Differential effects of prefrontal cortex ablation in neonatal, juvenile, and young adult rats

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Long-Evans hooded rats sustaining lesions in the medial (MF) or the orbital (OF) prefrontal cortex at various ages (10, 25, 40, or 60 days postnatally) were tested as adults on a series of behavioral tasks that are known to be sensitive to such lesions in adults. On spatial alternation learning, both the 40- and 60-day MF Ss were seriously impaired, whereas neither the 10- nor the 25-day MF Ss differed from controls. On a hoarding task, 25- and 60-day MF Ss hoarded less food than either controls or 10-day MF Ss. Lesions of OF cortex in males at 40 or 60 days significantly increased running-wheel activity; OF lesions in both sexes at 25 days of age or later decreased the rate of continuous reinforcement reacquisition relative to controls, whereas 10-day OF Ss did not differ from controls on either task. Thus, Ss with lesions of either frontal area at 10 days of age showed complete behavioral sparing on all measures. The effects of lesions at later ages varied with the behavioral task employed and with lesion locus. Although the 10-day Ss received a somewhat longer postoperative recovery interval than most of the later operates, these results cannot be explained on the basis of recovery time alone. (34 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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