Caltech New Brain-Machine Interface Reading Minds With Ultrasound
A less invasive method to decode the intentions of the brain. What happens in your brain when you scroll this page In other words, which areas of your brain work, what neurons do they talk to, what signals do they send to your muscles? The principal aim of neuroscientists developing brain-machine interfaces (BMI’s) is to map neural activity to corresponding behaviors. The instruments that read and interpret the mind’s activity and provide instruction to a computer.
The development of BMIs is mainly limited by the need for invasive brain surgery to read neural activity. But a new type of minimally invasive BMI has now been developed by a partnership in Caltech to read brain activity that corresponds to motion planning. It can accurately map brain activity from specific regions deep within the brain with a resolution of 100 microns utilizing functional ultrasound (FUS) technology.
A significant step towards developing less invasive yet highly able BMIs is the new FUS technology.
Sumner Norman, an Andersen Labor postdoc student and co-first author of the new study: “Invasive forms of brain-machine interfaces can give movement back to those who have lost it due to neurological injury or illness. “Unfortunately, only a few people with the most severe paralysis can implant electrodes on their brain. Functional ultrasound is an incredible new way of recording detailed brain activity without damaging the brain tissue. We have pushed the boundaries and are thrilled to predict ultrasound neuroimage movements. FUS is an enormous young technology – our first step in creating more high performance, less invasive BMI.” A new study is undertaken in collaboration between laboratory managers such as the Tianqiao and Chrissy Chen Brain Interface Center at Caltech Tianqiao, James G. Boswell and the Center for Neuroscience, Professors, and Leaders of Neuroscience and Chrisy G.Boswell. Shapiro is an associate professor at Chen Institute. On 22 March 2021, the Neuron newspaper published a paper describing the work.
All brain activity measurement tools generally have inconvenience. Implanted electrodes (electrophysiology) can measure activity very accurately at the neurons’ level. Still, of course, they need to be implanted into the brain. Non-invasive techniques such as FMRI can image the whole brain but require bulky and costly machinery. Non-invasive methods are needed. No surgery is needed, but electroencephalography (EEGs) can measure activity at a low spatial resolution only.
The ultrasound functions by emitting high-frequency sound pulses and measuring how the sound vibrations echo in the natural substance, for example, in several tissues of the human organism. The sound travels through these types of tissue at different speeds and mirrors the limits between them. This technique is usually used in utero and other diagnostic imagery for the fetus. The inner motion of organs can also be “heard” by ultrasound. As an ambulance, the red blood cells will, by approaching the sources of the Ultrasound waves, increase in pitch and decrease as they flow
away. “When part of the brain becomes more active, blood flow in the area increases. A key issue in this work was whether there is sufficient photo information to decode behavior if we have a technique like a functional ultrasound that gives us high-resolution pictures of brain flux dynamics in both space and time?” Shapiro says. Shapiro says. Shapiro says. Shapiro says. “Yeah, the answer. This procedure produced detailed images of the dynamic of neural signals in our target region, which other non-invasive techniques, such as fMRI, cannot be seen. Our electrophysiology details were producing, but the procedure was much less invasive.” This collaboration was launched as the ESPCI University of Paris, Inserm, and CNRS invited Mickael Tanter, a functional ultrasound pioneer, to give a workshop at Caltech in 2015. The talk was attended, and collaboration was proposed by former Andersen postdoctoral scholar Vasileios
Christopoulos. The NIH BRAIN initiative was awarded to Shapiro, Andersen, and Tanter to conduct research. Caltech was led by Norman, David Maresca (today assistant professor of technology at the Delft University), and Christopoulos (the former postdoctoral fellow from Shapiro laboratory). Maresca and Christopoulos are co-authors of the new research, together with Norman. The technology was developed using non-human primates who were taught to perform simple tasks involving the movement of their eyes or weapons in certain directions with certain indicators. The fUS measured brain activity in the postural parietal cortex (PPC) as Primates completed the tasks. For decades, the Andersen lab studied PPC and has previously produced electrophysiological maps of brain activity in the region. The researchers compared brain imaging activity in fUS to detailed electrophysiology data previously obtained to evaluate for accuracy.
Next, the team supported the Chen Brain-Machine Interface Center at Caltech to decode the non-human primate’s intentions before the action-driven changes of fUS images could be used.
Within seconds, the algorithm predicted which behavior the non-human primate would perform (eye movement or reach), movement direction (left or right), and when the move was planned.
“The first step was to indicate that ultrasound can collect brain signals related to the idea of physical motion planning,” says Maresca, an ultrasound imaging expert. For recording these signals, functional ultrasound imaging is ten times more sensitive and better than functional MRI. This finding is central to the success of ultrasound interfaces in the brain-machine.
