Neuromodulation outline
Modulatory signals tune how the nervous system responds---changing learning rates, adjusting precision, and gating which pathways are active.
The brain doesn't just process signals---it tunes how it processes them. Modulatory neurotransmitters like dopamine, norepinephrine, serotonin, and acetylcholine alter the responsiveness of neural circuits, changing learning rates, adjusting the precision of predictions, and gating which pathways are active. These signals don't carry content like "this is a dog" or "move your hand"; they broadcast context: how much to weigh this signal, how quickly to update, whether to exploit familiar routes or explore alternatives.
Think of neuromodulation as the brain's gain control. Dopamine spikes when predictions are violated---signalling "this matters, update your model." Norepinephrine tracks unexpected uncertainty---"something changed, pay attention." Acetylcholine marks expected uncertainty---"the world is volatile here, stay flexible." These modulators don't tell you what to learn; they tell you when and how much.
This architecture explains why the same event can produce very different behavioural outcomes depending on state. High arousal (elevated norepinephrine and cortisol) tightens the aperture---you fall back on familiar neural pathways, filter inputs aggressively, and execute with bias towards what you already know. Low arousal broadens sampling---you're more plastic, more exploratory, more willing to update. Dopamine shapes which updates stick: dopamine during an event strengthens the pathways that were active, making them more likely to fire next time the context recurs. This is why anticipation of reward activates much of the same machinery as reward itself, and why context around a reward becomes predictive---the modulatory signal marks the whole episode for consolidation.
Practically, this means state management is learning management. Regulate arousal and you regulate the plasticity-stability trade-off. If you need to explore or update, calm down---lower arousal broadens the system. If you need to execute a trained routine under pressure, a bit of urgency sharpens focus and tightens the model. But push too far in either direction and performance degrades: too calm and you're unfocused; too aroused and you're rigid.
How can you think with this?
These heuristics help you apply this neural system:
Ways to think with this
Practical ways to use this neural mechanism in understanding behaviour
WIP: State tunes the system
Modulatory signals don't carry content---they broadcast context. They tell the system how much to weigh incoming signals, how quickly to update, and whether to exploit familiar routes or explore alternatives. Dopamine marks prediction errors worth learning from. Norepinephrine tracks unexpected uncertainty. Acetylcholine marks expected volatility. These signals tune the gain on learning and attention, which means the same event produces different outcomes depending on state.
So what can you do? Manage state to manage learning. If you need to update or explore, calm down---lower arousal broadens the system and increases plasticity. If you need to execute a trained routine under pressure, a bit of urgency sharpens focus and tightens the model. But push too far in either direction and performance degrades: too calm and you're unfocused; too aroused and you're rigid.
WIP: Arousal gates flexibility
High arousal---elevated norepinephrine and cortisol---tightens the aperture. You fall back on familiar pathways, filter inputs aggressively, and execute with bias towards what you already know. Low arousal broadens sampling. You're more plastic, more exploratory, more willing to update. This means the plasticity-stability trade-off isn't fixed---it's tunable via state.
So what can you do? Regulate arousal to regulate the trade-off. Practise new behaviours in low-arousal conditions first, where the system is more willing to update. Then gradually introduce arousal so the new route consolidates under the conditions where you'll actually need it. And if you're stuck in rigid patterns under stress, the issue isn't lack of willpower---it's that high arousal has locked the system into exploitation mode.
WIP: Dopamine marks episodes for consolidation
Dopamine release during an event strengthens the pathways that were active, making them more likely to fire next time the context recurs. This is why anticipation of reward activates much of the same machinery as reward itself, and why context around a reward becomes predictive. The modulatory signal marks the whole episode, not just the outcome.
So what can you do? Pair new behaviours with contexts that naturally generate dopamine---novelty, surprise, small wins. This marks the episode for consolidation, making the pathway stickier with less repetition. And be careful what you practise while aroused or excited, because those episodes will consolidate strongly even if they weren't what you intended to train.
Referenced by
Sources
- analects/neurotransmitters-and-behaviour.md
- analects/addictive-work.md
- analects/predicting-human-behaviour.md