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Brain–Computer Interfaces - Index of

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BCIs Based on Signals from Between the Brain and Skull 235<br />

6.2.5 Tuebingen, Germany<br />

Birbaumer’s well-established EEG-based BCI work has led to an initial ECoGbased<br />

BCI study [43]. This work used <strong>of</strong>f-line analysis <strong>of</strong> ECoG and compared it<br />

to <strong>of</strong>f-line analysis <strong>of</strong> EEG recorded from different subjects under a slightly different<br />

paradigm. The algorithm performance on ECoG was comparable to that found<br />

for EEG results, although the maximum results for EEG were better than those for<br />

ECoG. However, the number <strong>of</strong> trials, sampling rates, and applied filtering (among<br />

other parameters) were different, making conclusions difficult. Of greater interest is<br />

a single ECoG recording experiment done with a completely paralyzed subject as<br />

part <strong>of</strong> a larger study comparing BCI detection algorithm function on brain activity<br />

from healthy subjects and subjects with complete paralysis [44]. The subject<br />

gave informed consent for surgical implantation <strong>of</strong> ECoG electrodes by using voluntarily<br />

control <strong>of</strong> mouth pH to communicate [44, 45]. However, the BCI detection<br />

algorithms in this study did not produce results greater than chance for any <strong>of</strong> the<br />

subjects who were completely paralyzed (4 with EEG electrodes and 1 with ECoG).<br />

See the Chapters “Brain–Computer Interface in Neurorehabilitation” and “Brain–<br />

Computer <strong>Interfaces</strong> for Communication and Control in Locked-in Patients” in this<br />

volume for further discussion <strong>of</strong> this issue.<br />

6.2.6 University Hospital <strong>of</strong> Utrecht<br />

Ramsey et al. [46] included ECoG analysis as a minor component (1 subject) <strong>of</strong> their<br />

fMRI study <strong>of</strong> working memory as a potential BCI input. They looked at the ECoG<br />

near the onset <strong>of</strong> a working memory load and reported the increased activity that<br />

occurred in averaged ECoG. Although they were able to show agreement between<br />

the fMRI and ECoG modalities, they did not do actual BCI detection experiments<br />

either online or <strong>of</strong>fline. Further, the necessary use <strong>of</strong> working memory in any task<br />

for which BCI operation <strong>of</strong> technology was desired makes this signal source appear<br />

to be only practical for detecting concentration or perhaps intent to perform a task.<br />

As such, working memory detection could be used to gate the output <strong>of</strong> another BCI<br />

detection method, blocking control signals from the other detection method unless<br />

working memory was also engaged. While this might improve BCI function during<br />

no-control periods, by requiring concentration during BCI operation, it may also<br />

limit BCI use for recreational tasks such as low intensity channel surfing. Further, it<br />

could falsely activate BCI function during composition tasks when the user was not<br />

yet ready to start BCI typing.<br />

6.2.7 The University <strong>of</strong> Michigan – Ann Arbor (Kipke)<br />

In a recent study using microelectrodes in rats performing a motor learning task<br />

in Kipke’s Neural Engineering Laboratory, ECoG from bone-screw electrodes was<br />

analyzed in addition to neural spike activity and local field potentials from microelectrodes<br />

[2]. This work found ECoG signals that occurred only during the learning<br />

period. Comparison <strong>of</strong> ECoG to local field potentials recorded from microelectrodes

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