Measuring Communication between Brain Regions
James Kent
Dr. Michelle Voss
Health, Brain, and Congition Lab
Elevator Talk
Overview
- How do we measure brain activity?
- How do we model brain activity?
- How do we know the model works?
Blood Oxygen Level Dependent (BOLD) Response
Ogawa, S., Lee, T. M., Kay, A. R., & Tank, D. W. (1990).
How do we measure brain activity?
How do we model brain activity?
The Brain during a Task
How do we model brain activity?
Condition A (Orange)
How do we model brain activity?
Condition A (Orange)
How do we model brain activity?
Condition B (Blurple)
How do we model brain activity?
Condition B (Blurple)
How do we model brain activity?
- Brain Regions Conditionally Correlated
- Activated vs Activated Together
How do we model brain activity?
But Data are Noisy
How do we model brain activity?
And Trials Occur Close Together
How do we model brain activity?
LSA
(least squares all)
- Computationally Cheap
- Works when intertrial interval is long
LSS
(least squares separate)
- Computationally Expensive
- Works regardless of inter trial interval
Estimate Activation (Betas) of Individual Trials
How do we model brain activity?
How Can We Tell If Our Estimations are Accurate?
Simulations!
- Assign the ground truth beta series correlation (e.g., 0.2, 0.4, etc.)
- Create data with the assigned correlation.
- Vary the inter trial interval/number of trials.
- Insert noise into the data.
- Calculate beta series correlation on the simulated data.
- Compare the ground truth with the observed correlations.
How do we know the model works?
Validity of Correlations
Inter Trial Interval
Number of Trials
Power to detect Differences
Inter Trial Interval
Number of Trials
Conclusions
Trials
LSA
LSS
Power
Bias
Interval
Power
Bias
Future/Current Directions
- Simulated vs. Real Data
- Find Real Effect Sizes
- Spatial Organization of Correlations
Aknowledgments
Health, Brain, and Cognition Lab
- Matt Sodoma
- Adriana Rivera-Dompenciel
NIH Funding: 5R01AG055500
Thesis Committee
- Dr. Michelle Voss
- Dr. Jatin Vaidya
- Dr. Vince Magnotta
- Dr. Jan Wessel
- Dr. Eliot Hazeltine
Florida International University
Talyor Salo (implemented LSA)
Questions?
Slides: slides.com/jameskent/2019-seminar
Simulations: github.com/jdkent/betaSeriesSimulations
HRF App: bit.ly/hrf_viz
Beta Series App: bit.ly/beta_series
Come to Hacky Hour!
uihackyhour.github.io
Come to the Neuroimaging Workgroup:
github.com/NeuroimagingUIowa/monthlyMeetingMinutes
2019-seminar
By James Kent
