[Eeglablist] Measuring clusters using numerical integration/ area under the curve

[Elizabeth J Kirkham]

Dear Makoto,

Thank you for your advice. I actually tried emailing the ERPLAB list after
emailing the EEGLAB list and got a helpful response from Steve Luck. So I
don't think my email to the EEGLAB list needs to go out anymore.

Best wishes,
Elizabeth

On 8 December 2016 at 02:52, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:

> Dear Elizabeth,
>
> While waiting for other experts in this list write you back, why don't you
> write to ERPLAB mailing list too if you haven't.
> http://erpinfo.org/erplab/erplab-email-list
>
> Personally I have no experience with it so I can't help you, sorry. I hope
> other researchers here can help you.
>
> Makoto
>
> On Mon, Dec 5, 2016 at 11:52 AM, Elizabeth J Kirkham <
> ekirkham1 at sheffield.ac.uk> wrote:
>
>> Dear all,
>>
>> I am using the area under the curve methodology to measure my ERP
>> waveforms. To do this, I am using ERPLAB's Measurement tool function, with
>> the settings "Numerical Intergration/Area between two fixed latencies",
>> "Rectified area (negative values become positive)".
>>
>> I want to examine the waveform over two clusters of electrodes (P5, P7
>> and TP7; and P6, P8 and TP8).
>>
>> There are two ways for me to examine these clusters, either (1) create
>> the cluster in ERPLAB (ERPLAB > ERP operations > ERP channel operations),
>> and then use the Measurement tool to find the Numerical Integration values
>> for the cluster, or (2) use the Measurement tool to find the Numerical
>> Integration values for each electrode separately, and then average them
>> together later (for example in Excel).
>>
>> I have found that these measures produce different output values. The
>> values are not the same in absolute terms, or in relative terms. (For
>> example, the values for one participant in conditions 1 and 2 are 0.523 and
>> 0.630 using the first method, and 1.698 and 1.641 using the second method.)
>>
>> I don't know if these different values are because I have made a mistake,
>> or if differences in output are to be expected when using numerical
>> integration?
>>
>> If it is the case that I have not made a mistake, is there a best
>> practice in terms of which way round to carry out the procedures? Should I
>> average the channels in ERPLAB, and then take the measurement, or take the
>> measurement for each channel separately, and then average the output
>> together?
>>
>> Thanks in advance,
>> Elizabeth
>>
>>
>> --
>> Elizabeth Kirkham
>> PhD Researcher
>>
>> Department of Psychology
>> The University of Sheffield
>> Floor E
>> Cathedral Court
>> 1 Vicar Lane
>> Sheffield
>> S1 2LT
>> UK
>>
>>
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>
>
>
> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>



-- 
Elizabeth Kirkham
PhD Researcher

Department of Psychology
The University of Sheffield
Floor E
Cathedral Court
1 Vicar Lane
Sheffield
S1 2LT
UK
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