Networks vs Regions outline
Brain regions are interesting in context with each other, not isolation; networks---distributed collections of regions working together---explain function better than individual spots.
Pop neuroscience loves to talk about brain regions. The amygdala is the fear centre. The prefrontal cortex is the smart bit. The hippocampus does memory. These are tidy stories, but they're misleading. No single region "does" anything interesting by itself. Regions are interesting only in context with each other---as nodes in distributed networks that work together to support behaviour.
The reason this matters is that brain regions organise around the kinds of information they process, and that organisation is topological---things that are related get put close together. Where your senses plug in---vision at the back, hearing at the sides, touch and movement at the top---you get maps of basic features. As you move away from these primary sensory regions into the spaces between them, you find regions that respond to combinations of information: motion perception (seeing and moving), language (hearing and producing speech with the mouth), face recognition (vision and memory and social significance). The brain is essentially a map of the statistical structure of the world and your interactions within it, built up from overlapping neural pathways.
This topological organisation means that understanding networks---collections of regions that fire together for particular functions---is far more useful than knowing what individual spots supposedly do. For example, talking about "the executive network" (dorsolateral prefrontal cortex and posterior parietal cortex, active during difficult reasoning) tells you more than saying "the prefrontal cortex is for decision-making," which is too vague to mean anything. The salience network (anterior insula and anterior cingulate) coordinates what gets attention. The default mode network (medial prefrontal, posterior cingulate, angular gyrus) activates during self-referential thought and mind-wandering. The affective networks (amygdala, insula, cingulate, prefrontal regions) work together to interpret bodily signals as emotions.
Because circuits are reused across tasks, the same region can participate in multiple networks depending on what else is active. The anterior cingulate appears in both the salience network and affective networks. The insula bridges body sense and emotion. This is why pinning behaviour to a single region is misleading---it's the configuration of active networks that determines what's happening, and that configuration shifts with task and context.
Practically, this means you change behaviour by changing which networks are recruited, not by "activating" a particular spot. Shift the task, change the environment, adjust the cues---and you recruit a different network configuration, which produces different processing and different outputs.
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: Networks transform inputs to outputs
Brain regions organise around the kinds of information they process, creating a topological map of the statistical structure of the world and your interactions within it. Networks---collections of regions that fire together---implement the transformations from perception to action. Understanding which networks are active tells you more about behaviour than knowing which individual regions light up.
So what can you do? Focus on changing network configurations, not activating single spots. Shift the task, change the cues, adjust the context---these recruit different network configurations, which produce different transformations from input to output. The same region can participate in multiple networks depending on what else is active, so the configuration matters more than the components.
WIP: Top-down and bottom-up routes converge in networks
Networks coordinate both top-down signals (goals, predictions, task-sets) and bottom-up signals (sensory input, bodily state). The configuration of active networks determines which top-down constraints apply and which bottom-up features get attended to. When top-down and bottom-up converge, processing is fluent. When they diverge, you get conflict or confusion.
So what can you do? Design contexts where the network configuration aligns top-down goals with bottom-up inputs. Set goals that match what the sensory environment and your bodily state support, so the networks recruited by each reinforce rather than compete. And when you're stuck, check whether the wrong network is active---sometimes the issue is that top-down and bottom-up are recruiting incompatible configurations.
Sources
- analects/brain-regions-to-networks.md
- analects/brain-structures-and-behaviour.md
- analects/making-meaning-in-the-brain.md