[FieldTrip] corticomuscular and intermuscular coherence

Julian Keil julian.keil at gmail.com
Wed Feb 5 14:02:27 CET 2014

Dear Ingmar,

I'm not too sure about how exactly coherence is calculated, but be aware that it is not possible to compute single trial coherence. This has been discussed numerous times on this list.

In case you absolutely need a single-trial analysis of connectivity, you might want to look up my recent paper:

Keil, J., Müller, N., Hartmann, T., & Weisz, N. (2013). Prestimulus Beta Power and Phase Synchrony Influence the Sound-Induced Flash Illusion. Cerebral Cortex (New York, NY : 1991), 1–11. doi:10.1093/cercor/bhs409

In this paper, I describe how to use the difference between the phases of two signals compared to the mean phase difference can give an indication of single trial functional connectivity.



Dr. Julian Keil

AG Multisensorische Integration
Psychiatrische Universitätsklinik
der Charité im St. Hedwig-Krankenhaus
Große Hamburger Straße 5-11, Raum E 307
10115 Berlin

Telefon: +49-30-2311-1879
Fax:        +49-30-2311-2209 

Am 05.02.2014 um 13:38 schrieb Vries, I.E.J. de:

> p.s.
> And if this is indeed the case, is there a way to change these settings, e.g. calculate the coherence for each trial separately?
> Greetings
> From: Vries, I.E.J. de
> Sent: 05 February 2014 13:29
> To: fieldtrip at science.ru.nl
> Subject: corticomuscular and intermuscular coherence
> Dear Fieldtrippers,
> I have a small question. When I run a ft_connectivityanalysis with coherence as method on a data set of 90 trials of each 15 seconds, the command window gives the output text that coherence is averaged over rpt (replicates). Besides that, for each trial of 15 seconds, 149 tapers are used. 
> My question, over which parts is the coherence calculated and then averaged. It seems to me now that first the coherence is calculated over all of the 149 * 90 = 13410 epochs, and then averaged over all of these. Is this the order that ft_connectivity analysis applies? I tried to look it up in the code but got a bit lost there with all the variable names etc... 
> Thanks in advance,
> Greetings,
> Ingmar
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