Single-cell recording from the brain of freely moving monkeys

Single-cell recording from the brain of non-human primates has traditionall y been performed in monkeys seated in a primate chair. However, this arrang ement makes long-term recordings difficult, causes stress that may confound the data, and prevents the manifestation of natural behaviors. Extending o ur previous neurophysiological studies in non-human primates (Ludvig et al. Brain Res. Protocols 2000;5:75-85), we have developed a method for recordi ng the electrical activity of single hippocampal neurons in freely moving s quirrel monkeys (Saimiri sciureus). The recording sessions lasted for up to 6 h, during which the monkeys moved freely around on the walls and the flo or of a large test chamber and collected food pellets. Stable action potent ial waveforms were readily kept throughout the sessions. The following fact ors proved to be critical in this study: (a) selecting squirrel monkeys for the experiments, (b) using a driveable bundle of microwires for the record ings, (c) using a special recording cable, (d) implanting the microwires in to the brain without causing neurological deficits, and (e) running the rec ording sessions in a special test chamber. The described method allows long -term extracellular recordings from the brain of non-human primates, withou t the stress of chairing, during a wide range of natural behaviors. Using t his model, new insights can be obtained into the unique firing repertoire o f the neurons of the primate brain. (C) 2001 Elsevier Science B.V. All righ ts reserved.