Clinical application of eye movement tasks as an aid to understanding Parkinson's disease pathophysiology.

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the basal ganglia. Most PD patients suffer from somatomotor and oculomotor disorders. The oculomotor system facilitates obtaining accurate information from the visual world.

[Frontal cortical dysfunction in Parkinson's disease (PD): Comparison of memory-based smooth-pursuit and anti-saccade tasks, and neuropsychological and motor symptom evaluations].

We reported recently that during a memory-based smooth-pursuit task, most Parkinson's disease (PD) patients exhibited normal cue-information memory but impaired smooth-pursuit preparation and execution. A minority of PD patients had abnormal cue-information memory or difficulty in understanding the task. To further examine differences between these two groups, we assigned an anti-saccade task and compared correct rates with various neuropsychological and motor symptom evaluations.

Similarity in Neuronal Firing Regimes across Mammalian Species.

Unlabelled: The architectonic subdivisions of the brain are believed to be functional modules, each processing parts of global functions. Previously, we showed that neurons in different regions operate in different firing regimes in monkeys. It is possible that firing regimes reflect differences in underlying information processing, and consequently the firing regimes in homologous regions across animal species might be similar.

[Visual tracking with/without passive whole-body rotation in Parkinson's disease (PD): Dissociation of smooth-pursuit and cancellation of vestibulo-ocular reflex (VOR)].

Although impaired smooth-pursuit in Parkinson's disease (PD) is well known, reports are conflicting on the ability to cancel vestibulo-ocular reflex (VOR) when the target moves with head, requiring gaze-pursuit. To compare visual tracking performance with or without passive whole-body rotation, we examined eye movements of 10 PD patients and 6 age-matched controls during sinusoidal horizontal smooth-pursuit and passive whole-body rotation (0.3 Hz, ± 10°).

Impaired smooth-pursuit in Parkinson's disease: normal cue-information memory, but dysfunction of extra-retinal mechanisms for pursuit preparation and execution.

While retinal image motion is the primary input for smooth-pursuit, its efficiency depends on cognitive processes including prediction. Reports are conflicting on impaired prediction during pursuit in Parkinson's disease. By separating two major components of prediction (image motion direction memory and movement preparation) using a memory-based pursuit task, and by comparing tracking eye movements with those during a simple ramp-pursuit task that did not require visual memory, we examined smooth-pursuit in 25 patients with Parkinson's disease and compared the results with 14 age-matched controls.

Normal aging affects movement execution but not visual motion working memory and decision-making delay during cue-dependent memory-based smooth-pursuit.

Aging affects virtually all functions including sensory/motor and cognitive activities. While retinal image motion is the primary input for smooth-pursuit, its efficiency/accuracy depends on cognitive processes. Elderly subjects exhibit gain decrease during initial and steady-state pursuit, but reports on latencies are conflicting.

No-go neurons in the cerebellar oculomotor vermis and caudal fastigial nuclei: planning tracking eye movements.

The cerebellar dorsal vermis lobules VI-VII (oculomotor vermis) and its output region (caudal fastigial nuclei, cFN) are involved in tracking eye movements consisting of both smooth-pursuit and saccades, yet, the exact role of these regions in the control of tracking eye movements is still unclear. We compared the neuronal discharge of these cerebellar regions using a memory-based, smooth-pursuit task that distinguishes discharge related to movement preparation and execution from the discharge related to the processing of visual motion signals or their memory. Monkeys were required to pursue (i.

Cue-dependent memory-based smooth-pursuit in normal human subjects: importance of extra-retinal mechanisms for initial pursuit.

Using a cue-dependent memory-based smooth-pursuit task previously applied to monkeys, we examined the effects of visual motion-memory on smooth-pursuit eye movements in normal human subjects and compared the results with those of the trained monkeys. These results were also compared with those during simple ramp-pursuit that did not require visual motion-memory. During memory-based pursuit, all subjects exhibited virtually no errors in either pursuit-direction or go/no-go selection.

