[Eeglablist] Huge alpha peaks in one person

[Tarik S Bel-Bahar]

Greetings Eric, some thoughts that may be useful below. In your case the
best solution might be to compare the data across several different kinds
of pre-processing steps, and show that the giant single-person peak is an
artifact or not. It may certainly be due to individual variability, take a
look at normal values and variability of alpha in studies that have used
large samples, and compare those published values to the values you are
getting. One question to consider is whether you see this giant peak for
one person at channel-level and at ICA-level, and whether the peak is
stronger with ICA. Another question is what the range of values is for
other individuals' alpha peaks. Last, try to double check your raw data,
both it it's continuous form, and with only "clean" epochs, in order to
determine whether the individual's data is normal at that level compared to
the data from other people.



On Sat, Apr 4, 2015 at 5:14 PM, Eric HG <erichg2013 at gmail.com> wrote:

> Hi everybody,
>
> There has been one resting-state EEG from a healthy subject that we have
> analyzed that has huge alpha peaks resulting in huge power values at
> baseline (like 15-17) in the alpha band and this is only when the subjects
> have their eyes closed. Has anyone experienced something like this? Could
> it be due to the preprocessing steps (I've used Butterworth filter: H-pass:
> 1 Hz and L-pass: 100 Hz, epoched the data and then removed the epochs with
> a lot of artifacts)?
> The ICA can easily separate the alpha peak components.
>
> Or can it just be due to individual variability?
>
> Best,
>
> Eric
>
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