Action preparation shapes processing in early visual cortex - PubMed (original) (raw)
Action preparation shapes processing in early visual cortex
Tjerk P Gutteling et al. J Neurosci. 2015.
Abstract
Preparation for an action, such as grasping an object, is accompanied by an enhanced perception of the object's action-relevant features, such as orientation and size. Cortical feedback from motor planning areas to early visual areas may drive this enhanced perception. To examine whether action preparation modulates activity in early human visual cortex, subjects grasped or pointed to oriented objects while high-resolution fMRI data were acquired. Using multivoxel pattern analysis techniques, we could decode with >70% accuracy whether a grasping or pointing action was prepared from signals in visual cortex as early as V1. These signals in early visual cortex were observed even when actions were only prepared but not executed. Anterior parietal cortex, on the other hand, showed clearest modulation for actual movements. This demonstrates that preparation of actions, even without execution, modulates relevant neuronal populations in early visual areas.
Keywords: MVPA; action preparation; feature perception; grasping; high-field fMRI; visual cortex.
Copyright © 2015 the authors 0270-6474/15/356472-09$15.00/0.
Figures
Figure 1.
Paradigm. A, Graphic depiction of the grasping/pointing setup in the MRI scanner. Subjects lay supine in the MRI bore. A posterior volume was scanned (indicated in red), here depicted on a single subject anatomy (right). The partial volume was chosen to encompass both the early visual areas and the anterior parietal areas. Subjects were able to see the grasping/pointing display (bottom) through prism glasses. Color cues were given through a back projection system, illuminating the grasping/pointing display. When not giving cues, the back projection illuminated the grasping/pointing display (white). Every trial started with an instruction color cue (red/green, 1 s duration) indicating whether the action should be performed on the left or right bar. After a 2.5–3.5 s interval, an auditory cue instructed the subject to either perform the action (single beep) or withhold it (double beep). In case of a go cue, the subject performed the action that was instructed at the start of the block of trials. B, The retinotopic mapping stimuli consisted of a rotating checkerboard wedge (left) and an expanding checkered ring stimulus (middle). The black arrows did not appear in the actual stimulus presentation. The orientation grating stimuli (rightmost picture) consisted of two gratings of equal orientation, which appeared on either side of a fixation point for two seconds, followed by eight seconds of rest.
Figure 2.
Grasping/pointing Searchlight results. Group results for the surface based searchlight grasping versus pointing analysis on a normalized brain. A, Classification results for the cue go condition, where action was executed. B, Classification results for the cue no-go condition, where the action had to be withheld. C, Classification scores during the instruction phase. The individual searchlight results were normalized, averaged across subjects, and smoothed for display purposes. The left hemisphere is depicted on the left (lateral and medial view) and the right hemisphere on the right. The color map represents classification scores.
Figure 3.
Kinematics. Grand averages of the obtained hand movements during the grasping/pointing task, recorded using a dataglove during the experiment. The left graph shows finger bend fractions during grasping for the index finger and thumb, in both go (solid line) and no-go (dotted line) conditions. Time 0 represents the auditory go-cue. In the no-go condition, an auditory stop-cue followed shortly after the first. The right graph depicts the movements during the pointing movement for the index finger in the go (solid line) and no-go conditions (dotted line).
Figure 4.
Orientation decoding results. Single-subject results of the surface based searchlight analysis of the orientation task in a medial view and flat map. A classifier was trained to discern gratings of 45° or −45° (leftward vs rightward tilt) for every surface based searchlight patch. The dotted red line indicates the edge of the scanned volume. Individual regions of interest of early visual areas V1–V3 are marked. The color map represents classification scores.
Figure 5.
ROI analysis. Classification scores of the grasping/pointing task for every ROI, thresholded to include only surface patches that can significantly classify orientation. For both hemispheres, mean classification values are depicted for the go condition (where a grasping or pointing action was performed), no-go condition (where the action was withheld), and instruction condition (the cue instructed the action target). Error bars denote the SEM. All classification scores are significantly above chance level (50%) corrected for multiple comparisons (Bonferroni corrected α of 0.0021, one sample t tests, all p < 0.00071).
Figure 6.
Laterality analysis. Classification scores of the grasping/pointing task for every ROI, as in Figure 5, but split between actions performed to targets to the left (top) and right (bottom). The ROIs are denoted by their hemisphere (e.g., “Left aIPS” refers to the aIPS in the left hemisphere). Error bars denote the SEM.
References
- Allport A. Selection for action: some behavioral and neurophysiological considerations of attention and action. In: Heuer H, Sanders AF, editors. Perspectives on perception and action. Hillsdale, NJ: Erlbaum; 1987. pp. 395–419.
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