[Summarized extracellular postsynaptic potential of a single axon, an EEG quantum in the rabbit neocortex]

The possibility to record an EEG quantum following negative spikes with small amplitude was studied in the rabbit's neocortex. In about half of the averagings of the focal post-spike ECoGs recorded with a low-resistance microelectrode the spike was followed by a microsignal of synaptic form. The small amplitude and the negative sign of the spike's main phase pointed to a true extracellular leading off of biopotentials. A relatively small ratio between the amplitudes of the spikes and the post-spike signals shows that the latter are not afterpotentials of the spikes. They do not reflect discrete PSPs of single synapses, because they were recorded with relatively thick microelectrodes. The latency of the post-spike signals corresponded to their monosynaptic nature. Hence, the recorded signals are the EEG quanta. Their recording is a relatively simple procedure.