of Circulation , Yang et al5 performed a mammoth screen for altered gene expression in heart failure using a newly developed technology, high-density DNA microarrays.6 Although conceptually simple, these assays …

Cerebellar flocculus and paraflocculus Purkinje cell activity during circular pursuit in monkey.

Responses from 69 Purkinje cells in the flocculus and paraflocculus of two rhesus monkeys were studied during smooth pursuit of targets moving along circular trajectories and compared with responses during sinusoidal pursuit and fixation. A variety of interesting responses was observed during circular pursuit. Although some neurons fired most strongly in a single preferred direction during clockwise (CW) and counterclockwise (CCW) pursuit, others had directional preferences that changed with rotation direction. Some of these neurons showed similar modulation amplitudes during CW and CCW pursuit, whereas other neurons showed a preference for a particular rotation direction. Response specificity also was observed during sinusoidal pursuit. Some neurons showed responses that were much stronger during centrifugal pursuit, others showed a preference for centripetal pursuit, and still others showed responses during both centripetal and centrifugal motion. Differences in preferred response direction were sometimes observed for centripetal versus centrifugal pursuit. CW/CCW and centrifugal/centripetal preferences were not explained by a breakdown in component additivity. That is, modulations in firing rate during pursuit along a circular trajectory equaled the sum of modulations during horizontal and vertical sinusoidal components as well as for diagonal components. Instead all responses were well fit by a model that expressed the instantaneous firing rate of each neuron as a multilinear function of the two-dimensional position and velocity of the eye. This model generalized well to performance at different sinusoidal frequencies. It did somewhat less well for responses during fixation, suggesting some separation in the neural mechanisms of dynamic and static positioning. The model indicates that position sensitivity accounted for approximately 36% of the modulation during circular pursuit, and velocity sensitivity accounted for approximately 64%. When position and velocity sensitivity vectors were aligned, responses were simpler and modulations were similar during CW versus CCW pursuit. In contrast, when these vectors pointed in different directions, response complexity increased. Nonaligned position and velocity influences tended to reinforce during circular pursuit in one direction and to cancel each other during pursuit in the opposite direction. They also tended to produce response differences during centripetal versus centrifugal sinusoidal pursuit. The distinct roles played by position and velocity in shaping Purkinje cell responses are compatible with the control signals required to generate smooth pursuit along circular and other two-dimensional trajectories.

The Relationship between Curvature and Velocity in Two-Dimensional Smooth Pursuit Eye Movements

Curvature and tangential velocity of voluntary hand movements are constrained by an empirical relation known as the Two-Thirds Power Law. It has been argued that the law reflects the working of central control mechanisms, but it is not known whether these mechanisms are specific to the hand or shared also by other types of movement. Three experiments tested whether the power law applies to the smooth pursuit movements of the eye, which are controlled by distinct neural motor structures and a peculiar set of muscles. The first experiment showed that smooth pursuit of elliptic targets with various curvature-velocity relationships was most accurate when targets were compatible with the Two-Thirds Power Law. Tracking errors in all other cases reflected the fact that, irrespective of target kinematics, eye movements tended to comply with the law. Using only compatible targets, the second experiment demonstrated that kinematics per se cannot account for the pattern of pursuit errors. The third experiment showed that two-dimensional performance cannot be fully predicted on the basis of the performance observed when the horizontal and vertical components of the targets used in the first condition were tracked separately. We conclude that the Two-Thirds Power Law, in its various manifestations, reflects neural mechanisms common to otherwise distinct control modules.

The Influence of Household Financial Debt on Monetary and Exchange Rate Policy: France and Britain compared

The structure of household financial debt may have a major effect on the ability of governments to use monetary policy as a means of influencing exchange rate values. This is illustrated by a discussion of the comparative situation of France and Britain during the 1992–93 ‘crisis’ in the European exchange rate mechanism. The large volume of floating rate household debt in the UK placed a significant limitation on the ability of the UK authorities to use monetary policy. By contrast, the lower volume of mainly fixed rate household debt in France enabled the French authorities to make full use of monetary policy as desired in the pursuit of exchange rate targets. As modern financial markets are highly volatile, governments should take policy measures to create more stable structures of household debt.

Directional defects in pursuit and motion perception in humans with unilateral cerebral lesions.

