Observations on the Onset and Propagation of Excitation Waves in Neural Tissue

Abstract

The onset and propagation of waves in an excitable medium were investigated using the retinal Spreading Depression (rSD). The rSD is an ideal tool for this purpose. The retina of chicken, which was used in all experiments, is a close to two-dimensional system, in which the wave can easily be observed by optical techniques in time and space. rSD waves can be elicited by a variety of stimuli. Between stimulus and onset of the wave a temporal delay is always present. We found that the wave velocity is a function of the duration of this delay. In this paper we show, that within this time increasing fluctuations occur of system parameters.Another set of experiments deals with spatial correlations in the rSD. In some experiments we found the onset of the wave to be about 300 µm locally displaced with respect to the point of stimulus.In collision experiments, the spread velocity of two wavefronts approaching each other was measured. We found a significant increase in the velocity. This increase in velocity takes place on the last 250 µm before collision. This distance resembles the one found for local displacements, indicating a common origin.

Tracking Waves and Vortex Nucleation in Excitable Systems with Anomalous Dispersion

“…Moreover, one finds a low-period limit below which no stable wave trains exist. Exceptions to this normal scenario are found in the catalytic reduction of NO with CO on Pt100 surfaces [4], the 1,4cyclohexanedione Belousov-Zhabotinsky (CHD-BZ) reaction [5,6], in neuronal tissue [7], and perhaps in other biological systems [8]. In these cases, the dispersion relation shows nonmonotonic behavior, but nonetheless extends to infinitely large periods.…”

Dynamics of excitation pulses with attractive interaction: Kinematic analysis and chemical wave experiments

“…1. Similar anomalous behavior can be found also in neuronal systems [21], where it is referred to as "supernormal excitability," and possibly in aggregating populations of the widely studied social amoeba Dictyostelium discoideum [22].…”

Macroscopic Self-Organized Electrochemical Patterns in Excitable Tissue and Irreversible Thermodynamics

“…The immobilization of the charges if it happens around an electrode tip, will make the electrode "blind" to events even as far as 50 µm away. We have more experimental evidence that gaps in the gel stops propagation no matter how thin the gap [41]. Also the circling wave experiments clearly show that the inner circle of tissue only rarely shows waves, the solution gap between inner circle and outer ring of tissue acting as a barrier to waves (see the arrangement of circling waves and more discussion in [29] [42]).…”