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Dear Woo-Suk With a TR of 8s it is very unlikely that your physiological components will be located at a single frequency. As the cardiac pulsation and respiration are non-stationary (their frequencies vary over time), the aliased noise will look like white noise in a spectrogram. So what you see in your fft is most likely due to scanner drift. Scanner drift can be removed using the SPM high-pass filter. For further information see: https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind00&L=SPM&P=R111434 or have a look at the paper bellow. Hope this helps Torben Torben Ellegaard Lund Assistant Professor, PhD The Danish National Research Foundation's Center of Functionally Integrative Neuroscience (CFIN) Aarhus University Aarhus University Hospital Building 10G, 5th floor Noerrebrogade 44 8000 Aarhus C Denmark Phone: +4589494380 Fax: +4589494400 http://www.cfin.au.dk [log in to unmask] Lund et al. Non-white noise in fMRI: Does modelling have an impact?. NeuroImage (2005) pp. 13 Den 02/07/2009 kl. 08.23 skrev Woo-Suk, Tae: > Dear SPM experts > > I have an aliasing problem in my FFT with time-course data. > > TR of EPIs was 8 sec. and it seem that there were aliasing > components in frequency domain > > graph related with low frequency drift, respitory and cardiac cycles. > > Can these aliasing components could be controlled by bandpass filter? > > > > Woo-Suk, Tae > Chuncheon, Korea >