Author/Editor		Logar, Vito; Škrjanc, Igor; Belič, Aleš; Brežan, Simon; Koritnik, Blaž; Zidar, Janez
Title		Identification of the phase code in an EEG during gripping-force tasks: a possible alternative approach to the development of the brain-computer interfaces
Type		članek
Source		Artif Intell Med
Vol. and No.		Letnik 44, št. 1
Publication year		2008
Volume		str. 41-9
Language		eng
Abstract		Background: The subject of brain-computer interfaces (BCIs) represents a vast and still mainly undiscovered land, but perhaps the most interesting part of BCIs is trying to understand the information exchange and coding in the brain itself. According to some recent reports, the phase characteristics of the signals play an important role in the information transfer and coding. The mechanism of phase shifts, regarding the information processing, is also known as the phase coding of information. Objective: The authors would like to show that electroencephalographic (EEG) signals, measured during the performance of different gripping-force control tasks, carry enough information for the successful prediction of the gripping force, as applied by the subjects, when using a methodology based on the phase demodulation of EEG data. Since the presented methodology is non-invasive it could be used as an alternative approach for the development of BCIs. Materials and methods: In order to predict the gripping force from the EEG signals we used a methodology that uses subsequent signal processing methods: simplistic filtering methods, for extracting the appropriate brain rhythm; principal component analysis, for achieving the linear independence and detecting the source of the signal; and the phase-demodulation method, for extracting the phase-coded information about the gripping force. A fuzzy inference system is then used to predict the gripping force from the processed EEG data. Results: The proposed methodology has clearly demonstrated that EEG signals carry enough information for a successful prediction of the subject's performance. Moreover, a cross-validation showed that information about the gripping force is encoded in a very similar way between the subjects tested. (Abstract truncated at 2000 characters)
Descriptors		ELECTROENCEPHALOGRAPHY HAND STRENGTH SIGNAL PROCESSING, COMPUTER-ASSISTED FUZZY LOGIC