Neural strength of visual attention gauged by motion adaptation

Single-cell and neuroimaging studies reveal that attention focused on a vis ual object markedly amplifies neural activity produced by features of the a ttended object. In a psychophysical study, we found that visual attention c ould modulate the strength of weak motion signals to the point that the per ceived direction of motion, putatively registered early in visual processin g, was powerfully altered. This strong influence of attention on early moti on processing, beside complementing neurophysiological evidence for attenti onal modulation early in the visual pathway, can be measured in terms of eq uivalent motion energy, and thus provides a useful metric for quantifying a ttention's effects.