Fig 4. Different sources of spiking covariance interact with different parts of the STDP rule.

Black: STDP rule. Red: spike train cross-covariances, from Eq (7). (A) Covariance from forward connections interacts with the potentiation side of the STDP rule. (B) Covariance from backward connections interacts with the depression side of the STDP rule. (C) Covariance from common input is temporally symmetric and interacts with both the potentiation and depression sides of the STDP rule.