Localization of the plane of regard in space

Poljac, Edita; Berg, Albert van den

doi:10.1007/s00221-004-2201-x

Cited by 6 publications

(2 citation statements)

References 32 publications

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“…RMSE values, computed as in the preceding text, yielded 3.1 vs. 12.7 and 4.7 vs. 14.3°(retinal vs. nonretinal model) for the rightward and the leftward dynamic gaze changes, respectively. This corroborates findings in previous literature that also made a clear case for the retinal coding and updating of target direction (Henriques et al 1998;Poljac and Van den Berg 2003).…”

Section: Reach Patternssupporting

confidence: 92%

Updating Target Distance Across Eye Movements in Depth

Pelt¹,

Medendorp²

2008

Journal of Neurophysiology

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We tested between two coding mechanisms that the brain may use to retain distance information about a target for a reaching movement across vergence eye movements. If the brain was to encode a retinal disparity representation (retinal model), i.e., target depth relative to the plane of fixation, each vergence eye movement would require an active update of this representation to preserve depth constancy. Alternatively, if the brain was to store an egocentric distance representation of the target by integrating retinal disparity and vergence signals at the moment of target presentation, this representation should remain stable across subsequent vergence shifts (nonretinal model). We tested between these schemes by measuring errors of human reaching movements (n = 14 subjects) to remembered targets, briefly presented before a vergence eye movement. For comparison, we also tested their directional accuracy across version eye movements. With intervening vergence shifts, the memory-guided reaches showed an error pattern that was based on the new eye position and on the depth of the remembered target relative to that position. This suggests that target depth is recomputed after the gaze shift, supporting the retinal model. Our results also confirm earlier literature showing retinal updating of target direction. Furthermore, regression analyses revealed updating gains close to one for both target depth and direction, suggesting that the errors arise after the updating stage during the subsequent reference frame transformations that are involved in reaching.

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Section: Reach Patternssupporting

confidence: 92%

Updating Target Distance Across Eye Movements in Depth

Pelt¹,

Medendorp²

2008

Journal of Neurophysiology

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“…a downward bias of reaching errors that was modulated by both target eccentricity and performing hand. Other studies on goal-directed arm-movements showed an overall vertical undershoot of the target position [1], [5], [30], [49], which can be due to a bias toward initial hand position [24] or, more likely, to an interference with the visuomotor transformation by sustained tonus in arm muscles when the arm is raised [49]. Whereas the former hypothesis cannot account for our pattern of errors, since we did not find any bias toward initial hand position in the horizontal component of reaching errors (i.e., an undershoot, instead of an overshoot, in reaching peripheral targets), the latter hypothesis fits better with our results.…”

Section: Discussionmentioning

confidence: 88%

Behavioral Investigation on the Frames of Reference Involved in Visuomotor Transformations during Peripheral Arm Reaching

et al. 2012

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BackgroundSeveral psychophysical experiments found evidence for the involvement of gaze-centered and/or body-centered coordinates in arm-movement planning and execution. Here we aimed at investigating the frames of reference involved in the visuomotor transformations for reaching towards visual targets in space by taking target eccentricity and performing hand into account.Methodology/Principal FindingsWe examined several performance measures while subjects reached, in complete darkness, memorized targets situated at different locations relative to the gaze and/or to the body, thus distinguishing between an eye-centered and a body-centered frame of reference involved in the computation of the movement vector. The errors seem to be mainly affected by the visual hemifield of the target, independently from its location relative to the body, with an overestimation error in the horizontal reaching dimension (retinal exaggeration effect). The use of several target locations within the perifoveal visual field allowed us to reveal a novel finding, that is, a positive linear correlation between horizontal overestimation errors and target retinal eccentricity. In addition, we found an independent influence of the performing hand on the visuomotor transformation process, with each hand misreaching towards the ipsilateral side.ConclusionsWhile supporting the existence of an internal mechanism of target-effector integration in multiple frames of reference, the present data, especially the linear overshoot at small target eccentricities, clearly indicate the primary role of gaze-centered coding of target location in the visuomotor transformation for reaching.

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Collision judgment of objects approaching the head

2005

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Recent investigations have indicated that human perception of the trajectory of objects approaching in the horizontal plane is precise but biased away from straight ahead. This is remarkable because it could mean that subjects perceive objects that approach on a collision course as missing the head. Approach within the horizontal plane through the eyes and the fixation point (the plane of regard) is special, as general motions will also have a component of motion perpendicular to the plane of regard. Thus, we investigated three-dimensional motion perception in the vicinity of the head, including vertical components. Subjects judged whether an object that moved in the mid-sagittal plane was going to hit below or above a well-known reference point on the face like the center of the chin or the forehead (perceptual task). Tactile and proprioceptive information about the reference point significantly improved precision. Precision did not change with distance of the approaching target or with fixation direction. Bias was virtually absent for these vertical motions. When subjects pointed with their index finger to the perceived location of impact on their face (visuo-motor task), they overestimated (1.7 cm) the horizontal eccentricity of the point of impact (pointing task). Vertical bias, however, was again virtually absent. Interestingly, when trajectories intersected the plane of regard, higher precision was observed in the perceptual task regardless of the other conditions. In contrast, neither bias nor precision of the pointing task changed significantly when the trajectories intersected the plane of regard. When asked to point to the location where a trajectory intersected the plane of regard, subjects overestimated the depth component of this intersection location by about 3 cm. The absence of perceptual and pointing bias in the vertical direction in contrast to the clear horizontal bias suggests that different (combinations of) cues are used to judge these components of the trajectory of an approaching object. The results of our perceptual task suggest a role for somatosensory signals in the visual judgment of impending impact.

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Localization of the plane of regard in space

Cited by 6 publications

References 32 publications

Updating Target Distance Across Eye Movements in Depth

Updating Target Distance Across Eye Movements in Depth

Behavioral Investigation on the Frames of Reference Involved in Visuomotor Transformations during Peripheral Arm Reaching

Collision judgment of objects approaching the head

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