Brain Computer Interfaces: Sci-Fi Meets Reality

If you could have a superpower, what would it be?

Flying? Shape-shifting? Mind-reading? Telepathy? Telekinesis?

Well, what if I told you, you could?

Enter Brain Computer Interfaces. But first, a brief introduction to:

The most complex object known in the universe 🧠

The brain receives information through our five senses, assembles it in a way that has meaning for us, and stores it into our memory. But against popular belief, the brain does not act alone. Working alongside it, is the spinal cord, together of which make up the central nervous system (CNS), and the spinal and cranial nerves, together of which make up the peripheral nervous system (PNS).

Composition

Cerebrum: The largest part of the brain, composed of the right and left hemispheres. Performs higher functions such as interpretation of our senses, speech, reasoning, and fine control of movement.

Cerebellum: Located under the cerebrum. Its function is to coordinate muscle movements, maintain posture, and balance.

Brainstem: Central core of the brain that connects the cerebrum and cerebellum to the spinal cord. It’s responsible for automatic functions such as breathing, heart rate, body temperature, digestion, and sneezing.

Limbic system: situated between the brainstem and the cerebral areas. Includes the hypothalamus (body temperature and hormones), amygdala (consolidation and emotion), and the hippocampus (learning and memory).

Lobes

Frontal Lobe

  • Personality, behavior, emotions
  • Judgment, planning, problem solving
  • Speech: speaking and writing
  • Body movement
  • Intelligence, concentration, self awareness

Parietal lobe

  • Interprets language, words
  • Sense of touch, pain, temperature
  • Interprets signals from vision, hearing, motor, sensory and memory
  • Spatial and visual perception

Occipital lobe

  • Interprets vision (colour, light, movement)

Temporal lobe

  • Understanding language
  • Memory
  • Hearing
  • Sequencing and organization

Neurons

The tree branch-like structures extending from the neuron are called dendrites, the area where neurons receive most of their information. There are receptors on the dendrites that are designed to pick up signals (from other neurons) that come in the form of chemicals called neurotransmitters. The signals picked up can cause electrical changes in the neuron that will be interpreted in the soma (cell body).

The soma takes all of the info from the dendrites and puts it together in an area called the axon hillock. If the signal is strong enough, it is then sent to the axon. At this point, the signal is called an action potential. The action potential travels down the axon, covered in myelin, an insulating material that helps prevent the signal from degrading.

The last step for the action potential is the axon terminals. When the signal reaches the axon terminals, it can cause the release of neurotransmitters. The structures on the far right of the diagram represent the dendrites of another neuron. When neurotransmitters are released from the axon terminals, it interacts with the dendrites of the other neuron and then the process repeats.

Now back to BCIs..

BCIs allows users to perform tasks using their brain signals instead of their muscles. The user generates brain signals which represent a certain intention, and the BCI decodes the signals and translates them into commands for an output device to accomplish it.

There are 3 types of BCIs:

  • Semi-invasive
  • Invasive

Electroencephalography (EEG)

It mostly records and measures post synaptic signals (that are excited by neurotransmitters binding to the receptors on the post synaptic membrane) from areas of the brain surrounding each electrode .

EEGs provide an image of electrical activity represented in waves of varying frequencies, amplitudes, and shapes. It can be used to measure spontaneous brain activity or brain activity that occurred during an event (event related potentials), like the completion of a task.

Clinical applications of EEGs include monitoring sleep for diagnosis of sleep disorders and other types of brain dysfunctions.

Electrocorticography (ECoG)

Some pros of ECoGs are that they record signals of higher amplitude than EEGs and offer better spatial resolution and spectral bandwidth.

In addition to lower-frequency (<40 Hz), ECoG includes higher-frequency (>40-Hz gamma band) activity up to 200 Hz. Gamma activity is important because it exhibits very precise functional localization; is highly correlated with specific aspects of motor, language, and cognitive function; and is linked to the firing rates of individual neurons.

Individual finger, hand, and arm movements have been decoded successfully from ECoG which can enable users to control a prosthetic hand or to select characters using motor-imagery. ECoGs have controlled 1- or 2-dimensional cursor movements using motor/sensory imagery or working memory.

Invasive

Invasive electrodes come in many forms: single electrodes, electrodes with multiple contacts at the tip or along the shaft, multi-electrode arrays (MEA), or combinations of all these.

Electrodes can have random lengths up to several cm or even mm in a MEA. Intracortical electrodes typically show local field potentials and detectable action potentials of 0–5 identifiable neurons per contact. Electrodes can be specifically targeted at specific cerebral areas although accuracy decreases with implantation depth.

The Future

BCIs can operate many different devices, from cursors to wheelchairs to robotic arms. A few people with severe disabilities are already using a BCI for basic communication and control in their daily lives.

They may eventually be used routinely to replace or restore useful functions for people severely disabled by neuromuscular disorders and improve rehabilitation for people with strokes, head trauma, and other disorders.

There are several headsets with scalp sensors on the market already that can be used with a computer to create a system for controlling software applications. Similar headsets have been incorporated into video games, some of which claim to enhance focus and concentration via EEG-based neurofeedback.

TL;DR

BCIs allows users to perform tasks using their brain signals instead of their muscles. The user generates brain signals which represent a certain intention, and the BCI decodes the signals and translates them into commands for an output device to accomplish it.

There are 3 types of BCIs: non-invasive, semi-invasive, and invasive.

EEGs are a non-invasive BCI technique used to measure electrical activity of the brain using electrodes, minuscule electrical conductors. They are most commonly placed on the scalp to detect the electrical activity of the neurons in the cerebral cortex.

EEGs provide an image of electrical activity represented in waves of varying frequencies, amplitudes, and shapes. They can be used for diagnosing sleep disorders.

ECoGs record activity from the cortical surface (on the brain) and are semi-invasive because they require a craniotomy/surgery to implant a subdural or epidural electrode array.

Invasive BCIs, as the name suggests, are more difficult due to surgical interventions. Recordings can be deeper but cannot cover the whole neocortex.

Invasive electrodes come in many forms: single electrodes, electrodes with multiple contacts at the tip or along the shaft, multi-electrode arrays (MEA), or combinations of all these.

BCIs must first be made suitable for long-term independent use as well as make progress in 3 critical areas: development of hardware, validation and dissemination, and proven reliability and value for many different user populations.

BCIs can operate many different devices, from cursors to wheelchairs to robotic arms. A few people with severe disabilities are already using a BCI for basic communication and control in their daily lives.

BCI Researcher and Innovator at TKS

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