The ACC is implicated in many, many, many things, but it always seems to rear its head when error-monitoring of some sort is involved. Any time you want to respond to a mis-prediction, an error of judgement, or some sort of high-level mismatch, you're pretty much guaranteed to see ACC involvement.
The theory goes that beyond some differential threshold, the ACC detects the mismatch between the perception (the tiger in my example) and the sensation (the actual input into the system) and then "does something".
We're not sure what that "something" is: it could -- to proceed by computational analogy -- raise an exception and signal some other process to regulate the system, or it may directly inhibit certain early visual neurons in an attempt to downplay percept.
The theory goes that beyond some differential threshold, the ACC detects the mismatch between the perception (the tiger in my example) and the sensation (the actual input into the system) and then "does something".
We're not sure what that "something" is: it could -- to proceed by computational analogy -- raise an exception and signal some other process to regulate the system, or it may directly inhibit certain early visual neurons in an attempt to downplay percept.
This theory could also be completely wrong.