Use Of Allocentric Information Research Articles

Further Evidence That People Rely on Egocentric Information to Guide a Cursor to a Visible Target.

Everyday movements are guided by objects’ positions relative to other items in the scene (allocentric information) as well as by objects’ positions relative to oneself (egocentric information). Allocentric information can guide movements to the remembered positions of hidden objects, but is it also used when the object remains visible? To stimulate the use of allocentric information, the position of the participant’s finger controlled the velocity of a cursor that they used to intercept moving targets, so there was no one-to-one mapping between egocentric positions of the hand and cursor. We evaluated whether participants relied on allocentric information by shifting all task-relevant items simultaneously leaving their allocentric relationships unchanged. If participants rely on allocentric information they should not respond to this perturbation. However, they did. They responded in accordance with their responses to each item shifting independently, supporting the idea that fast guidance of ongoing movements primarily relies on egocentric information.

The role of perception and action on the use of allocentric information in a large-scale virtual environment

In everyday life, our brain constantly builds spatial representations of the objects surrounding us. Many studies have investigated the nature of these spatial representations. It is well established that we use allocentric information in real-time and memory-guided movements. Most studies relied on small-scale and static experiments, leaving it unclear whether similar paradigms yield the same results on a larger scale using dynamic objects. We created a virtual reality task that required participants to encode the landing position of a virtual ball thrown by an avatar. Encoding differed in the nature of the task in that it was either purely perceptual (“view where the ball landed while standing still”—Experiment 1) or involved an action (“intercept the ball with the foot just before it lands”—Experiment 2). After encoding, participants were asked to place a real ball at the remembered landing position in the virtual scene. In some trials, we subtly shifted either the thrower or the midfield line on a soccer field to manipulate allocentric coding of the ball’s landing position. In both experiments, we were able to replicate classic findings from small-scale experiments and to generalize these results to different encoding tasks (perception vs. action) and response modes (reaching vs. walking-and-placing). Moreover, we found that participants preferably encoded the ball relative to the thrower when they had to intercept the ball, suggesting that the use of allocentric information is determined by the encoding task by enhancing task-relevant allocentric information. Our findings indicate that results previously obtained from memory-guided reaching are not restricted to small-scale movements, but generalize to whole-body movements in large-scale dynamic scenes.

The role of gaze and prior knowledge on allocentric coding of reach targets.

In this study, we investigated the influence of gaze and prior knowledge about the reach target on the use of allocentric information for memory-guided reaching. Participants viewed a breakfast scene with five objects in the background and six objects on the table. Table objects served as potential reach targets. Participants first encoded the scene and, after a short delay, a test scene was presented with one table object missing and one, three, or five table objects horizontally shifted in the same direction. Participants performed a memory-guided reaching movement toward the position of the missing object on a blank screen. In order to examine the influence of gaze, participants either freely moved their gaze (free-view) or kept gaze at a fixation point (fixation) throughout the trial. The effect of prior knowledge was investigated by informing participants about the reach target either before (preview) or after (nonpreview) scene encoding. Our results demonstrate that humans use allocentric information for reaching even if a stable retinal reference is available. However, allocentric coding of reach targets is stronger when gaze is free and prior knowledge about the reach target is missing.

Scene Configuration and Object Reliability Affect the Use of Allocentric Information for Memory-Guided Reaching.

Previous research has shown that egocentric and allocentric information is used for coding target locations for memory-guided reaching movements. Especially, task-relevance determines the use of objects as allocentric cues. Here, we investigated the influence of scene configuration and object reliability as a function of task-relevance on allocentric coding for memory-guided reaching. For that purpose, we presented participants images of a naturalistic breakfast scene with five objects on a table and six objects in the background. Six of these objects served as potential reach-targets (= task-relevant objects). Participants explored the scene and after a short delay, a test scene appeared with one of the task-relevant objects missing, indicating the location of the reach target. After the test scene vanished, participants performed a memory-guided reaching movement toward the target location. Besides removing one object from the test scene, we also shifted the remaining task-relevant and/or task-irrelevant objects left- or rightwards either coherently in the same direction or incoherently in opposite directions. By varying object coherence, we manipulated the reliability of task-relevant and task-irrelevant objects in the scene. In order to examine the influence of scene configuration (distributed vs. grouped arrangement of task-relevant objects) on allocentric coding, we compared the present data with our previously published data set (Klinghammer et al., 2015). We found that reaching errors systematically deviated in the direction of object shifts, but only when the objects were task-relevant and their reliability was high. However, this effect was substantially reduced when task-relevant objects were distributed across the scene leading to a larger target-cue distance compared to a grouped configuration. No deviations of reach endpoints were observed in conditions with shifts of only task-irrelevant objects or with low object reliability irrespective of task-relevancy. Moreover, when solely task-relevant objects were shifted incoherently, the variability of reaching endpoints increased compared to coherent shifts of task-relevant objects. Our results suggest that the use of allocentric information for coding targets for memory-guided reaching depends on the scene configuration, in particular the average distance of the reach target to task-relevant objects, and the reliability of task-relevant allocentric information.

