The dynamic spatio-temporal behavior of visual responses in thalamus and cortex.
Due to eye and object movements the visual world changes on a rather fast time scale and the neuronal network of the primary visual pathway has to immediately react to these changes. Accordingly the neuronal activity patterns in the visual thalamus and cortex show a pronounced dynamic behavior which reenters the circuitry such that the actual cell responses are also guided by the activation history of the network. Thus, spatial and temporal aspects of visual receptive fields change not only by means of the actual visual stimulation hut also as a consequence of the state of the network. In this short review we summarize the different aspects which can influence the temporal firing patterns of cells in the visual thalamus (lateral geniculate nucleus, LGN) mainly by demonstrating how their inter-spike interval distributions will change. We then show that these firing patterns are able to change the spatial shape of receptive fields in the visual cortex (see Fig. 12 for a summary diagram). Finally, by means of a biophysical model, we will argue that the observed changes could serve to adjust the temporal and spatial resolution within the primary visual pathway to the different demands for information processing in an attentive as compared to a non-attentive state.
Wörgötter
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Institut für Physiologie, Ruhr- Universität Bochum, D-44780 Bochum, Germany. worgott@neurop.ruhr-uni-bochum.de
Suder
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Funke
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