My main answer is that the “toy loop model”s here are pretty bad and shouldn’t be taken literally. I have an updated discussion here (posts 5-6 mostly), but even that has some issues; I made more progress in the last six months that I haven’t written up yet.
I’m more confident in the “‘Context’ in the striatum value function” section here. The convergence of many striatal neurons onto few “final answer” neurons (in both pallidum and SNr) seems pretty central to me. Kinda vaguely like the striatum is the final hidden layer, and pallidum / SNr / whatever neurons are “heads”, in a loose ML analogy.
To answer your question slightly, I’m working at a pretty high level (Marr’s “algorithm level”, I suppose) here. It’s possible to have a signal which is best thought of as exciting something, but is actually implemented by an inhibitory connection. For example, it could be “disinhibitory” (inhibiting an inhibitor). Swanson 2000 does indeed claim that pallidum-to-brainstem signals are disinhibitory, specifically by inhibiting the inhibitory striatum-to-brainstem signals.
But anyway, yeah, I would read this post as kinda “early attempt” rather than correct. A lot of the details are very much wrong. I’ll make the top-note more prominent.
My main answer is that the “toy loop model”s here are pretty bad and shouldn’t be taken literally. I have an updated discussion here (posts 5-6 mostly), but even that has some issues; I made more progress in the last six months that I haven’t written up yet.
I’m more confident in the “‘Context’ in the striatum value function” section here. The convergence of many striatal neurons onto few “final answer” neurons (in both pallidum and SNr) seems pretty central to me. Kinda vaguely like the striatum is the final hidden layer, and pallidum / SNr / whatever neurons are “heads”, in a loose ML analogy.
To answer your question slightly, I’m working at a pretty high level (Marr’s “algorithm level”, I suppose) here. It’s possible to have a signal which is best thought of as exciting something, but is actually implemented by an inhibitory connection. For example, it could be “disinhibitory” (inhibiting an inhibitor). Swanson 2000 does indeed claim that pallidum-to-brainstem signals are disinhibitory, specifically by inhibiting the inhibitory striatum-to-brainstem signals.
But anyway, yeah, I would read this post as kinda “early attempt” rather than correct. A lot of the details are very much wrong. I’ll make the top-note more prominent.