Progress in Neurobiology 66 (2002) 265–283 From single extracellular unit recording in experimental and human Parkinsonism to the development of a functional concept of the role played by the basal ganglia in motor control Thomas Boraud a,b , Erwan Bezard b,c,∗ , Bernard Bioulac b , Christian E. Gross b a Department of Physiology, Faculty of Medicine, The Hebrew University of Jerusalem, 12272 Ein Kerem Campus, 91120 Jerusalem, Israel b Basal Gang, Laboratoire de Neurophysiologie, CNRS UMR 5543, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France c Motac Neuroscience Ltd., Incubator Building, Grafton St, Manchester M13 9XX, UK Received 2 July 2001; accepted 12 December 2001 Abstract Parkinson’s disease (PD) is a progressive neurodegenerative disorder that affects the whole basal ganglia (BG). Various techniques have been used to study BG physiology and pathophysiology. Among these, extracellular single unit recording remains of particular importance. An impressive number of studies of BG electrophysiological activity have been carried out, both in non-human and in human primates, but the data collected show many omissions and disparities. BG activity has been well defined in the physiological situation, but remains far from clear in the Parkinsonian and virtually unexplored in the dopamine (DA)-replacement situation. This paper provides a brief synopsis of (i) recording techniques and (ii) BG electrophysiological activity in normal, Parkinsonian, and dopamine-replacement situations. We have restricted the data used to those obtained in BG structures of human and non-human primates. Only single unit recordings have been reported and four electrophysiological characteristics retained: mean firing frequency, firing pattern, periodic oscillation, and response to both passive and active movement. We have attempted to summarize (i) the commonly accepted characteristics of each BG structure in the three situations, (ii) discrepancies that exist, and (iii) missing elements. Then, the main successive theories aimed to explain the role played by BG in motor control are presented and discussed in the light of the most recently obtained results using the latest technological advances. © 2002 Elsevier Science Ltd. All rights reserved. Contents 1. Introduction ................................................................................. 266 2. Recording and analysis ....................................................................... 267 2.1. Single unit firing activity at rest .......................................................... 267 2.2. Single unit firing activity during movement ................................................ 268 2.3. Multi-channel single unit recording ....................................................... 269 3. Striatum ..................................................................................... 270 3.1. Normal ................................................................................. 270 3.2. Parkinsonism ............................................................................ 270 3.3. DA pharmacology ....................................................................... 270 4. STN ........................................................................................ 270 4.1. Normal ................................................................................. 270 4.2. Parkinsonism ............................................................................ 271 4.3. DA pharmacology ....................................................................... 271 Abbreviations: BG, basal ganglia; DA, dopamine; GABA, -aminobutyric acid; GPe, globus pallidus pars externalis; GPi, globus pallidus pars internalis; ISI, inter-spike interval; Joint-PSTH, joint peri-stimulus time histogram; MPTP, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; PANs, phasically active neurons; PD, Parkinson’s disease; PETH, peri-event time histogram; PSTH, peri-stimulus time histogram; SNc, substantia nigra pars compacta; SNr, substantia nigra pars reticulata; STN, subthalamic nucleus; TANs, tonically active neurons ∗ Corresponding author. Tel.: +33-556-571-687; Fax: +33-556-901-421. E-mail address: erwan.bezard@umr5543.u-bordeaux2.fr (E. Bezard). 0301-0082/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII:S0301-0082(01)00033-8