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Abstract:
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.
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