Tactile sensory coding during development: signaling capacities of neurons in kitten dorsal column nuclei

Abstract

The functional maturation of cuneate neurons was studied using reproducible tactile stimulation procedures and quantiative assessment of coding capacities in anesthetized (N2O/O2 plus barbiturate infusion) or decerebrate cats from 6 different age groups; neonatal (1-5 days), 10-15, 25-30, 55-63 and 83-90 days and an adult group. Cuneate neurons were distinguished from input fibers to the nucleus on criteria of spike configuration and time course and on response profiles. During the first 1-2 postnatal months, the capacity of cuneate PC neurons to signal information in a pattern code about vibration frequencies around 300 Hz is restricted because of poor phase locking and low responsiveness, which preclude an impulse periodicity reflecting the vibratory frequency. If tactile perceptual capacities for the distal limb depend on the dorsal column-lemniscal pathway, the subjective capacity of the kitten for detection, recognition and discrimination of tactile stimuli may be limited over the first 1-2 mo of postnatal life by functional immaturity at both peripheral and cuneate levels of the pathway.