Current-Source Density

Current-source density (CSD) analysis computes the second spatial derivative of multi-channel local field potentials to estimate transmembrane current density across the recording region.

Why it matters: CSD reveals the laminar pattern of synaptic activity — identifying current sinks (where excitatory synaptic currents flow into neurons) and sources (where return currents flow out). This is the standard method for determining which cortical layers are active during sensory processing.

Requirements: Multi-site recordings with regular inter-site spacing along the depth axis (laminar probes). Linear arrays with 25–100 µm spacing are typical.

Applications: Cortical layer identification, sensory response characterization, thalamocortical circuit analysis, and validation of probe placement depth.