A reassessment of the lower visual field map in striate-recipient lateral suprasylvian cortex

Abstract

Lateral suprasylvian visual cortex in the cat has been studied extensively, but its retinotopic organization remains controversial. Although some investigators have divided this region into many distinct areas, others have argued for a simpler organization. A clear understanding of the region’s retinotopic organization is important in order to define distinct areas that are likely to subserve unique visual functions. We therefore reexamined the map of the lower visual field in the striate-recipient region of lateral suprasylvian cortex, a region we refer to as the lateral suprasylvian area, LS.A dual mapping approach was used. First, receptive fields were plotted at numerous locations along closely spaced electrode penetrations; second, different anterograde tracers were injected at retinotopically identified sites in area 17, yielding patches of label in LS. To visualize the resulting data, suprasylvian cortex was flattened with the aid of a computer.Global features of the map reported in many earlier studies were confirmed. Central visual field was represented posteriorly, and elevations generally shifted downward as one moved anteriorly. Often (though not always) there was a progression from peripheral locations towards the vertical meridian as the electrode moved down the medial suprasylvian bank.The map had some remarkable characteristics not previously reported in any map in the cat. The vertical meridian’s representation was split into two pieces, separated by a gap, and both pieces were partially internalized within the map. Horizontal meridian occupied the gap. The area centralis usually had a dual representation along the posterior boundary of the lower field representation, and other fragments of visual field were duplicated as well. Finally, magnification appeared to change abruptly and unexpectedly, so that compressed regions of representation adjoined expanded regions. Despite its complexity, we found the map to be more orderly than previously thought. There was no clearcut retinotopic basis on which to subdivide LS’s lower field representation into distinct areas.

A neurochemical signature of visual recovery after extrastriate cortical damage in the adult cat

“…The feline LS cortex is a complex of extrastriate visual areas (Palmer et al, 1978;Sherk, 1986b;Grant and Shipp, 1991;Sherk and Mulligan, 1993) that exhibit functional similarity with areas MT/MST of primates (Payne, 1993), playing an important role in the processing of complex visual motion information (Rauschecker, 1988;Rudolph and Pasternak, 1996;Akase et al, 1998). LS cortex is relatively high level in the hierarchy of the cat visual system (Scannell et al, 1995).…”

“…In the visual system, most studies reporting training-induced recovery of function were conducted following damage to extrastriate visual cortex-lesions of the lateral suprasylvian (LS) visual cortex in cats, e.g. (Rudolph and Pasternak, 1996 Pasternak, 2004) or lesions in areas MT/MST of monkeys (Newsome and Pare, 1988;Rudolph and Pasternak, 1999).The feline LS cortex is a complex of extrastriate visual areas (Palmer et al, 1978;Sherk, 1986b;Grant and Shipp, 1991;Sherk and Mulligan, 1993) that exhibit functional similarity with areas MT/MST of primates (Payne, 1993), playing an important role in the processing of complex visual motion information (Rauschecker, 1988;Rudolph and Pasternak, 1996;Akase et al, 1998). LS cortex is relatively high level in the hierarchy of the cat visual system (Scannell et al, 1995).…”

“…Furthermore, training-induced recovery after LS lesions is always restricted to retrained visual field locations (Huxlin and Pasternak, 2004). The tighter retinotopic organization of early visual cortical areas (relative to higher level visual cortical areas: Palmer et al, 1978;Tusa et al, 1981;Sherk and Mulligan, 1993) suggests that recovery might be mediated by early levels of the visual cortical system. Area 18, a relatively low-level area in the cat visual cortical hierarchy, might be an ideal candidate to mediate training-induced recovery after LS lesions because of its strong interconnections with LS cortex.…”

Analysis of connectivity in the cat cerebral cortex

“…PLLS, ALLS, and DLS overlap with the lateral suprasylvian area in other parcellation schemes (Sherk, 1986;. We have treated PMLS, PLLS, AMLS, ALLS, VLS, and DLS as separate entities for the collation of connection data, but the precise disposition of visual areas in the lateral suprasylvian cortex remains unclear There is considerable evidence, however, for several visual areas within lateral suprasylvian sulcus (see Palmer et al, 1978;Komatsu et al, 1983;Blakemore and Zumbroich, 1986;Von Grunau et al, 1986;Zumbroich et al, 1986;Zumbroich and Blakemore, 1987;Gizzi et al, 1990;Toyama et al, 1990;Grant and Shipp, 1991;Bando et al, 1992;Takagi et al, 1992;Yin and Greenwood, 1992a,b;Sherk and Mulligan, 1993). 21a, area 21a, a visual area on the posterior part of the suprasylvian gyrus and the superior wall of the posterior part of the suprasylvian sulcus (Tusa and Palmer, 1980;Symonds and Rosenquist, 1984a;Rosenquist, 1985;Wimbourne and Henry, 1992;Dreher et al, 1993).…”

“…21a, area 21a, a visual area on the posterior part of the suprasylvian gyrus and the superior wall of the posterior part of the suprasylvian sulcus (Tusa and Palmer, 1980;Symonds and Rosenquist, 1984a;Rosenquist, 1985;Wimbourne and Henry, 1992;Dreher et al, 1993). 21a overlaps with the Clare-Bishop area in the parcellation of Sherk (1986) and Sherk and Mulligan (1993). 21b, area 21b, a visual area on the posterior part of the suprasylvian gyrus and the posterior wall of the posterior part of the suprasylvian sulcus (Tusa and Palmer, 1980;Symonds and Rosenquist, 1984a;Rosenquist, 1985).…”