The relationship between the efficiency of interhemispheric interactions via the corpus callosum and the speed and accuracy in making comparisons of information simultaneously presented to the right and left visual fields was studied by comparing bilateral (vs unilateral) advantages in matching letters, with evoked potential measures of interhemispheric transmission time ...

We have investigated the effects of 9.5% and 14.1% MAC concentrations of isoflurane on some psychometric measurements. Both concentrations depressed peak saccadic velocity (P < 0.01), choice reaction time (P < 0.05) and visual analogue scores for sedation (P < 0.05), but not the critical flicker fusion threshold. The incidence ...

Three experiments were conducted to clarify the function of spatiotopic and retinotopic visual persistence during pursuit and saccadic eye movements. Exps. 1 and 2 both showed spatiotopic visual integration for both types of eye movements, although shorter stimulus onset asynchrony (SOA) was set in Exp. 2. Exp. 3 was conducted ...

The functional integrity of the 'on' and 'off' neurovisual pathways has been examined in the central visual fields of normal (n = 13), glaucomatous (n = 21) and ocular hypertensive (n = 21) individuals. The detection thresholds to light increments (onsets = bright spots) and light decrements (offsets = dark ...

Each blink of the eyelids is associated with a concurrent suppression of vision that lasts as long as 200 msec. Saccadic eye movements are also associated with a concurrent suppression of vision. Previous studies suggested that blink and saccadic suppression may be the result of a single mechanism. Volkmann, Riggs, ...

Subjects were asked to foveate luminance defined, texture (orientation) defined, or motion defined targets while the reaction times of their saccadic eye movements were measured. With luminance defined targets, latencies followed the known bimodal distribution of fast ("express") and normal saccades, but in five highly trained subjects neither orientation nor ...

By investigating the visual processing involved when saccades are made to newly appearing targets, we show that this processing is significantly nonlinear and that texture boundary information predominates. We used the global, or center-of-gravity, effect whereby a saccadic eye movement directed to a target consisting of a pair of elements ...

Subjects were required to perceptually judge the location of flash targets presented at the time of a saccade at various positions scattered two-dimensionally on a dimly illuminated structured background. The saccade-contingent mislocalization was shown only in the direction parallel to the saccade, and not in the direction perpendicular to the ...

1. The first experiment of this study determined the effects of low-frequency stimulation of the monkey superior colliculus on spontaneous saccades in the dark. Stimulation trains, subthreshold for eliciting short-latency fixed-vector saccades, were highly effective at biasing the metrics (direction and amplitude) of spontaneous movements. During low-frequency stimulation, the distribution ...

Saccadic reaction times and amplitudes were determined in four human subjects and two rhesus monkeys when they made saccades to visual targets appearing in different spatial or temporal contexts. Two stimuli were presented at different positions, either simultaneously (global condition) or in random order (range condition). Both the gap and ...

Previously we have measured rapid-velocity vergence responses to targets at different distances that provided no disparity or accommodative stimulation. To evaluate the possibility that this rapid-velocity vergence occurs during saccades, the latencies of eye movement between two long dim luminous rods were compared under two conditions. Rapid-velocity vergence with an ...

The effect of unilateral circumscribed lesions in different areas of the frontal and parietal cortex on the distributions of saccadic reaction times (SRTs) was investigated in 32 patients under four stimulus conditions: (i) gap-random: a target light appeared 200 ms after extinction of a central fixation light randomly at 8 ...

The costs produced by invalid precues can depend on the spatial relationship between the cued location and the target location. If oculomotor programs mediate attention shifts, then the effect of varying the spatial relation between the cue and target should be the same for covert orienting (indexed by manual responses) ...

Saccadic eye movements and the adaptive control of their amplitudes were examined in patients with Wallenberg's lateral medullary syndrome. Half of the patients had permanent saccadic dysmetria. Their primary saccades had asymmetric amplitudes: those made in response to an ipsilateral target step (i.e. to the lesion side) tended to be ...

We studied reflexive and predictive saccades by direct current electro-oculography in nine patients with mild hemi-Parkinson's disease (hemi-PD) and in 16 age-matched controls. In five patients, the neurological syndrome was predominant on the right side of the body (RPD) and in four patients, on the left side (LPD). Reflexive saccades ...

This paper describes the first application of structural modeling to the visual system. Structural modeling, or path analysis, is a mathematical method that allows for the quantification of the functional strengths of anatomical connections between the structures that form a neural system. The objective was to demonstrate how structural modeling ...

