- 1-Task-specific shaping of feature-based attention in area MT

Visual perception depends on the effective prioritization of visual information in order to concur with the current behavioral context. Depending on the context's requirements, it is important to facilitate the processing of a certain feature (e.g. motion) in some situations, while in others another feature (e.g. color) is more crucial. We here address the question whether and how the specific requirements of a visual task influence modulation of neuronal activity by feature-based attention (FBA). We recorded neuronal responses from monkey motion-sensitive medio-temporal area (MT) in response to spatially attended or unattended motion stimuli, while monkeys were required to detect an instantaneous speed- or color-change of a pre-cued target stimulus. We found a strong influence of task requirements on several parameters of MT single cell responses: If the task required attention to speed, mean firing rates were higher, and response variability and latency to otherwise identical visual stimuli was lower as compared to the task requiring attention to color. This was evident even with attention directed to the stimulus outside the receptive field (RF) of the recorded neuron, moving in a direction 180 deg away from the preferred direction inside the RF. Importantly, this task-specific response modulation in the processing of visual motion was preceded by a spatially global and tuning-independent shift in the baseline activity of MT neurons before onset of visual stimuli. 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.