The coherence plot!

[Vladimir Litvak]

Hi,

Jan-Mathijs is right. There is nothing wrong with your analysis. What you
see is the TMS artifact which is a sharp pulse occuring in both channels
synchronously and therfore producing high coherence across the spectrum as
it should be. If you are not interest in the time period around the pulse,
you can just exclude it from your analysis. Otherwise, you are in the
difficult business of dealing with TMS artifacts and unless you want to make
it the topic of your reasearch, you should probably not spend too much
efforts on it.

You may find the following papers useful:

Litvak V, Komssi S, Scherg M, Hoechstetter K, Classen J, Zaaroor M, Pratt H,
Kahkonen S.<http://www.ncbi.nlm.nih.gov/pubmed/17574872?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
<http://www.ncbi.nlm.nih.gov/pubmed/17574872?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
Artifact
correction and source analysis of early electroencephalographic responses
evoked by transcranial magnetic stimulation over primary motor cortex.

Morbidi F, Garulli A, Prattichizzo D, Rizzo C, Manganotti P, Rossi
S.<http://www.ncbi.nlm.nih.gov/pubmed/17399798?ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
<http://www.ncbi.nlm.nih.gov/pubmed/17399798?ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
Off-line
removal of TMS-induced artifacts on human electroencephalography by Kalman
filter.
J Neurosci Methods. 2007 May 15;162(1-2):293-302. Epub 2007 Jan 7.

Thut G, Ives JR, Kampmann F, Pastor MA, Pascual-Leone
A.<http://www.ncbi.nlm.nih.gov/pubmed/15661302?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
<http://www.ncbi.nlm.nih.gov/pubmed/15661302?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
A
new device and protocol for combining TMS and online recordings of EEG and
evoked potentials.
J Neurosci Methods. 2005 Feb 15;141(2):207-17.

Fuggetta G, Fiaschi A, Manganotti
P.<http://www.ncbi.nlm.nih.gov/pubmed/16054397?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
<http://www.ncbi.nlm.nih.gov/pubmed/16054397?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum>
Modulation
of cortical oscillatory activities induced by varying single-pulse
transcranial magnetic stimulation intensity over the left primary motor
area: a combined EEG and TMS study.

With best wishes,

Vladimir


On Feb 20, 2008 9:09 AM, Muthuraman Muthuraman <muthuraman10 at hotmail.com>
wrote:

> Hello Fieldtrippers,
>
> The plot is attached with this mail.
>
> Thanking you
>
> WIth regards
> M.Muthuraman.
>
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The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.
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