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William H. Calvin
University of Washington
Seattle WA 98195-1800 USA
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|Calvin, W.H., Sypert, G.W., Ward, A.A., Jr. (1968).|
Structured timing patterns within bursts from epileptic neurons in undrugged monkey cortex.
Experimental Neurology 21:535-549.
copyright ©1968 by authors and publisher
EXPERIMENTAL NEUROLOGY 21, 535—549 ( 1968)
Structured Timing Patterns within Bursts from Epileptic Neurons in Undrugged Monkey Cortex
WILLIAM H. CALVIN, GEORGE W. SYPERT, AND ARTHUR A. WARD, JR.
Departments of Neurological Surgery, and of Physiology and Biophysics,
University of Washington School of Medicine, Seattle, Washington 98105
Received April 10,1968
While normal cortical neurons often show ill-defined, labile bursts during spontaneous firing, stereotyped high-frequency bursts every 50-200 msec are characteristic of the firing patterns of neurons near chronically alumina-induced epileptic foci in sensorimotor cortex of awake, undrugged rhesus monkeys. Computer-assisted analysis of the timing patterns within bursts revealed an unusually long interval between the first and second spikes of these epileptic bursts, with the later spikes of the burst time-locked to the second spike, not the first spike. In some neurons, this stereotyped "remainder" of the burst would begin at a highly variable time following the first spike. In other neurons, this first interval was bimodal, with the remainder of the burst starting either 3 or 4 msec following the first spike. In a third class of epileptic neuron, the first interval was unusually long and remarkably lacking in variability (8.6 + 0.2 msec). Other neurons, especially those located further away from the epileptogenic focus, showed less stereotyped bursts without the long first intervals. One explanation considered for these phenomena is that the neuron is being stimulated antidromically (first spike) and responds repetitively (remainder of the burst).Introduction
Bursts are a common feature of the spontaneous firing of many cortical neurons In epileptic neurons, they are the dominant feature of the spike train. This paper is concerned with the fine structure of the timing within such burst patterns, using methods described in the previous paper ( 5 ) .
For bursting neurons, mean frequency of firing would not be expected to provide an adequate characterization of information content. For example, the femoral summation of postsynaptic potentials (PSP) in neurons fed by such a bursting cell might be expected to provide a potent stimulus, perhaps explaining why epileptic bursting activity can disrupt normal activity of healthy cells. Even in normal cells, the observer can detect clusters of high-frequency firing (Fig. 1A); it is, however, difficult to decide where such a normal burst begins or ends, thus preventing one from explicitly....