Anatomical Evidence for Classical and Extra-classical Receptive Field Completion Across the Discontinuous Horizontal Meridian Representation of Primate Area V2

Abstract

In primates, a split of the horizontal meridian (HM) representation at the V2 rostral border divides this area into dorsal (V2d) and ventral (V2v) halves (representing lower and upper visual quadrants, respectively), causing retinotopically neighboring loci across the HM to be distant within V2. How is perceptual continuity maintained across this discontinuous HM representation? Injections of neuroanatomical tracers in marmoset V2d demonstrated that cells near the V2d rostral border can maintain retinotopic continuity within their classical and extra-classical receptive field (RF), by making both local and long-range intra- and interareal connections with ventral cortex representing the upper visual quadrant. V2d neurons located <0.9-1.3 mm from the V2d rostral border, whose RFs presumably do not cross the HM, make nonretinotopic horizontal connections with V2v neurons in the supra- and infragranular layers. V2d neurons located <0.6-0.9 mm from the border, whose RFs presumably cross the HM, in addition make retinotopic local connections with V2v neurons in layer 4. V2d neurons also make interareal connections with upper visual field regions of extrastriate cortex, but not of MT or MTc outside the foveal representation. Labeled connections in ventral cortex appear to represent the "missing" portion of the connectional fields in V2d across the HM. We conclude that connections between dorsal and ventral cortex can create visual field continuity within a second-order discontinuous visual topography.

The case for a dorsal V3 in the ‘third-tier’ of primate visual cortex: a reply to ‘the case for a dorsomedial area in the primate ‘third-tier’ visual cortex’

“…For example, the green and red tracer patterns of label just anterior to the injection sites are in what I would consider to be V3d; however, the pattern of label that could be seen in V3d is somewhat obfuscated by the large blue injection site that is probably in V3d. The V3d location of the blue injection seems clear because all blue label in V1 is in the lower visual field representation, and that the horizontal meridian in ventral V2 and what I would consider V3v are also labelled (which would be expected from an injection on the horizontal meridian, as shown previously by Jeffs et al [26]). If, on the other hand, the blue injection is partially overlapping the upper field [8].…”

Connections of the Dorsomedial Visual Area: Pathways for Early Integration of Dorsal and Ventral Streams in Extrastriate Cortex

“…Given that the topographic organization of V1 in the marmoset is highly consistent between cases (Fritsches and Rosa, 1996), this procedure results in estimates that are correct within 10% of the eccentricity actually observed in electrophysiological recordings in the same animals [see Palmer and Rosa (2006b) for examples of this technique applied to the analysis of MT connections]. These estimates included but, in many cases, extended considerably beyond the extents of the excitatory receptive fields of cells recorded near the injection sites, perhaps reflecting projections that contribute to "silent" receptive field surrounds (Angelucci et al, 2002) and those involved in establishing continuity across the visual field in areas that form second-order representations (Jeffs et al, 2009). …”

A simpler primate brain: the visual system of the marmoset monkey

“…The vertical meridian of the visual field is represented along the border with V1; the horizontal meridian is represented along the anterior border, where V2 abuts areas of the “third visual complex” (Jeffs et al, 2009; Rosa et al, 2013). Following the topology of V1, the lower visual field is represented in dorsal V2, and the upper visual field is represented in ventral V2.…”

“…In addition to the V1 input described above, major cortical afferents to V2 originate in the third visual complex (DM/V6 and VLP/V3), the fourth visual area (VLA/V4), the motion-sensitive areas MT and MTC, and other dorsal extrastriate areas (in particular, the dorsoanterior area, DA/V3a; Jeffs et al, 2009, 2013). These inputs are topographically organized.…”