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Brain–Computer Interfaces - Index of

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228 J.E. Huggins<br />

Fig. 3 Diagram <strong>of</strong> equipment setup for a BCI experiment during clinical monitoring<br />

therefore includes splitting the analog signals from the ECoG electrodes prior to<br />

digitization so that they can be sent both to the clinical recording equipment and to<br />

the BCI. This setup must be carefully tested according to hospital regulations for<br />

electrical safety. While signal splitting can increase the electrical noise apparent in<br />

the ECoG signals, it has been successfully used by several researchers [3, 17]. The<br />

sheer quantity <strong>of</strong> electrical devices that are used in the hospital presents an additional<br />

technical challenge that the high quality <strong>of</strong> clinical recording equipment can only<br />

partly overcome. Sources <strong>of</strong> electrical noise in a hospital room can range from autocycling<br />

pressure cuffs on a patient’s legs that are intended to reduce post-operative<br />

complications, to medical equipment being used in the next room (or occasionally<br />

by the patient sharing a semi-private room), to other electrical devices such as the<br />

hospital bed itself. Vulnerability to electrical noise may be increased by the location<br />

<strong>of</strong> the electrodes used as the ground and recording reference. These important electrodes<br />

may be ECoG electrodes, bone screw electrodes or scalp electrodes. When a<br />

scalp electrode is used as the reference, vulnerability to widespread electrical noise<br />

can easily result.<br />

5 Successful ECoG-Based BCI Research<br />

The use <strong>of</strong> ECoG for BCI research has advantages <strong>of</strong> signal quality, spatial resolution,<br />

stability, and (eventually) ease <strong>of</strong> BCI setup. ECoG can be obtained from<br />

large areas <strong>of</strong> the cortex, and ECoG shows event-related signal changes in both

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