Tuesday, July 06, 2021

More about insular cortex and pain: Musings, Part 2

A few months ago I had a dopamine spurt of some kind, and published a blog post to do with brain lateralization and insular cortex and implications about pain. Here is a link: A few new musings about pain and brain
Consider this a follow-up post to that one. 

Firstly, I want to include a link to the Tucker paper from 1984, the one I found buried in a book about brain and self/no self.
Tucker, D. M., & Williamson, P. A. (1984). Asymmetric neural control systems in human self-regulationPsychological Review, 91
(2), 185–215
(Obviously, I forgot to include this particular link at the time, even though I linked to all the other things that are connected and that mostly just swim in a school, like fish, in my mind somewhere. That's lock-down brain for you. It misses a few things.) 
Looks like I did link it in this old blogpost from 2012 though, about Iain McGilchrist's book on brain lateralization. Asymmetry of brain sides: size, structure, neurochemistry

Here is the abstract: 

Reviews the literature on the neurotransmitter substrates controlling motor readiness, showing that these substrates produce qualitative changes in the flow of information in the brain: Dopaminergic activation increases informational redundancy, whereas noradrenergic arousal facilitates orienting to novelty. Evidence that these neurotransmitter pathways are lateralized in the human brain is consistent with the left hemisphere's specialization for complex motor operations and the right hemisphere's integration of bilateral perceptual input. Principles of attentional control are suggested by the operational characteristics of neural control systems. The affective features of the activation and arousal systems are integral to their adaptive roles and may suggest how specific emotional processes dynamically regulate cognitive function. (4½ p ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)

This morning a member of the Dermoneuromodulating group posted an abstract to a paper about the insular cortex and pain from way back in 2010 which somehow escaped my attention at the time: 
Wiech K, Lin CS, Brodersen KH, Bingel U, Ploner M, Tracey I. Anterior insula integrates information about salience into perceptual decisions about painJ Neurosci. 2010;30(48):16324-16331. doi:10.1523/JNEUROSCI.2087-10.2010

Here is the abstract:

The decision as to whether a sensation is perceived as painful does not only depend on sensory input but also on the significance of the stimulus. Here, we show that the degree to which an impending stimulus is interpreted as threatening biases perceptual decisions about pain and that this bias toward pain manifests before stimulus encounter. Using functional magnetic resonance imaging we investigated the neural mechanisms underlying the influence of an experimental manipulation of threat on the perception of laser stimuli as painful. In a near-threshold pain detection paradigm, physically identical stimuli were applied under the participants' assumption that the stimulation is entirely safe (low threat) or potentially harmful (high threat). As hypothesized, significantly more stimuli were rated as painful in the high threat condition. This context-dependent classification of a stimulus as painful was predicted by the prestimulus signal level in the anterior insula, suggesting that this structure integrates information about the significance of a stimulus into the decision about pain. The anticipation of pain increased the prestimulus functional connectivity between the anterior insula and the midcingulate cortex (MCC), a region that was significantly more active during stimulation the more a participant was biased to rate the stimulation as painful under high threat. These findings provide evidence that the anterior insula and MCC as a “salience network” integrate information about the significance of an impending stimulation into perceptual decision-making in the context of pain.

Now, it's true that this 2010 paper is specifically about nociceptive pain, and we must bear in mind that there are a few other kinds now formally acknowledged by IASP.  

Also it talks about "activation level of bilateral anterior insular cortex." So it would seem that these researchers weren't interested in sifting out any info about lateralization in their study. Oh well... c'est la vie. 

I was prompted to dig up a 2015 Scientific American Mind article by Lydia Denworth on the connection between touch and insular cortex, mostly for the amazing illustrations of representative maps for somato-sensory cortex and for insular cortex. (Note: the link does not contain these images but the original does.)

Note that the insular cortex map is "hypothetical" - I guess this means that the researchers didn't go directly into the brain with probes the way Wilder Penfield did for the somatosensory cortex. However, I am willing to accept that it represents C-tactile afferents, those lovely little pleasure sensors all over the skin that the somatosensory cortex doesn't map very well for. 
In fact, if you compare the two maps they are like opposites. Big mouth, small mouth. Big hand, small hand. Small body, large body. Small head, large head. 

Anyway, I'm all out of dopamine, so, time to stop. 

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