Hierarchical Reconfiguration of Neurocognitive Task Set Representations Mediates Cognitive Flexibility.

Cognitive control organizes contexts, stimuli, and actions into hierarchically structured representations that support flexible, goal-directed behavior. This organization allows appropriate actions to be selected in response to changing demands, contexts, and sensory inputs. Critically, different hierarchical levels place unequal demands on flexibility: sensory-motor plans must be updated rapidly to enable behavioral flexibility, whereas higher-level contextual goals are typically updated less frequently. A behavioral consequence of managing these demands is the task switch cost, the performance penalty observed when task representations are reconfigured across trials. Here, we investigated the behavioral and neural sources of switch costs using a hierarchical control task that dissociates context reconfiguration from subordinate rule switching. Functional MRI and behavioral data were collected from healthy human participants (both male and female). Behaviorally, subordinate rule switches were faster than context switches but were more strongly influenced by task-irrelevant perceptual changes, whereas context switches were relatively insensitive to such interference. To characterize the neural basis of these effects, we introduced a novel measure "neural distance", which quantifies trial-to-trial reconfiguration of multivoxel activity patterns. Across the brain, larger neural distances predicted larger RT switch costs, linking representational reorganization to behavioral performance. Importantly, representational reconfiguration differed across hierarchical levels and anatomical systems. Subordinate rule updating was modulated by perceptual input and expressed in distributed perceptual and motor networks, whereas context reconfiguration engaged the lateral middle frontal cortex and was comparatively insulated from interference. Our results reveal the structure of neural representations supporting flexible updating and interference-shielded contextual representations subserving control behavior.