Nothing magical: pantomimed grasping is controlled by the ventral system

In a recent amendment to the two-visual-system model, it has been proposed that actions must result in tactile contact with the goal object for the dorsal system to become engaged (Whitwell et al., Neuropsychologia 55:41–50, 2014). The present study tested this addition by assessing the use of allocentric information in normal and pantomime actions. To this end, magicians, and participants who were inexperienced in performing pantomime actions made normal and pantomime grasps toward objects embedded in the Müller–Lyer illusion. During pantomime grasping, a grasp was made next to an object that was in full view (i.e., a displaced pantomime grasping task). The results showed that pantomime grasps took longer, were slower, and had smaller hand apertures than normal grasping. Most importantly, hand apertures were affected by the illusion during pantomime grasping but not in normal grasping, indicating that displaced pantomime grasping is based on allocentric information. This was true for participants without experience in performing pantomime grasps as well as for magicians with experience in pantomiming. The finding that the illusory bias is limited to pantomime grasping and persists with experience supports the conjecture that the normal engagement of the dorsal system’s contribution requires tactile contact with a goal object. If no tactile contact is made, then movement control shifts toward the ventral system.

Allocentric information is used for memory-guided reaching in depth: A virtual reality study

Previous research has demonstrated that humans use allocentric information when reaching to remembered visual targets, but most of the studies are limited to 2D space. Here, we study allocentric coding of memorized reach targets in 3D virtual reality. In particular, we investigated the use of allocentric information for memory-guided reaching in depth and the role of binocular and monocular (object size) depth cues for coding object locations in 3D space. To this end, we presented a scene with objects on a table which were located at different distances from the observer and served as reach targets or allocentric cues. After free visual exploration of this scene and a short delay the scene reappeared, but with one object missing (=reach target). In addition, the remaining objects were shifted horizontally or in depth. When objects were shifted in depth, we also independently manipulated object size by either magnifying or reducing their size. After the scene vanished, participants reached to the remembered target location on the blank table. Reaching endpoints deviated systematically in the direction of object shifts, similar to our previous results from 2D presentations. This deviation was stronger for object shifts in depth than in the horizontal plane and independent of observer-target-distance. Reaching endpoints systematically varied with changes in object size. Our results suggest that allocentric information is used for coding targets for memory-guided reaching in depth. Thereby, retinal disparity and vergence as well as object size provide important binocular and monocular depth cues.

Contextual factors determine the use of allocentric information for reaching in a naturalistic scene.

Numerous studies have demonstrated that humans incorporate allocentric information when reaching toward visual targets. So far, it is unclear how this information is integrated into the movement plan when multiple allocentric cues are available. In this study we investigated whether and how the extent of spatial changes and the task relevance of allocentric cues influence reach behavior. To this end, we conducted two experiments where we presented participants three-dimensional-rendered images of a naturalistic breakfast scene on a computer screen. The breakfast scene included multiple objects (allocentric cues) with a subset of objects functioning as potential reach targets (i.e., they were task-relevant). Participants freely viewed the scene and after a short delay, the scene reappeared with one object missing (target) and other objects being shifted left- or rightwards. Afterwards, participants were asked to reach toward the target position on a gray screen while fixating the screen center. We found systematic deviations of reach endpoints in the direction of object shifts which varied with the number of objects shifted, but only if these objects served as potential reach targets. Our results suggest that the integration of allocentric information into the reach plan is determined by contextual factors, in particular by the extent of spatial cue changes and the task-relevance of allocentric cues.

Dissociations between vision for perception and vision for action depend on the relative availability of egocentric and allocentric information

In three experiments, we scrutinized the dissociation between perception and action, as reflected by the contributions of egocentric and allocentric information. In Experiment 1, participants stood at the base of a large-scale one-tailed version of a Müller-Lyer illusion (with a hoop) and either threw a beanbag to the endpoint of the shaft or verbally estimated the egocentric distance to that location. The results confirmed an effect of the illusion on verbal estimates, but not on throwing, providing evidence for a dissociation between perception and action. In Experiment 2, participants observed a two-tailed version of the Müller-Lyer illusion from a distance of 1.5m and performed the same tasks as in Experiment 1, yet neither the typical illusion effects nor a dissociation became apparent. Experiment 3 was a replication of Experiment 1, with the difference that participants stood at a distance of 1.5m from the base of the one-tailed illusion. The results indicated an illusion effect on both the verbal estimate task and the throwing task; hence, there was no dissociation between perception and action. The presence (Exp. 1) and absence (Exp. 3) of a dissociation between perception and action may indicate that dissociations are a function of the relative availability of egocentric and allocentric information. When distance estimates are purely egocentric, dissociations between perception and action occur. However, when egocentric distance estimates have a (complementary) exocentric component, the use of allocentric information is promoted, and dissociations between perception and action are reduced or absent.

Left, right, left, right, eyes to the front! Müller-Lyer bias in grasping is not a function of hand used, hand preferred or visual hemifield, but foveation does matter

We investigated whether the control of movement of the left hand is more likely to involve the use of allocentric information than movements performed with the right hand. Previous studies (Gonzalez et al. in J Neurophys 95:3496–3501, 2006; De Grave et al. in Exp Br Res 193:421–427, 2009) have reported contradictory findings in this respect. In the present study, right-handed participants (N = 12) and left-handed participants (N = 12) made right- and left-handed grasps to foveated objects and peripheral, non-foveated objects that were located in the right or left visual hemifield and embedded within a Müller-Lyer illusion. They were also asked to judge the size of the object by matching their hand aperture to its length. Hand apertures did not show significant differences in illusory bias as a function of hand used, handedness or visual hemifield. However, the illusory effect was significantly larger for perception than for action, and for the non-foveated compared to foveated objects. No significant illusory biases were found for reach movement times. These findings are consistent with the two-visual system model that holds that the use of allocentric information is more prominent in perception than in movement control. We propose that the increased involvement of allocentric information in movements toward peripheral, non-foveated objects may be a consequence of more awkward, less automatized grasps of nonfoveated than foveated objects. The current study does not support the conjecture that the control of left-handed and right-handed grasps is predicated on different sources of information.