The propagation of information from neuron to neuron through the synapse is, as a new study has shown, a two-way process. Scientists have found that postsynaptic cells can influence the behavior and state of presynaptic cells. An article about the new-to-science phenomenon in the human brain appeared in Nature Communications.
In traditional neurobiology, it is commonly believed that connections between neurons are one-way. That is, excitation is transmitted from the first neuron through the synapse (contact site) to the dendritic outgrowth of the second neuron, and so on. This is true, but a new study by neurophysiologists at the Austrian Institute for Science and Technology has proven that signals can travel down the chain between neurons in the opposite direction as well.
The researchers, led by Peter Jonas, focused on studying the neural pathways of the hippocampus, a small part of the brain that performs very important functions related to emotion, memory, navigation, and other systems. Hippocampal cells are innervated by moss-like fibers, which the scientists studied in vitro on samples from the rat brain.
“We did an experiment in which we sent single pulses along the axon of the mossy fiber and then recorded the response on the dendrites of the pyramidal cells. It turned out that not only the axon influences dendrite behavior, but also vice versa. That is, the synapse works like a teacher who changes the pace of information delivery if he sees that students are overloaded with new information during the lesson,” Jonas explained.