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

The computational processes by which attention improves behavioral performance were character-ized by measuring visual cortical activity with func-tional magnetic resonance imaging as humans per-formed 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 unreal-istically large reduction in response variability. Instead, behavioral performance was well character-ized 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 perfor-mance predominantly by enabling efficient selection of the behaviorally relevant sensory signals