[Eeglablist] 'powbase'

[Kamia Kavi]

Hey Marius,



Thank you very much for your explanation. If possible, two more questions
about baseline:



1) If I want to test the impact of different baselines on the results, can
I simply just calculate these different baselines without recalculating all
the data again? If yes, how can I ‘only’ calculate the baseline?



2) Why do we prefer to divide the power values by the power values of the
baseline, rather than subtracting the values of the baseline from the power
values?



Best wishes,



Kamia


On Thu, Mar 22, 2018 at 10:17 AM, Marius Klug <marius.s.klug at gmail.com>
wrote:

> Hi Kamia,
>
> ERSPs are always interpreted in comparison to a baseline. There are
> several different ways of doing this, the most frequently used is dividing
> the power values (not dB transformed) or the epoch by the power values of
> the baseline. Usually this is done automatically by newtimef such that it
> computes the baseline (by thefault this is the prestimulus average) by
> itself. However, if you want, you can enter a baseline you precomputed
> yourself and use that one instead. This is done by using the 'powbase'
> parameter and providing a vector with the baseline power values for each
> frequency.
>
> In case you are unsure what you're doing here, don't use this parameter,
> but use the 'baseline' parameter and enter the millisecond frame which time
> points should be taken as baseline.
>
> I hope this helped!
>
> Best,
> Marius
>
> 2018-03-18 10:06 GMT+01:00 Kamia Kavi <kamiakavi at gmail.com>:
>
>> Can anyone explain what ‘powbase’ parameter do in ERSP and when we should
>> use this option?
>>
>>
>>
>> Best wishes,
>>
>>
>>
>> Kamia
>>
>>
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