Recovery of associative function following early amygdala lesions in rats.
Adult rats with amygdala lesions made at either Postnatal Day (PND) 10 or PND40 were tested on a series of reversal tasks that tap the ability to form stimulus-reward associations. PND40 rats were significantly impaired relative to both controls and PND10 rats on learning rate of the original discrimination and subsequent reversals. Analyses of discrete learning phases revealed that the impairment was specific to the postchance phase. The PND10 group was not impaired relative to controls on any measure. These results confirm prior findings that amygdala lesions sustained in adulthood impair the formation of stimulus-reward associations. They also demonstrate that substantial sparing or recovery of function is possible when the lesion is made during early development. Furthermore, the findings support the view that behavioral recovery may be more likely if the lesion is sustained near the time of peak synaptogenesis.