Editing Electrophysiology (section)

===Field potentials===
[[File:Field potential schematic.jpg|thumb|400px|A schematic diagram showing a field potential recording from rat hippocampus. At the left is a schematic diagram of a [[presynaptic terminal]] and postsynaptic neuron.  This is meant to represent a large population of synapses and neurons.  When the synapse releases glutamate onto the postsynaptic cell, it opens ionotropic glutamate receptor channels.  The net flow of current is inward, so a current sink is generated.  A nearby electrode (#2) detects this as a negativity.  An ''intracellular'' electrode placed inside the cell body (#1) records the change in membrane potential that the incoming current causes.]]
[[Extracellular field potential]]s are local current sinks or sources that are generated by the collective activity of many cells.  Usually, a field potential is generated by the [[neural synchronization|simultaneous activation]] of many neurons by [[synaptic transmission]].  The diagram to the right shows hippocampal synaptic field potentials.  At the right, the lower trace shows a negative wave that corresponds to a current sink caused by positive charges entering cells through postsynaptic [[glutamate receptor]]s, while the upper trace shows a positive wave that is generated by the current that leaves the cell (at the cell body) to complete the circuit.  For more information, see [[local field potential]].