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fMRI Methods Lecture 12 – Random stuff…

fMRI Methods Lecture 12 – Random stuff…. Correlation/Covariance. The idea with correlation is that two variables are related, enabling you to predict one from the other. Implies, but does not prove causality. Tricky business:. Rate of autism. Rate of atheists in the population.

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fMRI Methods Lecture 12 – Random stuff…

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  1. fMRI MethodsLecture 12 – Random stuff…

  2. Correlation/Covariance The idea with correlation is that two variables are related, enabling you to predict one from the other. Implies, but does not prove causality. Tricky business: Rate of autism Rate of atheists in the population

  3. Correlation with behavior Explain between-trial variability in behavior (reaction time, accuracy, memory, decision making variables, fear, bravery) with response amplitude. Explain between-subject variability in behavior with response amplitude. In both cases: look for brain areas that predict behavior. Places where the extent of behavior is encoded by strength of response (e.g. fear in Amygdala).

  4. Example Mirror system responses in autism: Dapretto et. al. Nat. Neurosci 2006

  5. Spurious correlations? Personality measure reliability ~ 0.8 fMRI measure reliability ~ 0.7 Correlation between the two should be < 0.74

  6. Spurious correlations? 64,000 voxels and multiple subjects… Lack of independence

  7. Solutions/Approaches Test for correlations in ROIs defined based on other criteria. Split your data into two halves and show reproducibility.

  8. Examples Identify ROI that responds to faces using one scan. Determine whether responses are correlated with face familiarity in this ROI and not in other ROIs using data from another scan. Say a word about correlations in rest scans

  9. Planning experiments Number of subjects and trials - power analysis Caveats and proper controls – Signal and noise, statistical interpretation.

  10. Auditory experiments Issues with sound presentation. Auditory system and language.

  11. To the lab!

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