We tested motion perception and smooth pursuit in 26 patients with unilateral cerebral hemispheric lesions. We used random dot cinematograms to test motion direction discrimination. We measured pursuit gain as they followed a predictable sinusoidal target moving horizontally at three different frequencies, and an unpredictable horizontal step-ramp target in the ipsilateral hemi-field. Six patients had defects in motion perception when the targets were moving towards the side of the lesions ('ipsi-directional' defects) and two had bi-directional defects. Motion perception defects occurred with lesions of the junction of Brodmann areas 19 and 37, a putative human homologue of the monkey V5 complex. Seven patients had ipsi-directional pursuit defects, five of whom had damage to the posterior limb of the internal capsule. Only two patients had ipsi-directional defects of both motion perception and sinusoidal smooth pursuit. Four patients had ipsi-directional defects of motion perception alone, and five patients had ipsi-directional pursuit defects alone. The two patients with bi-directional defects in motion perception had normal sinusoidal smooth pursuit. Patients with lesions at the 19/37 junction and defects of motion perception alone had normal pursuit of unpredictable step-ramp targets in the ipsilateral hemi-field. In contrast, patients with ipsi-directional sinusoidal pursuit defects had decreased ipsi-directional and increased contra-directional velocities with step-ramp targets. No patient group had a motion-specific directional defect in saccadic accuracy. We conclude that neither predictable nor unpredictable pursuit is necessarily impaired by lesions of the 19/37 junction that cause ipsi-directional defects of motion perception. These dissociations between smooth pursuit and motion perception provide evidence that the pursuit system operates as an interconnected network with parallel pathways, rather than as a simple sequential hierarchy of cortical areas.

SIMULTANEOUS DEBT AND EQUITY ISSUES AND CAPITAL STRUCTURE TARGETS

AbstractNumerous empirical studies find evidence that managers behave as if they pursue target debt ratios. A possible alternative to the use of conventional, separate issuances of debt and equity to effect desired adjustments toward a target ratio is the simultaneous issuance of such securities. We extend prior research on such issues by exploring their use in the pursuit of capital structure targets. We find that the issuance of securities in general and the use of simultaneous issues of debt and equity in particular are at least partially influenced by where a firm's capital structure is relative to the average position in its industry. Further, shareholders' reactions to the announced plan to issue and to the issuance of securities are influenced, in part, by whether the issue moves the firm toward or away from the average capital structure in the industry. We also find evidence that the infrequent use of simultaneous issues relative to unaccompanied debt and equity issues is explained by their comparative flotation costs.

Smooth pursuit eye movements with imaginary targets defined by extrafoveal cues

Initiation of smooth pursuit eye movements was studied using imaginary targets defined by pairs of small spots (“cues”) moving together in step-ramp motion. The arrangement of cues and imaginary target were either “two-sided”—cues far apart and imaginary target midway between, or “onesided” —cues 4 deg apart and imaginary target to one side of the cue pair. (1) Pursuit of two-sided stimuli was much better than pursuit of one-sided stimuli and was often as good as pursuit of a real foveal target. (2) Experiments with various cue configurations suggest an attribute required for vigorous pursuit: “foveal enclosure”. Configuration information is available to the pursuit system immediately after the onset of motion. (3) Pursuit of imaginary targets is markedly degraded by a background; the effect is strongest for a background at the fovea and weaker for an eccentric background, including one at the cue location.

Activity of medial vestibulospinal tract cells during rotation and ocular movement in the alert squirrel monkey.

1. Chronic unit and eye movement recording and microstimulation techniques were used to study the discharge properties of identified medial vestibulospinal tract (MVST) cells in the alert squirrel monkey. MVST cells were antidromically activated from the ventromedial funiculus at C1 and responded to orthodromic stimulation of the ipsilateral VIIIth nerve (Vi) at mono- or disynaptic latencies. Cell discharges were examined during imposed sinusoidal yaw rotation to activate horizontal semicircular canal afferents and during voluntary ocular pursuit and fixation of visual targets with the head held stationary. 2. MVST cells represented 15% (22 of 147 cells) of the population of horizontal canal-related cells recorded in the vestibular nuclei. Twelve MVST cells were monosynaptically related to Vi; of these cells, 7 (58%) were characterized as ipsilateral eye and head velocity, having a discharge modulation related to the velocity of both ipsilaterally directed eye movement and yaw rotation, and 3 also had an ipsilateral eye position sensitivity. Most (8 of 10, 80%) MVST cells disynaptically related to Vi responded only to contralateral head velocity; the other 2 cells carried a combined contralateral head and ipsilateral eye movement signal. A pause or burst of discharge associated with fast or saccadic eye movements made in any direction was not present on the 22 MVST cells. 3. The MVST is an output pathway of the vestibular nuclei through which the labyrinth controls reflex head movements. The results show that MVST cells transmit the movement and position of eyes in orbit, with vestibular signals, to the cervical spinal cord and suggest that the MVST may play a dynamic role in voluntary gaze stabilization and eye/head tracking.

