Representation of the visual field in the primary visual area of the marmoset monkey: Magnification factors, point‐image size, and proportionality to retinal ganglion cell density

Abstract

The primary visual area (V1) forms a systematic map of the visual field, in which adjacent cell clusters represent adjacent points of visual space. A precise quantification of this map is key to understanding the anatomical relationships between neurons located in different stations of the visual pathway, as well as the neural bases of visual performance in different regions of the visual field. We used computational methods to quantify the visual topography of V1 in the marmoset (Callithrix jacchus), a small diurnal monkey. The receptive fields of neurons throughout V1 were mapped in two anesthetized animals using electrophysiological recordings. Following histological reconstruction, precise 3D reconstructions of the V1 surface and recording sites were generated. We found that the areal magnification factor (M(A) ) decreases with eccentricity following a function that has the same slope as that observed in larger diurnal primates, including macaque, squirrel, and capuchin monkeys, and humans. However, there was no systematic relationship between M(A) and polar angle. Despite individual variation in the shape of V1, the relationship between M(A) and eccentricity was preserved across cases. Comparison between V1 and the retinal ganglion cell density demonstrated preferential magnification of central space in the cortex. The size of the cortical compartment activated by a punctiform stimulus decreased from the foveal representation towards the peripheral representation. Nonetheless, the relationship between the receptive field sizes of V1 cells and the density of ganglion cells suggested that each V1 cell receives information from a similar number of retinal neurons, throughout the visual field.

Representation of central and peripheral vision in the primate cerebral cortex: Insights from studies of the marmoset brain

“…We also confirmed that, as in other primates (e.g. Silveira et al, 1989;Azzopardi and Cowey, 1993) the representation of the visual field in V1 deviates significantly from that expected solely on the basis of the retinal ganglion cell density, with relatively more V1 neurons dedicated to the representation of the foveal space (Chaplin et al, 2013a).…”

“…If this is the case, the map is anisotropic (Van Essen et al, 1984;Gattass et al, 1987). Although we did observe anisotropy in marmoset V1 (Chaplin et al, 2013a), it was small in magnitude and appeared to vary slightly from case to case. For simplicity, an estimate of M, assuming no anisotropy, can be expressed as…”

“…Hubel and Wiesel (1974) observed that as eccentricity increases, the reduction in magnification is accompanied by a parallel decrease in resolution Chaplin et al, 2013a). The visual space is projected from the hemifield in 3D (shown in the right panel) onto the 2D plane using the area-preserving Lambert projection.…”

“…An estimate of the cortical magnification function of the marmoset was first given by , but the most in-depth analysis has been provided by Chaplin et al (2013a), which is based on measurements made on 3D surfaces reconstructed from histological slides. As we noted in this report, when the cortical surface of the marmoset V1 is physically flatmounted or computationally flattened from a 3D reconstructed model, it assumes a stereotypical oval shape, similar to that of V1 of other primate species ( Fig.…”

Relationship between Optical Coherence Tomography and Electrophysiology of the Visual Pathway in Non-Optic Neuritis Eyes of Multiple Sclerosis Patients

“…[34] This overrepresentation of the central visual field is largely formed at the retinal level and preserved in the OR. [35] Assuming uniform distribution of lesions within the OR, it is likely that OR fibers sub-serving central vision are damaged more extensively, which, in turn, may cause larger damage of the central (temporal) RNFL.…”