Nasotemporal overlap of crossed and uncrossed retinal ganglion cell projections in the Japanese monkey (Macaca fuscata)

Abstract

The nasotemporal overlap of crossed and uncrossed retinal ganglion cell projections were studied in 11 Japanese monkeys (Macaca fuscata) using HRP and fluorescent dyes (DAPI and RITC) as retrograde tracers and by physiological recordings of antidromic field potentials. A strip of nasotemporal overlap ran orthogonal to the horizontal meridian in all the whole-mount retinas studied. In HRP-labeled retinas of 6 monkeys, the width of the overlap gradually increased from 0.6 degrees in the central retina up to 5 degrees at eccentricity of 5 mm, and to 15 degrees at the extreme periphery. We also noted a clear asymmetric distribution of crossed and uncrossed retinal ganglion cell projections particularly in the perifoveal region; ipsilaterally projecting cells encircled the nasal edge of the fovea, whereas few contralaterally projecting cells were observed in the temporal edge. Soma-size analysis revealed that crossed projections in the temporal portion of the overlap arose mainly from large and small cells (presumably P alpha and P gamma cells, respectively); uncrossed projections in its nasal portion arose from medium-sized cells (presumably P beta cell). Direct evidence of the overlap as well as of the asymmetry was obtained in subsequent fluorescent dye experiments in 3 monkeys. Physiological studies on 2 additional monkeys confirmed the widening of the nasotemporal overlap towards the upper and lower parts of the retina. Moreover, in the nasal portion of the overlap, only slow potentials, which presumably reflect activities of P beta cells, were recorded after stimulation of the ipsilateral LGN as expected from the morphological study. The findings are discussed in relation to clinical observations of macular sparing and splitting, and with regard to the functional differences between P alpha and P beta cell systems on which binocular stereoscopic vision along the midsagittal plane may be based.

Visuotopic organisation of striate cortex in the marmoset monkey (Callithrix jacchus)

“…Thus, there must be another source for the representation in the ipsilateral field in primates. The most likely explanation is that the limited ipsilateral representation is a consequence of ipsi-and contralaterally projecting areas overlapping along a narrow strip of the retina, which is centred on the fovea and VM (Stone et al, 1973;Fukuda et al, 1989). However, we are not aware of any study of nasotemporal overlap in the marmoset.…”

Macular Ganglion Cell Layer and Peripapillary Retinal Nerve Fibre Layer Thickness in Patients with Unilateral Posterior Cerebral Artery Ischaemic Lesion: An Optical Coherence Tomography Study

“…30 It has been hypothesised that there is a difference in the anatomic location of the ganglion cell bodies and the location of receptive fields and the existence of a region in the vertical midline where an intermingling of ganglion cells projects ipsilaterally and contralaterally. [30][31][32] Validation of these findings is important to understand the mechanisms behind neuronal degeneration and bring implications for the management of these patients: GCL analysis could bring a direct correlation to visual field loss, a better understanding of disease mechanisms, and provide novel targets for therapy in these patients. As neuro-rehabilitation techniques are being developed, a deeper knowledge of mechanisms behind the human visual system TRD could prevent the death of ganglion cells connecting to spared cortical areas.…”

Optic nerve axons: life and death before birth

“…In primates, the ganglion cells that originate these axons lie perfectly spatially separated 59 to the nasal (for fibres that cross) or temporal (uncrossed fibres) side of a line that runs vertically through the foveola. The control of crossing is complex ( Figure 6); a number of guidance cues interact to conduct the crossover and have been the subjects of excellent reviews.…”