Bioelectrics

Neurons are enclosed in semipermeable membranes.  Electrochemical forces are charged and directed by protein pumps and channels that move ions (sodium +1, potassium +1, and chloride -1) through this membrane.

At rest, sodium-potassium pumps use energy to move sodium ions out and potassium ions in (at a ratio of 3 to 2) each against their concentration gradient creating a resting galvanic potential effected by ion concentrations.

When a neuron is triggered, channels allow ion flow driven by electrical and concentration driving forces. Sodium channels open first, allowing sodium ions to flow in, then potassium channels open allowing potassium ions to flow out. Within a few milliseconds, the process ends and the neuron returns to its resting state.

This neural activation causes a minute spike in ion flux which contributes to triggering (or inhibiting) associated neurons and can be measured locally with sensitive electromagnetic field sensing instrumentation.

You can learn more about neurons in this video 2-Minute Neuroscience: The Neuron.

Creating a Mind Machine Interface (MMI) requires, of course, connecting to a brain. Indirect connections can be made using sensors that track things like eye movements, breathing patterns, or other voluntary movement. Direct connections can be made using sensors that read bioelectric signals coming from the brain’s neural activity.

One method of measuring bioelectric signals from the brain is Electroencephalography (EEG) which measures signals directly at the brain. However, the mapping and interpretation of these signals is complex, specialized, and unique to an individual’s synaptic connection mapping (which is more unique than fingerprints). EEG is explained nicely in this great blog post by Bryn Farnsworth, Ph.D: What is EEG (Electroencephalography) and How Does it Work?.

The brain’s neural firing activity can also be measured utilizing the peripheral nervous system. The mapping of the peripheral neural pathways are independent of the brain’s synaptic connection mapping (as shown in this Biology Dictionary definition of the nervous system). So by connecting at the end away from the brain (the neuromuscular junction) the mapping is well defined and the control intent of the brain is easily differentiated.

Electromyography (EMG) involves coupling to the signals of cellular ionic flux on the surface of skin (surface EMG) with specially designed silver-chloride electrodes, or through the skin with subcutaneous electrodes that pierce the skin. These electrical signals are extremely small (measured in microvolts) and are buried in electrical noise several thousand times larger than the EMG signal.

You can learn more about EMG in this EMG article at Johns Hopkins or this blog post on EMG at SimpliFaster.

The design goals for EMG measurement are to produce meaningful signals optimally correlated to the true level of neural activity and ideally immune from environmental and superfluous interference.

Primarily required are: optimized bioelectric signal coupling to the target ionic flux, precision interfacing and amplification electronic circuitry, measurement noise reduction techniques, and advanced signal processing algorithms that extract, differentiate, and identify neural signaling signatures.

Optimizing these measurement technologies and techniques for useful applications is the focus of our research at Applied Neural Research Corp.