Organization of visual inputs to interneurons of lateral geniculate nucleus of the cat

Abstract

1. Two groups of interneurons that are involved in the organization of the lateral geniculate nucleus (LGN) are described. The cell bodies of one group lie within the LGN; these units are referred to as intrageniculate. The cell bodies of the other group are found immediately above the LGN at its border with the perigeniculate nucleus; these units are referred to as perigeniculate. 2. Intrageniculate interneurons have center-surround receptive fields that resemble those of relay (principal) cells. They can be subdivided into brisk or sluggish and sustained or transient categories. They are stimulated transsynaptically from the visual cortex and have a characteristic variation in the latency of their spike response to such stimulation both at threshold and for suprathreshold stimuli. The pathway for this stimulation appears to be via cortical efferents to the LGN. Intrageniculate interneurons receive direct, monosynaptic retinal inputs, as determined by recording simultaneously from such interneurons and from the ganglion cells which provide excitatory input to them. Similar to relay cells, they are shown to have one or two major ganglion cell inputs. 3. Perigeniculate interneurons are generally binocularly innervated and give on-off responses to small spot stimuli throughout their receptive field. They respond well to rapid movement of large targets. They respond to electrical stimulation of the retina with a spike latency that falls between that of brisk transient and brisk sustained relay cells. This latency is one synaptic delay longer than that of brisk transient relay cell activation and suggests that they are excited by axon collaterals of these relay cells. Electrical stimulation of the visual cortex is also consistent with this model; the latency of the response of perigeniculate interneurons is approximately one synaptic delay longer than the latency of the response of brisk transient relay cells. 4. The interneuronal pathways described are consistent with proposed circuits that subserve the generation of IPSPs that arise in response to optic nerve and visual cortical stimulation. We now show that such inhibition has feed-forward (intrageniculate) and feed-back (perigeniculate) components that are mediated by two different classes of geniculate interneurons. It is suggested that the intrageniculate interneurons are involved in precise, spatially organized inhibition and that the perigeniculate interneurons are part of a more general, diffuse inhibitory system that modulates LGN excitability.

Temporal interactions in the cat visual system. II. Suppressive and facilitatory effects in the lateral geniculate nucleus

“…Unlike cells of the recurrent pathway (perigeniculate neurons), which are reported to respond well only to larger stimuli (Sanderson, 197 1;Dubin and Cleland, 1977;So and Shapley, 198 1;Xue et al, 1988) the intrageniculate interneurons should be driven maximally by small spots and less vigorously by large stimuli (Dubin and Cleland, 1977). Offset suppression observed in this study was, however, usually as strong for large stimuli as for small.…”

“…Studies of perigeniculate neurons indicate that they respond transiently and frequently respond equally to stimulus onset and offset (Sanderson, 1971;Dubin and Cleland, 1977;AhlsCn and Lindstriim, 198 1;So and Shapley, 198 1;Xue et al, 1988). In contrast, intracellular recordings from identified intrageniculate interneurons indicate that they give sustained responses similar in time course to those of sustained projection neurons (Sherman and Friedlander, 1988).…”

Linking Attention to Learning, Expectation, Competition, and Consciousness

“…Likewise, the data of Sillito, et al (1994, pp. 479-482) (Dubin and Cleland, 1977;Weber, Kalil, and Behan, 1989); see Figure 2d. (Grossberg, 1999a;Grossberg and Raizacla, 2000;Grossberg and Seitz, 2003;Grossberg and Williamson, 2001;Raizacla and Grossberg, 2001).…”

Temporal dynamics of binocular disparity processing with corticogeniculate interactions

“…The LGN comprises relay cells, which are exeitatory and project to cortex, and interneurono that ean inhibit relay cells (Sillito & Kemp, 1983). Doth intcrneurons and relay cells receive direct input from the retina (Dubin & Cleland, 1977). IIVhen the eortieo-thaJamie input is aboli:;hed (e.g., by aspiration or chernicaJ inactivation of eortex), then cells in the LGN show no orientation or length tuning (Sillito & Murphy, 1993).…”

“…Feedback from cortex is excitatory (Montero, 1990), but it goes to both interneurons (Weber, Kalil, & Behan, 1989) and relay cells (Dubin & Cleland, 1977). Due to this complex pattern of eonnections, eonflieting results have been reported: there are reports of exeitatory influences (Kalil & Chase, 1970), inhibitory influences (Hull, 1968), and rnixecl effects (Marrocco & McClurkin, 1985).…”