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Quantum Sensors Measure Brain Activity with Pinpoint Accuracy

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Quantum sensors could be used to indicate early biomarkers for brain diseases in space and time, based on the results of a University of Sussex (England) study. Researchers showed that quantum sensors, when used with magnetoencephalography (MEG), can track changes in the brain, such as a slowdown in brain activity, spatiotemporally.

In the future, the sensors could be used to scan patients periodically to check for changes in brain activity, according to the researchers.

“The sensors contain a gas of rubidium atoms, said professor Peter Kruger, who leads the Quantum Systems and Devices lab at the University of Sussex. “Beams of laser light are shone at the atoms, and when the atoms experience changes in a magnetic field, they emit light differently. Fluctuations in the emitted light reveal changes in the magnetic activity in the brain.”

The researchers used two types of sensors in the work: optically pumped magnetometers (OPMs) and superconducting quantum interference devices (SQUIDs). Both were used to measure brain response, and both sensors were paired with MEG, a noninvasive technique to detect and record the magnetic fields associated with electrical activity in the brain.

Using OPMs and SQUIDs to measure brain responses to flash and pattern reversal stimuli, the team observed highly reproducible signals with consistency across different participants in the experiment and different visual stimuli.

The researchers said that typically, MEG is used with a SQUID array to measure the brain’s magnetic fields. However, while both sensors performed well in experiments, the researchers found that OPM-MEG was better than SQUID-MEG at tracking brain signals in space and time. They believe that a primary reason for this is because the OPM sensors can be placed closer to the visual cortex than the SQUIDs.

The researchers then recorded visually evoked brain fields to demonstrate that closer sensors could be exploited to improve temporal resolution. The temporal resolution of OPMs showed a twofold improvement, compared to SQUIDs.

Tests showed that OPM-MEG could record neurophysiological signals of a common origin at different locations at different times. Simultaneous vector recordings of visually evoked brain fields in the primary and associative visual cortex, where the researchers consistently found a time lag on the order of 10 to 20 ms, illustrated the capability for improved spatiotemporal signal tracing.

“We have shown for the first time that quantum sensors can produce highly accurate results in terms of both space and time,” researcher Aikaterini Gialopsou said. “While other teams have shown the benefits in terms of locating signals in the brain, this is the first time that quantum sensors have proved to be so accurate in terms of the timing of signals.”

According to Kruger, quantum technology is what makes the sensors so accurate. “The quantum sensors are accurate within milliseconds, and within several millimeters,” he said. The highly accurate sensors could allow scientists to track brain signals in ways that are inaccessible to other types of sensors.

As a noninvasive investigational tool, the OPM-MEG quantum sensor could provide information about propagating signals, source localization, neural speed, and brain circuits. The benefits of OPM-MEG could be important at the research and clinical levels — its high spatiotemporal resolution could allow scientists to better investigate neural networks. It could also be applied in clinical populations at different stages of a disease.

Further, in patients with mild cognitive symptoms, the sensors could be used to monitor the progression of the disease over years and evaluate therapy response. At the preclinical stage, the sensors could be used to detect potential biomarkers for people at risk of developing a disease such as Alzheimer’s disease.

Researcher Aikaterini Gialopsou with the magnetic shield where participants’ brain signal measurements are taken. Using two types of sensors, a team at the University of Sussex showed, for the first time, that quantum sensors produce highly accurate results of brain activity in terms of both space and time. Courtesy of the University of Sussex.
Researcher Aikaterini Gialopsou with the magnetic shield where participants’ brain signal measurements are taken. Using two types of sensors, a team at the University of Sussex showed, for the first time, that quantum sensors produce highly accurate results of brain activity in terms of both space and time. Courtesy of the University of Sussex.
“It’s our hope with this development, that in discovering this enhanced function of quantum brain scanners, the door is opened to further developments that could bring about a quantum revolution in neuroscience,” Gialopsou said. “This matters because, although the scanners are in their infancy, it has implications for future developments that could lead to crucial early diagnosis of brain diseases, such as ALS, MS, and even Alzheimer’s. That’s what motivates us as a team.”

The research was published in Scientific Reports (www.doi.org/10.1038/s41598-021-01854-7).

Photonics Handbook
GLOSSARY
quantum
Smallest amount into which the energy of a wave can be divided. The quantum is proportional to the frequency of the wave. See photon.
quantum optics
The area of optics in which quantum theory is used to describe light in discrete units or "quanta" of energy known as photons. First observed by Albert Einstein's photoelectric effect, this particle description of light is the foundation for describing the transfer of energy (i.e. absorption and emission) in light matter interaction.
Sensors & DetectorsResearch & Technologyeducationquantumquantum sensorsopticsoptical sensorsquantum opticsquantum optical sensorBiophotonicsbrainmedicalmagnetometryBiometrologyEuropeUniversity of Sussexlasersdevicesbrain activityTest & Measurement

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