Companies Collaborate to Develop Ultrasound-Based Brain-Computer Interface (BCI)
In 2023, significant advancements have been made in the field of brain-computer interface (BCI) technology. Neuralink, Paradromics, and Synchron, three prominent BCI developers, have made significant progress in their clinical trials, bringing the reality of fully implantable BCIs closer than ever before. However, a recent collaboration between Forest Neurotech and Butterfly Network has introduced a groundbreaking approach to BCI development using ultrasound technology.
The joint research effort, backed by a $20 million investment, aims to harness Butterfly Network’s compact ultrasound-on-a-chip technology to create a minimally invasive ultrasound BCI device for academic and research purposes. Unlike traditional BCI systems that rely on electrical signals, Forest Neurotech’s proposed device will use high-frequency sound waves to interface with the brain.
The scientific principles behind this approach are both unusual and simple. Direct focused ultrasound (FUS) waves have the ability to alter neurons’ action potentials, which are the ionic currents used by brain cells to communicate with each other. Additionally, ultrasound can estimate neural activity within brain regions by measuring changes in blood flow using the doppler effect. This technique, known as functional ultrasound imaging (fUSI), enables researchers to visualize and analyze neural activity.
By incorporating Butterfly Network’s ultrasound technology, Forest Neurotech aims to build a BCI with submillimeter accuracy in stimulating and recording brain activity. Ultrasound offers several advantages over other neural stimulation and imaging techniques. For stimulation, focused ultrasound waves can precisely target specific regions throughout the brain from outside the skull, providing flexibility and non-invasiveness. In contrast, electrical stimulation techniques are limited in their spatial reach, requiring invasive surgical procedures to access deep brain regions.
When it comes to recording brain activity, ultrasound also presents unique advantages. While recording deep neural activity through the skull is not feasible, it is possible to remove a piece of the skull and place the ultrasound device directly on the brain’s surface. Butterfly Network’s ultrasound-on-a-chip technology, which combines audio generation, steering, and recording capabilities into a compact device, will enable Forest Neurotech to stimulate brain regions using steered and focused ultrasound waves and measure neural activity through fUSI.
The fUSI technique estimates changes in neural activity by measuring changes in blood flow. As neurons require blood flow to function, an increase in neural activity leads to an increase in blood flow. By projecting ultrasound at a specific brain region and analyzing the returning sound waves, fUSI can estimate changes in blood flow and, consequently, the electrochemical activity of neurons. This technique has proven to be highly effective in imaging neural activity, surpassing initial expectations.
While ultrasound has been known to both record and control neural activity since the 1950s, the exact mechanisms behind its effects on neurons remain a mystery. Recent experiments involving isolated brain tissue from rodents have shown that high-frequency sound waves can open specific calcium ion channels, triggering neuronal firing. However, further research is needed to fully understand the physics of this interaction.
Forest Neurotech’s BCI system will require the implantation of multiple Butterfly ultrasound chips in a user’s skull to facilitate both stimulation and recording. While ultrasound stimulation can effectively penetrate bone, fUSI recording techniques are impeded by the skull’s attenuation of sound waves. To overcome this limitation, the transducers will be placed directly into the skull, flush with the surface of the dura, a protective membrane covering the brain.
The development of an ultrasound-based BCI holds immense potential for advancing our understanding of the brain and enhancing the capabilities of BCIs. By leveraging ultrasound technology, researchers can achieve precise and non-invasive stimulation and recording of brain activity. This collaboration between Forest Neurotech and Butterfly Network represents a significant step forward in the field of BCI development.
The collaboration between Forest Neurotech and Butterfly Network to develop an ultrasound-based BCI is truly groundbreaking. The use of ultrasound technology opens up new possibilities for non-invasive and precise stimulation and recording of brain activity. This approach offers advantages over traditional electrical stimulation and imaging techniques, which are often limited by their invasive nature and spatial reach.
The ability to use ultrasound to both stimulate and record neural activity is a significant advancement. While the exact mechanisms behind ultrasound’s effects on neurons remain unknown, recent experiments have provided valuable insights. The combination of Butterfly Network’s ultrasound-on-a-chip technology and Forest Neurotech’s expertise in BCI development holds great promise for the future of neuroscience and neurotechnology.
Functional ultrasound imaging (fUSI) is a particularly exciting technique that allows researchers to estimate changes in neural activity by measuring changes in blood flow. This non-invasive method provides a deeper understanding of brain function and can potentially revolutionize our ability to study and treat neurological disorders.
However, it is important to acknowledge the challenges associated with ultrasound recording through the skull. The attenuation of sound waves by the skull necessitates the placement of transducers directly on the brain’s surface, requiring a surgical procedure. Despite this limitation, the benefits of ultrasound-based BCIs far outweigh the additional invasiveness.
Overall, the collaboration between Forest Neurotech and Butterfly Network represents a significant milestone in BCI development. The use of ultrasound technology has the potential to revolutionize our understanding of the brain and pave the way for more advanced and effective BCIs. As research in this field continues to progress, we can expect further breakthroughs that will shape the future of neuroscience and neurotechnology.
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