Somatosensory Information Processing in the Aging Population

Zheng Zhang, Eric M. Francisco, Jameson K. Holden, Robert G. Dennis, Mark Tommerdahl

While it is well known that skin physiology - and consequently sensitivity to peripheral stimuli - degrades with age, what is less appreciated is that centrally mediated mechanisms allow for maintenance of the same degree of functionality in processing these peripheral inputs and interacting with the external environment. In order to demonstrate this concept, we obtained observations of processing speed, sensitivity (thresholds), discriminative capacity, and adaptation metrics on subjects ranging in age from 18 to 70. The results indicate that although reaction speed and sensory thresholds change with age, discriminative capacity, and adaptation metrics do not. The significance of these findings is that similar metrics of adaptation have been demonstrated to change significantly when the central nervous system (CNS) is compromised. Such compromise has been demonstrated in subject populations with autism, chronic pain, acute NMDA receptor block, concussion, and with tactile-thermal interactions. If the metric of adaptation parallels cortical plasticity, the results of the current study suggest that the CNS in the aging population is still capable of plastic changes, and this cortical plasticity could be the mechanism that compensates for the degradations that are known to naturally occur with age. Thus, these quantitative measures - since they can be obtained efficiently and objectively, and appear to deviate from normative values significantly with systemic cortical alterations - could be useful indicators of cerebral cortical health.