The origin of efferent pathways from the primary visual cortex, area 17, of the macaque monkey as shown by retrograde transport of horseradish peroxidase

Abstract

The retrograde transport of horseradish peroxidase has been used to identify efferent cells in area 17 of the macaque. Cells projecting to the lateral geniculate nucleus are small to medium sized pyramidal neurons with somata in lamina 6 and the adjacent white matter. The projection to the parvocellular division arises preferentially from the upper half of lamina 6, while that to the magnocellular division arises preferentially from the lower part of the lamina. The projection to both superior colliculus and inferior pulvinar arises from all sizes of pyramidal neurons lying in lamina 58 (Lund and Boothe, '75); at least pyramidal neurons of lamina 5B send collateral axon branches to both destinations. Injections with extensive spread of horseradish peroxidase show that many cells of lamina 4B and the large pyramidal neurons of upper lamina 6 also project extrinsically but their terminal sites have not been identified. Other studies have indicated that cells of laminae 2 and 3 project to areas 18 and 19. Therefore every lamina of the visual cortex, with the exception of those receiving a direct thalamic input, contains cells projecting extrinsically. Further, each lamina projects to a different destination and from Golgi studies can be shown to contain cells with specific patterns of dendritic branching which relate to the distribution of thalamic afferents and to the patterns of intracortical connections. These findings emphasise the significance of the horizontal organisation of the cortex with relation to the flow of information through it and contrast with the current concept of columnar organisation shown in physiological studies.

Further studies on the size specificity of commissural projecting neurons of layer III in areas 17,18,19 and the lateral suprasylvian area of the cat's visual cortex.

“…It seems noteworthy that heterotopical areas 17, 18 and 19 were free from labeling, and this corresponds well with sparse degeneration in the upper part of the LS, particularly, at the levels indicated in Figure 4, after the lesion affecting the lateral gyrus on the opposite side (SHOUMURA, 1972;SANIDES, 1978). LUND et al (1975) noted that the area where HRP is taken up for axonal transport does not correspond to the whole brown area around the injection site but is localized in the area immediately surrounding the injection. With this respect in mind, it is presumed that in 7810 and 7908 the enzyme was taken up largely by axons entering the outer layers of the LS, and that the small number of labeled neurons in the lower layers is due to the small number of com- Note that the area of strong HRP reaction immediately surrounding the needle track is largely limited to the superficial layers of the cortex.…”

“…It has been demonstrated in monkeys that the cells of origin of commissural fibers are confined to one or two layers and to a narrow size range; such cells in the visual (WONG-RILEY, 1974;LUND et al, 1975;WINFIELD, GATTER and POWELL, 1975) and somatosensory (JONES and WISE, 1977) cortices are all large to medium-sized pyramids in the lower layer III, while some neurons of layer V have been found to supply commissural fibers in the frontal cortex (JACOBSON and TROJANOWSKI, 1974). Similar results have been obtained by studing Nissl preparations of the monkey's visual cortex (the region of area 18 just adjacent to striate cortex) after a large lesion of the occipital cortex on the other side or section of the corpus callosum (GLICKSTEIN and WHITTERIDGE, 1976) and of the visual cortex of human brains congenitally lacking the corpus callosum (SHOUMURA, ANDO and KATO, 1975).…”

Corticogeniculate feedback sharpens the temporal precision and spatial resolution of visual signals in the ferret

“…Injection of SADΔG-ChR2-mCherry into the LGN caused expression of ChR2 and mCherry in retinogeniculate neurons, thalamic reticular nucleus neurons, LGN interneurons, and CG neurons, because these populations have axon terminals in the LGN. Importantly, because CG neurons are the only visual cortical neurons with axon terminals in the LGN (26)(27)(28), they are the only neurons in the cortex expressing ChR2 and mCherry following injection of virus into the LGN (Fig. 1C and SI Appendix, Fig.…”

“…G-deleted rabies virus is taken up by axon terminals and moves exclusively in the retrograde direction to infect cell bodies but is prohibited from crossing synapses (22)(23)(24)(25). We took advantage of the fact that CG neurons are the only visual cortical neurons that project axons to the LGN (26)(27)(28), combined with the exclusively retrograde action of G-deleted rabies virus, to selectively infect CG neurons following injection of virus into the LGN (29) (Fig. 1A).…”

Circuits for Multisensory Integration and Attentional Modulation Through the Prefrontal Cortex and the Thalamic Reticular Nucleus in Primates

“…Pathways from the thalamus that terminate extensively in the superficial cortical layers, or the prevalent cortical projections form layer VI to the thalamus, are considered to be modulatory pathways. Some studies have provided evidence that driver pathways, at least in the thalamus, have large terminals, whereas modulatory pathways have small terminals / 1,68,72,86,87,88,96,104,113,138,139,151,153 /.…”