[Eeglablist] High frequency narrow-band peaks in spontaneous EEG

[Makoto Miyakoshi]

Dear Abby,

We recently encountered a huge single peak beta from frontal. However, only
7/170 subjects showed it. I found it in the process of IC clustering using
spectra only.

Yours seems to be artifactual since all the channels show similar level of
it (i.e. the distribution is not dipolar). I would hypothesize that this is
some kind of either aliasing or direct external noise at 17Hz with
harmonics on 34Hz. It's hard to underpin the cause, I know...

We SCCN use phasespace marker which is basically flashing LED in infrared
or something, and it sometimes generates near-30Hz noise like this.

Makoto



On Wed, Jun 22, 2016 at 12:11 PM, Dickinson, Abigail <
ADickinson at mednet.ucla.edu> wrote:

> Hi everyone,
>
> I wondered if anyone who studies spontaneous EEG/high frequency
> oscillations has ever come across individuals who show high frequency
> narrow-band peaks?
>
> In a substantial number of data sets we are seeing a distinct peak which
> varies substantially in frequency between participants (17-33Hz). The peak
> in power is present to some degree in all channels throughout the original
> recording. In addition, removing EMG and EOG using ICA does not impact the
> presence of the peak, which is also present in all reconstructed channel
> data.
>
> We have tested for coherence (short circuit) between channels and the
> phase coherence is random, suggesting that this is not a volume conductance
> issue. Alternative filtering and referencing techniques have also been
> tested, none of which have any impact on the presence of the peak.
>
> Details of the recording & processing are included below, and figures
> demonstrating examples of the peaks in two different participants can be
> seen here: https://db.tt/22JIkdun
>
> I'd be really grateful to know if this is something others have seen in
> spontaneous EEG, or if anyone had any ideas as to what might be causing
> these peaks?
>
> Best wishes,
>
> Abby
>
>
> Original data: 128 Channel EEG; Fs= 500Hz; Eyes-open resting state
> Filter : 1 to 120 Hz FIR
> Average Reference
> Cleaned by visual inspection, later ICA
> Power Spectrum calculation: Average of every 1000ms using Welch method
>
>
>
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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