1. Psycho-Physiological Interaction (PPI) May 8, 2013, 1.15 – 2.45 pm http://www.cbs.mpg.de/events/teaching/asf bc pw: mpi-brain13

2. Connectivity analysis  Psycho-Physiological Interactions (PPI)  Granger Causality Techniques (GCM)  Dynamic Causal Modeling (DCM)

3. Psycho-Physiological Interaction (PPI)

4. ρ = 0.12

5. Psycho-Physiological Interaction (PPI) ρ = 0.12 ρ □ = 0.46 > 0.12 Attention

6. Psycho-Physiological Interaction (PPI) attention no attention V1 activity V5 activity SPM{Z} time V5 activity PPI example: attentional modulation V1 Friston et al. 1997, NeuroImage 6:218-229 Büchel & Friston 1997, Cereb. Cortex 7:768-778 V1 x A = V5 V5 Attention

7. Psycho-Physiological Interaction (PPI) y = V1·β 1 + A·β 2 + (V1 x A)·β 3 + β 4 + ε c = [0 0 1 0] PPIs can be tested by a GLM with the form How to compute the interaction term? 1. Product between physiological time course “V1” and psychological variable “Attention” (only valid for block design) Friston et al. 1997, NeuroImage 6:218-229 2. Deconvolution of physiological variable “V1” before calculating the interaction term, Re-convolution of interaction term with HRF (SPM8) Gitelman et al. 2003, NeuroImage 19:200-7

8. Psycho-Physiological Interaction (PPI): Example data

9.  single subject data  audio/visual experiment  block design  sound off/on: 13s/13s  visual off/on: 20s/20s  contrasts:  visual (vs. baseline)  sound (vs. baseline)  resolution:  in plane 64x64 pixel a 3x3mm  10 axial slices, thickness+gap 7mm  repetition time 1s  728 volumes (ca. 12 min) conditions timesteps (volumes) VISUAL AUDIO Question: Does the sound modulate the connection between V1 and other brain regions ?

10. Psycho-Physiological Interaction (PPI): Starting SPM 1. Spatial pre-processing 2. Statistics 3. Selection of VOI (seed region) 4. Specify the PPI (build the regressors) 5. PPI-Statistics (use the regressors)

11. 1. Preprocessing

12. Realign and unwarp Slicetime correction Unified segmentation and normalization Smoothing not in detail in this lecture

13. 2. Statistics

14. 1. Specify the design 2. Review the design 3. Parameter estimation 4. Results (Contrasts)

15. 2. Statistics: specify design

16. Reference slice in slicetime correction? First slice: Microtime onset = 1 Middle slice: Microtime onset = 16/2

17. 2. Statistics: specify design right mouse click: select all

18. 2. Statistics: specify design Everything again for second condition “AUDIO” largest distance of 2 trials of same condition = 40 s High-pass filter: 60 s >> 40 s VISUAL AUDUIO in the destination directory: design specification: SPM.mat

19. 2. Statistics: review a model

21. cutoff: 1/60 Hz

22. 2. Statistics: parameter estimation

23. in the destination directory (SPM.mat): parameter estimates: beta_000x.img, beta_000x.hdr

24. 2. Statistics: results

25. 1 0 0 <= OK

26. 2. Statistics: results Right mouse click

27. 2. Statistics: results in the destination directory (SPM.mat): conimgs: con_000x.img/.hdr, tmaps: spmT_000x.img/.hdr

28. 3. Selecting a VOI 3. Selecting a seed region (VOI)

29. 3. Selecting a VOI Right mouse click We may adjust the data for effects of interest, but we did not compute any F contrasts time course

30. 4. Generate regressors for PPI

32. 1 physiological (time course in V1) psychological (audio condition) interaction

33. 5. PPI statistics

34. Choose a new directory! Otherwise the stats results and SPM.mat will be overwritten! Right mouse click: “Select all” Press 3 x for 3 regressors

35. 5. PPI statistics PPI.Y PPI.P PPI.ppi PPI.YPPI.P PPI.ppi 0 0 10 in the ppi destination directory: design specification: SPM.mat

36. 5. PPI statistics Choose correct SPM.mat in the directory of PPI (not first statistics) in the ppi destination directory (SPM.mat): parameter estimates: beta_000x.img, beta_000x.hdr

37. 5. PPI statistics

38. Y 0 P 0 ppi 10

39. 5. PPI statistics 1. Use left mouse button and move red cursor to a region of interest 2. Use right mouse button to search the local maximum

40. 5. PPI statistics

41. Thank you Thank you for your attention