Connectivity of quadriceps-coupled Ia inhibitory interneurones (Ia-int) and recording and stimulation protocols
A-C illustrate the criteria used for identification of quadriceps-coupled Ia inhibitory interneurones. A, ability to follow stimulation frequencies of more than 150 Hz. B, recurrent inhibition by activation of the L6 ventral root (VR-L6). C, antidromic activation from the PBSt motonuclei (Intraspinal) which shows collision with orthodromic action potentials. Voltage calibration is the same in the three panels and refers to microelectrode recordings only. For further details see text. ME, microelectrode recording; CDP, cord dorsum potential. D illustrates the general experimental arrangement. Mn, motoneurone.