Retinotopic and directional deficits of smooth pursuit initiation after posterior cerebral hemispheric lesions.

We investigated the initiation of ocular smooth pursuit with horizontal ramp targets in 16 patients with unilateral posterior cerebral lesions. Four of the 16 patients had directional pursuit asymmetry, in which smooth eye movement velocities were reduced toward the lesion, independent of target location on the retina. Of seven patients with normal visual fields for the target, two had a retinotopic eye movement deficit consisting of impaired smooth pursuit of targets moving in both horizontal directions in the hemifield contralateral to their lesion. Patients with retinotopic deficits and normal visual fields, and those with directional deficits, had impairment of smooth pursuit similar to that caused by unilateral lesions of cortical areas MT (middle temporal) and MST (medial superior temporal) in monkeys. All but one patient with either of these defects had a lesion near the junction of Brodmann's areas 19, 37, and 39, providing evidence that this region includes the human homologues of monkey areas MT and MST. One patient with a retinotopic pursuit defect and normal visual fields had a lesion of the rostral superior temporal sulcus, which may have included the homologue of the superior temporal polysensory area of monkeys.

Lesions of the frontal eye field impair pursuit eye movements, but preserve the predictions driving them

Visually guided eye movements are driven by a mix of current signals (e.g. visual motion) and prior experience (predictive strategies). Previously, large ablations of the frontal eye field (FEF) impaired visually guided smooth pursuit. This study examined if the pursuit decrement could be laid to a selective loss in predictive signals. Normal monkeys demonstrated some of the same predictive eye movements documented in humans. They pursued periodic visual targets with near-zero phase lag. When such targets suddenly disappeared, the monkeys continued smooth pursuit without visual guidance for several reaction times. These epochs of 'blind pursuit' achieved a peak velocity proportional to the prior target frequency just experienced by the monkey. With predictable step-ramp targets smooth eye movements sometimes preceded target motion (anticipatory pursuit). Reaction time to begin pursuit was influenced by the target velocity of prior trials. Small unilateral ablations of 'low threshold' FEF showed smooth pursuit if the fundus of the arcuate sulcus was thoroughly removed. On the step-ramp targets the slowing was evident in both the initial 100 ms and subsequent portions of pursuit. During sine pursuit blind epochs were more slowed by surgery than were visually guided epochs of pursuit. Ipsilateral anticipatory pursuit was abolished in one subject, but not in the other subject with pursuit deficits. Otherwise, pursuit after surgery continued to display the influence of predictive strategies. The average phase lag of periodic pursuit remained much less than the pursuit system's reaction time. Blind epochs persisted after the periodic target disappeared, albeit with a lower peak velocity. Reaction time to begin pursuit of step-ramp targets remained a function of the monkey's experience on prior trials. It is argued that the FEF pursuit deficits do not reflect the loss of visual motion signals or the loss of some 'cognitive' signal such as a prediction about the target's motion, but rather can be explained as a motor deficit.

Frontal eye field lesions impair predictive and visually-guided pursuit eye movements

The study initially explored the frontal eye field's (FEF) control of predictive eye movements, i.e., eye movements driven by previous rather than current sensory signals. Five monkeys were trained to pursue horizontal target motion, including sinusoidal targets and "random-walk" targets which sometimes deviated from a sine motion. Some subjects also tracked other target trajectories and optokinetic motion. FEF ablations or cold lesions impaired predictive pursuit, but also degraded visually guided foveal pursuit of all targets. Unilateral lesions impaired pursuit of targets moving in both horizontal orbital fields and in both directions of movement. Saccadic estimates of target motion were generally accurate. The slow-phase velocity of optokinetic pursuit (collected after 54 s of OKN) also appeared normal. Pursuit recovered over 1-3 weeks after surgery but the deficits were then reinstated by removal of FEF in the other hemisphere. Thereafter, a slight deficit persisted for up to 10 weeks of observation in two subjects. The pattern of symptoms suggests that FEF lies subsequent to parietal area MST and prior to the pontine nuclei in controlling pursuit eye movements.