–1–

InstaCorr• On-the-fly

All data hereinfrom Alex Martin,
et al. [NIMH IRP]

instantaneous
correlation map ofresting state data withinteractively selected
seed voxel• Setup phase:
prepares data forcorrelations (several-to10+ seconds)• Correlation phase:
you select seed voxel,
correlation map
appears by magic

–2–InstaCorr: Outline of 2 Phases• Setup phase:★ Masking: user-selected or Automask★ Bandpass and other filtering of voxel time series★ Blurring inside mask = the slowest part

• Correlation phase:★ Correlate selected seed voxel time series with allother prepared voxel time series★ Make new dataset, if needed, to store results★ Save seed time series for graphing★ Redisplay color overlay★ Optional: compute FDR curve for correlationso This can be slow, so is not turned on by default

–3–

InstaCorr: Setup• Open Define Overlay, choose InstaCorr frommenu in top right corner

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InstaCorr: Setup• Open Define Overlay, choose InstaCorr frommenu in top right corner• Then press Setup ICorr button to get control panel

–5–InstaCorr:Setup
Doesnʼt have to be
current underlay• Mostly self-explanatory (I hope) — cf. Help
• Global Orts = extra time series to be projected outof dataset before correlation★ All columns in selected 1D file★ e.g., movement parameters★ The first Ignore rows (time points) will be skipped• When ready, press one of the Setup buttons

–6–

InstaCorr: Setup• Text output to shell window details the setup procedures:++ InstaCorr preparations:+ Automask from'/Users/rwcox/data/Resting/ZSS/s620/s620_rest_r1+orig.BRIK' has197234 voxels+ Extracting dataset time series+ Filtering 197234 dataset time series+ bandpass: ntime=139 nFFT=160 dt=3.5 dFreq=0.00178571
Nyquist=0.142857 passband indexes=6..56
Most of the CPU time
+ Spatially blurring 139 dataset volumes+ Normalizing dataset time series++ InstaCorr setup: 197234 voxels ready for work: 15.43 sec

–7–InstaCorr: The Fun Part

• In image viewer, set crosshairs to desired seed voxel• Right-click popup menu → InstaCorr Set• Shortcut: Shift+Ctrl+Left-click sets new crosshairlocation, then does InstaCorr Set• InstaCorr SeedJump jumps focus to current seed

–8–InstaCorr: The Fun Part

• In graph window:★ Set Ignore with FIM→Ignore menu (or I key)
★ Set seed overlay with FIM→PickIdeal menu
• When you change seed voxel, saved overlay timeseries will change (but you have to refresh graph to see it)InstaCorr: Effects of Blurring–9–0mm

1mm

2mm

3mm

4mm

5mm

6mm

7mm

• Is this a pure vascular/cardiac effect being
progressively smeared? Or real neural correlations
seen via BOLD? Or some of both? Venograms?
★ Dataset was RETROICOR-ized; mask is whole brain

InstaCorr: Effects of Blurring–10–3 mm7 mm• Similar calculations, but with FreeSurfer-generated
gray matter mask instead of Automask from EPI data
★ Blurring is done only inside the masko Using a discrete PDE-based iterative approach

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InstaCorr: SVD-based “Blurring”

Gaussian 5mm

3dLocalSVD 5mm• Similar calculations, with Automask from EPI data,using 3dLocalSVD over 5 mm radius sphere (67 voxels)★ Project each vector onto 2-dim principal subspace★ Too slow to do interactively (at this time)

–12–

InstaCorr: SVD-based “Blurring”

Gaussian 5mm

3dLocalSVD 5mm• Volume rendering of InstaCorr maps (threshold at r=0.5)★ Renderer updates automatically if DynaDraw is on• SVD smoothing has cleaner spatial structure?
★ Or has it lost some information?

–13–

InstaCorr: Options and Notions• Underlay doesnʼt have to be EPI data; could be anat
★ Can use InstaCorr in multiple AFNI controllers• FDR: setenv AFNI_INSTACORR_FDR YES★ Will slow things down by a significant factor• Saving A_ICOR dataset: overwrites previous copies• Future Possibilities:★ Select ROI-based Orts to be detrended?
o Based on ROIs from FreeSurfer or atlases?

★ Or multiple seeds (partial + multiple correlations)?
★ Interactive local SVD “smoothing”? (needs speedup)★ Group analysis InstaCorr (in standardized space)o Not quite “Insta” any more; ≈ 0.1×#Subjects sec per seedo External script to do subject setups?

★ Use time series subsets? (e.g., for block design data)