The featured paper is ‘Interoception: the sense of the physiological condition of the body’ by A.D (Bud) Craig, which is a review article of some considerable depth and very kindly recommended by the Neurocritic as being useful in the construction of a model of the Insular Cortex. This is an impressive paper, very rich in concepts which are elaborated upon as the article develops. The article is developed with a bottom-up approach – so we first go through the physiological characteristics of the afferent pathways before moving onto the higher level concepts involving rerepresentation in the Insular cortex as well as their implications.
Craig identifies the following Gemeingefuhl (which is German for bodily feelings) as including
There is then a discussion of how Charles Sherrington and William James conceptualised the role of these bodily feelings with these conceptualistions being highly influential. Craig’s discussion of his model of interoception involves a detailed discussion of the neurophysiology of lamina I afferents. He outlines the function of the lamina I spinothalamocortical system in conveying interoceptive information to the autonomic/homeostatic centres and then a thalamocortical representation of the physiological body state. Craig then proposed that it is the rerepresentation in the non-dominant anterior insular cortex that leaves us with the sensation of how we feel.
There is a very detailed discussion at the level of the spinothalamic pathway and the ventromedial thalamic nucleus. The paper gets particularly interesting after this with a lot of neuroimaging evidence for activation of the Insular Cortex in response to activities where information would be expected to be transmitted through the lamina I afferents e.g. thermal pain, graded itch, respiration and so on. Along the way we learn that some of the activity was incorrectly attributed to the secondary somatosensory region instead of the Insular Cortex. Craig also draws parallels between the thermal grid paradigms and the central pain syndrome with theoretical predictions informing further research paradigms that may point to treatments. An argument for considering the Insular Cortex as the limbic sensory cortex and the Anterior Cingulate Cortex as the limbic motor cortex are discussed and connections between the Insular Cortex and the amygdala, hypothalamus, brainstem regions and orbitofrontal cortex are emphasised. The relationship between and roles of the Anterior Cingulate Cortex and the Insular Cortex are developed further.
However what I found particularly interesting was the influence of Antonio Damasio. Indeed Craig discusses Damasio’s ‘Somatic Marker’ hypothesis which looks at how interoceptive information is remapped in the nervous system and the implications this has for interactions with others. Like an earlier paper by Craig, this is an impressive work that has many implications but which requires close study.
Craig A.D. How do you feel? Interoception: the sense of the physiological condition of the body. Nature Reviews. Neuroscience. Vol 3.
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