Intrinsic signal optical imaging evidence for dorsal V3 in the prosimian galago (Otolemur garnettii)

Abstract

Currently, we lack consensus regarding the organization along the anterior border of dorsomedial V2 in primates. Previous studies suggest that this region could be either the dorsomedial area, characterized by both an upper and a lower visual field representation, or the dorsal aspect of area V3, which only contains a lower visual field representation. We examined these proposals by using optical imaging of intrinsic signals to investigate this region in the prosimian galago (Otole-mur garnettii). Galagos represent the prosimian radiation of surviving primates; cortical areas that bear strong resemblances across members of primates provide a strong argument for their early origin and conserved existence. Based on our mapping of horizontal and vertical meridian representations, visuotopy, and orientation preference, we find a clear lower field representation anterior to dorsal V2 but no evidence of any upper field representation. We also show statistical differences in orientation preference patches between V2 and V3. We additionally supplement our imaging results with electrode array data that reveal differences in the average spatial frequency preference, average temporal frequency preference, and sizes of the receptive fields between V1, V2, and V3. The lack of upper visual field representation along with the differences between the neighboring visual areas clearly distinguish the region anterior to dorsal V2 from earlier visual areas and argue against a DM that lies along the dorsomedial border of V2. We submit that the region of the cortex in question is the dorsal aspect of V3, thus strengthening the possibility that V3 is conserved among primates.

A new view of dorsal visual cortex in macaques revealed by submillimeter fMRI

“…Similar organizational schemes have been proposed for New World monkeys (e.g. Lyon and Kaas, 2001;2002a) and Prosimians (Fan et al, 2012;Lyon and Kaas, 2002b), although the majority of New World monkey studies favour alternative models (e.g. Figure 1B, C).…”

Morphological and neurochemical comparisons between pulvinar and V1 projections to V2

“…One important development has been data indicating that there are likely to be multiple types of cortical drivers (Sherman and Guillery,2011; Viaene et al,2011; Wei et al,2011). Another development suggests that, at least in the mouse, there are both driver and modulator class reciprocal connections from the primary sensory cortices to adjoining cortices (Covic and Sherman,2011; De Pasquale and Sherman,2011). This second point finds some support from the work of Soares et al (2004), who, working with the cebus monkey, showed a mixture of both excitation and inhibition of V2 responses after pulvinar blockade with GABA.…”

Topographic organization of areas V3 and V4 and its relation to supra-areal organization of the primate visual system

“…1A, left). This model is based on electrophysiological recordings and anatomical studies in Old World monkeys (Zeki, 1978; Gattass et al, 1988; Kaas & Lyon, 2001; Lyon & Kaas, 2001), but also has been reported in New World monkeys (Lyon et al, 2002) and prosimians (Fan et al, 2012) using optical imaging. Similar to area V2, area V3 is proposed to form a “second-order” representation of visual space with a discontinuity in the representation of the horizontal meridian that anatomically separates upper and lower visual field representations in ventral and dorsal occipital cortex, respectively.…”