The collaboration of Fergus Campbell, Gerald Westheimer and John Robson in the 1950s produced insight into the nature of accommodation microfluctuations and instigated work which has led to the current view that the nominally steady-state accommodation response exhibits temporal variations which can be characterized by two dominant regions of activity: ...

To explain the veridical percept of the spatial ordering of objects and the generation of eye movements to peripheral targets, Lotze (1885 Microcosmos. Edinburgh: T. & T. Clark) proposed that there is a position label (local sign) for each retinal element. To estimate the precision of local sign information, we ...

Bilateral foveal lesions were made by laser photocoagulation in adult monkeys. One day post-lesion, animals fixated with a new retinal locus inferior to the fovea (in the visual field) that they used permanently. Fixation stability improved modestly over two days. Initially, saccades maladaptively brought the lesioned foveae to visual targets. ...

Two rhesus monkeys were trained to move a handle on a two-dimensional (2D) working surface in directions specified by a light at the plane. They first captured with the handle a light on the center of the plane and then moved the handle in the direction indicated by a peripheral ...

Previously, a simple method for recording galvanic nystagmus (GN) using conventional electronystagmography (ENG) was demonstrated. The present study reports on investigations made to examine the applicability of that technique. During a standard stimulus over 20 s, amplitudes and rate of saccades show no tendency to diminish. In a series of ...

Two commercially-available high frequency electrical stunners producing either AC sinewaves (146 V; 1592 Hz) or DC squarewaves (162V; 1642 Hz) having different waveforms were tested for their effectiveness in stunning pigs and compared with conventional 50 Hz sinusoidal waveforms. Seventy-nine pigs were stunned using the highest voltage settings, allowed to ...

Saccadic reaction times (SRTs) of three human subjects were analyzed. The gap paradigm was used (i.e. fixation point offset precedes target onset) to obtain high proportions of express saccades (i.e. saccades of extremely short reaction times) in the SRT distributions. In one set of experiments, the luminance of the (red) ...

We studied the eyelid movements of six patients with unilateral, isolated, facial paralysis using the magnetic search coil. The most significant abnormality consisted of a reduction in the magnitude of the orbicularis oculi contraction with slowing of the peak velocity of the closing phase of the blink. The closing phase ...

If an observer's fixation point is extinguished just prior to the onset of a peripheral target, the latency to saccade to that target is reduced. We show that this "gap effect" is not specific to visual targets. Observers made saccades to a light flash or to a white-noise burst. A ...

To elucidate the possible traffic safety risks induced by visual field defects, a method was developed based on a driving simulator. The capacity to detect stimuli of different sizes appearing in 24 different positions on the screen in front of the driver was measured. Two groups of normal subjects and ...

This study examined the behavior of the presaccadic spike potential (SP) in 20 normal, right-handed subjects for self-paced 10 degree saccades along vertical, horizontal and oblique meridians. The SP was recorded differentially between posterior parietal sites and a linked ear reference. The SP amplitude showed clear directional tuning properties with ...

Saccadic suppression is a decline in detectability of a weak flash presented during a saccadic eye movement. We examined the hypothesis of Matin [Psychol. Bull. 81, 899 (1974)] that saccadic suppression may be due to increased stimulus uncertainty during the saccade. Uncertainty could arise from variability and inhomogeneities in the ...

The latency to initiate a saccade (saccadic reaction time) to an eccentric target is reduced by extinguishing the fixation stimulus prior to the target onset. Various accounts have attributed this latency reduction (referred to as the gap effect) to facilitated sensory processing, oculomotor readiness, or attentional processes. Two experiments were ...

Previous findings that dissimilarity judgments for rectangles are strongly subadditive, that qualitative individual differences are always present, and that four-parameter psychophysical maps can reproduce the average ratings (Schönemann & Lazarte, 1987) are replicated. However, the present study in addition suggests that the metric for bounded response transformation, previously used to ...

Hemispheric differences for feature perturbations were investigated in two experiments. Stimulus displays consisting of five small squares arranged in a single row were presented tachistoscopically, with the subject instructed to state in which square a horizontal tick mark was located. Ticks could occur in any of the three middle squares, ...

We used a double-step paradigm to examine saccadic responses occurring at short intervals (50-150 ms) after the presentation of a 2-8 degrees step. Saccades occurring 60-110 ms after the second step had amplitudes independent of the step size. The amplitudes scaled to step size for intervals greater than 110 ms. ...

We studied the reaction times and initial directions of hand movements and saccades of human subjects who fixated and pointed as quickly as possible at eccentric targets which were presented unexpectedly. The targets were positioned on a horizontal bar which was placed in front of the subject. Different stimulus conditions ...

