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Frank Tong, Amy Wong, Ming Meng, Thomas J. McKeeff; Brain areas involved in attentional control and perception of ambiguous figures. Journal of Vision 2002;2(7):677. doi: 10.1167/2.7.677.
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To what extent are attention-related brain areas involved in monitoring versus controlling incoming perceptual information? Ambiguous figures such as the Necker cube provide an ideal stimulus to explore this question because observers report spontaneous reversals while viewing such stimuli yet appear to retain some degree of voluntary control over perception. Here, we monitored fMRI activity while subjects maintained fixation and provided an online report of their perceptual interpretation of a Necker cube. Before each trial, subjects were visually instructed to either: 1) passively monitor the stimulus, 2) actively attempt to initiate a perceptual switch (‘active’ condition), or 3) attempt to sustain a single percept throughout the trial (‘stay’ condition). Behavioral data revealed that subjects could successfully control their perception to some extent, though not absolutely (mean switch times for active = 2.2 s, passive = 3.7 s, stay = 6.9 s, trial duration = 12 s). fMRI analyses across all three conditions revealed extensive activation in visual, parietal, and prefrontal and anterior cingulate cortex. Comparisons between voluntary control conditions (active and stay) and passive viewing revealed more restricted activation in parietal and frontal brain area previously implicated in visual attention. Some subjects also showed differential activity in the anterior cingulate and/or extrastriate visual areas. Importantly however, all brain areas showing greater activity during voluntary control also revealed highly robust responses during passive viewing (relative to fixation baseline) and only slightly, though significantly, enhanced responses during voluntary control conditions. Our findings indicate considerable overlap between the brain regions involved in controlling or biasing the perception of ambiguous figures and those involved in monitoring perception. These results are consistent with the notion that voluntary control of perception is imposed through the selective allocation of attention and the activation of stored perceptual representations. Moreover, the voluntary control of perception seems to rely on the very brain areas that serve to monitor perception from moment-to-moment.
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