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Eye-specific effects of binocular rivalry in the human lateral geniculate nucleus - PubMed

  • ️Sat Jan 01 2005

. 2005 Nov 24;438(7067):496-9.

doi: 10.1038/nature04169. Epub 2005 Oct 23.

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Eye-specific effects of binocular rivalry in the human lateral geniculate nucleus

John-Dylan Haynes et al. Nature. 2005.

Abstract

When dissimilar images are presented to the two eyes, they compete for perceptual dominance so that each image is visible in turn for a few seconds while the other is suppressed. Such binocular rivalry is associated with relative suppression of local, eye-based representations that can also be modulated by high-level influences such as perceptual grouping. However, it is currently unclear how early in visual processing the suppression of eye-based signals can occur. Here we use high-resolution functional magnetic resonance imaging (fMRI) in conjunction with a new binocular rivalry stimulus to show that signals recorded from the human lateral geniculate nucleus (LGN) exhibit eye-specific suppression during rivalry. Regions of the LGN that show strong eye-preference independently show strongly reduced activity during binocular rivalry when the stimulus presented in their preferred eye is perceptually suppressed. The human LGN is thus the earliest stage of visual processing that reflects eye-specific dominance and suppression.

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Competing interests statement

The authors declare that they have no competing financial interests.

Figures

Figure 1
Figure 1

(a) Left and right LGN were localised for each participant as the regions in left and right lateral posterior thalamus responding stronger to contralateral than to ipsilateral hemifield stimulation. (b) Eye-specific stimulation. In alternate runs either the right eye alone (top) or the left eye alone (bottom) was stimulated with a double-wedge stimulus that was presented in blocks of 30 sec. For each voxel in the LGN (see a) we extracted the fMRI signal amplitude during stimulation blocks (gray shaded regions) for stimulation of each eye separately (shown here for one voxel in mean corrected scanner units). (c) We then investigated for each voxel whether the fMRI responses were stronger to stimulation of left eye (positive T-values) or right eye (negative T-values). The middle graphs show the color-coded distribution of these ocular-preferences for a coronal section through one participant’s right LGN (dashed box in a), and the bottom two rows show the raw fMRI signal distribution for a left-eye biased and a right-eye biased voxel during periods where either the left or the right eye was stimulated (grey shaded periods in b). Although the raw signal distributions largely overlap, there was a significant bias for these two voxels as indicated by the means and standard errors for each distribution (open circle, filled square; see Supplemental Fig. S1 for full results).

Figure 2
Figure 2

Binocular rivalry stimulus. (a) A red grating was presented to the left eye and an orthogonal blue grating to the right eye while both simultaneously rotated clockwise. They were viewed through red/blue anaglyph glasses, so that the blue grating was visible to the right eye and the red grating was visible to the left eye. During each scanning run the two were presented continuously for 5 minutes, leading to multiple perceptual alternations between the two monocular images while the other image was suppressed. Participants used response buttons to continuously indicate during each run whether they currently perceived either the red or blue grating. (b) Histogram of dominance phase durations averaged across participants, which reveals that dominance phases were relatively long compared to typical rivalry stimuli and could be well fitted by a gamma-distribution function (bold black line).

Figure 3
Figure 3

Rivalry-related responses in LGN and V1. (a) Event-related BOLD-fMRI signal changes in LGN averaged across participants timelocked to perceptual transitions from red to blue (left) and from blue to red (right)(error bars=SE across participants). Event-related averages were computed separately for voxels with left-eye preference (red circles) and right-eye preference (blue squares) in the independent localiser sessions. The solid line shows the independent prediction of a parameter-free forward model of the hemodynamic response to perceptual transitions reported by the participants (see Experimental Procedures). A good fit between behaviourally predicted and observed hemodynamic responses is apparent. (b) As in a, but now for voxels in primary visual cortex.

Figure 4
Figure 4

Percept preference in LGN and V1. A “percept preference” measure was obtained separately for left-eye dominated voxels (red bars) and right-eye dominated voxels (blue bars) by subtracting the average BOLD signal during blue-dominance from the average BOLD signal during red-dominance (see Supplementary Information). Positive values indicate that signal was higher during dominance of the red percept, and negative values that signal was higher during dominance of the blue percept (data for all 4 subjects; error bars=SE across voxels).

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