Roger Tootell - US grants

The experiments in this proposal are directed towards the anatomical and functional organization of extrastriate visual cortex in the primate. There are two general sets of experiments, one on human cortical anatomy, and the other on functional organization in the monkey. In the human experiments, autopsied visual cortex is flattened, sectioned and stained for either myelin, cytochrome oxidase, or the monoclonal antibody CAT-301 to look for anatomical homologues of macaque cortical visual areas V2, V3, MT and LIP, and perhaps V3A and MST. If such homologous areas can be demonstrated in the human, this should clarify the etiology of specific perceptual defects due to cortical damage in certain patients (e.g. Pearlman et al, 1979; Damasio et al, 1980; zihl eta al, 1983). There are three experiments int he scond set of experiments on monkey organization. All of these experiments will use optical recordings, the double-label deoxyglucose technique and/or electrophysiological mapping to demonstrate and map the functional architecture. One of these experiments is directed towards area MT, where tests will be done for direction, velocity and other types of columns, and for intrinsic differences in activity. Another experiment is a test for color columns (wavelength preference maps) in any cortical visual area, with special focus on areas V1 and V4. In the final experiment, orientation columns will be labelled throughout visual cortex, in both New and Old World monkeys. The presence or absence of orientation columns in each area will serve as a criteria for homology between different areas in the two families of primate.

The experiments in this proposal are directed towards understanding the anatomical and functional organization of three cortical areas in primate visual cortex. There are three sets of experiments in cortical area MT of the Old World monkey. In the first set, we make long microelectrode perforations through area MT, recording single unit activity in response to a range of visual stimuli. The visual stimuli are all designed to reveal differences in receptive fields. Later those differences can be correlated with histological labelling of the area MT "bands" (labelled with deoxyglucose and specific visual stimuli) or the area MT "patches" (labelled with cytochrome oxidase). In the second set, we use a new double-label deoxyglucose protocol to investigate the functional architecture of area MT. One experiment compares the architecture of the bands to the patches. Two other double-labelled deoxyglucose experiments will be done in the awake behaving monkey. These experiments are designed to examine functional organization in higher-tier cortical visual areas. In the third set, we inject various neural tracers into visual areas of the brain, to find which areas (or which columns in which areas) share connections with the MT bands or the MT patches. The final set of experiments is designed to begin studying areas V3 and DM. In one experiment, we plan to record from cells in the area DM "stripes" and "interstripe" regions, to see how those cells respond. In another, we use deoxyglucose and cytochrome oxidase staining techniques to investigate the functional organization of area V3. Finally, we use neural tracers to try to discover the specific connections with the V3 patches and interpatches.