The Journal of Neuroscience, October 1, 1999, 19(19):8646-8655
Extinction of Behavior in Infant Rats: Development of
Functional Coupling Between Septal, Hippocampal, and Ventral Tegmental
Regions
H. P.
Nair and
F.
Gonzalez-Lima
Institute for Neuroscience and Department of Psychology, University
of Texas at Austin, Austin, Texas 78712
Learning of a behavior at a particular age during the postnatal
period presumably occurs when the functional brain circuit mediating
the behavior matures. The inability to express a learned behavior, such
as inhibition, may be accounted for by the functional dissociation of
brain regions comprising the circuit. In this study we tested this
hypothesis by measuring brain metabolic activity, as revealed by
fluorodeoxyglucose (FDG) autoradiography, during behavioral extinction
in 12- and 17-d-old rat pups. Subjects were first trained on a straight
alley runway task known as patterned single alternation (PSA), wherein
reward and nonreward trials alternate successively. They were then
injected with FDG and given 50 trials of continuous nonreward (i.e.,
extinction). Pups at postnatal day 12 (P12) demonstrated significantly
slower extinction rates compared to their P17 counterparts, despite the
fact that both reliably demonstrated the PSA effect, i.e., both age
groups distinguished between reward and nonreward trials during
acquisition. Covariance analysis revealed that the dentate gyrus,
hippocampal fields CA1-3, subiculum, and lateral septal area were
significantly correlated in P17 but not P12 pups. Significant
correlations were also found between the lateral septal area, ventral
tegmental area, and the medial septal nucleus in P17 pups. Similar
correlative patterns were not found in P12 and P17 handled control
animals. Taken together, these results suggest that septal,
hippocampal, and mesencephalic regions may be functionally dissociated
at P12, and the subsequent maturation of functional connectivity
between these regions allows for the more rapid expression of
behavioral inhibition during extinction at P17.
Key words:
brain imaging; hippocampus; covariance; extinction; development; rat
Copyright © 1999 Society for Neuroscience 0270-6474/99/19198646-10$05.00/0
Previous Article | Next Article
