Simulation Before Vision: Interoceptive Origins of Offline Simulation and the Evolution of Mental Imagery

How did visual imagery evolve, and what adaptive problem did it originally solve? The broader research tradition has carried an implicit and largely unexamined assumption that simulation emerged as an extension of the visual system. I argue that the origins of imagery lie not in the visual cortical network but in interoceptive systems. Offline simulation is only useful if organised around outcomes that matter; interoception is central to encoding the bodily costs and rewards that define what those outcomes are. Drawing on comparative neuroanatomy, phylogenetic evidence, and the neuroscience of offline simulation, I show that this interoceptive architecture was established before elaborated visual cortex existed. Motor simulation constituted its earliest form, with visual information gradually incorporated to contribute discriminative specificity to an already-functional architecture. It was only after the nocturnal bottleneck, with the substantial re-elaboration of visual cortex in the primate lineage, that vision assumed its dominant role within this simulation architecture. The visual system was recruited to solve the discriminability problem that relatively coarse interoceptive signals alone could not resolve. A major implication is that imagery and emotion are not linked through downstream amplification, as the dominant view proposes, but are co-generated from the same underlying system and explains why emotional disturbance can abolish imagery capacity entirely. This account reconceptualises mental imagery not as an extension of visual perception but as a component of a broader simulation system whose logic was shaped by the demands of predicting and evaluating bodily states.