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  • Title: [Differences in the functional organization of the frog and cat visual centers].
    Author: Mkrtycheva LI, Samsonova VG.
    Journal: Neirofiziologiia; 1975; 7(1):5-11. PubMed ID: 1207794.
    Abstract:
    Functional characteristics of neuronal responses of the frog tectum and the cat primary visual cortex were obtained under identical experimental conditions, the intensity and duration of flashes changing within the limits of 6 log. units. The comparison of the characteristics reveals a predominance of neurons with a short summation time and relatively lower thresholds in frogs, the response latencies being 5--7 times longer than those in cats. Nearly all the tectum units can react only to a very narrow range of photic energy different for different cells. In cats most cells react to changes in brightness within a range of 4--5 log. units; the units with a long summation time produce short latency responses with relatively higher thresholds. The revealed differences and comparison of various functional characteristics of neurons in the visual centre of both animals show that frogs possess fixed mechanisms of time and spatial interaction providing for the detection of stimulus brightness by means of inhibitory interaction of single units. In cats such interaction of neural populations and mutual inhibition between adjacent units of the visual cortex are not prominent. Complication and overlapping of interneuronal connections result in the convergence of day and night vision signals to one neuron and in the ability of single cells to react to the whole "working" light range used by the cat visual system.
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