The Life and Legacy of Arthur D. Craig, Jr.: A Pioneer in Interoception.

A.D. (Bud) Craig (1951-2023) redefined the concept of interoception and provided a novel, revolutionary understanding of the neural basis for human awareness. In unsurpassed anatomical-physiological studies in monkeys, Craig showed that the insular cortex is the primary sensory cortex for interoception, or the image of the "material me" that provides a homeostatic representation of the physiological condition of the body. He showed that the insula contains a postero-anteriorly organized somatotopic map of the interoceptive sensations, and that it encodes both the localization and the intensity discrimination of interoceptive sensations. In seminal work in humans, he demonstrated that the interoceptive feelings are re-represented, and multimodally integrated, in anterior portions of the insula in sequence of increasingly homeostatically efficient representations that integrate all salient neural activity. He further showed that subjective awareness is associated with activation of the anterior insular cortex and suggested that this brain region also is critical for fluid intelligence and the perception of time. His work has led to a paradigm shift in our understanding of interoception and how interoceptive sensations underlie consciousness, a topic that long has been considered elusive, or even beyond our comprehension.