Neurophysiology of pain-peripheral aspects. Speculation concerning the possibility of a unitary peripheral cutaneous input system for pressure, hot, cold and tissue damage.
The gate theory of pain is criticized at three levels: (1) at the dorsal horn "gate", where pre-synaptic inhibition in the primary afferent endings may go beyond mere reduction of synaptic power at the afferent endings and induce antidromic impulses (dorsal root reflexes) that may modulate peripherally by blocking; (2) central to the "gate", where postsynaptic neuronal repetitive (epileptiform) firing is believed to be an important underlying mechanism in clinical chronic pain syndromes; and, (3) in the periphery, where there is more to input coding than a balance between the ratio of large and smaller fiber inputs. Contrary to the belief of many sensory neurophysiologists, the present authors contend that pattern theory is viable; and that specificity, while important and not to be ignored, should be considered as only a partially evolved refinement superimposed on a basic underlying spatial and temporal patterning of input that probably requires central decoding, which begins in the dorsal horn.