Spinal learning: central modulation of pain processing and long-term alteration of interneuronal excitability as a...

The influence of nociceptive peripheral input on the response characteristics of spinal interneurons may result in long-term alterations of interneuronal excitability and modify their responses to subsequent stimuli. Such neuromodulation has been found to result in physiological changes including hyperalgesia, lowering of pain thresholds, expansion of receptive fields and changes in response behaviors of muscles. These types of alterations may contribute to clinically significant findings including muscle spasm, hypomobility, edema, chronic pain, recurrences in areas of previous injury and resistance to treatment. This article reviews studies concerning plasticity of response behaviors of interneurons including habituation, spinal learning, spinal fixation, neuromodulation and the effects of substance P. Potential clinical and chiropractic application are discussed and a brief review of clinically relevant studies of chiropractic adjustments are cited.