W5L2 - fMRI Research 2
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What is reverse inference
Drawing conclusions about cognitive processes from the presence of activation
What is the steps/logic in reverse inference, where is the problem
• ) This study: Task A, Brain Region Z active • ) Other study: Cognitive process X, Brain Region Z active • ) Hence, Activation of Z = Cognitive Process X Problem: (2) Not exclusive. Brain Region Z activate for many other cognitive processes/tasks
Example of Reverse Inference Problem: Pre-Frontal Cortex. What has been suggested of anterior and posterior regions
More anterior regions (front) = Abstract Information • Dorsal Axis: Abstractness of Rules • Ventral Axis: Abstractness of Memory Representation More posterior regions (back) = Specific content
Example of Reverse Inference Problem: Pre-Frontal Cortex. What other studies found
Frontal cortex activated in lots of tasks - Relative specialization instead of absolute specialization. “More strongly” as task difficult increases
What is the “Multi-Demand” Network
Activation in a region - Does not imply region is doing that. Many regions interact with one another for cognitive task
In examining cognitive processes, what are the 2 things experiments must ensure
• ) Quality of Task -> Experiment must manipulate cognitive process of interest • ) Specificity of Region -> Is it only this region that is activated?
Why can’t we interpret null results in fMRI
No region was significantly stronger activated for task A vs. task B. Cannot conclude region is not involved in A/B • ) Statistical tests make it difficult for H1, not for H0 - can’t interpret null • ) Our method might just not be sensitive enough to detect small differences (e.g. 3x3x3mm. Might not pick up layer-dependent activity)