Thursday, April 20, 2006

Lose Yourself

You better lose yourself in the music, the moment
You own it, you better never let it go
You only get one shot, do not miss your chance to blow
This opportunity comes once in a lifetime yo

--Eminem, Lose Yourself

When the Brain Loses Its Self: Prefrontal Inactivation during Sensorimotor Processing
Ilan I. Goldberg, Michal Harel, and Rafael Malach
Neuron, Vol 50, 329-339, 20 April 2006

A common theme in theories of subjective awareness poses a self-related “observer” function, or a homunculus, as a critical element without which awareness can not emerge. Here, we examined this question using fMRI. In our study, we compared brain activity patterns produced by a demanding sensory categorization paradigm to those engaged during self-reflective introspection, using similar sensory stimuli. Our results show a complete segregation between the two patterns of activity. Furthermore, regions that showed enhanced activity during introspection underwent a robust inhibition during the demanding perceptual task. The results support the notion that self-related processes are not necessarily engaged during sensory perception and can be actually suppressed.
Let's say you're interested in the "neural correlates of consciousness", specifically that peculiar variant sometimes known as self-awareness. When contemplating the nature of your own self-awareness, it seems obvious that you are not focused on your existence as a unique entity, a human being with a "unitary" sense of self, 24 hours a day, or even during sober non-drug-addled waking hours. It would be a surprising, in fact, if the brain regions most active during self-reflective introspection were the exact same ones most active while you're engaged in a demanding perceptual task. You don't have the cognitive resources available to do both at the same time (at least, to do both very well at the same time). And it seems readily apparent that when you're daydreaming or introspecting, you're less aware of your physical surroundings.

Nevertheless, the paper by Goldberg et al. comes to this obvious conclusion: there was "a complete segregation between the two patterns of activity" [self-reflective introspection vs. demanding perceptual task].

Now what does this mean? According to the authors,
Our results show a clear segregation between regions engaged during self-related introspective processes and cortical regions involved in sensorimotor processing. Furthermore, self-related regions were inhibited during sensorimotor processing. Thus, the common idiom ‘‘losing yourself in the act’’ receives here a clear neurophysiological underpinnings. [sic... oh copy editor!?!]
What did they actually show in their experiment? The task conditions were as follows:
  1. Categorization/Slow - view pictures or listen to short musical clips presented once every 3 seconds. Classify the pictures as animal/non-animal and the tunes as trumpet/non-trumpet.
  2. Categorization/Fast - same as above, but stimuli presented once every second.
  3. Introspection/Slow - same stimuli presented at the slow rate, but think about your emotional reaction to each one and rate it as high or low.
Oh, they didn't have an Introspection/Fast condition?? But maybe you'd be less "self-aware" if you had to react to the stimuli more quickly...

ANYWAY, in the Categorization/Slow versus Introspection/Slow comparison,
Regions selectively activated by the introspection task were found within the superior frontal gyrus (SFG) extending medially to the anterior cingulate region and caudally to the paracingulate region; the latter region showed similar activation also in the right hemisphere. Additional focus was found in the posterior part of the middle frontal gyrus, just anterior to the precentral sulcus. Finally, bilateral activations were found in the posterior part of the inferior frontal gyrus extending to the anterior insula. ... No cortical region showed the opposite preference, i.e., significantly higher activations to slow categorization versus introspection.
So a pretty wide swath of superior and medial frontal cortex was activated to a greater extent in the introspection task, but presumably similar (other) regions were engaged by both tasks. As predicted, the Categorization/Fast condition engaged sensorimotor cortex to a greater extent than the Categorization/Slow condition.

I guess the key finding here is that SFG and other introspective frontal regions were deactivated (i.e., below resting baseline levels) in the categorization conditions, and this is the supposed neurophysiological underpinning of "losing yourself."

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