Astral Codex Ten

striatum

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striatum

Article

striatum is a recurring concept in the Astral Codex Ten archive, appearing 2 times across 2 issues between March 26, 2021 and September 30, 2022. The archive places it in contexts such as ""If there’s a predator nearby”, he writes “the flee-predator region will put in a very strong bid to the striatum""; “especially in a GABAergic circuit like the striatum”. It most often appears alongside dopamine, 5HT2A serotonin, acetylcholine.

Metadata

  • Category: Concepts
  • Mention count: 2
  • Issue count: 2
  • First seen: March 26, 2021
  • Last seen: September 30, 2022

Appears In

Source Context

Recovered passages from the original issue text. When the raw archive preserved outbound links inside the source passage, they are listed directly under the quote.

Toward A Bayesian Theory Of Willpower
March 26, 2021 · Original source
I've previously quoted Stephan Guyenet on the motivational system of lampreys (a simple fish used as a model organism). Guyenet describes various brain regions making "bids" to the basal ganglia, using dopamine as the "currency" - whichever brain region makes the highest bid gets to determine the lamprey's next action. "If there's a predator nearby", he writes "the flee-predator region will put in a very strong bid to the striatum".
Inline links: motivational system of lampreys
Highlights From The Comments On Unpredictable Reward
September 30, 2022 · Original source
One neuroscientific perspective on this is that in order for dopamine to track reward prediction *error* (RPE), it is logically necessary that some other piece of neural circuitry track reward prediction *per se*, often called "value." Those of us who think that dopamine is computing RPE on a moment-by-moment basis (the first derivative of value; see Kim, Malik et al., Cell, 2020) therefore generally also believe that some other part of the brain, especially the ventral striatum (aka nucleus accumbens) and perhaps also the prefrontal cortex, maintains an estimate of value that gets updated by dopamine. And indeed, there are dozens of papers reporting that neural firing in these brain regions correlate with value over and above RPE.
Most people think this is the case because when you put subjects in an fMRI scanner and have them do tasks where they get reward or learn cues that are associated with reward, you robustly get RPE-related BOLD activity in the NAc, and only rarely/more weakly in the ventral tegmental area (VTA), which contains the dopamine neurons that project to the NAc. So when you see those nice fMRI maps, the NAc is lit up in red. But the physiological basis of this fMRI signal is hotly debated (for example, it could represent primarily synaptic input rather than actual neuronal firing, especially in a GABAergic circuit like the striatum), and in single-unit recordings in mice, rats, and monkeys, it is unequivocal that dopamine neurons in the VTA show much more RPE signaling than the striatum.
That said, it is also true that (1) NAc neurons correlate strongly with value and also respond to some extent to rewards, predicted and unpredicted; (2) cocaine or amphetamine in the NAc (and another region of the ventral striatum called the olfactory tubercle), which dramatically elevate dopamine levels, elicit robust responses; and (3) in the context of the "liking vs. wanting" framework you allude to, Kent Berridge and others have argued that the NAc contains a "hedonic hotspot", along with closely linked regions like the prefrontal cortex and ventral pallidum. This is an operational definition meaning that when you infuse opioid receptor agonists into said region, the animals react with pleasure, and conversely if you lesion/block activity in these areas, they don't show these behaviors as much, or even start showing defensive behaviors.