New scientific research has discovered a type of neuron that would act as a kind of clock or metronome, keeping the brain in sync.

These brain cells, called metronomic neurons , may play a key role in coordinating neural activity.

Gamma waves: the female conductors of the orchestra?

Our brain is like a big concert hall. To be able to direct and manage numerous and complex cognitive processes, it is necessary that several groups of neurons are activated and, like the different members of a musical orchestra, work in harmony to produce a symphony of processes that allow us to perceive and interact with our environment.

But as with orchestras, the brain may need a conductor to keep all its parts active and in sync. In this regard, several neuroscientists argue that gamma rhythms — brain waves that fluctuate at a frequency of about 40 cycles per second — may play this role.

It is believed that these oscillations of gamma waves would act as a kind of clock or metronome that coordinates the transfer of information from one group of neurons to another, so there seems to be ample evidence to suggest that the role of gamma waves in cognitive processing is fundamental.

During decades of research in humans and other animals, patterns have been found in many areas of the brain that have been associated with a variety of cognitive processes, such as attention or working memory. Some studies have even linked alterations in these gamma oscillations to various neurological diseases, including Alzheimer’s disease and schizophrenia.

However, there seems to be no absolute consensus. Some neuroscientists believe that the role that gamma waves would play would not be as decisive, and claim that these rhythms could correlate with, but not provide a significant contribution to, brain activity.

Metronome neurons: studies in mice

To investigate whether gamma waves actually play a role in the coordination of neural activity, neuroscientists Moore and Shin at Brown University began their study in mice , discovering that a previously unknown set of neurons would be acting as a metronome.

These newly discovered cells were firing rhythmically at gamma frequencies (30-55 cycles per second), regardless of what was happening in the outside environment, and the probability of an animal detecting a sensory stimulus was associated with the ability of these neurons to manage time.

Moore and Shin began their research as a general search for brain activity related to touch perception. To do this, they implanted electrodes in a specific area of the mouse’s somatosensory cortex, which is responsible for processing sensory input. Then, they measured neural activity while observing the rodents’ ability to feel subtle taps on their whiskers.

The researchers focused on gamma oscillations and decided to analyze a specific group of brain cells, called fast-accelerating interneurons , because previous studies had suggested that they might be involved in generating these fast rhythms. The analysis revealed that, as they expected, the degree to which these cells would fire at gamma frequencies predicted how well the mice would be able to detect contact with their whiskers.

But when the neuroscientists went deeper into the study, they found something strange. They expected that the cells that would be activated in response to a sensory stimulus would show the strongest links to perceptual accuracy. However, by examining the cells, this link had been weakened. Then, they realized that perhaps the cells are not sensory and act as timekeepers, regardless of what is happening in the environment.

By repeating the analysis only with the cells that did not respond to the sensory stimulus, the link with perceptual accuracy became stronger. In addition to not being disturbed by the external environment, this specific subset of neurons tended to increase regularly at gamma-range intervals, like a metronome. Moreover, the more rhythmic the cells were, the better the animals seemed to detect the whiskers . What seemed to be happening, following the initial metaphor of the concert hall, is that the better the conductor is at managing time, the better the orchestra will do.

The Clocks of the Brain

We’ve all heard of the internal clock or the biological clock. This is because our brain responds to the passage of time through physiological systems that allow us to live in harmony with the rhythms of nature, such as the cycles of day and night, or the seasons.

The human brain uses two “clocks”. The first is our internal clock, which allows us to detect the passage of time and is essential to our daily lives. With this clock we can, for example, measure the time that has elapsed between two activities, know how much time we have spent doing a task such as driving or studying, since otherwise this type of task would be extended indefinitely without us having any notion of the time that has passed.

The second watch could not only run parallel to the first, but also compete with it. This brain system would be housed inside the first clock, and would work in collaboration with the cerebral cortex to integrate temporal information . This mechanism would be executed, for example, in the moments in which our body pays attention to how time has passed.

Just as necessary is the feeling of being aware of the time that has passed as maintaining a memory of what we have done during the process. And this is where a brain structure such as the hippocampus comes into play, responsible for processes such as inhibition, long-term memory or space, as well as playing a fundamental role in remembering the passage of time, according to the latest scientific studies.

In the future it will be essential to continue developing new treatments and researching the relationship of these brain structures and our internal clocks with neurodegenerative diseases such as Alzheimer’s and other types of dementia, as well as with mental disorders and brain diseases involving processes of degeneration of the notion of time and body space.

Bibliographic references:

  • Brown University (2019). Neuroscientists discover neuron type that acts as brain’s metronome. Science Daily. Available at: https://www.sciencedaily.com/releases/2019/07/190718112415.htm.