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22Recent multivariate analyses of brain data have boosted our understanding of the organizational 23 principles that shape neural coding. However, most of this progress has focused on perceptual 24 visual regions (Connolly et al., 2012), whereas far less is known about the organization of more 25 abstract, action-oriented representations. In this study, we focused on humans' remarkable ability 26 to turn novel instructions into actions. While previous research shows that instruction encoding 27 is tightly linked to proactive activations in fronto-parietal brain regions, little is known about the 28 structure that orchestrates such anticipatory representation. We collected fMRI data while 29 participants (both males and females) followed novel complex verbal rules that varied across 30 control-related variables (integrating within/across stimuli dimensions, response complexity, 31 target category) and reward expectations. Using Representational Similarity Analysis 32 (Kriegeskorte et al., 2008) we explored where in the brain these variables explained the 33 organization of novel task encoding, and whether motivation modulated these representational 34 spaces. Instruction representations in the lateral prefrontal cortex were structured by the three 35 control-related variables, while intraparietal sulcus encoded response complexity and the fusiform 36 gyrus and precuneus organized its activity according to the relevant stimulus category. Reward 37 exerted a general effect, increasing the representational similarity among different instructions, 38 which was robustly correlated with behavioral improvements. Overall, our results highlight the 39 flexibility of proactive task encoding, governed by distinct representational organizations in 40 specific brain regions. They also stress the variability of motivation-control interactions, which 41 appear to be highly dependent on task attributes such as complexity or novelty. 42 Significance Statement 43In comparison with other primates, humans display a remarkable success in novel task contexts 44 thanks to our ability to transform instructions into effective actions. This skill is associated with 45 proactive task-set reconfigurations in fronto-parietal cortices. It remains yet unknown, however, 46how the brain encodes in anticipation the flexible, rich repertoire of novel tasks that we can 47 achieve. Here we explored cognitive control and motivation-related variables that might 48 2 orchestrate the representational space for novel instructions. Our results showed that different 49 dimensions become relevant for task prospective encoding depending on the brain region, and 50 that the lateral prefrontal cortex simultaneously organized task representations following different 51 control-related variables. Motivation exerted a general modulation upon this process, diminishing 52 rather than increasing distances among instruction representations. 53 3

Recent multivariate analyses of brain data have boosted our understanding of the organizational principles that shape neural coding. However, most of this progress has focused on perceptual visual regions (Connolly et al., 2012), whereas far less is known about the organization of more abstract, action-oriented representations. In this study, we focused on humans' remarkable ability to turn novel instructions into actions. While previous research shows that instruction encoding is tightly linked to proactive activations in frontoparietal brain regions, little is known about the structure that orchestrates such anticipatory representation. We collected fMRI data while participants (both males and females) followed novel complex verbal rules that varied across control-related variables (integrating within/across stimuli dimensions, response complexity, target category) and reward expectations. Using representational similarity analysis (Kriegeskorte et al., 2008), we explored where in the brain these variables explained the organization of novel task encoding, and whether motivation modulated these representational spaces. Instruction representations in the lateral PFC were structured by the three control-related variables, whereas intraparietal sulcus encoded response complexity and the fusiform gyrus and precuneus organized its activity according to the relevant stimulus category. Reward exerted a general effect, increasing the representational similarity among different instructions, which was robustly correlated with behavioral improvements. Overall, our results highlight the flexibility of proactive task encoding, governed by distinct representational organizations in specific brain regions. They also stress the variability of motivation-control interactions, which appear to be highly dependent on task attributes, such as complexity or novelty.

The success of humans in novel environments is partially supported by our ability to implement new task procedures via instructions. This complex skill has been associated with the activity of control-related brain areas. Current models link fronto-parietal and cingulo-opercular networks with transient and sustained modes of cognitive control, based on observations during repetitive task settings or rest. The current study extends this dual model to novel instructed tasks. We employed a mixed design and an instruction-following task to extract phasic and tonic brain signals associated with the encoding and implementation of novel verbal rules. We also performed a representation similarity analysis to capture consistency in task-set encoding within trial epochs. Our findings show that both networks are involved while following novel instructions: transiently, during the implementation of the instruction, and in a sustained fashion, across novel trials blocks. Moreover, the multivariate results showed that task representations in the cingulo-opercular network were more stable than in the fronto-parietal one. Our data extend the dual model of cognitive control to novel demanding situations, highlighting the high flexibility of control-related regions in adopting different temporal profiles.

Human's success in novel environments is supported by our ability to implement new task procedures via instructions. This complex skill has been associated with the activity of control-related brain areas.Current models link fronto-parietal and a cingulo-opercular networks with transient and sustained modes of cognitive control, based on observations during repeated task settings or rest (Dosenbach et al. 2008).In the current study we extended this dual model to novel task instructions. For this, we employed a mixed design and an instruction-following task to extract phasic and tonic brain signals associated with the encoding and implementation of novel verbal rules. We also performed a representation similarity analysis to capture consistency in task set encoding within trial epochs. Our findings show that both networks are involved while following novel instructions: transiently, during the implementation of the instruction, and in a sustained fashion, across novel trials blocks. Moreover, the multivariate results showed that task representations in the cingulo-opercular network were more stable than in the frontoparietal one. Our data extends the dual model of cognitive control to novel demanding situations, highlighting the high flexibility of control-related regions in adopting different temporal dynamics.

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