Twelve normal subjects (aged 22-80 yr, mean 47 yr) performed three blocks of 20 saccades made to LED targets stepped back and forth. The first and last blocks were performed at a (slow) rate of 0.18 Hz, while the middle block was performed at the faster rate of 1.15 Hz. ...

Horizontal single-step stimuli were presented to 19 subjects with congenital nystagmus (CN). When the stimulus jump was in the same direction as the waveform beat, spatial and temporal measurements of the responses revealed that saccades occurring between 90 and 180 msec after the stimulus were directed to an average of ...

1. We studied the latencies and amplitudes of saccades to moving targets in normal human subjects. Targets underwent ramp or step-ramp motions. The goal was to determine how the saccadic system uses information about target velocity. 2. For simple ramp motion saccadic latency decreased as target speed increased. A threshold ...

This study assessed the prevalence and characteristics of light-gazing by all visually impaired children referred during a 2 1/2-year period. Light-gazing (compulsive staring into lights) is one of the many clinical signs of cortical visual impairment (CVI), and in the present study it occurred in 60 per cent of children ...

The ocular-following responses elicited by brief unexpected movements of the visual scene were studied in human subjects. Response latencies varied with the type of stimulus and decreased systematically with increasing stimulus speed but, unlike those of monkeys, were not solely determined by the temporal frequency generated by sine-wave stimuli. Minimum ...

We have studied the effects of the ablation of the cerebellar vermal area corresponding to lobules VI - VIII and of the flocculus - paraflocculus of both sides on the spontaneous eye movements performed in the light and in the dark in head-restrained pigmented rats. These effects have been compared ...

We have studied the dynamics of human saccades along various cardinal (horizontal and vertical) and oblique directions in two different experimental paradigms yielding fast and slow saccades, respectively. We found that the saturation of vectorial peak velocity with amplitude, which is already well known from earlier studies on fast saccades, ...

Are the horizontal and vertical components of oblique saccades produced by two separate pulse generators or by a single, vectorial pulse generator? To investigate this question, purely horizontal and vertical ("cardinal") saccades as well as oblique saccades with a meridional direction of +/- 45 deg (horizontal and vertical components of ...

In order to study the cooperation of peripheral motor subsystems, the degree of curvature of human saccades along cardinal (right, up, left, down) and oblique directions was computed from an extensive set of experimental data. Our curvature measure allows comparison of fast and slow saccade trajectories elicited in different experimental ...

We have studied the effects of lesion of the inferior olive on the spontaneous eye movements performed both in the light and dark in head restrained pigmented rats. The inferior olive lesion was made at least 1 month before study with 3-acetylpyridine and eye movements were recorded through a phase ...

In the alert monkey we have compared the properties of saccades elicited by a visual stimulus (V-saccades) with those generated by electrical stimulation in the superior colliculus (E-saccades). We found that whereas there exists a graded relation between E-saccade amplitude and current strength, E-saccade direction is remarkably independent of electrical ...

We tested the state of retinal correspondence at different positions in the visual field of ten observers with strabismic and/or anisometropic amblyopia, four strabismic subjects with alternating fixation and three normal controls. Correspondence was evaluated by the subjective displacement of dichoptic stimuli; to estimate the displacement, we used red-green filters, ...

1. When a downward saccade is made between equidistant targets, convergence consistently occurs during the saccade: about 1 deg overconvergence after an 8 deg saccade, with either binocular or monocular viewing, with either far (3 m) or near (30 cm) viewing distance. 2. During binocular viewing, this unnecessary convergence is ...

The static or dynamic visual cues required for equilibrium as well as for foot guidance in visually guided locomotion in man were studied using a variety of locomotion supports and illumination and visual conditions. Stroboscopic illumination (brief flashes) and intermittent lighting (longer flashes) were used to control and to vary ...

Spontaneous saccadic eye movements were recorded in seven head-restrained pigmented rats by means of a phase detection search coil system, both in the light and in the dark. In an illuminated environment, all the rats made numerous spontaneous saccades with an average amplitude of 13.2 deg (+/- 2.2 SD) and ...

Perimetry analyzes the efficiency of the entire visual system, but reveals the deterioration of even one of its components. Optic nerve changes, especially those of ischemic nature, which most frequently involve the middle and advanced age, cause typical perimetric findings. Manual kinetic perimetry is particularly indicated for the detection and ...

We measured the detection of motion before, during and after a saccade to explore the effects of a saccade on motion perception. To isolate the low-level motion mechanism, the stimulus was a random-dot field displaced by small distance (0.3 deg) within a stationary frame. The displacement signaled motion clearly if ...