The response time paradox in functional magnetic resonance imaging analyses

Orthogonal neural encoding of targets and distractors supports multivariate cognitive control

The complex challenges of our mental life require us to coordinate multiple forms of neural information processing. Recent behavioural studies have found that people can coordinate multiple forms of attention, but the underlying neural control process remains obscure. We hypothesized that the brain implements multivariate control by independently monitoring feature-specific difficulty and independently prioritizing feature-specific processing. During functional MRI, participants performed a parametric conflict task that separately tags target and distractor processing. Consistent with feature-specific monitoring, univariate analyses revealed spatially segregated encoding of target and distractor difficulty in the dorsal anterior cingulate cortex. Consistent with feature-specific attentional priority, our encoding geometry analysis revealed overlapping but orthogonal representations of target and distractor coherence in the intraparietal sulcus. Coherence representations were mediated by control demands and aligned with both performance and frontoparietal activity, consistent with top-down attention. Together, these findings provide evidence for the neural geometry necessary to coordinate multivariate cognitive control.

From vision to memory: How scene-sensitive regions support episodic memory formation during child development

Previous brain imaging studies have identified three brain regions that selectively respond to visual scenes, the parahippocampal place area (PPA), the occipital place area (OPA), and the retrosplenial cortex (RSC). There is growing evidence that these visual scene-sensitive regions process different types of scene information and may have different developmental timelines in supporting scene perception. How these scene-sensitive regions support memory functions during child development is largely unknown. We investigated PPA, OPA and RSC activations associated with episodic memory formation in childhood (5-7 years of age) and young adulthood, using a subsequent scene memory paradigm and a functional localizer for scenes. PPA, OPA, and RSC subsequent memory activation and functional connectivity differed between children and adults. Subsequent memory effects were found in activations of all three scene regions in adults. In children, however, robust subsequent memory effects were only found in the PPA. Functional connectivity during successful encoding was significant among the three regions in adults, but not in children. PPA subsequently memory activations and PPA-RSC subsequent memory functional connectivity correlated with accuracy in adults, but not children. These age-related differences add new evidence linking protracted development of the scene-sensitive regions to the protracted development of episodic memory.

Common and distinct BOLD correlates of Simon and flanker conflicts which can(not) be reduced to time-on-task effects

The ability to identify and resolve conflicts between standard, well-trained behaviors and behaviors required by the current context is an essential feature of cognitive control. To date, no consensus has been reached on the brain mechanisms involved in exerting such control: while some studies identified diverse patterns of activity across different conflicts, other studies reported common resources across conflict tasks or even across simple tasks devoid of the conflict component. The latter reports attributed the entire activity observed in the presence of conflict to longer time spent on the task (i.e., to the so-called time-on-task effects). Here, we used an extended Multi-Source Interference Task (MSIT) which combines Simon and flanker types of interference to determine shared and conflict-specific mechanisms of conflict resolution in fMRI and their separability from the time-on-task effects. Large portions of the activity in the dorsal attention network and decreases of activity in the default mode network were shared across the tasks and scaled in parallel with increasing reaction times. Importantly, the activity in the sensory and sensorimotor cortices, as well as in the posterior medial frontal cortex (pMFC) - a key region implicated in conflict processing - could not be exhaustively explained by the time-on-task effects.