Dr. AD (Bud) Craig has spent his career as a functional neuroanatomist tracing the path of the interoceptive (homeostatic) signals from both the skin and deep tissues to the insular cortex. After over 30 years in the field he has published a comprehensive description of his work called How Do You Feel?: An Interoceptive Moment with Your Neurobiological Self. In BSP 121 we talk about some of his key discoveries. Although the book is must-read for students and scientists, the goal of our discussion was to make this material accessible to listeners of all backgrounds.
We kept the use of anatomical terms to a minimum but we did talk about how neurons with very small fibers send their signals up the spinal cord to a dedicated area in the thalamus. This is the pathway that is traditional labeled "pain and temperature," but Craig has established that that is an over-simplication. Instead this pathway constitutes the main sensory pathway to the autonomic nervous system. After we talked about why this is important, we also discussed the pathway from the thalamus to the insular cortex. This pathway appears to be unique to primates and in humans the anterior insula integrates signals from all over the body. This is why Dr. Craig argues that we have a much more refined sense of our bodies and our emotions than other species enjoy. We also touched on the role of the insulas (right and left) in mental illness.