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Valentin Wyart, Vincent de Gardelle, Jacqueline Scholl, Christopher Summerfield; Rhythmic fluctuations in evidence accumulation during decision making in the human brain. Journal of Vision 2012;12(9):1113. doi: 10.1167/12.9.1113.
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Categorical choices are preceded by the accumulation of sensory evidence in favour of one action or another. Current decision-making models assume that momentary evidence is integrated continuously over hundreds of milliseconds in the form of a decision variable, a quantity that maps the accumulated evidence onto an appropriate action. However, the notion that evidence accumulation occurs at a constant rate is inconsistent with a rich psychological literature describing how human perception is limited by a central bottleneck, giving rise to cognitive blinks of few hundreds of milliseconds during which sensory information is perceived as lagging or even missed. During perceptual categorisation, we found that both the encoding of momentary evidence in human EEG signals and its impact on choice were modulated rhythmically by the phase of ongoing delta oscillations at 2 Hz over the parietal cortex. By contrast, fluctuations in beta-band activity (10-30 Hz) over the motor cortex encoded the accumulated evidence as a response preparation signal. These findings draw a clear distinction between a central stage at which momentary evidence is weighted, and a motor stage at which the accumulated evidence is mapped onto action. They also suggest that the attentional bottleneck identified as responsible for cognitive blinks might impose a cyclic sampling constraint on evidence accumulation, with successive samples competing for limited processing capacity before being integrated.
Meeting abstract presented at VSS 2012
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