1. Barbora Ondrejickova Methods for Dummies 23rd November 2016
1st-level analysis: Basis Functions, Parametric Modulation and Correlated Regressors
Barbora Ondrejickova
Methods for Dummies
23rd November 2016

2. Basis Functions The canonical haemodynamic response function Peak
Brief
Stimulus
Undershoot
Initial
Peak

3. Finite impulse response
Basis Functions
Fourier basis
Finite impulse response
Gamma functions
Informed basis set

4. Basis Functions
Informed Basis Set

5. Basis Functions
Canonical HRF: combination of 2 Gamma functions (best guess of BOLD response)

6. Basis Functions
Canonical HRF: combination of 2 Gamma functions (best guess of BOLD response)
Variability captured by Taylor expansion:
Temporal derivative (account for differences in the latency of response)

7. Basis Functions
Canonical HRF: combination of 2 Gamma functions (best guess of BOLD response)
Variability captured by Taylor expansion:
Temporal derivative (account for differences in the latency of response)
Dispersion derivative (account for differences in the duration of response)

8. Basis Functions E.g. rapid motor response to faces Canonical
+ Temporal
+ Dispersion
+ FIR
(Henson et al, 2001)

9. Basis Functions

10. Basis Functions

11. Parametric Modulation

12. Parametric Modulation
(Gläscher & O’Doherty 2010)

13. Correlated Regressors
If 2 parameters, A and B are correlated then the parametrically modulated regressors will also be correlated.
Thus trial-by-trial changes in BOLD activation might be due to both the regressors, making it difficult to assign responsibility to one. I.e. they share descriptive variability.

14. Correlated Regressors

15. Take Home 1. Informed Basis Set 2. Parametric Modulation
3. Corralated regressors

16. Resources Special thanks to Dr Guillaume Flandin Sources:
Previous MfD Lecture slides
Lecture slides, Rik Hensen
Lecture slides, Mona Gaverthttp://
Lectures, Sara Bengstsson and Christian Ruffhttp://
MRC CBSU Wikihttp://imaging.mrc-cbu.cam.ac.uk/imaging/DesignEfficiency#Correlation_between_regressors
Review article, Mumford et al.
Henson et al (2001)
Gläscher & O’Doherty (2010)