Selection mechanisms

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Chapter 6 endnote 15 & 18, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

[note 15] Depending on the context, whether you read horizontally or vertically, you’ll perceive the central symbol as a “B” or a “13.” Your control network helps select the winning concept ​— ​letter or number? ​— ​in each moment.


[note 18] Your control network helps select between emotion and non-emotion concepts (is this anxiety or indigestion?), between different emotion concepts (is this excitement or fear?), between different goals for an emotion concept (in fear, should I escape or attack?), and between different instances (when running to escape, should I scream or not?).

I would be remiss if I did not point out that there are other selection mechanisms in the brain, in addition to the control network, that help to resolve competition between predictions.

According to the work of neuroscientist Gerald Edelman and his colleagues, several other selection mechanisms might exist.[1] In the brainstem, groups of cells bathe the brain in chemicals (neurotransmitters). As a group, these chemicals are called neuromodulators, but you may have heard of some by name, because occasionally they get some press: dopamine, serotonin, norepinephrine, and so on. Among other things, these chemicals change the signal-to-noise ratio in various parts of the brain, particularly when something is about to happen that requires effort or is relevant to the body’s energy budget. Edelman and his colleagues propose that the brain uses these chemicals as a selection mechanism. Interesting, there is only one set of regions in the cortex that project to the cell beds in the brain stem to control this proposed selection mechanism: the body-budgeting regions of the interoceptive network![2]

The second mechanism comprises the connections between cortical neurons that run through the thalamus. The thalamus is large subcortical region made up of nucleus groups; it sends and receives projections to every region of the cortex. Class 1 projections from the thalamus bring the sensory information to the cortical column for comparison with the prediction (to compute prediction errors); Class 2 (matrix) projections tune the predictions and prediction errors.[3] The thalamus acts like a gateway for incoming sensory input; one way to reduce prediction error is to close this gateway. Body budgeting areas of the cortex modulate this gateway.[4][5] In a way, the thalamus also acts like a hub for predictions between cortical regions.[6]


Notes on the Notes

  1. For an accessible discussion, read Edelman, Gerald. M., & Giulio Tononi. 2000. A Universe of Consciousness. New York: Basic.
  2. Mesulam, M. Marcel. 2000. "Behavioral anatomy: Large-scale networks, association cortex, frontal syndromes, the limbic system and hemispheric specialization. In Principles of Behavioral and Cognitive Psychology, second edition, edited by M. Marcel Mesulam, 1-120. New York: Oxford University Press.
  3. Sherman, S. Murray, and R. W. Guillery. 2011. "Distinct functions for direct and transthalamic corticocortical connections." Journal of neurophysiology 106 (3): 1068-1077.
  4. Zikopoulos, Basilis, and Helen Barbas. 2006. "Prefrontal projections to the thalamic reticular nucleus form a unique circuit for attentional mechanisms." Journal of Neuroscience 26 (28): 7348-7361.
  5. Zikopoulos, Basilis, and Helen Barbas. 2007. "Parallel driving and modulatory pathways link the prefrontal cortex and thalamus." PLoS One 2 (9): e848.
  6. Larkum, Matthew. 2013. "A cellular mechanism for cortical associations: an organizing principle for the cerebral cortex." Trends in Neurosciences 36 (3): 141-151.