|
|
As sensory stimuli and behavioral demands change, the attentive brain
quickly identifies task-relevant stimuli and associates them with appropriate
motor responses. The effects of attention on sensory processing vary across
task paradigms, suggesting that the brain may use multiple strategies and
mechanisms to highlight attended stimuli and link them to motor action. In
order to better understand factors that contribute to these variable effects,
we studied sensory representations in primary auditory cortex (A1) during two
instrumental tasks that shared the same auditory discrimination but required
different behavioral responses, either approach or avoidance. In the approach
task, ferrets were rewarded for licking a spout when they heard a target tone
amidst a sequence of reference noise sounds. In the avoidance task, they were
punished unless they inhibited licking to the target. To explore how these
changes in task reward structure influenced attention-driven rapid plasticity
in A1, we measured changes in sensory neural responses during behavior.
Responses to the target changed selectively during both tasks but did so with
opposite sign. Despite the differences in sign, both effects were consistent
with a general neural coding strategy that maximizes discriminability between
sound classes. The dependence of the direction of plasticity on task suggests
that representations in A1 change not only to sharpen representations of
task-relevant stimuli but also to amplify responses to stimuli that signal
aversive outcomes and lead to behavioral inhibition. Thus, top-down control of
sensory processing can be shaped by task reward structure as well as task
sensory discrimination. Ongoing studies are exploring the control signals that
produce the task-dependent effects in A1 with recordings in non-primary
auditory cortex and frontal cortex.
|