Mirror image: neurons in the brain begin to clone after reaching a ‘tipping point’ of activity

Subatomic particles do it. Now the observation that groups of brain cells seem to have their own version of quantum entanglement, or “spooky action at a distance”, could help explain how our minds combine experiences from many different senses into one memory.

Previous experiments have shown that the electrical activity of neurons in separate parts of the brain can oscillate simultaneously at the same frequency – a process known as phase locking. The frequency seems to be a signature that marks out neurons working on the same task, allowing them to identify each other.

Dietmar Plenz and Tara Thiagarajan at the National Institute of Mental Health in Bethesda, Maryland, wondered whether more complicated signatures also link groups of neurons. To investigate, they analysed neuronal activity using arrays of electrodes implanted in the brains of two awake macaque monkeys and embedded in dish-grown neuron cultures.


In both cases, the researchers noticed that the voltage of the electrical signal in groups of neurons separated by up to 10 millimetres sometimes rose and fell with exactly the same rhythm. These patterns of activity, dubbed “coherence potentials”, often started in one set of neurons, only to be mimicked or “cloned” by others milliseconds later. They were also much more complicated than the simple phase-locked oscillations and always matched each other in amplitude as well as in frequency.

Perfect clones

“The precision with which these new sites pick up on the activity of the initiating group is quite astounding – they are perfect clones,” says Plenz.

Importantly, cloned signals only appeared after one region had reached a threshold level of activity. Plenz likens this to the “tipping point” in human societies when a trend becomes adopted by large numbers of people. This threshold might ensure that our attention is only captured by significant stimuli rather than by every single signal.

Since the coherence potentials seemed unique, each one could represent a different memory Plenz suggests. Their purpose may be to trigger activity in the various parts of the brain that store aspects of the same experience. So a smell or taste, say might trigger a coherence potential that then activates the same potential in neurons in the visual part of the brain.

Karl Friston at University College London calls the discovery “a missing piece of the jigsaw puzzle” in terms of brain message transmission.

Journal reference: PLoS Biology, DOI: 10.1371/journal.pbio.1000278