INCREASED OXIDATIVE-METABOLISM IN MIDDLE SUPRASYLVIAN CORTEX FOLLOWING REMOVAL OF AREAS 17 AND 18 FROM NEWBORN CATS

We measured changes in metabolic activity in middle suprasylvian (MS) cortex of cats subjected to early or late removal of areas 17 and 18 t o localize shifts in activity possibly indicative of regions within MS cortex that may receive expanded inputs and be involved in the sparin g of some visual behaviors following early primary visual cortex damag e. Cytochrome oxidase (GO) activity was measured in MS cortex of matur e, intact cats and of others with areas 17 and 18 removed in adulthood (P180), or on postnatal day 28 (P28) or postnatal day 1 (P1). Not les s than 9 months after the ablation, brain sections were prepared and r eacted for the presence of CO. The density of CO reactivity in each of the six cortical layers in MS cortex was measured and standardized ag ainst densities from ventral periaqueductal gray or hy pothalamus on t he same section. Following lesions on P1, significant increases in CO activity occurred in deep layer III and in layer IV of the medial bank of the MS sulcus, including all of area PMLS and the posterior portio n of AMLS. In contrast, there were no significant differences in the l evel of CO activity among P28, P180, or intact cats for any of the cor tical layers, and all had lower levels than the P1 cats. This metaboli c change provides an anatomical marker for localizing adjustments in M S cortex and can be linked to amplified projections into MS cortex fro m the thalamus (LPm and A and C laminae of the dorsal lateral genicula te nucleus) and ventral posterior suprasylvian cortex following pi abl ations. Furthermore, this neurochemical analysis implicates a distinct region of MS cortex as the cortical locus of some spared visual funct ions following early primary visual cortex damage.