Goals

• understand beta series correlations
• compare task and rest data
• first level comparison
• graph theory measures
• multiple parcellations

Hemodynamic Response Function (HRF)

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?

Beta Series Correlations

• 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?

• Computationally Cheap
• Works when intertrial interval is long

• Computationally Expensive
• Works regardless of inter trial interval

Estimate Activation (Betas) of Individual Trials

How do we model brain activity?

Task Switching

Task 1: High or Low

Task 2: Odd or Even

4

Task Switching

Task 1: High or Low

Task 2: Odd or Even

4

Validation of Beta Series

Treat resting state fMRI AS IF task switching was performed.

Hypothesis: There should be a normal distribution of correlations between regions with a mean of 0.

Methods

1. Run fmriprep on all participants for both the task and rest data
2. calculate beta series for both task and rest
3. use the Schaefer (2018) atlas to define regions
4. generate correlations between regions

Compare within/between network correlation

Compare within/between network correlation

Task - Rest

Graph Theory Measures

Participation Coefficient:

how much a parcel connects to all other parcels, with 1 meaning the parcel is connected to all other parcels equally.

Result:

Default network has increased participation coefficient during task relative to rest.

Task Positive Regions

Instead of using the Schaefer atlas, use task activations.

Task activation