A new technique for chronic single-unit extracellular recording in freely behaving animals using pipette electrodes

Using extracellular pipette electrodes made of glass or plastic whose tip diameters ranged from 60 to 100 microns, it was possible to record the activity of single identified neurons in freely behaving animals. Multiple pipettes can be reliably positioned and attached to the sheath. Large signals can be obtained from neurons having soma diameters as small as 70 microns. We have used this technique to monitor the activity of an identified interneuron (B4/B5) during feeding behavior in the marine mollusk Aplysia californica. The technique can also be used in reduced or in vitro preparations for rapidly mapping the neural activity of a ganglion without removing its sheath.