Using an EEG-Based Brain-Computer Interface for Virtual Cursor Movement with BCI2000

Summary

In this video, we demonstrate the steps required to run a brain-computer interface experiment, including setting up the EEG cap, calibrating the system, and training the user to move a cursor in two dimensions using imagined movements.

Abstract

A brain-computer interface (BCI) functions by translating a neural signal, such as the electroencephalogram (EEG), into a signal that can be used to control a computer or other device. The amplitude of the EEG signals in selected frequency bins are measured and translated into a device command, in this case the horizontal and vertical velocity of a computer cursor. First, the EEG electrodes are applied to the user s scalp using a cap to record brain activity. Next, a calibration procedure is used to find the EEG electrodes and features that the user will learn to voluntarily modulate to use the BCI. In humans, the power in the mu (8-12 Hz) and beta (18-28 Hz) frequency bands decrease in amplitude during a real or imagined movement. These changes can be detected in the EEG in real-time, and used to control a BCI ([1],[2]). Therefore, during a screening test, the user is asked to make several different imagined movements with their hands and feet to determine the unique EEG features that change with the imagined movements. The results from this calibration will show the best channels to use, which are configured so that amplitude changes in the mu and beta frequency bands move the cursor either horizontally or vertically. In this experiment, the general purpose BCI system BCI2000 is used to control signal acquisition, signal processing, and feedback to the user [3].

Protocol

Experimental Procedure

1. Connecting the EEG Electrodes
   1. Electrodes will be attached to the scalp using an EEG cap; this simplifies the process of ensuring that the electrodes are in the proper location on the scalp, as specified by the 10-20 international system.
   2. To place the cap, mark the vertex on the subject's scalp using a felt-tip pen or some other similar method. To do so, begin by locating the nasion and inion on the subject. Using a tape measure, find the distance between these two locations. The point midway between the two points, or 50% of the distance, is the vertex. Make a mark at that point for later reference. Other 10-20 points....

Discussion

1. It is vital that the electrode impedances are low, but that too much gel was not used to lower the impedance. A single bad channel can affect all the others through the common-average reference. If the impedance cannot be reduced after several tries, it is recommended that a quick-insert electrode be used, which can simply be inserted into the bad electrode through the hole that the needle is placed through for injecting the gel, and taped in place.
2. During the first session, the subject may have difficulty imagining the requ.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
BCI2000- Compatible Amplifer System	g.USBamp		http://www.gtect.at
BCI2000- Compatible Amplifer System	Tucker-Davis Technologies	Rx5 or Rx 7	http://www.tdt.com
EEG cap	Electro-cap International		http://www.electro-cap.com At a minimum, the cap should have electrodes over hand and feet areas (C3, C4, and Cz). Additional channels can be used for control (CP3, CP4, CPz) and for spatial filtering as well, which will improve the signal quality.
Conductive gel	Electro-cap International		http://www.electro-cap.com
PC			Running Windows XP or Vista (at least Pentium 4, 2 GHz, 1 GB RAM)
Two monitors			Each at least 19in (one for the subject and one for the researcher)