The Role of the Adjacency between Background Cues and Objects in Visual Localization during Ocular Pursuit

Perception ◽  
1989 ◽  
Vol 18 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Stefan Mateeff ◽  
Joachim Hohnsbein
Keyword(s):  
Eye Movement ◽  
Target Position ◽  
Stimulus Presentation ◽  
Visual Localization ◽  
Target Intensity ◽  
Target Path ◽  
Stationary Background ◽  
Direction Opposite ◽  
Light Target

Subjects used eye movements to pursue a light target that moved from left to right with a velocity of 15 deg s−1. The stimulus was a sudden five-fold decrease in target intensity during the movement. The subject's task was to localize the stimulus relative to either a single stationary background point or the midpoint between two points (28 deg apart) placed 0.5 deg above the target path. The stimulus was usually mislocated in the direction of eye movement; the mislocation was affected by the spatial adjacency between background and stimulus. When an auditory, rather than a visual, stimulus was presented during tracking, target position at the time of stimulus presentation was visually mislocated in the direction opposite to that of eye movement. The effect of adjacency between background and target remained the same. The involvement of processes of subject-relative and object-relative visual perception is discussed.

scholarly journals Role of Primate Cerebellar Hemisphere in Voluntary Eye Movement Control Revealed by Lesion Effects

2009 ◽  
Vol 101 (2) ◽  
pp. 934-947 ◽  
Author(s):  
Masafumi Ohki ◽  
Hiromasa Kitazawa ◽  
Takahito Hiramatsu ◽  
Kimitake Kaga ◽  
Taiko Kitamura ◽  
...  
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Smooth Pursuit ◽  
Movement Control ◽  
Cerebellar Hemisphere ◽  
Target Velocity ◽  
Eye Movement Control ◽  
Pursuit Eye Movements ◽  
Catch Up

The anatomical connection between the frontal eye field and the cerebellar hemispheric lobule VII (H-VII) suggests a potential role of the hemisphere in voluntary eye movement control. To reveal the involvement of the hemisphere in smooth pursuit and saccade control, we made a unilateral lesion around H-VII and examined its effects in three Macaca fuscata that were trained to pursue visually a small target. To the step (3°)-ramp (5–20°/s) target motion, the monkeys usually showed an initial pursuit eye movement at a latency of 80–140 ms and a small catch-up saccade at 140–220 ms that was followed by a postsaccadic pursuit eye movement that roughly matched the ramp target velocity. After unilateral cerebellar hemispheric lesioning, the initial pursuit eye movements were impaired, and the velocities of the postsaccadic pursuit eye movements decreased. The onsets of 5° visually guided saccades to the stationary target were delayed, and their amplitudes showed a tendency of increased trial-to-trial variability but never became hypo- or hypermetric. Similar tendencies were observed in the onsets and amplitudes of catch-up saccades. The adaptation of open-loop smooth pursuit velocity, tested by a step increase in target velocity for a brief period, was impaired. These lesion effects were recognized in all directions, particularly in the ipsiversive direction. A recovery was observed at 4 wk postlesion for some of these lesion effects. These results suggest that the cerebellar hemispheric region around lobule VII is involved in the control of smooth pursuit and saccadic eye movements.

Réponses évoquées par les mouvements oculaires d'exploration (réponse lambda): Rôle des afférences intervenant à divers moments du processus oculo-moteur

Perception ◽  
1972 ◽  
Vol 1 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Nicole Lesèvre ◽  
A Rémond
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Visual Effects ◽  
Experimental Conditions ◽  
Initial Portion ◽  
Vertical Movements ◽  
Black Field ◽  
Fixation Points ◽  
Lambda Response

