[Active selection of afferent information--the principle underlying peripheral correction of the function of spinal...

The paper presents data obtained in experiments on the study of primary afferent depolarization and retuning of segmental reactions to afferent signals during fictitious locomotion and fictitious scratching in immobilized decorticated, decerebrated and spinal cats. Fictitious locomotion was accompanied by sustained hyperpolarization, while fictitious scratching--by sustained depolarization of primary afferent central terminals. On the background of tonic changes periodic waves of primary afferent depolarization coinciding with the rhythm of efferent activity were observed. In different ipsilateral lumbosacral segments these periodic waves occurred in phase. The data are presented about the groups of afferent fibres in which central endings display tonic and phasic changes of primary afferent depolarization. Fictitious locomotion led to tonic increase and fictitious scratching--to tonic decrease in a number of evoked segmental reflex reactions. These tonic changes served as the background on which segmental reactions were modulated with the rhythm of locomotor and scratching generators. It is shown that the modulation of polarization of central primary endings by locomotor and scratching generators is the reason for many changes in reflex reactions. The conclusion is made that due to modulation of presynaptic inhibition the generators perform an active tonic and phase-dependent selection of afferent information. The role of such active selection in the peripheral correction of the function of locomotor and scratching generators is discussed.