Striatal dopamine modulates basal ganglia output and regulates social context-dependent behavioral variability through D1 receptors.
Journal of Neuroscience. 2010-04-21; 30(16): 5730-5743
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Leblois A(1), Wendel BJ, Perkel DJ.
(1)Department of Otolaryngology, University of Washington, Seattle, Washington 98195, USA.
Cortico-basal ganglia (BG) circuits are thought to promote the acquisition of
motor skills through reinforcement learning. In songbirds, a specialized portion
of the BG is responsible for song learning and plasticity. This circuit generates
song variability that underlies vocal experimentation in young birds and
modulates song variability depending on the social context in adult birds. When
male birds sing in the presence of a female, a social context associated with
decreased BG-induced song variability, the extracellular dopamine (DA) level is
increased in the avian BG nucleus Area X. These results suggest that DA could
trigger song variability changes through its action in Area X. Consistent with
this hypothesis, we report that DA delivered to Area X weakens the output signal
of the avian cortico-BG circuit. Acting through D(1) receptors, DA reduced
responses in Area X to song playback and to electrical stimulation of its
afferent cortical nucleus HVC (used as a proper name). Specifically, DA reduced
the response to direct excitatory input and decreased firing variability in Area
X pallidal neurons, which provide the output to the thalamus. As a consequence,
DA delivery in Area X also decreased responses to song playback in the cortical
output nucleus of the BG loop, the lateral magnocellular nucleus of the anterior
nidopallium. Further, interfering with D(1) receptor transmission in Area X
abolished social context-related changes in song variability. In conclusion, we
propose that DA acts on D(1) receptors in Area X to modulate the BG output signal
and trigger changes in song variability.