Organization of corticothalamic projections from parietal cortex in cat

Abstract

Corticothalamic projections from areas 5a, 5b, and 7 of cat parietal cortex were studied with autoradiographic techniques. Each cortical area was identified by its cytoarchitectural characteristics and the patterns of termination were related to the thalamic nuclear groups. Injections of 3H-leucine in cortical area 5a were associated with terminal labeling primarily in the spinal recipient zone of the ventral lateral nucleus (VLsp) and the medial division of the posterior group (POm). The corticothalamic projections of area 5a are loosely topographically organized; medial parts of 5a project heavily to rostral and lateral parts of VLsp and sparsely to POm, while lateral parts of 5a project to more medial and caudal parts of VLsp and heavily to POm. Cortical area 5b projects primarily to the rostral portions of the lateral posterior nucleus (LP). These projections also appear to be topographically organized. The part of area 5b on the marginal gyrus projects to more ventral parts of rostral LP, while area 5b on the middle suprasylvian gyrus projects to more dorsal and lateral parts of rostral LP. Cortical area 7 projects to LP and the pulvinar (Pul). Rostral parts of area 7 project heavily to dorsal and lateral parts of LP and lightly to Pul; more caudal portions of area 7 projects relatively more heavily to Pul. The reticular, central lateral, and paracentral nuclei also receive projections, especially from the suprasylvian gyrus. The results are discussed with regard to putative sensory response characteristics of these cortical areas and to general thalamocortical organization.

Ultrastructural analysis of projections to the pulvinar nucleus of the cat. I: Middle suprasylvian gyrus (areas 5 and 7)

“…The cells of the PUL have large visual receptive fields that often lack clear boundaries; they respond more robustly to diffuse illumination than to small visual cues (Godfraind et al, 1972;Mason, 1981 by saccadic eye movements. Sudkamp and Schmidt (2000) identified three general classes of neurons in the feline PUL: "S" neurons are active during saccadic eye movements, "V" neurons are responsive to visual stimuli and unresponsive to eye movements, and "SV" neurons respond to both stationary ON and OFF stimuli and to sudden stimulus shifts.These response properties are similar in many respects to those of neurons in the parietal cortex, an area that establishes extensive reciprocal connections with the PUL (de V Clüver and Campos-Ortega, 1969;Heath and Jones, 1971;Robertson and Cunningham, 1981;Niimi et al, 1983;Raczkowski and Rosenquist, 1983;Avendaño et al, 1985;Olson and Lawler, 1987). In the cat, these cortical areas are primarily located within the middle suprasylvian gyrus (MSg) or cytoarchitectonically in areas 5 and 7 (Gurewitsch and Chachaturian, 1928).…”

“…These response properties are similar in many respects to those of neurons in the parietal cortex, an area that establishes extensive reciprocal connections with the PUL (de V Clüver and Campos-Ortega, 1969;Heath and Jones, 1971;Robertson and Cunningham, 1981;Niimi et al, 1983;Raczkowski and Rosenquist, 1983;Avendaño et al, 1985;Olson and Lawler, 1987). In the cat, these cortical areas are primarily located within the middle suprasylvian gyrus (MSg) or cytoarchitectonically in areas 5 and 7 (Gurewitsch and Chachaturian, 1928).…”

Distribution, morphology, and synaptic targets of corticothalamic terminals in the cat lateral posterior-pulvinar complex that originate from the posteromedial lateral suprasylvian cortex

“…The cat lateral posterior (LP) and pulvinar nuclei receive input from a wide array of cortical areas concerned with vision or visuomotor control. These areas include cortical areas 17, 18, 19, 20, and 21 as well as the variety of visual areas that surround the lateral suprasylvian and ectosylvian sulci (Niimi and Sprague, 1970;Jones and Powell, 1971; Graybiel, 1978, 1983;Graybiel and Berson, 1980;Robertson and Cunningham, 1981;Updyke, 1981;Tong et al, 1982;Olson and Graybiel, 1983;Raczkowski and Rosenquist, 1983; ReinosoSuarez and Roda, 1985). However, despite the quantity of detailed information regarding these corticothalamic projections, the function of these massive inputs remains enigmatic.…”

The isolated occlusion of the angular gyri artery. A correlative neurological and anatomical study--case report.

“…But some of them are the result of the corticocortical, interhemispheric, corticofhalamic (thalamocortical) and other fiber system damage -the so-called "disconnection syndrome." 25 Our patient had most of these signs, but also some others: hemianopsy, hemihypesthesia, hemiparesis and central facial weakness. The hemianopsy in this case is the result not only of optic radiations damage, but also of the parietal cortex lesion and consecutive visual inattention and neglect of the contralateral halffield of space.…”

“…25 Finally, the parietal cortex perhaps subserves the decoding of sign language. 29 On the basis of the above mentioned facts it is clear that parietal cortex damage (especially of the left hemisphere) produces: astereognosis, finger agnosia, disphasia, alexia, agraphia, acalculia, right-left and extrapersonal space disorientation.…”