statistics for high dimensional biological recordings dr cyril pernet, centre for clinical brain...
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STATISTICS FOR HIGH DIMENSIONAL BIOLOGICAL RECORDINGS
Dr Cyril Pernet,
Centre for Clinical Brain Sciences
Brain Research Imaging Centre
cyril.pernet@ed.ac.ukhttp://www.sbirc.ed.ac.uk/cyril/
Biological Recordings
• Behavioural / Electrophysiology / MRI images
• 1D: Single channel (time / freq)• 2D: Classification ‘images’ (can actually be spectrograms)• 3D: MRI (xyz) and MEEG (channels x time / freq / trials) • 4D: fMRI (time * xyz) and MEEG (channels x freq x time x
trials)
Biological Recordings
Often we want:
To ensure data are ok for analyses high dimensional outliers detection, weighting, etc.
To analyse each ‘cell’ in the data matrix = ‘massive univariate analyses’ multiple comparisons issue
To find features in the data to distinguish conditions / groups dimension reduction (ICA), classification (MVPA)
My toys
• General linear model (WLS, IRLS)
• Robust statistics (trimmed means, winsorized variance, skipped correlations, half space/mid-covariance determinant, MAD, S-outliers, etc)
• Bootstrap and permutations
• Cross-validation
Example 1: EEG outlier detection• Weighted least square of MEEG
–> weights based on time course similarity: 1. dimension reduction (PCA) 2. outlier detection (MAD) 3. weighting (WLS)
OLS – face 1 vs 2 seems a bit different WLS – face 1 vs 2 seems identicalBias is trial variability in face 2 leads to small diff. in OLS
Example 2: MCC• Threshold-Free Cluster Enhancement (widthe x heighth )• Smith and Nichols 2009 - Integrate the cluster mass at
multiple thresholds ; used for fMRI/TBSS
Example 2: MCC for N dimensions• Threshold-Free Cluster Enhancement:• Pernet et al 2014 validation for electrophysiology to
optimize parameter selection
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