Cognitive processes involved in smooth pursuit eye movements: behavioral evidence, neural substrate and clinical correlation.

Smooth-pursuit eye movements allow primates to track moving objects. Efficient pursuit requires appropriate target selection and predictive compensation for inherent processing delays. Prediction depends on expectation of future object motion, storage of motion information and use of extra-retinal mechanisms in addition to visual feedback.

[Cerebellum and eye movement control -- neuronal mechanisms of memory-based smooth-pursuit and their early clinical application].

Recent studies implicate the cerebellum in cognitive functions in addition to its well-established roles in motor control and learning. Using a memory-based smooth-pursuit task that separates visual working memory from motor preparation and execution, monkeys were trained to pursue (i.e.

Submovement composition of head movement.

Limb movement is smooth and corrections of movement trajectory and amplitude are barely noticeable midflight. This suggests that skeletomuscular motor commands are smooth in transition, such that the rate of change of acceleration (or jerk) is minimized. Here we applied the methodology of minimum-jerk submovement decomposition to a member of the skeletomuscular family, the head movement.

Vestibular-related frontal cortical areas and their roles in smooth-pursuit eye movements: representation of neck velocity, neck-vestibular interactions, and memory-based smooth-pursuit.

Smooth-pursuit eye movements are voluntary responses to small slow-moving objects in the fronto-parallel plane. They evolved in primates, who possess high-acuity foveae, to ensure clear vision about the moving target. The primate frontal cortex contains two smooth-pursuit related areas; the caudal part of the frontal eye fields (FEF) and the supplementary eye fields (SEF).

Memory-based smooth pursuit: neuronal mechanisms and preliminary results of clinical application.

Using a memory-based smooth-pursuit task, macaque monkeys were trained to pursue (i.e., go) or not pursue (i.

Neuronal activity in medial superior temporal area (MST) during memory-based smooth pursuit eye movements in monkeys.

We examined recently neuronal substrates for predictive pursuit using a memory-based smooth pursuit task that distinguishes the discharge related to memory of visual motion-direction from that related to movement preparation. We found that the supplementary eye fields (SEF) contain separate signals coding memory and assessment of visual motion-direction, decision not-to-pursue, and preparation for pursuit. Since medial superior temporal area (MST) is essential for visual motion processing and projects to SEF, we examined whether MST carried similar signals.

Difficulty in terminating the preceding movement/posture explains the impaired initiation of new movements in Parkinson's disease.

To determine whether the difficulty of initiating volitional movements in Parkinson's disease is primarily due to impaired termination of preceding movement/posture or to impaired initiation of new movement, patients with Parkinson's disease and age-matched controls were first asked to visually fixate a stationary spot and simultaneously align wrist position accurately with it. They were then requested to make rapid movements of eyes and wrist to a test stimulus presented in the peripheral visual field. We analyzed latencies of ocular and manual movements to the test stimulus in two conditions; in the overlap task the stationary spot remained on during illumination of the test stimulus requiring subjects to terminate fixation and wrist positioning themselves to initiate new movements.

Oscillatory eye movements resembling pendular nystagmus in normal juvenile macaques.

Purpose: Juvenile monkeys being trained on smooth-pursuit tasks exhibit ocular oscillations resembling pendular nystagmus. The purpose of this study was to analyze these oscillations, the effects of gabapentin on them, and responses of cerebellar floccular neurons to understand possible neuronal mechanisms.

Methods: Four monkeys were trained for horizontal and vertical smooth pursuit; in two, saccades were also tested.

Neuronal activity in the caudal frontal eye fields of monkeys during memory-based smooth pursuit eye movements: comparison with the supplementary eye fields.

