Tag Archives: DARPA brain

Decoding Brain Signals with a Credit Card

A man unable to speak after a stroke has produced sentences through a system that reads electrical signals from speech production areas of his brain, researchers reported in July 2021…The participant had a stroke more than a decade ago that left him with anarthria—an inability to control the muscles involved in speech. Because his limbs are also paralyzed, he communicates by selecting letters on a screen using small movements of his head, producing roughly five words per minute.

To enable faster, more natural communication, neurosurgeon Edward Chang of the University of California, San Francisco, tested an approach that uses a computational model known as a deep-learning algorithm to interpret patterns of brain activity in the sensorimotor cortex, a brain region involved in producing speech . The approach has so far been tested in volunteers who have electrodes surgically implanted for non-research reasons such as to monitor epileptic seizures.

In the new study, Chang’s team temporarily removed a portion of the participant’s skull and laid a thin sheet of electrodes smaller than a credit card directly over his sensorimotor cortex. To “train” a computer algorithm to associate brain activity patterns with the onset of speech and with particular words, the team needed reliable information about what the man intended to say and when….So the researchers repeatedly presented one of 50 words on a screen and asked the man to attempt to say it on cue. Once the algorithm was trained with data from the individual word task, the man tried to read sentences built from the same set of 50 words, such as “Bring my glasses, please.” 

With the new approach, the man could produce sentences at a rate of up to 18 words per minute, Chang says…The system isn’t ready for use in everyday life, Chang notes. Future improvements will include expanding its repertoire of words and making it wireless, so the user isn’t tethered to a computer roughly the size of a minifridge.

Excerpts from Kelly Servick, Brain signals ‘speak’ for person with paralysis, Science, July 16, 2021

Planting Electronics in Brains

 An implantable brain device that literally melts away at a pre-determined rate minimizes injury to tissue normally associated with standard electrode implantation, according to research led by a team from the Perelman School of Medicine at the University of Pennsylvania. …Thin, flexible neural electrode arrays with fully bioresorbable construction based on patterned silicon nanomembranes (Si NMs) as the conducting component.

“Dissolvable silicon electronics offer an unprecedented opportunity to implant advanced monitoring systems that eliminate the risks, cost, and discomfort associated with surgery to extract current devices used for post-operative monitoring,” said senior co-author Brian Litt, MD,….“This study tested the usefulness of temporary, dissolvable monitoring systems capable of providing continuous streams of data for guiding medical care over predetermined periods of time — from days to months — before dissolving.”

The device is made of layers of silicon and molybdenum that can measure physiological characteristics and dissolve at a known rate, as determined by its thickness. For example, the team used the device to record brain waves in rats under anesthesia, as well as voltage fluctuations between neurons (EEGs), and induced epileptic spikes in intact live tissue. A separate experiment demonstrated a complex, multiplexed array made from these materials that could map rat-whisker sensing capabilities at high resolution.

These electrophysiological signals were recorded from devices placed at the surface of the brain cortex (the outer layer of tissue) and the inner space between the scalp and skull. Chronic measurements were made over a 30-day period, while acute experiments demonstrated device operations over three to four hours.

The type of neurophysiologic features measured by the new device are commonly used for diagnosing and treating such disorders as epilepsy, Parkinson’s disease, depression, chronic pain, and conditions of the peripheral nervous system. “….

This work was funded by the Defense Advanced Research Projects Agency, the Penn Medicine Neuroscience Center,  and others.

See Next-Gen Electrodes: Proof-of-Concept Animal Study Shows that Flexible, Dissolvable Silicon Electronic Device Holds Promise for Brain Monitoring , Press Release, May 5, 2016

See also Nature Materials

The US Military and the Peripheral Nervous System