Spiral Waves in Disinhibited Mammalian Neocortex

Abstract

Spiral waves are a basic feature of excitable systems. Although such waves have been observed in a variety of biological systems, they have not been observed in the mammalian cortex during neuronal activity. Here, we report stable rotating spiral waves in rat neocortical slices visualized by voltage-sensitive dye imaging. Tissue from the occipital cortex (visual) was sectioned parallel to cortical lamina to preserve horizontal connections in layers III-V (500-m-thick, ϳ4 ϫ 6 mm 2 ). In such tangential slices, excitation waves propagated in two dimensions during cholinergic oscillations. Spiral waves occurred spontaneously and alternated with plane, ring, and irregular waves. The rotation rate of the spirals was ϳ10 turns per second, and the rotation was linked to the oscillations in a one-cycle-one-rotation manner. A small (Ͻ128 m) phase singularity occurred at the center of the spirals, about which were observed oscillations of widely distributed phases. The phase singularity drifted slowly across the tissue (ϳ1 mm/10 turns). We introduced a computational model of a cortical layer that predicted and replicated many of the features of our experimental findings. We speculate that rotating spiral waves may provide a spatial framework to organize cortical oscillations.

Delays and weakly coupled neuronal oscillators

“…Most of these rhythms (at least in vertebrates) are generated by the coherent oscillations of many coupled neurons. Sometimes they are synchronous and in other cases they are organized into patterns such as waves (for example in the swimming pattern of the lamprey; Cohen et al 1992) or even rotating waves (in certain brain slice preparations; Huang et al 2004. ) Thus, one of the outstanding theoretical questions in our understanding of neural rhythms is how the coupling interacts with the intrinsic dynamics to generate these patterns of oscillations.…”

The importance of different timings of excitatory and inhibitory pathways in neural field models

“…Travelling waves of activity are also of interest. Experimentally, these can be induced by stimulating pharmacologically treated neural tissue slices (Pinto & Ermentrout 2001a;Huang et al 2004); they have also been observed in several different areas of the cortex of awake animals, often when no stimulation 152…”

Channel noise-induced phase transition of spiral wave in networks of Hodgkin-Huxley neurons

“…Stable rotating spiral waves in rat neocortical slices visualized by voltagesensitive dye imaging were found in experiments [6,7]. As noted in [6,7], spiral waves might serve as pacemakers for the emergent population to generate periodic activity in a nonoscillatory network without the need for individual cellular pacemakers. It is interesting to simulate and investigate the formation and breakup of spiral waves in networks of neurons with different topologies.…”

“…breakup, channel noise, factor of synchronization, probability of long-range connection Collective electrical behaviors of neurons and oscillators in networks often have spatiotemporal patterns [1][2][3][4][5][6][7][8][9][10][11]. A spiral wave is one such spatial pattern and is often observed in excitable and oscillatory media.…”