[Generation of action potentials by cortical neurons in turtles. Dendritic and somatic spikes]

Action potentials in single neurons were studied intracellularly in the general cortex of the turtle. It is shown that neurons generate full spikes and, besides them, partial spikes of different amplitude. The partial spikes can be combined into a full spike. The threshold of generation and the amplitude of each partial spike are not constant values, they fluctuate within certain limits spontaneously and gradually without any change in the resting potential of the neuron. Somatic spike and dendritic spikes can be distinguished. Zones of the dendritic spikes initiation are located at different distances from the soma. Under orthodromic activation of cortical neurons the dendritic spikes are generated in succession and conducted to the soma electrotonically with a decrement. The dendritic spikes can reach the threshold for initiation of a somatic spike.