Table 1.

Summary of estimators

Estimator	Notation
Cov	Covariance matrix
P	Partial covariance matrix
L1-reg	L1-regularized partial covariance matrix
L2-reg	L2-regularized partial covariance matrix
Partial-MI	Partial mutual information
c-Granger	Conditional Granger causality
C${}_{\mathbf{s}\mathbf{p}\mathbf{k}}$	Spike-train cross-correlogram–based connectivity
Δc	Differential covariance matrix
Δp	Partial differential covariance matrix
ΔL	Linear DDC
ΔR	General nonlinear DDC
ΔReLU	Nonlinear DDC with ReLU nonlinearity