# [Eeglablist] Time- frequency analysis

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Fri Dec 4 10:11:41 PST 2015

```Dear Leonardo,

> 1- Does that mean, I can't do time-frequency analysis using
"Time-frequency transforms" of EEGLAB because I don't have epochs in my
data)? Is this could be a limitation of Time-frequency transforms (only
dealing withe epoch data rather than continuous one)?

I think EEGLAB GUI also let you transform continuous EEG into
time-frequency data. If you call pop_newtimef() or newtimef() function, it
is absolutely possible.

> 2- In same "Time-frequency transforms" option, what is the meaning of the
word "log" that we find it in both "Log spaced" and "log power" parameters?

If you linear-space 1 to 10,

linspace(1,10,10)

ans =

1     2     3     4     5     6     7     8     9    10

If you log-space 1 to 10,

>> logspace(log10(1),log10(10),10)

ans =

1.0000    1.2915    1.6681    2.1544    2.7826    3.5938    4.6416
5.9948    7.7426   10.0000

For frequency plot, always use log scale. It'll weight 4-8Hz theta and
40-80Hz gamma equally.

> 3- For baseline, when to select the option "Use standard deviation
(STD)", "Single trial DIV baseline", and "Single trial STD baseline"?  When
we change from one to another, does that change the dB unit or not, knowing
that the default option "Use divisive baseline" produces bar column in dB.
However, this bar color will be changed (e.g., std.) when we change the
option into "Use Single trial STD baseline".

I believe the difference is how to take the baseline. It's my guess but
sounds like the default is the std of the baseline period after averaging,
while the 'single trial' option calculates it at single trials (I don't
know exactly how). The dB unit will be the same, but the baseline values
would be different since they are differently calculated.

Makoto

On Thu, Dec 3, 2015 at 9:42 AM, Leonardo Lion <llionname at gmail.com> wrote:

> Hi everyone,
>
> My question is about applying ht e Time- frequency analysis on my
> continuous dataset (I don't have any epoch in the data).
>
> In the EEGLAB, under the "Time-frequency transforms" option, there is a
> parameter called "Sub-epoch time limits". In the help of this parameter was
> written that "sub epochs may be extracted (note that this function aims at
> plotting data epochs not continuous data). You may select the new epoch
> limits in this edit box".
>
>
> 1- Does that mean, I can't do time-frequency analysis using
> "Time-frequency transforms" of EEGLAB because I don't have epochs in my
> data)? Is this could be a limitation of Time-frequency transforms (only
> dealing withe epoch data rather than continuous one)?
>
> 2- In same "Time-frequency transforms" option, what is the meaning of the
> word "log" that we find it in both "Log spaced" and "log power" parameters?
>
> 3- For baseline, when to select the option "Use standard deviation (STD)",
> "Single trial DIV baseline", and "Single trial STD baseline"?  When we
> change from one to another, does that change the dB unit or not, knowing
> that the default option "Use divisive baseline" produces bar column in dB.
> However, this bar color will be changed (e.g., std.) when we change the
> option into "Use Single trial STD baseline".
>
>
> Kind regards,
> Leonardo
>
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--
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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