Parallax-sensitive remapping of visual space in occipito-parietal alpha-band activity during whole-body motion

Abstract

Gutteling TP, Selen LP, Medendorp WP. Parallax-sensitive remapping of visual space in occipito-parietal alpha-band activity during whole-body motion. J Neurophysiol 113: 1574 -1584, 2015. First published December 10, 2014 doi:10.1152/jn.00477.2014Despite the constantly changing retinal image due to eye, head, and body movements, we are able to maintain a stable representation of the visual environment. Various studies on retinal image shifts caused by saccades have suggested that occipital and parietal areas correct for these perturbations by a gaze-centered remapping of the neural image. However, such a uniform, rotational, remapping mechanism cannot work during translations when objects shift on the retina in a more complex, depth-dependent fashion due to motion parallax. Here we tested whether the brain's activity patterns show parallax-sensitive remapping of remembered visual space during whole-body motion. Under continuous recording of electroencephalography (EEG), we passively translated human subjects while they had to remember the location of a world-fixed visual target, briefly presented in front of or behind the eyes' fixation point prior to the motion. Using a psychometric approach we assessed the quality of the memory update, which had to be made based on vestibular feedback and other extraretinal motion cues. All subjects showed a variable amount of parallaxsensitive updating errors, i.e., the direction of the errors depended on the depth of the target relative to fixation. The EEG recordings show a neural correlate of this parallax-sensitive remapping in the alphaband power at occipito-parietal electrodes. At parietal electrodes, the strength of these alpha-band modulations correlated significantly with updating performance. These results suggest that alpha-band oscillatory activity reflects the time-varying updating of gaze-centered spatial information during parallax-sensitive remapping during wholebody motion. spatial updating; EEG; alpha power; whole-body motion; remapping WE PERCEIVE THE WORLD as a stable reality, despite the ubiquitous changes in visual input due to our own movements. We do not perceive a visual shift when we make a saccade, even though the image of the world moves briskly on our retinas (Bridgeman and Nardello 1994; Schlag and Schlag-Rey 2002; von Helmholtz 1867). Also, when we walk around, our perception seems not to be disturbed by the even more complex changes in the optic flow on our retinas (see Angelaki and Hess 2005 for review). How does our brain create this percept of visual stability?There is evidence that the brain codes dynamic visual representations of the environment, which are remapped in gaze-centered coordinates when the eyes move. Various cortical and subcortical regions have been implicated in this remapping during saccadic eye movements in both primates (Colby and Goldberg 1999;Duhamel et al. 1992) In geometric terms, when the body translates through space, world-stationary objects move at different speeds and in different directions relative to the ret...

Alpha-band transcranial alternating current stimulation modulates precision, but not gain during whole-body spatial updating

“…A fixedinterval procedure was used, equally spaced over 9 locations, spanning 8 degrees of visual angle, with a maximum of 12 degrees depending on subject performance. Due to the general underestimation of self-motion in these updating tasks (Clemens et al, 2012;Gutteling et al, 2015) probe locations were shifted towards the fixation point (consistent with an underestimation of motion), but always contained the veridical location.…”

“…In Gutteling et al (2015), we showed that alpha band power across occipital-parietal areas switches hemispheres when a target location reverses sides relative to the body midline (which was aligned with gaze) during the motion. More specifically, an increase of power was observed in the hemisphere to which the target representation was remapped.…”

“…The stimulation covered either the left or right parieto-occipital areas because these regions have shown the largest alpha band modulation in previous updating experiments (Gutteling et al, 2015;Gutteling and Medendorp, 2016). Subjects were pseudorandomly assigned to either the left or right montage group, while counterbalancing gender between groups.…”

“…In contrast to saccades, the neural underpinnings of spatial updating across head and body motion have been studied much less. It is only recently that studies suggest that remapping can also account for updating across whole-body motion (Gutteling et al, 2015;Gutteling and Medendorp, 2016). Evidence is based on neural oscillations in the alpha band (8-12 Hz), whose power increases and decreases have been associated with the selective inhibition and engagement of neuronal populations, respectively (Jensen and Mazaheri, 2010).…”

Spatially modulated alpha-band activity does not mediate tactile remapping and fast overt orienting behavior

“…In one study, participants received tactile stimulation on the index or little finger of one hand while fixating the same hand's middle finger (Buchholz et al, 2011). While planning a saccade to the tactile location, posterior parietal alpha-band activity was suppressed in the hemisphere opposite to finger location relative to gaze, as it has been reported for visual paradigms as well (Gutteling et al, 2015). In another study, touch to uncrossed and crossed hands also resulted in externally coded parietal alphaband suppression (Schubert et al, 2018).…”