# [Eeglablist] ERSP parameters in STUDY

Tue Feb 2 14:19:32 PST 2010

```Thank you Bradley for your comments,
I did try doing it without baselining, and still the same. My experience now
tells me:
1- Baselining does not have any effect on observable frequencies in ersp
analysis
2- cycles [] option and the epoch length have the major effects, such that
you need to specify smaller wavelets (as in cycle [1 0.2] or DFT option
cycle[0]) if you need to look at the smaller frequencies, but this may not
show the whole epoch (time window is smaller in ersp window) and cuts out
the first and the last portion of the original epochs.

My question to you all is: how can we keep the time range same as long as
the epoch length for the lower frequencies? Is the wavelet overlapping has
anything to do with that? How do we set this?I know the factor in cycles [x
(factor)] determines the increments of the cycles as we go up in the
frequency dimension, but which parameter assigns the wavelet overlap?

Baris

On Thu, Jan 28, 2010 at 9:28 PM, Bradley Voytek <bradley.voytek at gmail.com>wrote:

> Well if you set the basline to be only 100ms long, then you can't
> reasonably expect to look at frequencies below about 10Hz. The
> rationale being that a 10Hz oscillation has--by definition--10
> oscillations per second, or a period of 100ms. If you work with the
> definition that to get a reasonable measure of TF baseline activity
> you need at least one full oscillation, then you can only look at
> frequencies with periods of 100ms or shorter.
>
> In short, use a longer baseline.
>
>
> On Thu, Jan 28, 2010 at 05:39, Baris Demiral <demiral.007 at googlemail.com>
> wrote:
> > Data is filtered  highpass 0.3Hz and lowpass 40Hz, and epochs were set
> from
> > -300ms to 1000ms to event onset. Baseline is -100-0ms. I wonder there are
> > some parameters I should set beforehand.  Any ideas? Or at least, am I
> the
> > only one experiencing this problem, or is this a bug? That is what I am
> > trying to understand.
> >
> > On Wed, Jan 27, 2010 at 6:55 PM, Bradley Voytek <
> > wrote:
> >>
> >> Probably the length of time you're using for your event window and/or
> >> baseline. What are these settings?
> >>
> >>
> >> On Wed, Jan 27, 2010 at 07:34, Baris Demiral <
> >> wrote:
> >> > Dear all,
> >> > When I run ERSP pre-computation for a study with default parameters I
> >> > end up
> >> > with a frequency-time plot starting from 12Hz. No value below is
> shown.
> >> > I use EEGLABv7.2. What do you think is the problem?
> >> > Baris
> >> > --
> >> > SB Demiral, PhD.
> >> > Department of Psychology
> >> > 7 George Square
> >> > The University of Edinburgh
> >> > Edinburgh, EH8 9JZ
> >> > UK
> >> > Phone: +44 (0131) 6503063
> >> >
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> >
> >
> >
> > --
> > SB Demiral, PhD.
> > Department of Psychology
> > 7 George Square
> > The University of Edinburgh
> > Edinburgh, EH8 9JZ
> > UK
> > Phone: +44 (0131) 6503063
> >
>

--
SB Demiral, PhD.
Department of Psychology
7 George Square
The University of Edinburgh
Edinburgh, EH8 9JZ
UK
Phone: +44 (0131) 6503063
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