P300 elaborations
Gianluca Moro
please find a first data elaboration to reveal evoked potentials:
Section 4.7 of report: http://www.giammy.com/files/bci.html
http://www.giammy.com/files/bci.pdf
(the relevant part is at the end of the mail)
I here attach the the graph and the primary data (readable in Matlab)
The columns keeps the following data:
# f(Hz) C giroX giroY F3 FC6 P7 T8 F7 F8 T7 P8 AF4 F4 AF3 O2 O1 FC5
the relevant ones are from column 6 to column 19.
Matlab sequence to get the graph is:
>> load('data.20111014.1.summed')
>> data = data_20111014_1
>> plot(1:256, data(:,6)-mean(data(:,6)), 1:256,data(:,15)-mean(data(:,15)), 1\
:256,data(:,16)-mean(data(:,16)))
>> legend('F3', 'F4', 'AF3')
the mean is removed (just to have all the signals centered in 0),
after the elaboration, which is just an average on raw data.
bye
giammy
P.S: if these results are correct and reproducible, the simple used elaboration
(just a media) is a big added value for the following realtime
implementation.
Any comment is welcome!
\section{A first manual P300 elaboration}
\label{first-manual-P300-elaboration}
% 20111109
Referring to the Audio Evoked Potential test described in section
\ref{evoked-potential}, \textbf{Test: Evoked potential}, we present
a preliminary manual data analysis.
\begin{figure}[t]
\includegraphics[angle=0,width=140mm]{data-20111014-1-summed.png}
\caption{Graph of evoked potentials}
\end{figure}
The test emitted high frequency sounds, with 33 low frequency sounds
(random rare events).
The plotted signals are the resulting media of all the acquisitions
corresponding to the 2s interval around the rare events.
We report just the signal corresponding to F3, F4, AF3 (the position
of the sensors must be verified): in these signals the peak is more
evident.
The rare event occurs at sample 128, while the peak occurs about
30 samples after (a quarter of second).
This seems to suggest that the Emotiv Epoc can record an evoked
potential, but is preliminary data and preliminary report: more test -
and in realtime configuration, must be done!
--
Gianluca Moro
N.s.A - Note su Android http://www.giammy.com/nsa
Medical Brain Computer Interface https://groups.google.com/group/medical-bci/
