Attentional Enhancement via Selection and Pooling of Early Sensory Responses in Human Visual Cortex

SummaryThe computational processes by which attention improves behavioral performance were characterized by measuring visual cortical activity with functional magnetic resonance imaging as humans performed a contrast-discrimination task with focal and distributed attention. Focal attention yielded robust improvements in behavioral performance accompanied by increases in cortical responses. Quantitative analysis revealed that if performance were limited only by the sensitivity of the measured sensory signals, the improvements in behavioral performance would have corresponded to an unrealistically large reduction in response variability. Instead, behavioral performance was well characterized by a pooling and selection process for which the largest sensory responses, those most strongly modulated by attention, dominated the perceptual decision. This characterization predicts that high-contrast distracters that evoke large responses should negatively impact behavioral performance. We tested and confirmed this prediction. We conclude that attention enhanced behavioral performance predominantly by enabling efficient selection of the behaviorally relevant sensory signals.

► Effects of attention on human contrast discrimination and cortical response measured
► Computational analysis examined how cortical responses could account for behavior
► Unrealistic amount of noise reduction needed to account for performance enhancement
► Instead, efficient selection via max pooling fully accounted for better performance