A Task-Based Functional MRI Double Dissociation of Visual Language and Feature Processing in Healthy Adults

Task-based functional MRI (fMRI) can identify spatial and temporal brain configurations of blood-oxygen-level-dependent (BOLD) activity for dissociable cognitive functions. Evidence for the discriminability of spatial/temporal/functional combinations (i.e., cognitive modes) can be achieved through the dissociation of task-based BOLD signal changes following whole-brain dimension reduction. A double dissociation can be achieved by task-induced BOLD-change activation of mode A in condition A but not B, and vice versa for activation in mode B. In this study, we analyzed the Coherence-Semantic task from the Midnight Scan Club dataset to test for a double dissociation of Focus on Visual Features (FoVF) from Language (LAN) modes.

The Coherence-Semantic task involved 10 healthy participants scanned over 10 sessions on a 3-Tesla MRI scanner. The task included (1) identifying coherent or random movements of dots (Coherence condition) and (2) identifying a noun versus a verb (Semantic condition). fMRI data were analyzed by combining finite impulse response multivariate multiple regression with whole-brain dimensionality reduction. The dissociations were evaluated at the level of subject-specific task-induced BOLD changes using repeated-measures ANOVAs comparing the Coherence and Semantic conditions.

A double dissociation was observed: FoVF showed task-induced increases in BOLD activation during the Coherence condition, with no significant task-related activation during the Semantic condition, and vice versa for LAN. The default mode (DM) also showed task-related deactivation in both conditions.

This double dissociation provides evidence for the temporal and functional discriminability of FoVF and LAN, contributing to evidence supporting the discriminability of cognitive modes detectable by fMRI.