Cat parastriate cortex: a primary or secondary visual area

Abstract

The purpose of this study was to determine to what extent the cat parastriate cortex processes afferent geniculate activity in a way similar to that in area 17. The area explored was located on the lateral gyrus between the Horsley-Clarke coordinates A1 to 4 and L3 to 4. The receptive-field properties of area 18 cells and their responses to electrical stimulation of afferent and efferent pathways were measured with the same methods as described previously in area 17. Mutual correlations among these items were calculated and compared with the respective data from area 17. The results of this correlative analysis revealed numerous similarities between the two areas with regard to their afferent and efferent connections and their intrinsic organization. Consequently, the structure of the receptive fields and their numerical distribution resembled those in area 17. The same was true for the correlations between receptive-field parameters and afferent and efferent connectivity. The main differences were that area 18 cells had larger receptive fields and responded to considerably higher stimulus velocities. It is suggest-d that these differences are caused by the fact that area 18 receives subcortical afferents of the Y-type, whereas the dominant input to area 17 comes from the X-system. It is concluded that the area investigated in this study is organized in parallel to area 17 and deals with other aspects of visual information than area 17.

Subcortical Representation of Non-Fourier Image Features

“…C, Histogram of accounted variance between the envelope and contrast-reversing TF tuning curves for 24 Y-cells, median r 2 ϭ 0.73. different image features; area 17 represents Fourier features and area 18 represents both Fourier and non-Fourier features (Zhan and Baker, 2006;Issa et al, 2008). Despite this difference, a common principle appears to govern the cortical transformation of the LGN signal by individual neurons in areas 17 and 18: the alignment of LGN receptive fields along oriented axes in space and time (Hubel and Wiesel, 1962;Tretter et al, 1975). As such, the difference in the image features represented by these areas may emerge because of the qualitative difference in their LGN input.…”

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

“…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.…”

“…Thus, each cortical area must have the potential to influence the relay of retinal information to the other. In this context, it is important to note that area 18 receives input from the thickest, fastest axons in the afferent pathway (Tretter et al, 1975;Höllander and Vanegas, 1977;LeVay and Ferster, 1977;Geisert, 1980) and that the thickest and presumably fastest feedback axons originate in area 18. This loop must therefore provide the first corticogeniculate signal in response to any stimulus condition.…”

“…This loop must therefore provide the first corticogeniculate signal in response to any stimulus condition. Given the relative conduction times of X and Y axons (Cleland et al, 1971(Cleland et al, , 1976Tretter et al, 1975), area 18 could well provide a preemptive influence on the responses of X-type relay cells and through them the function of the striate cortex.…”

“…Receptive fields in area 18 are substantially larger than those in area 17 (Tretter et al, 1975;Orban and Kennedy, 1981), and the retinotopic map in area 18 is substantially more compressed along the mediolateral axis (Tusa et al, 1978(Tusa et al, , 1979Cynader et al, 1987). The existing evidence therefore suggests that, although the axons match anatomically, there are substantial differences in the f unctional connectivity of the two pathways.…”