This is the third part of a series looking at building a model of the Insular Cortex, part of the brain that is thought to play an important role in emotions and awareness. In the 2009 paper ‘How Do You Feel Now? The Anterior Insula and Human Awareness‘ Craig outlines an elegant model of the Insular Cortex which integrates neurophysiological findings. In developing the current model, I thought Craig’s model of the Insular Cortex would be a useful starting point for refining the model covered in Part 1 (see Appendix).
In his multifaceted review of Insular Cortex function, Craig suggests that the Anterior Insular Cortex (AIC) acts as the Limbic Sensory Cortex whilst the Anterior Cingulate Cortex (ACC) acts as the Limbic Motor Cortex. This is justified on the basis of both afferent and efferent connections. Thus Craig notes that efferents from the AIC pass to the Parabrachial Nucleus which is a sensory nucleus. He also notes that the ACC efferents pass through the Periaqueductal grey matter which is involved in motor control.
Craig cites multiple studies showing coactivation of the ACC and AIC and notes both sensory and motor streams in the neighbouring Frontal Cortex. Craig also mentions that both regions receive input from Lamina 1 of the Spinothalamic Tracts. Craig presents an elegant model of complementing ACC and AIC function.
Craig presents two phenomenological correlates of these functions which I found a bit tricky to fully understand at first. For the AIC as a proposed Limbic Sensory Cortex he suggests that this is the anatomical location for feeling of an emotion. That much is straightforward. However Craig then proposes that the ACC as a proposed Limbic Motor Cortex is the anatomical location for the sense of agency or motivation which he suggests is associated with each emotion. Elsewhere he writes that this is where behaviours are initiated. My difficulty is based in semantics. In philosophical terms, a sense of agency is associated with the ability to make a decision but also to act in the world. In psychology there are various definitions of motivation. For instance motivation can be a process that leads to an intention to achieve goals or it can be the process leading to the attainment of those goals.
However Craig argues that emotions are associated with motivation or agency. That each emotion is associated with a corresponding intention to act. Emotions cannot occur without a desire to act. This is a big leap. In order to accept Craig’s model we must also accept that emotions are inextricably linked to acts. Reflecting on this it is true that we express our emotions using muscles of facial expression. There is little difficulty in imagining the facial expressions associated with each emotion. In this sense it is easy to see how an emotion must be associated with an act.
Craig goes one step further though and refers to behaviours. Here again a little reflection suggests that this is not unreasonable. Why else would we have emotions? These are feelings that have powerful effects on us. Emotions reach ‘us’ quickly and directly in a way that casual sensory information does not. Our experiences are more memorable when associated with strong feelings. In evolutionary terms why would our emotions not be linked to behaviours? Indeed this is a central tenet of Cognitive-Behavioural Therapy which has proven to be eminently successful as a psychotherapeutic model.
Still I hold some reservations. Does each emotion have a corresponding associated act? How many emotions or grades of emotions are there? How do we account for features of a Depressive stupor. Surely there must be some emotions which do not have an associated intention to act. As with any model there are limitations within the framework of assumptions and adopting them for the moment it is always possible to return to them at a later date.
Craig has thus suggested that the AIC and ACC act as limbic sensory and motor cortices respectively. Each is associated with a corresponding phenomenological experience – the ‘feeling’ and the ‘sense of wanting to act’ in response to this emotion respectively.
Insular Cortex Resources on this Site
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