The pattern of projection of cortical areas 17, 18, and 19 onto the laminae of the dorsal lateral geniculate nucleus in the cat

Abstract

The projection of cortical areas 17, 18, and 19 onto the laminar part of the dorsal lateral geniculate nucleus was investigated with degeneration methods and with the autoradiographic axon tracing method. In agreement with previous accounts, degenerating cortical axons stained by the Nauta method were restricted to laminae A, A1, C and to the interlaminar zones. In contrast, adjacent sections stained with the Fink-Heimer method showed fine dust like degeneration throughout all of the laminae of the nucleus. Comparisons of Fink-Heimer degeneration resulting from lesions of area 17 with that resulting from lesions of areas 18 and 19 further suggested that the area ) projection is heavier and more uniform than the projections from areas 18 and 19. Autoradiographic tracing of axons after intracortical injections of 3H-proline provided detailed demonstrations of the cortical projection patterns that confirmed the Fink-Heimer results. Following restricted injections of areas 17 or 18 the termination zones in the dorsal lateral geniculate nucleus consisted of columns of labeled tissue oriented perpendicular to the laminae of the nucleus. Area 17 was found to project heavily and uniformly throughout all of the laminae of the nucleus. The projection from area 18 also extended throughout all of the laminae of the nucleus, but was sparser and less uniformly distributed than that from area 17. Projections from area 18 distributed more heavily to the interlaminar zones and to lamina C than to laminae A, A1 C1, C2 or C3. A projection from area 19 to laminae C1, C2 and C3 was also demonstrated autoradiographically.

Comparison of the Laminar Distribution of Input from Areas 17 and 18 of the Visual Cortex to the Lateral Geniculate Nucleus of the Cat

“…There is evidence that projections both to and from area 18 are unevenly distributed through the depth of the A layers (Updyke, 1975;Geisert, 1985;Erisir et al, 1998); therefore, for both the areas 17 and 18 axon populations, each A layer was subdivided into top, middle, and bottom thirds. To ensure that the mediolateral distribution of boutons could be assessed accurately, the layers were also divided into 90-mwide columns oriented perpendicular to the laminar borders.…”

“…In the cat, it involves at least three separate cortical areas, 17, 18, and 19 (Kawamura et al, 1974;Updyke, 1975), each of which forms a characteristic pattern of corticof ugal connections. In particular, although bulk labeling experiments have shown that the area 17 and 18 pathways both terminate in all of the layers and compartments of the dLGN complex, there is evidence to suggest subtle differences in their bouton distributions (Updyke, 1975) and choice of postsynaptic targets (Vidnyánszky and Hámori, 1994).…”

“…In the cat, it involves at least three separate cortical areas, 17, 18, and 19 (Kawamura et al, 1974;Updyke, 1975), each of which forms a characteristic pattern of corticof ugal connections. In particular, although bulk labeling experiments have shown that the area 17 and 18 pathways both terminate in all of the layers and compartments of the dLGN complex, there is evidence to suggest subtle differences in their bouton distributions (Updyke, 1975) and choice of postsynaptic targets (Vidnyánszky and Hámori, 1994). Because areas 17 and 18 have different retinotopic organizations (Tusa et al, 1978(Tusa et al, , 1979Cynader et al, 1987), afferent inputs (Höllander and Vanegas, 1977;LeVay and Ferster, 1977;Dreher et al, 1980;Geisert, 1980), visual response properties (Hubel and Wiesel, 1965;Tretter et al, 1975;Orban and Callens, 1977;Movshon et al, 1978;Orban and Kennedy, 1981;Orban et al, 1981a,b;Price et al, 1994), and response latencies (Tretter et al, 1975), it follows that each group of dLGN cells must receive a functionally distinct pattern of corticofugal influence.…”

“…Although the geniculate layers are generally assumed to be homogeneous, there is some evidence that projections both to (Geisert, 1985) and from (Updyke, 1975) area 18 are differentially distributed with respect to the depth of the A layers. These layers were therefore subdivided into top, middle, and bottom thirds, so that the frequency of boutons could be examined separately for each division.…”

Temporal dynamics of binocular disparity processing with corticogeniculate interactions

“…It seems dear from these results that feedback plays a role in spatially loca.li"'ed processing. Evidence to support this comes from the precise topography of the feedback projections (Updyke, 1975). This means that a simple role as the sourec of arousal cannot be conjectured for the feedback projections.…”