Task preparation in monkeys

The way we react to a stimulus depends on what task we are doing. We can prepare a task even before we know what stimulus will appear. Unlike merely remembering a stimulus or delaying execution of a response, advance task preparation is an abstract cognitive process that configures the brain to respond in a task-appropriate way. We studied this process in a macaque monkey using a task switching paradigm. Following a task cue, the animal had to judge whether the stimulus was more red than green (task 1) or whether the outside was brighter than the inside (task 2), and press a left or a right button to indicate the judgement. Possible stimuli were drawn from a single set of colored squares with a bright and dark pattern. Thus neither the task cue nor the stimulus uniquely identified the correct response. We recorded from 180 neurons in the parietal posterior cortex (PPC). We found that 25% of cells were responsive to task information in the interval between task cue and target presentation. In a control experiment only 2 out of 13 task cue cells responded to the sensory properties of the cue. We conclude that the PPC codes task information independent from perceptual or motor position.