The brain’s billions of neurons form an incredibly complex network that seems to work in a synchronized manner. Because electrical signals in the organ form larger patterns that are called brain waves, it has been thought that only a large number of cells working together can have an important influence on the rest of the brain’s function. Now experiments on the cortex area of mouse brains suggests that even a single cell in the brain can have large implications on the rest of the organ’s electrical activity.
From a statement by the Howard Hughes Medical Institute:
Studying anesthetized rats, they used one electrode to spur a neuron to fire rapidly and used another electrode nearby to activate the local neuronal connections. A third electrode was used to pick up the larger pattern emitted by all the neurons in the area. They wanted the overall brain state to remain constant during the experiment, but instead found that tickling one neuron could cause the entire brain state to change.
“Initially, this was very inconvenient,” says Dan [Yang Dan]. But then the researchers realized that the phenomenon deserved more attention. Looking more closely, they verified that a neuron firing at high frequency could switch the brain from a “non-REM pattern” of activity to a “REM pattern,” and vice versa.
The result was counterintuitive. “Every neuron makes connections to roughly 1,000 other neurons, but most of those are quite weak,” says Dan. A target cell won’t respond unless many, many neurons that connect to it fire at the same time and therefore she says it’s surprising that a single neuron could change the activity of the whole brain. “Single neurons have more weight than we used to think,” she says.
Dan doesn’t yet know how one cell could exert such power. The researchers had to repeatedly and rapidly fire a cell to cause the pattern to switch, so they might be emulating the effect of many cells firing at once. A neuron doesn’t normally fire in that way, so it is an open question whether the activity of a single neuron could change overall brain pattern under normal circumstances.
Press release: Breaking the Waves: A Single Neuron Can Change the Activity of the Whole Brain …
Research abstract: Visual Coding and Cortical Plasticity: From Synapse to Perception
Image: Pyramidal neurons forming a network in the brain. These are nerve cells from the cerebral cortex that have one large apical dendrite and several basal dendrites. Colour-enhanced light microscopy Credit: Dr Jonathan Clarke. Wellcome Images