A REVIEW OF RECENT APPLICATIONS OF CROSS-CORRELATION METHODOLOGIES TOHUMAN MOTOR UNIT RECORDING

This article reviews some recent applications of time and frequency do main cross-correlation techniques to human motor unit recording. These techniques may be used to examine the pre-synaptic mechanisms involve d in control of motoneuron activity during on-going motor tasks in man without the need for imposed and artificial perturbations of the syst em. In this review we examine, through several examples, areas in whic h insights have been gained into the basic neurophysiological processe s that bring about motoneuron firing in man and illustrate how these p rocesses are affected by central nervous system pathology. We will dem onstrate that synchronization and coherence may be revealed between hu man motor unit discharges and give examples that support the hypothesi s that these phenomena are generated by activity in a focused common c orticospinal input to spinal motoneurons. Disruption of central motor pathways due to diseases of the nervous system leads to pathophysiolog ical alterations in the activity of these pre-synaptic motoneuron inpu ts that can be revealed by cross-correlation analysis of motor unit di scharges. The significance of these studies and outstanding questions in this field are discussed (C) 1997 Elsevier Science B.V.