The amygdala part of the limbic system doesn’t process beliefs

Does your desk light switch on or off when other people in the office switch their desk lights on or off? Something in the wiring would probably be wrong if it did. And wouldn’t you expect that other desk lights would still operate normally if your desk light’s bulb burned out, although everyone may be plugged into the same electrical circuit?

It surprised the researchers of this 2015 CalTech/MIT study when:

“Two patients with bilateral amygdala lesions performed a belief reasoning test.

Both patients showed typical test performance and cortical activity when compared with nearly 500 healthy controls.”

The study’s overall frame of reference was expressed as:

“Humans use a so-called “theory-of-mind” to reason about the beliefs of others. Neuroimaging studies of belief reasoning suggest it activates a specific cortical network. The amygdala is interconnected with this network and plays a fundamental role in social behavior.”

The experimental test:

“Was designed to optimize functional contrast in those brain regions thought to be involved in attempts, be they successful or unsuccessful, to evaluate the veracity of another person’s belief about the world.”

A “belief reasoning test” about others’ beliefs is a cerebral exercise. The amygdala, in contrast, is the central hub of a person’s limbic system.

The way I look at it is:

  • The “belief reasoning test” had no emotional content that reliably activated a person’s amygdala in other research.
  • fMRI scans confirmed that limbic system areas in the 2 lesioned subjects weren’t activated during the test.
  • Apply the logic of Occam’s razor, and we arrive at the test results.

I’m not sure why the researchers stated the results:

“Suggest a reevaluation of the role of the amygdala and its cortical interactions in human social cognition.”

Per the analogy, if your desk light’s bulb burned out, would you be surprised that it didn’t affect the normal operations of desk lights in other offices, although they all may be plugged into the same circuit?

Maybe this study will clue in researchers that areas of the limbic system such as the amygdala are not slaved to the cerebrum. It’s hard to change the current research mindset/social meme of cerebral dominance, though, so maybe the clue will be missed. “Amygdala lesions do not compromise the cortical network for false-belief reasoning”


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