Representation of heading direction in far and near head space

Abstract

Manipulation of objects around the head requires an accurate and stable internal representation of their locations in space, also during movements such as that of the eye or head. For far space, the representation of visual stimuli for goal-directed arm movements relies on retinal updating, if eye movements are involved. Recent neurophysiological studies led us to infer that a transformation of visual space from retinocentric to a head-centric representation may be involved for visual objects in close proximity to the head. The first aim of this study was to investigate if there is indeed such a representation for remembered visual targets of goal-directed arm movements. Participants had to point toward an initially foveated central target after an intervening saccade. Participants made errors that reflect a bias in the visuomotor transformation that depends on eye displacement rather than any head-centred variable. The second issue addressed was if pointing toward the centre of a wide-field expanding motion pattern involves a retinal updating mechanism or a transformation to a head-centric map and if that process is distance dependent. The same pattern of pointing errors in relation to gaze displacement was found independent of depth. We conclude that for goal-directed arm movements, representation of the remembered visual targets is updated in a retinal frame, a mechanism that is actively used regardless of target distance, stimulus characteristics or the requirements of the task.

Spatial updating across saccades during manual interception

“…We assessed to what extent interception errors depend on the initial and final eccentricities of the interception point relative to gaze in a spatial updating paradigm, in which a saccade is made between viewing and reaching toward a moving target. In a control task involving stationary targets, we replicated the previous findings (i.e., gaze-centered overshoots and updating; Baker, Harper, & Snyder, 2003;Henriques et al, 1998;Medendorp & Crawford, 2002;Poljac & van den Berg, 2003;Pouget et al, 2002;Sorrento & Henriques, 2008;Van Pelt & Medendorp, 2007; see Supplementary material). Similar but more variable effects occurred for interception.…”

Specificity of Human Parietal Saccade and Reach Regions during Transcranial Magnetic Stimulation

“…This bias effect in accuracy most likely reflects an influence of the experimental configuration, in which the targets were aligned horizontally with the fixation location. As observed in previous studies (Bock, 1986;Henriques et al, 1998;Henriques and Crawford, 2000;Medendorp and Crawford, 2002;Pouget et al, 2002;Poljac and Van Den Berg, 2003), baseline horizontal errors for reaches to peripheral targets are biased relative to gaze-position angle; therefore, any rTMS-induced errors reported here are relative to these baseline errors (supplemental Fig. S1, available at www.jneurosci.org as supplemental material).…”

Mixed visual reference frames: perceiving nonretino-centric visual quantities in a retino-centric frame

“…Thus, the retinal flow limitation on the precision of heading perception points to a retinal position reference of head-centric flow signals. This conclusion is supported by a recent study by (Poljac & van den Berg, 2003). They found that pointing towards memorized perceived heading direction showed the same type of retino-centric errors following a saccadic eye movement as pointing towards single LED targets.…”