Task-specific, dimension-based attentional shaping of motion processing in area MT

Non-spatial selective attention is based on the notion that specific features or objects in the visual environment are effectively prioritized in cortical visual processing. Feature-based attention (FBA) in particular, is a well-studied process that dynamically and selectively enhances neurons preferentially processing the attended feature attribute (e.g. leftward motion). In everyday life, however, behavior may require high sensitivity for an entire feature dimension (e.g. motion). Yet, evidence for feature dimension-specific attentional modulation on a cellular level is lacking. We here investigate neuronal activity in macaque motion-selective medio-temporal area (MT) in an experimental setting requiring the monkeys to detect either a motion change or a color change. We hypothesized that neural activity in MT is enhanced if the task requires perceptual sensitivity to motion. Despite identical visual stimulation, we found that mean firing rates were higher in the motion task, and response variability and latency were lower as compared to the color task. This task-specific response modulation in the processing of visual motion was independent from the relation between attended and stimulating motion direction. It emerged already in the absence of visual input, and consisted of a spatially global and tuning-independent shift of the MT baseline activity. The results provide single cell support for the hypothesis of a feature dimension-specific top-down signal emphasizing the processing of an entire feature class.