Following my proposal of generating and refining a model of the Insular Cortex on this blog, the Neurocritic left some very helpful comments amongst which was a recommendation to have a look at some papers by AD Craig on interoception. The featured paper is by Craig from 2003 and although it is a fairly short article it is information dense and the points are synthesised throughout. Along the way Craig is proposing a very detailed model of how the Insular cortex might be representing emotional awareness. This is interesting as it fits quite neatly with the original model proposed on this blog which says that the insular cortex might be modulating the intensity of the emotions we feel (although I go on to suggest that the GABA receptors may be mediating this).
The article is well written being both easy to understand (although it does require focus) and economical (in use of space) in the process. I was a little bit more interested in the Insular Cortex when reading the article which begins with a description of the homeostatic afferent pathway. The idea is that there are small diameter afferent fibres that convey information of homeostatic importance (e.g. thermal, chemical and hormonal status) to the spinal cord lamina I neurons and trigeminal dorsal horn which in turn pass the information to multiple areas including the Anterior Cingulate Cortex, Insula and Interoceptive Cortex. These in turn project to the Right Anterior Insula where Craig argues that there is a re-representation of the interoceptive map. In effect he says that the Right Anterior Insula represents emotional awareness. With regards to the pathways outlined in the article, these are very neatly summarised in a diagram which shows a complex interconnected hierarchy of areas related to interoception.
Again in terms of the Insular Cortex, Craig talks about the interoceptive cortex (forming part of the insular cortex) responding to noxious stimuli in proportion to the strength of the stimulus as a clear example of the importance of this area in the processing of emotionally significant events. Craig also comments on differences between primate and non-primate neuroanatomy and how this might potentially be utilised to infer phenomenological experiences (or lack thereof) in specific cases.
This is an information rich and very useful paper that can be used in the construction of an insular cortex model. I’ll come back to this as I refine the model and translate it into some assumptions. Thanks to Neurocritic for just the kind of paper that’s needed for this task.
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