Maturation of extinction behavior in infant rats: Large-scale regional interactions with medial prefrontal cortex, orbitofrontal cortex, and anteriorcingulate cortex

The ability to express a behavior during the postnatal period may be relate d to developmental changes in the recruitment of particular neural systems. Here, we show that developmental changes in the functional interactions in volving three cortical regions (the medial prefrontal cortex, orbitofrontal cortex, and anterior cingulate cortex) are associated with maturation of e xtinction behavior in infant rats. Postnatal day 17 (P17) and P12 pups were trained in a straight-alley runway on an alternating schedule of reward an d nonreward [patterned single alternation (PSA)] or on a pseudorandom sched ule of partial reinforcement (PRF); the pups were then injected with fluoro deoxyglucose (FDG) and shifted to continuous nonreward (extinction). Handle d control groups exposed to the same training environment but not trained o n a particular schedule were included. Among P17 pups, extinction proceeded faster in PSA pups relative to PRF pups. No differences were found between P12 groups. FDG uptake, an index of acute changes in functional activity, was quantified in the three cortical regions and 27 other brain regions of interest. A multivariate covariance analysis, seed partial least squares, r evealed that functional relationships involving the three cortical regions and large-scale systems of regions throughout the rostrocaudal extent of th e brain changed with training in P17 pups. The cortical regions were primar ily uncoupled in the younger group. The data suggest that functional matura tion of the frontal cortical regions and their interactions with other brai n systems are related to the maturational shift in behavior.