Theory 23/Circuit causality/Optogenetics
Causality Needs a Timing Window
The claim
Whether a neuron drives a behaviour is set by the ratio of its activation time to the integration window of the downstream circuit, so the same cell can be causal or irrelevant depending on when it fires.
01Mechanism
Downstream neurons integrate over a short window; a signal arriving outside it is discarded regardless of its strength.
02Prediction
Effect should depend on stimulation timing within the window.
03Refutation
Effect independent of timing would remove the integration argument.
04What makes it checkable
Optogenetics now allows activation on millisecond timescales, so timing can be varied while the cell is held fixed.
05Why it was not testable before
Lesions and pharmacology could not control timing.