Increased oxidative metabolism in middle suprasylvian cortex following removal of areas 17 and 18 from newborn cats

Abstract

We measured changes in metabolic activity in middle suprasylvian (MS) cortex of cats subjected to early or late removal of areas 17 and 18 to localize shifts in activity possibly indicative of regions within MS cortex that may receive expanded inputs and be involved in the sparing of some visual behaviors following early primary visual cortex damage. Cytochrome oxidase (CO) activity was measured in MS cortex of mature, 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 less than 9 months after the ablation, brain sections were prepared and reacted for the presence of CO. The density of CO reactivity in each of the six cortical layers in MS cortex was measured and standardized against densities from ventral periaqueductal gray or hypothalamus on the 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 portion of AMLS. In contrast, there were no significant differences in the level of CO activity among P28, P180, or intact cats for any of the cortical layers, and all had lower levels than the P1 cats. This metabolic change provides an anatomical marker for localizing adjustments in MS cortex and can be linked to amplified projections into MS cortex from the thalamus (LPm and A and C laminae of the dorsal lateral geniculate nucleus) and ventral posterior suprasylvian cortex following P1 ablations. Furthermore, this neurochemical analysis implicates a distinct region of MS cortex as the cortical locus of some spared visual functions following early primary visual cortex damage.

Task-specific reversal of visual hemineglect following bilateral reversible deactivation of posterior parietal cortex: A comparison with deactivation of the superior colliculus

“…There was no indication of physical damage or necrosis. Moreover, there was no alteration in cytochrome oxidase activity in pMS cortex compared to unimplanted animals (Long et al, 1996). We conclude that neither the presence of the cryoloops nor their repeated deactivation over several months altered the structure or long-term function of MS sulcal cortex.…”

Removal of two halves restores the whole: Reversal of visual hemineglect during bilateral cortical or collicular inactivation in the cat

“…4; cf. Long et al, 1996). This is important because cytochrome oxidase is a sensitive measure for abnormally functioning cortex (Pasternak & Merigan, 1994).…”

Complex motion selectivity in PMLS cortex following early lesions of primary visual cortex in the cat

“…Previous authors have suggested that the relatively normal response properties observed in PMLS cortex are caused by increased and0or novel projections from either the A or C layers of the LGN~Fig. 6Aa!, a tecto-thalamo-cortical circuit six Ab!, a retino-thalamo-cortical pathway~6Ac!, or novel computations that occur within PMLS~Labar et al, 1981;Tong et al, 1984Tong et al, , 1991Spear, 1988Spear, , 1995Kalil et al, 1991;Guido et al, 1992;Payne et al, 1993;Long et al, 1996;Payne & Lomber, 1998;Moore et al, 2001;Boire et al, 2004!. All of these mechanisms are likely to be involved in residual direction selectivity in PMLS.…”