Arm movement metrics influence saccade metrics when looking and pointing towards a memorized target location (original) (raw)
Related papers
Influence of arm movements on saccades in humans
European Journal of Neuroscience, 2000
When reaching for an object we usually look at it before we touch it with the hand. This often unconscious eye movement prior to the arm movement allows guiding of the ®nal part of the hand trajectory by visual feedback. We examined the temporal and spatial coordination of this control system by psychophysical measurements of eye and arm movements of naive human subjects looking or looking and pointing as fast as possible to visual targets in physical and virtual-reality setups. The reaction times of saccades to a step-displaced target were reduced, and the number of corrective saccades decreased, when the subject had to produce a corresponding simultaneous hand movement to the same target. The saccadic reaction time was increased when saccade and hand movement went in opposite directions. In a double-step task the reaction time for the second saccade was longer than for the ®rst. Co-use of the hand leads to an additional increase of saccadic reaction time. Taken together this study shows an improvement in initial saccades if they are accompanied by hand movements to the same target. This effect might ensure that the reach target is foveated early and accurately enough to support the visual feedback control of the hand near the target. Longer reaction times for the second saccade to double-step displaced targets might re¯ect a saccadic refractory time intensi®ed by simultaneous arm movements. These results are discussed in the light of recent ®ndings from our laboratory on saccade-and reach-related neurons in the superior colliculus of macaque monkeys.
Eye-hand coordination: saccades are faster when accompanied by a coordinated arm movement
Journal of neurophysiology, 2002
When primates reach for an object, they very often direct an eye movement toward the object as well. This pattern of directing both eye and limb movements to the same object appears to be fundamental to eye-hand coordination. We investigated interactions between saccades and reaching movements in a rhesus monkey model system. The amplitude and peak velocity of isolated eye movements are positively correlated with one another. This relationship is called the main sequence. We now report that the main sequence relationship for saccades is changed during coordinated eye and arm movements. In particular, peak eye velocity is approximately 4% faster for the same size saccade when the saccade is accompanied by a coordinated arm movement. Saccade duration is reduced by an equivalent amount. The main sequence relationship is unperturbed when the arm moves simultaneously but in the opposite direction as the eyes, suggesting that eye and arm movements must be tightly coordinated to produce th...
Reaching affects saccade trajectories
Experimental Brain Research, 2001
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Coordination of hand movements and saccades: evidence for a common and a separate pathway
Experimental Brain Research, 1991
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 were used in the experiments. Knowledge of the target position or the presence of an auditory co-stimulus slightly affected the reaction times of saccades in response to visual stimuli. Auditory co-stimuli reduced the reaction times considerably when the targets were presented after a delay of 200 ms after extinction of the central fixation point. Similar reductions were observed in the reaction times of the hand movements. However, these reductions were seen in hand responses to undelayed as well as delayed target presentations. The saccades were always made in the correct direction when the target was presented without delay. When the target was delayed about 50% of the saccades were made in the wrong direction. Even for undelayed targets the hand sometimes made mistakes. The number of mistakes increased to 35 % when the target presentation was accompanied by the sound pulse. For delayed targets the proportion of wrong hand movements was about 50%. For such targets saccades and hand movements were practically always made in the same direction. If visual information is available, saccades and hand movements are generated independently of each other. However, if visual information is not present at the appropriate time and the target position has to be guessed, saccades and hand movements are generated on the basis of shared information. We suggest that saccades can be generated by two different mechanisms. One mechanism uses only visual information while the other one uses visual as well as cognitive information. The first mechanism is exclusively used for the generation of saccades while the second one has a more general purpose * Present address:
The delays in sensorimotor pathways pose a formidable challenge to the implementation of stable error feedback control, and yet the intact brain has little trouble maintaining limb stability. How is this achieved? One idea is that feedback control depends not only on delayed proprioceptive feedback but also on internal models of limb dynamics. In theory, an internal model allows the brain to predict limb position. Earlier we had found that during reaching, the brain estimates hand position in real-time in a coordinate system that can be used for generating saccades. Here we tested the idea that the estimate of hand position, as expressed through saccades, depends on an internal model that adapts to dynamics of the arm. We focused on the behavior of the eyes as perturbations were applied to the unseen hand. We found that when the hand was perturbed from stable posture with a 100-ms force pulse of random direction and magnitude, a saccade was generated on average at 182 ms postpulse onset to a position that was an unbiased estimate of real-time hand position. To test whether planning of saccades depended on an internal model of arm dynamics, arm dynamics were altered either predictably or unpredictably during the postpulse period. When arm dynamics were predictable, saccade amplitudes changed to reflect the change in the arm's behavior. We suggest that proprioceptive feedback from the arm is integrated into an adaptable internal model that computes an estimate of current hand position in eye-centered coordinates.
