Brain and BCI

BCI Introduction

•In summary:

–A BCI is a communication system based on direct measures of brain activity rather than physical movement. 

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–To use a typical BCI, a user must put on an electrode cap and perform specific mental tasks.

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–BCIs are not like the devices portrayed in sci-fi stories. They can’t read minds. They are currently very slow.

EEG

Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by the firing of neurons within the brain.

Types of BCI

•BCI systems can be classified under different categories based on which type of signals are used, whether invasive or non invasive, whether feedback is provided or not. Accordingly the major classifications of BCI systems are:

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1.Invasive BCI:- In this type electrodes are implanted directly in to the grey matter of the brain during neuro-surgery thereby direct neural contact via pins. This is used for repairing damaged sight and provides new functionality to paralyzed people. Eg: ECoG based BCI.

2.Partially Invasive BCI:- Electrodes are implanted inside the skull but outside the brain rather than within the grey matter.

3.Non Invasive BCI:- Here electrodes placed on the skull. Limitation is poor signal resolution because skull dampens the signal. Eg: EEG based BCI.

4.Cell culture BCI:- In this type of BCI devices to interface with neural cells and entire neural networks in cultures outside animals, and recording is done from individual neurons grown on semiconductor chip to learn how human brain performs at cellular level.

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1.ElectroCorticography (ECoG) based BCI:- uses electrical activity of brain taken from beneath the skull, electrodes placed above the cortex beneath the dura matter.

2.EEG based BCI:- uses EEG signals from the scalp. The advantages are ease of use, noninvasive, reproducibility, low set up cost but extensive training is required before users can work, susceptibility to noise.

3.Magneto Encephalography (MEG) based BCI:- This is a non invasive BCI which uses the magnetic fields produced by electrical activity of brain.

4.fMRI based BCI:- used for non invasive BCI. It measures blood flow in brain using MRI. Blood flow correlates to neural activity.

5.NIRS (near infra red spectroscopy) based BCI:- uses the Infrared signals from the brain for their operation.

How EEG Works

Brainwaves (EEGs) reflect the brain’s electrical activity. A neuron at rest is like a little battery. Whenever it is active, its voltage briefly changes.

About

Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by the firing of neurons within the brain.

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