[The spread of excitation in surviving neocortical slices]

The propagation of excitation has been studied in neocortical guinea pig slices maintained in vitro. Stimuli were given at different distances from the chosen neuron. Comparison of latencies of the evoked impulse reactions indicated a complex structure and configuration of the vertically oriented ensemble of comparatively synchronously activated neurons. It is assumed that such an ensemble has a narrow (less than 300 microns) top layer II, a wide (approximately 600 microns and more) middle part in layer V and a narrowed (approximately 300 microns) basis in layer VI. A heterogeneity of the ensemble (the module) with respect to vertical propagation of excitation is found.