User:Ahtippur/sandbox

Flexible brain-computer interfaces (fBCIs) are microelectode arrays fabricated on layers of polymers (e.g. polyimide) as seen in  flexible electronics 1) to record and process neuronal signaling patterns and 2) to use this data to control an external device. The increased bendability and deformability of these devices make them less harmful after immediate implantation and long-term to brain tissues and helps them access areas of the brain that stiffer silicon-based arrays cannot. Peripheral flexible microelectrode arrays can attain resolutions comparable to those of invasive silicon-based arrays and higher than peripheral silicon-based arrays, making them good candidates for  BCIs requiring the ability to resolve signaling on the microscale.

Brain-Computer Interface Background
Brain-computer interfaces (BCIs) allow communication directly between the brain and external devices, allowing patients for example to operate an arm remotely or move a wheelchair by thinking about it. The origin of BCIs was the electroencephalogram (EEG). Created in 1924 by the Germany physicist and professor Hans Berger, this device used silver-foil electrodes attached to a patient's scalp to record brain activity via a galvanometer. Today, EEG has become an important diagnostic and research tool in studying patients' neuronal signalling patterns in vivo and can record neuronal signaling with high temporal resolution; it has also been pursued since the 1980s in noninvasive BCI research. Though there have been some successes in using this technology (including Lawrence Farwell and Emanual Donchin helping Locked-In syndrome patients communicate using a speech synthesizer, Jessica Bayliss at the University of Rochester allowing patients to control their environment by turning lights on and off, and Bin He at the University of Minnesota using EEG to control the flight of a virtual helicopter in 3D space). Though EEGs have potential in BCI applications because of their high temporal resolution, they are limited due to susceptibility to environmental noise and the need to train patients extensively to properly use them.

More widespread is the use of microelectrodes in BCIs for recording neuronal signalling. Developed originally in the late 1930s and early 1940s, microelectrodes are usually thin, rigid rods with a sharp tip, allowing the electrode to be inserted into the brain and record extracellular neuronal signals from the extracellular or intracellular neuron space. DThese penetrating microelectrodes have been organized into arrays

-Started in 1970s.

-Some big pioneers and events they were a part of: Fetz (UW), Georgopoulos (JHU), Nicoleilis (Duke), and others.

-Current state (Braingate, Kuiken videos)

Flexible Electronics Background
-Silicon is stiff (139 GPa); does not flex or conform to situations

-Flexible electronics where polymers or other flexible materials (i.e. silk) are printed with circuitry, allowing the "chips" to bend

-Started to be developed in 1960s and 1970s; use in society in started in early 2000s

-Examples of use (e.g. chip that wraps around wrist)

Integration
-External device will stay the same; fBCI means the microelectrode array recording signals will be different

-Fabrication example for flexible microelectrode array or BCI and description of the high resolution, multiplexed devices created (Viventi et al. 2011, LaPlaca et al. 2010, one more paper I have)

Benefits and Drawbacks of fBCIs
-Mechanical mismatch between soft brain tissue (0.2 kPa) and silicon microelectrode array

-As shown by LaPlaca et al. 2010 and others, flexible electrode shows more compliance

-Will not cause tissue damage (hemorrhaging, inflammation), unlike silicon penetrating arrays

-Expected to be durable long term (10 years)

Applications and Current Uses of fBCIs
-Viventi: Record neuronal signaling with high resolution, so detect micropatterns of epilepsy

-LaPlaca: Research pathologies of traumatic brain damage and strokes using flexible arrays

-Other papers I have where research findings came from flexible electrode use

-Viventi: fBCI records neuronal signaling when person looks at screen; can use this information to go backwards and decode from neuronal signaling pattern where the person is looking

-Places were fBCI can go (between hemispheres, into sulci, etc.)

Future Aims of fBCI Technology
-Record from two hemispheres to better control a device like a prosthetic arm (fBCI between hemispheres)

-High resolution neuronal activity with larger arrays to get detailed information on brain patterns, decode patterns to control external devices such as a wheelchair or television cursor

-Microelectrode array records epilepsy (and other stuff) with high spatial resolution, then produces electrical currents in certain patterns to counteract the electrical activity of the epilepsy

-Flexible electrode to be able to record and stimulate areas of the brain that are deep or hard to get to (e.g. for deep brain stimulation)