Figure 2. Distribution of latencies of PSPs evoked from group I and II muscle afferents, MLF and LVN.

A–C, the minimal latencies (ordinates) of PSPs evoked from muscle nerves (Q and/or Sart) in individual interneurones, with respect to group I afferent volleys, ranked from the shortest to the longest. A, latencies of monosynaptic and disynaptic EPSPs and disynaptic IPSPs from group I afferents. The dotted line separates the monosynaptically and disynaptically evoked PSPs. B, latencies of monosynaptic and disynaptic EPSPs and disynaptic IPSPs evoked from ipsilateral group II afferents, measured from the group I volleys. The estimated range of delays of the earliest arrival of group II afferent impulses (relative to the group I volleys) is indicated by the two continuous horizontal lines. The grey area indicates EPSPs in a range where additional criteria (see text) had to be used to define the linkage as mono- or disynaptic. C, disynaptic EPSPs and IPSPs evoked from contralateral group I and II afferents, measured as in A. The continuous horizontal lines indicate the timing of group II afferent volleys as in B. The dotted line separates PSPs evoked from group I and group II afferents, defined according to latency and threshold (as in A). The shaded area indicates the overlap in latencies compatible with disynaptic connection from either group I or group II afferents. D and E, latencies of EPSPs and IPSPs evoked from MLF and LVN measured from the first positive components of the descending volleys evoked by the third of a train of three stimuli. The dotted lines separate the monosynaptically and disynaptically evoked PSPs. The shaded area in E indicates latencies of EPSPs evoked from LVN that could be mono- or disynaptically evoked, but which were differentiated on the basis of temporal facilitation (see text).