High Resolution Detection of Stationary and Evolving 2D-Current Source Density within Neuronal Microcircuits

The use of a high-density microelectrode arrays (>4000 microelectrodes) allows the recordings of evoked and on-going field activity of the whole hippocampal formation and other tissues with high spatiotemporal resolution. From these recordings it is possible to obtain the current source density (CSD) which separates the current generators into sinks and sources; this differentiation provides the means to distinguish correlated, disjoint loci of activity and track them separately at near to cell resolution. By obtaining the vectorial average of an area regarded as sink or source, we obtain a putative center of action, or center of mass that can be traced in time. Thus, successive centers would reveal the immediate nearby correlated units that “inherit” or otherwise are affected by this activity revealing a putative route of transfer of information that can be quantitated with high spatiotemporal definition. For structured tissues, this methodology provides a means to infer effective information transmission with clear parameters that can be further analyzed in several ways. Importantly, the CSD over time reveals patterns of activity obscured by the representation of activity in the voltage domain, which can aid to uncover synaptic interactions in restricted microcircuits.