Experiments are reported the aim of which was to elucidate the cause of each of the components of the lambda response, and particularly to evaluate the role of ‘on’ and ‘off’ visual effects which appear at various times during the oculomotor process and also the possible influence of non-visual mechanisms. Eight subjects with normal sight were studied under the following conditions: (i) horizontal eye movements of 12° were guided by fixation points placed on a dimly-lit uniform black field of 20°; a checkerboard of 6° aperture was placed in this field so as to be integrated into the oculomotor process at different times—at the beginning, during and at the end of the eye movement; (ii) successive horizontal eye movements of 3°, 7° and 11° scanned a checkerboard of 20°, each square of which had a 40′ aperture; (iii) the checkerboard was moved with an amplitude and period similar to those of the eye movements in (ii), but this time with gaze fixed. Horizontal and vertical movements of both eyes were recorded with an EOG. An EEG of the parieto-occipital regions was obtained using eight linked bipolar derivations in line on two montages, median longitudinal and right-left transverse. The EEG and EOG data were digitalized and a numerical programme of waveform recognition was used to identify the beginning of the saccade which triggers the averaging out of the EEG before (100 ms) and after (500 ms) the eye movement. A discussion of the results, taking into account the latency of the different components and their reinforcements or inhibition depending on experimental conditions, suggests that the two initial components of lambda response (including the initial portion of the classical lambda wave) might be due to visual effects (‘off effect’) that arise at the start of the movement or slightly before it at the time that the saccadic suppression begins. The later components could be attributed to visual effects brought into play towards the end of the movement (‘on effect’), when perception becomes normal again. It is, however, difficult to explain some of the results related to the amplitude of lambda components without bringing in a mechanism of non-visual origin (corollary discharge).

scholarly journals Action of taxol on mitosis: modification of microtubule arrangements and function of the mitotic spindle in Haemanthus endosperm.

1983 ◽  
Vol 96 (2) ◽  
pp. 527-540 ◽  
Author(s):  
J Molè-Bajer ◽  
A S Bajer
Keyword(s):  
Equatorial Region ◽  
Polar Regions ◽  
Higher Plant ◽  
Chromosome Fragments ◽  
Immunocytochemical Method ◽  
And Function ◽  
Spindle Function ◽  
Direction Opposite

We have studied the effect of taxol on mitosis in Haemanthus endosperm. Immuno-Gold Stain (IGS), a new immunocytochemical method (17), was used to visualize microtubules (MTs) in the light microscope. Observations on MT arrangements were correlated with studies in vivo. Chromosome movements are affected in all stages of mitosis which progresses over at least 10(4) range of taxol concentrations. The three most characteristic effects on MTs are: (a) enhancement of the lateral associations between MTs, seen especially during the reorganization of the polar region of the spindle, (b) promotion of MT assembly, leading to the formation of additional MTs in the spindle and MT arrays in the cytoplasm, and (c) an increase in MT stability, demonstrated in their increased cold resistance. In this report, the emphasis is on the primary, immediate effects, occurring in the first 30 min of taxol action. Effects are detected after a few mins, are reversible, and are concentration/time dependent. The spindle and phragmoplast are remarkably modified due to the enhancement of lateral associations of MTs and the formation of abundant nonkinetochore and polar, asterlike MTs. The equatorial region of the interzone in anaphase may be entirely depleted of MTs, and the spindle may break perpendicular to the spindle axis. Mitosis is completed in these conditions, providing evidence for the motile autonomy of each half-spindle. Trailing chromosome arms in anaphase are often stretched and broken. Chromosome fragments are transported away from the polar regions, i.e., in the direction opposite to that expected (5, 6). This supplies the first direct evidence of pushing by elongating MTs in an anastral higher plant spindle. These observations draw attention to the relation between the lateral association of MT ends to assembly/disassembly and to the role of such an interaction in spindle function and organization.

scholarly journals Temporal Interactions of Air-Puff–Evoked Blinks and Saccadic Eye Movements: Insights Into Motor Preparation

2005 ◽  
Vol 93 (3) ◽  
pp. 1718-1729 ◽  
Author(s):  
Neeraj J. Gandhi ◽  
Desiree K. Bonadonna
Keyword(s):  
Eye Movement ◽  
Target Location ◽  
Low Frequency ◽  
Saccadic Eye Movements ◽  
Stimulus Presentation ◽  
Motor Preparation ◽  
Threshold Level ◽  
Saccade Latency ◽  
Sensory Response ◽  
Temporal Interactions

