modalities.fmri.fmristat.hrf¶
Module: modalities.fmri.fmristat.hrf¶
Computation of the canonical HRF used in fMRIstat, both the 2-term spectral approximation and the Taylor series approximation, to a shifted version of the canonical Glover HRF.
References¶
- Liao, C.H., Worsley, K.J., Poline, J-B., Aston, J.A.D., Duncan, G.H.,
Evans, A.C. (2002). ‘Estimating the delay of the response in fMRI data.’ NeuroImage, 16:593-606.
Functions¶
- nipy.modalities.fmri.fmristat.hrf.spectral_decomposition(hrf2decompose, time=None, delta=None, ncomp=2)¶
PCA decomposition of symbolic HRF shifted over time
Perform a PCA expansion of a symbolic HRF, time shifted over the values in delta, returning the first ncomp components.
This smooths out the HRF as compared to using a Taylor series approximation.
- Parameters:
- hrf2decomposesympy expression
An expression that can be lambdified as a function of ‘t’. This is the HRF to be expanded in PCA
- timeNone or np.ndarray, optional
None gives default value of np.linspace(-15,50,3251) chosen to match fMRIstat implementation. This corresponds to a time interval of 0.02. Presumed to be equally spaced.
- deltaNone or np.ndarray, optional
None results in default value of np.arange(-4.5, 4.6, 0.1) chosen to match fMRIstat implementation.
- ncompint, optional
Number of principal components to retain.
- Returns:
- hrf[sympy expressions]
A sequence length ncomp of symbolic HRFs that are the principal components.
- approx
TODO
- nipy.modalities.fmri.fmristat.hrf.taylor_approx(hrf2decompose, time=None, delta=None)¶
A Taylor series approximation of an HRF shifted by times delta
Returns original HRF and gradient of HRF
- Parameters:
- hrf2decomposesympy expression
An expression that can be lambdified as a function of ‘t’. This is the HRF to be expanded in PCA
- timeNone or np.ndarray, optional
None gives default value of np.linspace(-15,50,3251) chosen to match fMRIstat implementation. This corresponds to a time interval of 0.02. Presumed to be equally spaced.
- deltaNone or np.ndarray, optional
None results in default value of np.arange(-4.5, 4.6, 0.1) chosen to match fMRIstat implementation.
- Returns:
- hrf[sympy expressions]
Sequence length 2 comprising (hrf2decompose,
dhrf) wheredhrfis the first derivative of hrf2decompose.- approx
TODO
References
Liao, C.H., Worsley, K.J., Poline, J-B., Aston, J.A.D., Duncan, G.H., Evans, A.C. (2002). ‘Estimating the delay of the response in fMRI data.’ NeuroImage, 16:593-606.