Neuromag event values

Christian Hesse c.hesse at FCDONDERS.RU.NL
Wed Apr 18 09:26:23 CEST 2007


FT automatically extracts trigger values (onset and offset) from
channel STI014. I am not 100% sure why the values are scaled as they
are (it is what is written in the file), but it turns out that if you
divide all your trigger values by the "magnitude of the smallest non-
zero trigger value" you will have nice integers again. Alternatively
you could just tell trialfun to look for the funny trigger values.

Hope this helps,

On 18 Apr 2007, at 00:12, Daniel Kislyuk wrote:

> What Neuromag system do you have? With the newer models it's enough to
> look at the channel STI 014 only, where the events are very clearly
> coded in an easily extractible way.
> -daniel
> On 4/18/07, Myles Reilly <myles.reilly at> wrote:
>> Hello,
>> I have been trying timelockanalysis on continuous Neuromag data.
>> It does do the average but the results don't match averages
>> calculated by
>> Neuromag applications. In Fieldtrip I can see a single event
>> named 'trigger' that has 2 values, [3.0953e-004]
>> and [6.1907e-004]. There are actually two triggers with the values
>> 1 and 2.
>> Interestingly 3.0953 * 2 = 6.196 so I wonder if there is a
>> calibration
>> factor at work here.
>> I suspect both triggers are being averaged together.
>> Thank you for any direction you can give me on this,
>> Myles

Christian Hesse, PhD, MIEEE

F.C. Donders Centre for Cognitive Neuroimaging
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Tel.: +31 (0)24 36 68293
Fax: +31 (0)24 36 10989

Email: c.hesse at

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