The fate of axon terminals in visual cortex during transsynaptic atrophy of the lateral geniculate nucleus

1971 ◽  
Vol 34 (1) ◽  
pp. 53-60 ◽  
Author(s):  
B.G. Cragg
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Axon Terminals ◽  
Lateral Geniculate

The β sector of the rabbit's dorsal lateral geniculate nucleus

1988 ◽  
Vol 233 (1270) ◽  
pp. 17-32 ◽  
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Cortical Neurons ◽  
Main Part ◽  
Small Region ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Axon Terminals ◽  
Perigeniculate Nucleus ◽  
Lateral Geniculate ◽  
Dorsal Lateral Geniculate

The β sector of the rabbit’s dorsal lateral geniculate nucleus is a small region of nerve cells scattered among the fibres of the geniculocortical pathway. In its topographical relations it resembles the perigeniculate nucleus of carnivores, which contains neurons driven by geniculate and visual cortical neurons and which sends inhibitory fibres back into the geniculate relay. We have traced retinogeniculate, geniculocortical and corticogeniculate pathways in rabbits by using horseradish peroxidase or radioactively labelled proline and have found that the β sector resembles the perigeniculate nucleus in receiving no direct retinal afferents, sending no efferents to the visual cortex (V–I), and receiving afferents from the visual cortex. The corticogeniculate afferents are organized so that the visual field map in the β sector and the main part of the lateral geniculate relays are aligned, as are the maps in the cat’s perigeniculate nucleus and the main part of the geniculate relay of carnivores. Electron microscopical studies show similar types of axon terminals in the rabbit and the cat for the main part of the geniculate relay on the one hand and for the β sector and the perigeniculate nucleus on the other. Earlier observations that the proportion of putative inhibitory terminals (F-type terminals) is lower in the rabbit’s than the cat’s geniculate region are confirmed. A major difference between the β sector and the perigeniculate nucleus has been revealed by immunohistochemical staining for GABA. Whereas almost all of the cat’s perigeniculate cells appear to be GABA ergic, the proportion in the β sector is much lower, and not significantly different from that found in the main part of the rabbit’s geniculate relay. It is concluded that the β sector shares many of the organizational features of the perigeniculate nucleus. A common developmental origin seems probable, but the functional differences remain to be explored.

scholarly journals Elastic Net Model of Ocular Dominance: Overall Stripe Pattern and Monocular Deprivation

1994 ◽  
Vol 6 (4) ◽  
pp. 615-621 ◽  
Author(s):  
Geoffrey J. Goodhill ◽  
David J. Willshaw
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Primary Visual Cortex ◽  
Ocular Dominance ◽  
Monocular Deprivation ◽  
Elastic Net ◽  
Global Order ◽  
Stripe Pattern ◽  
Lateral Geniculate ◽  
Stripe Width

The elastic net (Durbin and Willshaw 1987) can account for the development of both topography and ocular dominance in the mapping from the lateral geniculate nucleus to primary visual cortex (Goodhill and Willshaw 1990). Here it is further shown for this model that (1) the overall pattern of stripes produced is strongly influenced by the shape of the cortex: in particular, stripes with a global order similar to that seen biologically can be produced under appropriate conditions, and (2) the observed changes in stripe width associated with monocular deprivation are reproduced in the model.

Oscillations and Long-Lasting Correlations in a Model of the Lateral Geniculate Nucleus and Visual Cortex

2000 ◽  
Vol 84 (4) ◽  
pp. 1863-1868 ◽  
Author(s):  
Kyle L. Kirkland ◽  
Adam M. Sillito ◽  
Helen E. Jones ◽  
David C. West ◽  
George L. Gerstein
Keyword(s):  
Experimental Data ◽  
Visual Cortex ◽  
Cell Membrane ◽  
Lateral Geniculate Nucleus ◽  
Feedback Inhibition ◽  
Frequency Range ◽  
Lateral Geniculate ◽  
Low Threshold ◽  
Thalamocortical System

We have previously developed a model of the corticogeniculate system to explore cortically induced synchronization of lateral geniculate nucleus (LGN) neurons. Our model was based on the experiments of Sillito et al. Recently Brody discovered that the LGN events found by Sillito et al. correlate over a much longer period of time than expected from the stimulus-driven responses and proposed a cortically induced slow covariation in LGN cell membrane potentials to account for this phenomenon. We have examined the data from our model, and we found, to our surprise, that the model shows the same long-term correlation. The model's behavior was the result of a previously unsuspected oscillatory effect, not a slow covariation. The oscillations were in the same frequency range as the well-known spindle oscillations of the thalamocortical system. In the model, the strength of feedback inhibition from the cortex and the presence of low-threshold calcium channels in LGN cells were important. We also found that by making the oscillations more pronounced, we could get a better fit to the experimental data.

scholarly journals Contrast Sensitivity Is Enhanced by Expansive Nonlinear Processing in the Lateral Geniculate Nucleus

2008 ◽  
Vol 99 (1) ◽  
pp. 367-372 ◽  
Author(s):  
Thang Duong ◽  
Ralph D. Freeman
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Visual Processing ◽  
Linear Prediction ◽  
Visual Pathway ◽  
Low Contrast ◽  
Response Data ◽  
Lateral Geniculate ◽  
Nonlinear Processing ◽  
Contrast Response

The firing rates of neurons in the central visual pathway vary with stimulus strength, but not necessarily in a linear manner. In the contrast domain, the neural response function for cells in the primary visual cortex is characterized by expansive and compressive nonlinearities at low and high contrasts, respectively. A compressive nonlinearity at high contrast is also found for early visual pathway neurons in the lateral geniculate nucleus (LGN). This mechanism affects processing in the visual cortex. A fundamentally related issue is the possibility of an expansive nonlinearity at low contrast in LGN. To examine this possibility, we have obtained contrast–response data for a population of LGN neurons. We find for most cells that the best-fit function requires an expansive component. Additionally, we have measured the responses of LGN neurons to m-sequence white noise and examined the static relationship between a linear prediction and actual spike rate. We find that this static relationship is well fit by an expansive nonlinear power law with average exponent of 1.58. These results demonstrate that neurons in early visual pathways exhibit expansive nonlinear responses at low contrasts. Although this thalamic expansive nonlinearity has been largely ignored in models of early visual processing, it may have important consequences because it potentially affects the interpretation of a variety of visual functions.

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