Task context is broadly encoded in the human brain

Abstract

Cognitive control depends on the task context as a top-down modulatory influence on ongoing processing. Cognitive neuroscience theories of cognitive control have associated the maintenance of context, and its deployment as a control signal, with neural populations in the dorsolateral prefrontal cortex (DLPFC). Importantly, however, the way information about the task context is propagated and used throughout the brain remains largely unspecified. A longstanding hypothesis is that neural representations of context in DLPFC directly influence neural processing only where this information is needed to resolve competition, integrating top-down context inputs from DLPFC conjunctively with local processing. However, an alternative hypothesis is that context is broadcast and maintained more widely throughout the brain than necessary. In this way, context is available for integration with local populations when needed. Here, we tested these hypotheses by analyzing a large multisession fMRI data set collected while participants performed a context-dependent task using a hierarchical rule that features one superordinate context versus a control task that used a non-hierarchical, flat rule. Across a range of analyses, we found that the superordinate task context is robustly and widely coded throughout the cortex, evident in every largescale cortical network. Across a range of controls, the superordinate context was the only task feature to show this property. Indeed, context accounted for the most variance in cortex-wide activity patterns across analyses. In contrast, the integration of this context with coding of other task features was evident in only a subset of context-coding regions, principally those in higher-order control and attentional networks and visual perceptual stream areas. These latter areas showed interactions with context that were consistent with object-based attentional modulation, as needed by the task. These results provide initial empirical support for a context broadcast model of top-down control in the brain.