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

[Makoto Miyakoshi]

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
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