[Eeglablist] How to deal with 1/f noise in

Gangadhar Garipelli gangadhar.garipelli at epfl.ch
Fri Nov 12 06:36:32 PST 2010

Hello Arnaldo,

Thanks for the attempt! :-)

Yes, it is a bit tricky to record such slow oscillations. Conventional
or classical-EEG is usually high pass at 0.5Hz. However, FbEEG is
becoming a standard. Please check Vanhatalo et al, 2005 [1] for an
excellent report on FbEEG and hardware (using DC coupled amplifiers)
other related requirements.

Reference :
[I] Vanhatalo S, Viopio J, Kaila K. Full-band EEG (FbEEG): An emerging
standard in electroencephalography. Clin. Neurophysiol., 116(1):1-8, 2005.

On 11/12/2010 03:04 PM, Arnaldo Batista wrote:
> Hi
> Can´t help you, but thought being generally the EEG data high-pass filtered
> in the acquisition step, and how can you retain signal at such low
> frequencies?
> Thanks
> Arnaldo
> -----Original Message-----
> From: eeglablist-bounces at sccn.ucsd.edu
> [mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Gangadhar Garipelli
> Sent: 05 November 2010 11:51
> To: eeglablist at sccn.ucsd.edu
> Subject: [Eeglablist] How to deal with 1/f noise in the low frequency
> oscillations for on-line experiments?
> Dear all,
> I work with low frequency oscillations of the brain while a human
> subject is cognitively engaged in a task. From the off-line analysis
> (using zero-phase band pass FIR filters on full-band EEG), I discovered
> that task-related cognitive signals are located in the range of [0.2
> 0.3]Hz and in [0.6 0.8]Hz. The fluctuations/oscillations ( formally
> called very low frequency oscillations VLFO, or infra slow oscillations
> ISO) below 0.2Hz are REAL devil due to 1/f nature. The noise power is
>> 100 times higher than signal's power.
> Now as per my experimental demands, I need to estimate on-line in
> real-time the signals mentioned in the above range and manipulate
> stimulus presentation. Ideally, this eventually means I need to have a
> very sharp high pass filter with almost zero group/phase delay. Which
> sounds impossible!
> However, I should come up with a decent trade-off between SNR and
> phase-delay. Do you have any suggestions? All suggestions ranging from
> signal processing/machine-learning to hardware to solve this problem are
> most welcome!
> Thanks in advance!
> Sincerely,

Gangadhar GARIPELLI,
Doctoral assistant,
ELB 141, Station-11,
CH-1015, Lausanne, Switzerland.

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