Estimating post-synaptic potentials in tonically discharging human motoneurons

The activity of single motor units in human muscles can be recorded with relative ease, and the spike train of a single motor unit precisely reflects the spike train of the parent motoneurone. This has led to the proposal of a number of methods to estimate stimulus-evoked post-synaptic potentials in human motoneurones. All of these methods rely on manipulating the spike trains of motor units over a number of trials. All are based on a number of assumptions, all have limitations, and none so far have passed the test of a direct comparison of the estimate of the shape of the post-synaptic potential with a direct intracellular measurement of it. These techniques are summarised in this review.