Summary: Researchers developed an innovative method to measure human brain activity at the cellular level, unveiling how our brain processes numbers.
Utilizing microelectrodes during “awake” brain surgery, the researchers found that individual neurons specialize in handling specific numbers, becoming especially active when their “preferred” number is presented.
This breakthrough brings us a step closer to understanding the mechanisms of cognitive functions. It’s made possible by patients with brain tumors, who participated in studies during their surgeries.
Key Facts:
- The method developed by the team from TUM allows for the detection of human brain activity at the cellular level.
- Researchers found that individual neurons in the human brain specialize in handling specific numbers.
- The development of the procedure was possible due to patients with brain tumors who agreed to have sensors implanted and performed test tasks during their surgeries.
Source: TUM
Measuring human brain activity down to the cellular level: until now, this has been possible only to a limited extent.
With a new approach developed by researchers at the Technical University of Munich (TUM), it will now be much easier. The method relies on microelectrodes along with the support of brain tumor patients, who participate in studies while undergoing “awake” brain surgery.
This enabled the team to identify how our brain processes numbers.
We use numbers every day. It happens in a very concrete way when we count objects. And it happens abstractly, for example when we see the symbol “8” or do complex calculations.
In a study published in the journal Cell Reports, a team of researchers and clinicians working with Simon Jacob, Professor of Translational Neurotechnology at the Department of Neurosurgery at TUM’s university hospital Klinikum rechts der Isar, was able to show how the brain processes numbers.
The researchers found that individual neurons in the brains of participants were specialized in handling specific numbers. Each one of these neurons was particularly active when its “preferred” number of elements in a dot pattern was presented to the patient. To a somewhat lesser degree this was also the case when the subjects processed number symbols.
“We already knew that animals processed numbers of objects in this way,” says Prof. Jacob.
“But until now, it was not possible to demonstrate conclusively how it works in humans. This has brought us a step closer to unravelling the mechanisms of cognitive functions and developing solutions when things go wrong with these brain functions, for example.”
Recording individual neurons is a challenge
To get to this result, Prof. Jacob and his team first had to solve a fundamental problem.
“The brain functions by means of electrical impulses,” says Simon Jacob. “So it is by detecting these signals directly that we can learn the most about cognition and perception.”
There are, however, few opportunities for direct measurements of human brain activity. Neurons cannot be individually recorded through the skull. Some medical teams surgically implant electrodes in epilepsy patients.
However, these procedures do not reach the brain region believed to be responsible for processing numbers.
Innovative advancement of established approaches
Simon Jacob and an interdisciplinary team therefore developed an approach that adapts established technologies and opens up entirely new possibilities in neuroscience. At the heart of the procedure are microelectrode arrays that have undergone extensive testing in animal studies.
To ensure that the electrodes would produce reliable data in awake surgeries on the human brain, the researchers had to reconfigure them in close collaboration with the manufacturer.
The trick was to increase the distance between the needle-like sensors used to record the electrical activities of a cell.
“In theory, tightly packed electrodes will produce more data,” says Simon Jacob.
“But in practice the large number of contacts stuns the implanted brain region, so that no usable data are recorded.”
Patients support research
The development of the procedure was possible only because patients with brain tumors agreed to support the research team. While undergoing brain surgery, they permitted sensors to be implanted and performed test tasks for the researchers.
According to Simon Jacob, the experimental procedures did not negatively affect the work of the surgical team.
A greater number of medical centers can conduct studies
“Our procedure has two key advantages,” says Simon Jacob. First, such tumor surgeries provide access to a much larger area of the brain.
“And second, with the electrodes we used, which have been standardized and tested in years of animal trials, many more medical centers will be able to measure neuronal activity in the future“ says Jacob.
While epilepsy operations are performed only at a small number of centers and on relatively few patients, he explains, many more university hospitals perform awake operations on patients with brain tumors.
“With a significantly larger number of studies with standardized methods and sensors, we can learn a lot more in the coming years about how the human brain functions,” says Simon Jacob.
About this numeric processing and neuroscience research news
Author: Paul Hellmich
Source: TUM
Contact: Paul Hellmich – TUM
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Human acute microelectrode array recordings with broad cortical access, single-unit resolution, and parallel behavioral monitoring” by Simon Jacob et al. Cell Reports
Abstract
Human acute microelectrode array recordings with broad cortical access, single-unit resolution, and parallel behavioral monitoring
Highlights
- Microelectrode arrays are implanted in patients undergoing awake brain surgery
- Open craniotomies grant access to large parts of the left-hemispheric cortex
- High-quality neuronal activity is obtained at multiple levels of resolution
- Human parietal cortex neurons are tuned to non-symbolic and symbolic numbers
Summary
There are vast gaps in our understanding of the organization and operation of the human nervous system at the level of individual neurons and their networks.
Here, we report reliable and robust acute multichannel recordings using planar microelectrode arrays (MEAs) implanted intracortically in awake brain surgery with open craniotomies that grant access to large parts of the cortical hemisphere.
We obtained high-quality extracellular neuronal activity at the microcircuit, local field potential level and at the cellular, single-unit level.
Recording from the parietal association cortex, a region rarely explored in human single-unit studies, we demonstrate applications on these complementary spatial scales and describe traveling waves of oscillatory activity as well as single-neuron and neuronal population responses during numerical cognition, including operations with uniquely human number symbols.
Intraoperative MEA recordings are practicable and can be scaled up to explore cellular and microcircuit mechanisms of a wide range of human brain functions.
