Neurochemistry of learning: The role of dopamine in recently-learned behavior versus habits.
Cecile Morvan and her research associates are observing the performance of
simple behaviors in rats - e.g., entering a food compartment in response to a
tone (an auditory CS). Disruption of brain dopamine activity strongly disrupts
the animal's ability to perform these tasks (just as it disrupts behavior in
humans). However, when the animal repeats that behavior hundreds of times
(i.e., the response becomes a habit), disruption of
brain dopamine activity no longer disrupts the behavior. In some way, the
"habit" has become invulnerable to dopamine disruption. We are
pursuing the following questions: What are the neurobiological changes that
permit well-learned behaviors to occur when dopamine transmission is
compromised? It is possible that the neural representation of the
behavior may shift from dopamine target regions of the brain to regions that
are not DA-innervated. Alternatively,
the behavioral representation may remain in the same DA-innervated anatomical
site, but (glutamatergic) input signals to the region may become stronger over
the course of training, and therefore less dependent upon dopamine
facilitation.
Neurochemistry of
Learning: Nucleus accumbens coding of
reward expectation. Neuropharmacology and electrophysiology.
Veronica Dobrovitsky and her team are testing the hypothesis that dopamine
transmission at D1 receptors within the nucleus accumbens sets the threshold
for reward expectation (generated by conditioned stimuli associated with
varying probabilities of reward delivery) to generate behavioral approach
responses. In collaborative studies conducted at
Neurochemistry of time perception: Timing behavior during dopamine manipulations
These experiments are being conducted in collaboration with Dr. Peter Balsam's laboratory at Barnard. Rats have been trained to demonstrate an estimation of elapsed time periods. We are asking how this time estimation is affected by manipulations of dopamine transmission - dopamine receptor blockade and elevations in dopamine activity.
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