Following the initial, sensory response to stimulus presentation, activity in many saccade-related burst neurons along the oculomotor neuraxis is observed as a gradually increasing low-frequency discharge hypothesized to encode both timing and metrics of the impending eye movement. When the activity reaches an activation threshold level, these cells discharge a high-frequency burst, inhibit the pontine omnipause neurons (OPNs) and trigger a high-velocity eye movement known as saccade. We tested whether early cessation of OPN activity, prior to when it ordinarily pauses, acts to effectively lower the threshold and prematurely trigger a movement of modified metrics and/or dynamics. Relying on the observation that OPN discharge ceases during not only saccades but also blinks, air-puffs were delivered to one eye to evoke blinks as monkeys performed standard oculomotor tasks. We observed a linear relationship between blink and saccade onsets when the blink occurred shortly after the cue to initiate the movement but before the average reaction time. Blinks that preceded and overlapped with the cue increased saccade latency. Blinks evoked during the overlap period of the delayed saccade task, when target location is known but a saccade cannot be initiated for correct performance, failed to trigger saccades prematurely. Furthermore, when saccade and blink execution coincided temporally, the peak velocity of the eye movement was attenuated, and its initial velocity was correlated with its latency. Despite the perturbations, saccade accuracy was maintained across all blink times and task types. Collectively, these results support the notion that temporal features of the low-frequency activity encode aspects of a premotor command and imply that inhibition of OPNs alone is not sufficient to trigger saccades.

scholarly journals The role of attention in eye-movement awareness

2018 ◽  
Vol 80 (7) ◽  
pp. 1691-1704 ◽  
Author(s):  
Aoife Mahon ◽  
Alasdair D. F. Clarke ◽  
Amelia R. Hunt
Keyword(s):  
Eye Movement ◽  
Movement Awareness

scholarly journals A dynamic, imperturbable link between midbrain activity and saccade velocity

2020 ◽  
Vol 123 (2) ◽  
pp. 451-453
Author(s):  
Joshua A. Seideman
Keyword(s):  
Eye Movement ◽  
Strong Evidence ◽  
Neural Control ◽  
Oculomotor Control ◽  
Saccadic Eye Movement ◽  
Saccade Velocity ◽  
Midbrain Structure ◽  
Instantaneous Control ◽  
Dynamic Moment

We make a saccadic eye movement once every few hundred milliseconds; however, the neural control of saccade execution is not fully understood. Dynamic, moment-by-moment variations in saccade velocity are typically thought to be controlled by neurons in the lower, but not the upper regions of the brainstem. In a recent report, Smalianchuk et al. (Smalianchuk I, Jagadisan UK, Gandhi NJ. J Neurosci 38: 10156–10167, 2018) provided strong evidence for a role of the superior colliculus, a midbrain structure, in the instantaneous control of saccade velocity, suggesting the revision of long-standing models of oculomotor control.

scholarly journals PRECISION OF VISUAL LOCALIZATION USING DYNAMIC GROUND CONTROL POINTS

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 363-370
Author(s):  
P. Trusheim ◽  
C. Heipke
Keyword(s):  
Rapid Development ◽  
Sliding Window ◽  
Bundle Adjustment ◽  
Ground Control ◽  
Visual Localization ◽  
Control Points ◽  
Automated Driving ◽  
Sliding Windows ◽  
Ground Control Points

Abstract. Localization is one of the first steps in navigation. Especially due to the rapid development in automated driving, a precise and reliable localization becomes essential. In this paper, we report an investigation of the usage of dynamic ground control points (GCP) in visual localization in an automotive environment. Instead of having fixed positions, dynamic GCPs move together with the camera. As a measure of quality, we employ the precision of the bundle adjustment results. In our experiments, we simulate and investigate different realistic traffic scenarios. After investigating the role of tie points, we compare an approach using dynamic GCPs to an approach with static GCPs to answer the question how a comparable precision can be reached for visual localization. We show, that in our scenario, where two dynamic GCPs move together with a camera, similar results are indeed obtained to using a number of static GCPs distributed over the whole trajectory. In another experiment, we take a closer look at sliding window bundle adjustments. Sliding windows make it possible to work with an arbitrarily large number of images and to still obtain near real-time results. We investigate this approach in combination with dynamic GCPs and vary the no. of images per window.

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