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Peng Zhang, Sheng He; Voluntary attention can modulate eye-specific neural signals prior to the site of interocular competition. Journal of Vision 2008;8(6):244. doi: 10.1167/8.6.244.
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Visual attention can enhance the neural activity to an attended stimulus in many cortical areas. A central question in understanding the top-down modulating mechanism of attention is how early in the processing hierarchy attentional effects can be seen. Exogenous attention has been shown to affect processing of monocular signals, but it remains unclear whether voluntary endogenous attention could also modulate monocular neural signals in an eye-specific fashion. In this study, a monocular stimulus competed against high contrast continuous flash suppression (CFS) noise presented to the opposing eye, both centered on a fixation cross. Two identical monocular stimuli, one in each eye, were presented to the left or to the right of the competing stimuli. Subjects did not know which lateral stimulus was presented to the left eye and which to the right eye, but they were instructed to attend to one of the peripheral stimuli and press a key as soon as the central suppressed target emerged from suppression. Results show that the central suppressed stimulus took less time to emerge from suppression when observers attended to the flanking stimulus presented in the same eye than in the opposing eye as the detection target. Also, there is no reduction in the strength of this ocular-specific attention effect when the intensity of the peripheral stimulus was considerably decreased, thus ruling out the possible contribution of stimulus-related suppression from the peripheral attended stimulus to the central competing stimulus in the fellow eye. These findings suggest that voluntary (endogenous) spatial attention can selectively modulate neural signals at the eye-specific level of visual information processing, prior to the site of interocular competition.
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