Recently, we examined the neuronal substrate of predictive pursuit during memory-based smooth pursuit and found that supplementary eye fields (SEFs) contain signals coding assessment and memory of visual motion direction, decision not-to-pursue ("no-go"), and preparation for pursuit. To determine whether these signals were unique to the SEF, we examined the discharge of 185 task-related neurons in the caudal frontal eye fields (FEFs) in 2 macaques. Visual motion memory and no-go signals were also present in the caudal FEF but compared with those in the SEF, the percentage of neurons coding these signals was significantly lower.

Activity of pursuit-related neurons in medial superior temporal area (MST) during static roll-tilt.

Recent studies have shown that rhesus macaques can perceive visual motion direction in earth-centered coordinates as accurately as humans. We tested whether coordinate frames representing smooth pursuit and/or visual motion signals in medial superior temporal area (MST) are earth centered to better understand its role in coordinating smooth pursuit. In 2 Japanese macaques, we compared preferred directions (re monkeys' head-trunk axis) of pursuit and/or visual motion responses of MSTd neurons while upright and during static whole-body roll-tilt.

Representation of neck velocity and neck-vestibular interactions in pursuit neurons in the simian frontal eye fields.

The smooth pursuit system must interact with the vestibular system to maintain the accuracy of eye movements in space (i.e., gaze-movement) during head movement.

Reafferent head-movement signals carried by pursuit neurons of the simian frontal eye fields during head movements.

The smooth-pursuit system is important to precisely track a slowly moving object and maintain its image on the foveae during movement. During whole-body rotation, the smooth-pursuit system interacts with the vestibular system. The caudal part of the frontal eye fields (FEF) contains smooth pursuit-related neurons that signal eye velocity during pursuit.

Relating neuronal firing patterns to functional differentiation of cerebral cortex.

It has been empirically established that the cerebral cortical areas defined by Brodmann one hundred years ago solely on the basis of cellular organization are closely correlated to their function, such as sensation, association, and motion. Cytoarchitectonically distinct cortical areas have different densities and types of neurons. Thus, signaling patterns may also vary among cytoarchitectonically unique cortical areas.

Memory and decision making in the frontal cortex during visual motion processing for smooth pursuit eye movements.

Cortical motor areas are thought to contribute "higher-order processing," but what that processing might include is unknown. Previous studies of the smooth pursuit-related discharge of supplementary eye field (SEF) neurons have not distinguished activity associated with the preparation for pursuit from discharge related to processing or memory of the target motion signals. Using a memory-based task designed to separate these components, we show that the SEF contains signals coding retinal image-slip-velocity, memory, and assessment of visual motion direction, the decision of whether to pursue, and the preparation for pursuit eye movements.

Discharge of pursuit neurons in the caudal part of the frontal eye fields during cross-axis vestibular-pursuit training in monkeys.

Previous studies in monkeys have shown that pursuit training during orthogonal whole body rotation results in task-dependent, predictive pursuit eye movements. We examined whether pursuit neurons in the frontal eye fields (FEF) are involved in predictive pursuit induced by vestibular-pursuit training. Two monkeys were rotated horizontally at 20 degrees/s for 0.

Otolith inputs to pursuit neurons in the frontal eye fields of alert monkeys.

The smooth-pursuit system must interact with the vestibular system to maintain the accuracy of eye movements in space during head movement. Maintenance of a target image on the foveae is required not only during head rotation which activates primarily semi-circular canals but also during head translation which activates otolith organs. The caudal part of the frontal eye fields (FEF) contains pursuit neurons.

Discharge of pursuit-related neurons in the caudal part of the frontal eye fields in juvenile monkeys with up-down pursuit asymmetry.

The smooth-pursuit system uses retinal image-slip-velocity information of target motion to match eye velocity to actual target velocity. The caudal part of the frontal eye fields (FEF) contains neurons whose activity is related to direction and velocity of smooth-pursuit eye movements (pursuit neurons), and these neurons are thought to issue a pursuit command. During normal pursuit in well-trained adult monkeys, a pursuit command is usually not differentiable from the actual eye velocity.