WIDESPREAD ACTIVATION OF BARREL CORTEX BY SMALL NUMBERS OF NEONATALLYSPARED WHISKERS

Activity-dependent plasticity in rodent whisker barrel cortex was exam ined by means of high-resolution 2-deoxyglucose (2-DG) with immunohist ochemical double labeling. Hamsters with all but one, two, or four fol licles ablated on postnatal day 7 received 2-DG injections as adults. Autoradiograms of follicle-ablated animals showed heavy activation of the entire barrel field during normal behavior, despite the missing wh iskers. The intensity of 2-DG labeling was significantly reduced if th e whiskers spared after follicle ablation were trimmed prior to the 2- DG injection, demonstrating that the widespread activation was driven by the spared whiskers. This widespread metabolic activation of the ad ult barrel field after neonatal follicle ablation was in sharp contras t to the somatotopically appropriate 2-DG labeling in barrel fields of normal adults subject to acute trimming of most whiskers, but was sim ilar to that seen in normal adult animals with all whiskers intact. Th e results demonstrate large-scale plasticity of barrel circuitry follo wing neonatal sensory deprivation, and provide a powerful functional a natomical setting to investigate underlying mechanisms.