Neural substrate of self-awareness

Researchers (Philippi and others) have investigated a patient with extensive damage in a location that has been suggested as the source of self-awareness to evaluate that hypothesis. (see citation below). The patient, known as R, has bilateral damage to the insula, anterior cingulate and medial prefrontal cortices. Some believe these areas are essential for basic self-awareness. But there are other views too.

 

In order to help settle this question, the team did a very thorough imaging of the damage and gave the patient a battery of tests to establish the extent of his self-awareness. R had amnesia which eliminated much of his autobiographical self-awareness. He also was not aware of his own loss of a sense of smell. These limitations were due to damage outside the area being studied. But aside from these two limitations, his self-awareness was intact.

 

Here is in the paper a very clear description of the types of self-awareness they tested for and the tests used. Those of you that have an interest in the components of self-awareness would find this interesting, and can read the original. The gust is that they recognized three types of self-awareness: core (feelings of the body, elementary self-consciousness, personal agency, ownership of actions and sensory perceptions, self-recognition, sentience); extended (autobiography, self-concept using physical, affective and personality traits); introspective (introspection, reflection on own mental states, actions/consequences, social skills).

 

The results severely weaken the idea that the insula, anterior cingulate and medial prefrontal cortices are essential for self-awareness. The paper cites other evidence in keeping with their results. What are the alternatives as the authors see it?

By contrast, the hypothesis implicating brainstem nuclei in generating the ‘‘primordial feelings’’ essential to Core SA is entirely compatible with our findings (as R does not have brainstem damage), and is in keeping with the fact that selective damage to brainstem tegmentum has long been associated with impaired consciousness. Furthermore, this hypothesis is also consistent with the striking presence of core SA and basic emotional functioning found in children who are missing their cortex due to hydranencephaly.

Intact regions of R’s cerebral cortex, such as the posteromedial cortex (which includes the posterior cingulate, the precuneus, and the retrosplenial cortices) and the inferior parietal lobule, could constitute the critical substrate for preserved SA in R. Both of these areas are critical nodes of the Default Mode Network. Activity in the posteromedial cortex, in particular, has been consistently associated with consciousness. Of note, R had preserved functional connectivity within this region of the brain. Intracranial recordings have also associated the posteromedial cortex with self-referential processing. Moreover, Dastjerdi and colleagues found that intracranial electrodes placed near the retrosplenial cortices responded preferentially to autobiographical memory stimuli. These findings are consistent with neuropsychological research which has implicated the retrosplenial cortex in autobiographical memory retrieval. R’s intact retrieval of some autobiographical knowledge might be mediated in part by the retrosplenial cortices. More generally, our findings are compatible with hypotheses invoking distributed neural systems as a substrate for SA and its components.

 

To me this suggests a system of great antiquity that is based in the brain stem, passes through the mid-brain to the cortex, and is dispersed in the cortex. The same picture as can be seen in consciousness in general – driven by the brain stem, up to reticular formation, passing through the thalamus and involving much of the cortex. Why should awareness of self be much different from awareness of the rest of the world?

Note:

Sorry, I don’t know how this happened. The citation is copied from ReasearchBlogging is usually for posting there but does not work. Here is another link

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0038413

 

 

ResearchBlogging.org

Philippi CL, Feinstein JS, Khalsa SS, Damasio A, Tranel D, & et al (2012). Preserved Self-Awareness following Extensive Bilateral Brain Damage to the Insula, Anterior Cingulate, and Medial Prefrontal Cortices PLoS ONE, 7 (8) : 10.1371/journal.pone.0038413

2 thoughts on “Neural substrate of self-awareness

  1. Is there a reason that the doi link directs right back to this page and not the article?

    JK: Thank you for letting me know. I have put a correct link in a note at the bottom of the posting. I do not know how to amend the ReasearchBlogging citation.

Leave a Reply to Nick Cancel reply

Your email address will not be published. Required fields are marked *