[Eeglablist] Processing Startle in EEGlab

[Tara Miskovich]

Hello all,

I am having difficulty with a script I obtained for processing startle data
in EEGlab:

%% High pass filter
        [HP28_1,HP28_2] = butter(2,28/(EEG.srate/2),'high');    % generate
filter coefficient for 4th order 28Hz High pass Butterworth filter
        EEG.data = filtfilt(HP28_1,HP28_2,EEG.data);  %apply that filter to
ORB channel; filter order is divided by 2 because we use the filtfilt
function to avoid phase shifts in the data

%% Rectify
        EEG.data = abs(EEG.data); %the 'abs' function rectifies the data

%% Low pass filter
        [LP30_1,LP30_2] = butter(2,30/(EEG.srate/2),'low');    % generate
filter coefficient for 4th order 30Hz Low pass Butterworth filter
        EEG.data = filtfilt(LP30_1,LP30_2,EEG.data);  %%apply that filter
to ORB channel; filter order is divided by 2 because we use the filtfilt
function to avoid phase shifts in the data

%% Epoch and baseline correct
        EventCodes = num2cell(unique([EEG.event.type])); %Extract event
codes for epoching
        EEG = pop_epoch( EEG, EventCodes, [-0.05 0.25], 'epochinfo',
'yes');  %Epoch file for events that indicate startle probes
        EEG = pop_rmbase( EEG, [-50   0]); %Baseline correct

%% Mark and reject trials with excessive artificat
        Artifact = squeeze(max(EEG.data(1,1:find(EEG.times==0),:)) - min(
EEG.data(1,1:find(EEG.times==0),:)) > 40); %Identify trials with greater
than 40 microvolt deflections in baseline
        EEGNA = pop_select(EEG,'notrial', find(Artifact)); %Reject these
trials

%% Score startle peaks
        STLResponse =
squeeze(max(EEG.data(1,find(EEG.times==20):find(EEG.times==100),:)));
%Identify peak response of startle trials in scoring window
        STLResponse = [[EEG.event.type]' STLResponse]; %Store peak values
by event type

I get the following output:

pop_epoch():64 epochs selected
Epoching...
pop_epoch():64 epochs generated
pop_epoch(): checking epochs for data discontinuity
pop_rmbase(): Removing baseline...
Warning: Concatenation involves an empty array with an incorrect number of
rows.
This may not be allowed in a future release.

I am not sure what is the issue here, but after "STLResponse =
squeeze(max(EEG.data(1,find(EEG.times==20):find(EEG.times==100),:)));
%Identify peak response of startle trials in scoring window" I end up with
an empty 0 by 64 matrix.

I am just a little new to this and can't seem to figure out what is going
on here.

Thank you!
Tara
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