Abstract
In single-unit recording studies, feature-based attention has been shown to enhance the responses of neurons tuned to an attended feature while simultaneously suppressing responses of neurons tuned away from the attended feature (Martinez-Trujillo and Treue, 2004). But how do these attentional modulations occurring at the neuronal level influence perception? While the facilitory effects of feature-based attention on perception have been widely observed, the role of attentional suppression is not as well understood. Here, we investigated the perceptual consequences of suppression using a 4AFC task in which 4 random dot patterns (RDPs) were presented, one in each quadrant; subjects selected the quadrant containing coherent motion. At the beginning of each trial, subjects viewed either a valid cue that correctly indicated the impending direction of coherent motion, a neutral cue that contained no directional information, or an invalid cue that indicated a direction systematically offset from the actual target direction. We fit our reaction-time and accuracy data using the linear ballistic accumulator (LBA) model (Brown and Heathcote, 2008) in order to assess the effects of attention cues on the speed of sensory information accumulation (‘drift rate’) during decision making. The average drift rate estimates were highest for valid cue trials and gradually decreased as the offset between the invalid cue and target approached the orthogonal direction of the stimulus (i.e., 90°); intermediate drift rates were observed on neutral trials. In contrast with the neurophysiological data, where suppression was maximal for directions opposite of the attended direction, we observed a recovery of performance when the offset between the invalid cue and target exceeded 90° and approached 180° (see Supplementary Figure). Our data raise the possibility that additional processing steps intercede between attentional modulations observed in MT and the final perceptual experience of the observer.