Jul 09, 2021 08:00:00

Human learning may be related to the timing of neuron firing and the 'deviation' of brain waves.

For many years, brain researchers have

treated 'firing', when nerve cells (neurons) reach action potentials , as a measure of brain activity. However, a new treatise published by an American research team suggests that not only the frequency with which neurons fire, but also the 'timing of fire' may play an important role in the brain.

Phase precession in the human hippocampus and entorhinal cortex: Cell
https://www.cell.com/cell/fulltext/S0092-8674(21)00496-7

A New Kind of Information-Coding Seen in the Human Brain | Quanta Magazine
https://www.quantamagazine.org/a-new-kind-of-information-coding-seen-in-the-human-brain-20210707/

Joshua Jacobs, an associate professor of brain research at Columbia University, who co-authored a paper published in Cell , the premier journal in the field of life sciences, said, 'What really matters is how much neuron activity occurs. It's not exactly when it happens. '

Previously, a phenomenon related to the continuous increase and decrease of brain waves and the timing of neuronal firing has been confirmed in place cells in the hippocampus. Place cells are neurons that fire when an animal passes through a specific place (place receptive field), and the place receptive field changes flexibly due to changes in the environment. Kamran Diba , a neuroscientist at the University of Michigan, states that the human brain adjusts receptive fields to the current environment, whether on the highway or at home.

A specific place cell corresponds to a specific place receptive field, and the corresponding place cell ignites faster toward the center of the place receptive field. Then, as the distance from the center increases, the firing slows down, and when it eventually enters another place receptive field, new corresponding place cells start firing.

However, it is known that not only the firing speed changes when heading toward the center of the place receptive field, but also the rhythm for theta waves that appear in the hippocampus with a consistent rhythm of 4 Hz to 8 Hz. As it approaches the center of the place receptive field, the phase of the place cell firing timing with respect to theta waves advances. This is a phenomenon called 'theta phase precession', and by examining the relationship between theta wave phase and place cell firing timing, is the animal approaching or moving away from the center of the place receptive field? Can be judged.

So far, theta phase aging in place cells has been confirmed in mice, bats, marmosets, etc. However, in humans, it is difficult to monitor neuron firing unless it is an invasive method, and it seems that a clear pattern could not be confirmed. So the research team analyzed theta phase aging using data collected from 13 epilepsy patients who already had electrodes implanted to map the electrical signals of seizures. In addition, this data was observed about individual neuron firing with electrodes while the patient moved the joystick and moved around in the VR space.

As a result of analyzing the data, the research team reports that theta phase precession was confirmed in 12% of the monitored neurons. Human brain waves are more complex than rodents, and there is less neural activity devoted to location navigation, so advanced statistical analysis was required to detect theta phase precession.

When an animal moves from one place receptive field to another, theta phase precession delays the firing of the last neuron associated with the first place receptive field, while accelerating the firing of the first neuron in the next place receptive field. Therefore, the firing of the two neurons occurs at about the same time.

It is believed that this phenomenon strengthens the synapses of the two neurons and helps to infiltrate the brain with the routes that animals travel. In recent years theta phase precession is time and image have been studied results announcement to be involved in recognition of possible brain have associated time and images in the same way to recognize the spatial position Sex is suggested.

The lead author of the treatise, Salman Qasim of Columbia University, argues that theta phase precession may be a universal information coding mechanism across mammals. 'If we don't track the relative timing of neural activity, we may lack a lot of information coding,' he said.

For many years, strengthening synapses has been considered important for humans to learn things, but humans do not necessarily require vast amounts of learning data like artificial intelligence training, and learn from just a few cases. It is possible. It is hoped that thinking that theta phase precession is related to learning may explain why the brain learns information quickly.