Summary: Researchers at the Technical University of Munich (TUM) have developed a reliable method to record human brain activity at the cellular level, revealing how individual neurons respond to numbers.
Using microelectrode arrays during awake brain surgery, the team showed that single neurons can be tuned to specific quantities: a neuron becomes most active when its preferred number of items is shown and responds, to a lesser extent, to symbolic number representations such as numerals.
This advance brings us closer to understanding the neural mechanisms of numerical cognition and offers a practical approach for wider clinical and research use, made possible by the participation of patients undergoing tumor surgery.
Key Facts:
- The team from TUM adapted microelectrode array technology to record human neuronal activity with single-cell resolution.
- Individual neurons in the human parietal cortex show tuning for specific non-symbolic and symbolic numbers.
- The method was validated in awake craniotomy procedures with consenting patients who performed behavioral tasks while recordings were made.
Source: TUM
Recording human brain activity at single-cell resolution
Directly measuring the electrical activity of individual neurons in the human brain has been technically limited. The approach developed by researchers at the Technical University of Munich uses planar microelectrode arrays (MEAs) implanted intracortically during awake brain surgery. Open craniotomies performed for tumor removal provide broad cortical access, enabling recordings across large portions of the hemisphere.
By collecting extracellular signals at multiple spatial scales—from local field potentials and microcircuit activity to single-neuron spikes—the team could examine how neurons in the parietal association cortex behave during numerical tasks. These experiments demonstrate both population-level dynamics, such as traveling oscillatory waves, and precise single-unit responses tied to number processing.
Numbers are a constant part of human life: we count physical items, recognize numeral symbols, and perform abstract calculations. The study shows that the human brain represents quantity in a way that mirrors findings from animal studies, with individual neurons preferring particular numerosities. When participants viewed dot arrays displaying a given number of elements, neurons tuned to that numerosity fired robustly. The same neurons also responded, though less strongly, to symbolic representations such as Arabic numerals.
“Previous animal work suggested number-selective neuronal responses,” explains Simon Jacob, Professor of Translational Neurotechnology at TUM’s Department of Neurosurgery. “Now we can show how similar mechanisms operate in the human parietal cortex, taking us closer to understanding the cellular basis of numerical cognition.”
Technical challenges and innovations
Recording single neurons in humans presents major hurdles. Neurons cannot be recorded through the skull, and most clinical electrode implants target different brain regions. To reach parietal areas implicated in number processing, the team adapted MEAs that had been tested extensively in animal models. Working closely with the manufacturer, they reconfigured the arrays for use in awake tumor surgeries, increasing the spacing between needle-like contacts to avoid overstimulating the tissue and to yield stable, high-quality signals.
Dense contact packing can, in theory, provide more channels, but in practice it may disturb local tissue and reduce data quality. The adjusted design balances spatial coverage with signal reliability, enabling robust single-unit and microcircuit recordings during clinical procedures.
Patient participation and broader applicability
This work was made possible by patients with brain tumors who consented to intraoperative research recordings and performed brief behavioral tasks while awake. According to the investigators, the research did not interfere with standard surgical care. Because awake tumor surgeries are performed at many neurosurgical centers, and because the MEA technology used here is standardized and grounded in animal research, the method can be adopted by more hospitals than the relatively few centers that perform intracranial epilepsy monitoring.
Expanding access to intraoperative MEA recordings across centers should accelerate discoveries about how individual neurons and local circuits support human cognition. With a larger, standardized dataset, researchers can probe not only numerical processing but also memory, perception, language, and other complex brain functions, and ultimately inform strategies to treat disorders that impair these processes.
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., published in Cell Reports.
Abstract
Human acute microelectrode array recordings with broad cortical access, single-unit resolution, and parallel behavioral monitoring
Highlights
- Microelectrode arrays implanted during awake brain surgery enable high-quality multiscale recordings.
- Open craniotomies permit access to extensive regions of the left-hemispheric cortex, including parietal association areas.
- Data capture spans microcircuit dynamics, local field potentials, and single-unit neuronal activity.
- Neurons in the human parietal cortex are tuned to both non-symbolic quantities and symbolic number representations.
Summary
Large gaps remain in our knowledge of human nervous system organization at the cellular and microcircuit levels. This study reports robust acute multichannel recordings from planar MEAs implanted intracortically during awake tumor surgeries with open craniotomies. High-quality extracellular signals were obtained across spatial scales, enabling analysis of oscillatory traveling waves, single-neuron responses, and population activity during numerical cognition tasks. Intraoperative MEA recordings are feasible and scalable, opening the door to systematic exploration of cellular and microcircuit mechanisms that underlie diverse human brain functions.