Topographic patterns of V2 cortical connections in macaque monkeys

Abstract

Patterns of connections of dorsal and ventral portions of the second visual area (V2) were used to evaluate and extend current theories of cortical organization and processing streams in macaque monkeys. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and up to four different fluorochromes in V2 labeled neurons and terminations in V2 and in 1) caudal (DLc) and rostral (DLr) subdivisions of dorsolateral cortex between V2 and the middle temporal area (MT); 2) regions we define as dorsomedial (DM) and dorsointermediate (DI) areas; 3) MT, medial superior temporal area (MST), and fundal superior temporal area (FST); 4) the dorsal part of inferior temporal (TEO) cortex; and 5) two locations in posterior parietal cortex. The largest extrastriate connection zone was DLc, which occupied the caudal one-third to one-half of the fourth visual area (V4) region of other proposals. Based on the connection pattern, foveal vision in DLc is represented adjacent to foveal vision in V2, with the lower quadrant represented dorsally and the upper quadrant ventrally, as in V2, but within a much less extensive region of cortex. The sparser connections of DLr formed a more compressed but parallel visuotopic pattern. A third visuotopic pattern of connections was located in a moderately myelinated region of cortex just rostral to dorsomedial V2. Whereas the region would include parts of dorsal visual area 3 (V3), V3a, and possibly other areas of other proposals, we interpret the connection pattern as reflecting a dorsomedial visual area, DM, with foveal vision represented caudolaterally and other parts of the lower and upper quadrants represented more medially and rostrally. A fourth pattern of label in dorsointermediate cortex suggested the location and organization of another visual area (DI). Most of a fifth connection pattern with MT was congruent with the known visuotopic organization of MT area, but visuotopically mismatched foci of connections were observed as well. Sparser foci of label in MST suggested a rostrodorsal representation of foveal vision, with paracentral vision represented more caudally. Separate dorsal and ventral foci of label in FST were consistent with previous evidence for dorsal (FSTd) and ventral (FSTv) visual areas. Finally, connections with TEO and posterior parietal cortex were sparse. Our results suggest that much of visual cortex organization is similar in New and Old World monkeys.

The case for primate V3

“…Possible explanations for the V3/DM discrepancies are that New World monkeys have a different organization of caudal visual cortex than their Old World cousins. However, this does not explain why some connectional results in macaques also support the concept of an area DM near the dorsal border of V2 [19,20,26,38]. Additionally, larger New World cebus monkeys show retinotopic maps with organization more similar to those reported for macaques than for the smaller New World monkeys [39].…”

“…(b) Van Essen et al [17] did not conclusively show that ventral V1 was connected to V3v and, along with functional differences reported between V3d and V3v, treated each region as an independent area, and renamed V3v as VP. (c) Connectional and microelectrode mapping evidence from Kaas and co-workers [18][19][20] suggested the presence of area DM in place of V3d. (d ) More recent work from Lyon & Kaas [21] found anatomical support for both V3d and V3v.…”

Modular Organization of Occipito-Temporal Pathways: Cortical Connections between Visual Area 4 and Visual Area 2 and Posterior Inferotemporal Ventral Area in Macaque Monkeys

“…(Cusick et al, 1988;Steele et al,1991;. Similar observations have been made by Stepniewska and Kaas (1996) in macaque monkeys. According to this view, V4 is homologous with DLc, whereas VOT and DOT would be contained within DLr.…”

Two Retinotopic Visual Areas in Human Lateral Occipital Cortex

“…3B). Kaas and colleagues (Stepniewska and Kaas, 1996;Stepniewska et al, 2005) have proposed a similar scheme that subdivides this region into a caudal part (DLc) and a rostral part (DLr). Gattass et al (1988) reported that V4d and V4t each contained a map of the lower visual quadrant, and that these areas were separated by a representation of the horizontal meridian.…”