The CBD Imaging Analysis Modeled Correct Recall Trials
The imaging model used recall trials associated with correct responses. Its brain-activation findings therefore describe a selected component of task performance rather than all correct and incorrect attempts together.
The experiment linked a task to BOLD activity
Participants at clinical high risk of psychosis received a single 600 mg CBD dose or placebo before functional MRI. They learned word pairs and later recalled the missing member of each pair. The authors modeled the blood-oxygen-level-dependent response using trials associated with correct recall.
The selection defines the neural comparison
Restricting a model to correct responses can help compare activity during successful task execution. It does not supply the same information as modeling error-related processing or every attempted trial. A difference in activation during successful recall should not be relabeled as a measured improvement in the number of items remembered.
The behavioral null remains relevant
The study found no significant group difference in task performance despite selected regional imaging differences. It did not establish prevention of psychosis or everyday cognitive improvement. The small parallel-group design and trial-selection rule should accompany a mechanistic interpretation, rather than converting a BOLD signal into an individual clinical treatment response.
Related analysis: brain activation and the null task-performance result.
Research cited
Bhattacharyya and colleagues (2018). Effect of Cannabidiol on Medial Temporal, Midbrain, and Striatal Dysfunction in People at Clinical High Risk of Psychosis. DOI: 10.1001/jamapsychiatry.2018.2309.
