Multiple single unit recording in the cortex of monkeys using independently moveable microelectrodes

Simultaneous recording from multiple single neurones presents many technica l difficulties. However, obtaining such data has many advantages, which mak e it highly worthwhile to overcome the technical problems. This report desc ribes methods which we have developed to permit recordings in awake behavin g monkeys using the 'Eckhorn' 16 electrode microdrive. Structural magnetic resonance images are collected to guide electrode placement. Head fixation is achieved using a specially designed headpiece, modified for the multiple electrode approach, and access to the cortex is provided via a novel recor ding chamber. Growth of scar tissue over the exposed dura mater is reduced using an anti-mitotic compound. Control of the microdrive is achieved by a computerised system which permits several experimenters to move different e lectrodes simultaneously, considerably reducing the load on an individual o perator. Neurones are identified as pyramidal tract neurones by antidromic stimulation through chronically implanted electrodes; stimulus control is i ntegrated into the computerised system. Finally, analysis of multiple singl e unit recordings requires accurate methods to correct for non-stationarity in unit firing. A novel technique for such correction is discussed. (C) 19 99 Elsevier Science B.V. All rights reserved.