Proprioceptive Guidance of Saccades in Eye-Hand Coordination
Journal of Neurophysiology, 2006
The saccade generator updates memorized target representations for saccades during eye and head movements. Here, we tested if proprioceptive feedback from the arm can also update hand-held object locations for saccades, and what intrinsic coordinate system(s) are used in this transformation. We measured radial saccades beginning from a central light-emitting diode to sixteen target locations arranged peripherally in eight directions and two eccentricities on a horizontal plane in front of subjects. Target locations were either indicated by 1) a visual flash, 2) by subject actively moving the hand-held central target to a peripheral location, 3) by the experimenter passively moving the subject's hand, 4) through a combination of the above proprioceptive and visual stimuli. Saccade direction was relatively accurate, but subjects showed task-dependent systematic overshoots and variable errors in radial amplitude. Visually-guided saccades showed the smallest overshoot, followed by saccades guided by both vision and proprioception, while proprioceptively-guided saccades showed the largest overshoot. In most tasks, the overall distribution of saccade endpoints was shifted and expanded in a gaze-or headcentered cardinal coordinate system. However, the active proprioception task produced a tilted pattern of errors, apparently weighted toward a limb-centered coordinate system. This suggests the saccade generator receives an efference copy of the arm movement command but fails to compensate for the arm's inertia-related directional anisotropy. Thus, the saccade system is able to transform hand-centered somatosensory signals into oculomotor coordinates and combine somatosensory signals with visual inputs, but it appears to have a poorly calibrated internal model of limb properties.
The Influence of Motor Training on Human Express Saccade Production
Journal of Neurophysiology, 2009
Express saccadic eye movements are saccades of extremely short latency. In monkey, express saccades have been shown to occur much more frequently when the monkey has been trained to make saccades in a particular direction to targets that appear in predictable locations. Such results suggest that express saccades occur in large number only under highly specific conditions, leading to the view that vector-specific training and motor preparatory processes are required to make an express saccade of a particular magnitude and direction. To evaluate this hypothesis in humans, we trained subjects to make saccades quickly to particular locations and then examined whether the frequency of express saccades depended on training and the number of possible target locations. Training significantly decreased saccade latency and increased express saccade production to both trained and untrained locations. Increasing the number of possible target locations (two vs. eight possible targets) led to onl...
Contrasting effects of exogenous cueing on saccades and reaches
Journal of Vision, 2018
Previous studies have shown that eye and arm movements tend to be intrinsically coupled in their behavior. There is, however, no consensus on whether planning of eye and arm movements is based on shared or independent representations. One way to gain insight into these processes is to compare how exogenous attentional modulation influences the temporal and spatial characteristics of the eye and the arm during single or combined movements. Thirteen participants (M ¼ 22.8 years old, SD ¼ 1.5) performed single or combined movements to an eccentric target. A behaviorally irrelevant cue flashed just before the target at different locations. There was no effect of the cue on the saccade or reach amplitudes, whether they were performed alone or together. We found no differences in overall reaction times (RTs) between single and combined movements. With respect to the effect of the cue, both saccades and reaches followed a similar pattern with the shortest RTs when the cue was closest to the target, which we propose reflects effector-independent processes. Compared to when no cue was presented before the target, saccade RTs were generally inhibited by the irrelevant cue with increasing cue-target distance. In contrast, reach RTs showed strong facilitation at the target location and less facilitation at farther distances. We propose that this reflects the presence of effectordependent processes. The similarities and differences in RTs between the saccades and reaches are consistent with effector-dependent and-independent processes working in parallel.
Human Movement Science, 2004
The present experiment examined the one-target advantage (OTA) with regard to saccadic eye movements. The OTA, previously found with manual pointing responses, refers to the finding that movements are executed faster when the limb is allowed to stop on the target compared to the situation where it has to proceed and hit a second target. Using an adapted limb movement OTA task, saccades of 5°and 15°were made to (a) a single target (one-target), (b) one target and immediately to another target without a change in direction (two-target-extension), and (c) one target and immediately back to the start location (two-target-reversal). Unlike manual movements, the movement times for the initial saccade in the two-target-extension condition were not prolonged compared to either of the other two conditions. Moreover, this pattern of results was found for both the shorter and longer amplitude saccades. The results indicate that the OTA does not occur in the oculomotor system and therefore is not a general motor control phenomenon.