In the cat, cerebral hemispherectomy sustained neonatally results in a remarkable degree of recovery and/or sparing of function as compared with the effects of a similar lesion but sustained in adulthood. We have proposed that this effect is due to a combination of reduced neuronal loss within partially denervated structures and a lesion-induced reorganization of corticofugal projections arising from the remaining intact hemisphere in the neonatally lesioned animal. The current study was designed to assess the physiological consequences of these anatomical changes utilizing [¹⁴C]2-deoxy-D-glucose autoradiography. A total of 17 adult cats were studied. Seven animals served as intact controls, five received a left cerebral hemineodecortication as neonates (NH; mean age 11.4 days), and five sustained the same lesion in adulthood (AH). Histological analysis indicated that the lesion was very similar between the two age groups and essentially represented a unilateral hemineodecortication. Local CMR_glc (LCMR_glc; μmol 100 g^-1 min^-1) values were calculated for 50 structures bilaterally and indicated that in the remaining intact contralateral (right) cerebral cortex (including all areas measured), AH cats exhibited a significantly (p < 0.05) lower level of LCMR_glc (ranging from 20 to 72 μmol 100 g^-1 min^-1) than NH (ranging from 49 to 81 μmol 100g^-1 min^-1). In comparison, the rates of NH cats within the cerebral cortex were very similar to those seen in intact animals (ranging from 48 to 119 μmol 100 g^-1 min^-1). Ipsilateral to the lesion in AH cats, the structures spared by the resection, including the basal ganglia and thalamus, exhibited LCMR_glc rates of between 23 and 69 μmol 100 g^-1 min^-1, which were significantly lower (p < 0.05) than in NH cats (range 47–72 μmol 100 g^-1 min^-1). Considering all structures, both age-at-lesion groups exhibited a lower level of metabolism compared with similar measurements for intact control animals (LCMR_glc range 45–75 μmol 100 g^-1 min^-1). However, this depression of glucose metabolism was more pronounced in the AH cats (p < 0.05). These results indicate that following neonatal hemineodecortication, LCMR_glc is maintained at a higher level in many regions of the brain than in animals that sustain the same resection in adulthood. This higher level of glucose metabolism in NH animals suggests that the lesion-induced anatomical reorganization of structures not directly injured by the lesion plays a functional role that is probably responsible for the greater degree of recovery and/or sparing of function in these early lesioned cats.

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Cerebral Metabolism following Neonatal or Adult Hemineodecortication in Cats: I. Effects on Glucose Metabolism Using [ 14 C]2-Deoxy-D-Glucose Autoradiography