Unexpected synaptic connections. (a) In a left dlc (l-dlc) interneuron excitation is seen after variable delays as skin stimulation strength to the opposite right side increases (asterisk). The inset shows the probable pathway. (b) In a RB neuron, IPSPs (depolarising at resting membrane potential) occur during swimming, shown in a motor nerve recording (vr). Some IPSPs are mid-cycle (open arrowheads) and others are early-cycle (filled arrowhead). The histogram shows the phase distribution of 148 IPSPs in the swimming cycle. (c) Stimulating an aIN to fire an action potential leads directly to depolarising IPSPs at short latency in a RB neuron. (d) In a dla, fast on-cycle EPSPs, presumed to come from dINs, are seen on 77% of cycles during swimming.