Effects of thermosensory aging well demonstrated by cold stimulations with high temporal resolution

Abstract

Introduction: The method of limits (MLi) is the most commonly used paradigm to measure the threshold of thermal stimuli. However, the threshold measured by MLi is dependent on reaction time (RT). Because RT in adults increases with age, the inclusion of RT in the MLi paradigm may result in an overestimation of thermal threshold in the older individuals. Methods: A device with a very rapid cooling rate (300°C/s) was employed to measure cool thresholds by using the method of levels (MLe), a method independent of RT, in 11 older patients and 14 younger adults. Results: Compared with the MLi, the MLe resulted in a greater than 2°C gain in threshold measurement accuracy in older patients. Discussion: The MLe confirmed that cool perception threshold is dependent on age. The use of MLe provides new opportunities for the study of mechanisms underlying age‐associated alterations in thermal perception. Muscle Nerve 60: 141–146, 2019

Spinal integration of hot and cold nociceptive stimuli by wide-dynamic-range neurons in anesthetized adult rats

“…The heating or cooling rate could be adjusted from 0.1 to 300°C/second. 11 The device we used provides 5 independent stimulation areas of 8 mm 2 granting the possibility to perform very precise stimulation to a slower heating or cooling ramp (Fig. 1 ).…”

Method of levels not limits for assessment of cooling detection thresholds

“…In this issue of Muscle & Nerve , Despres and colleagues provide convincing evidence that stepping ramps of cooling (method of levels) provides more accurate measurement of cooling detection thresholds compared with continuous ramps to detection (method of limits). They attribute the higher thresholds from use of method of limits testing to reaction times inherent in this method.…”

“…Despres and colleagues emphasize the fast response of their thermoelectric unit (a change in temperature from ambient up to 300°C/s). These fast ramp rates, assuming that they are correctly reported, do not appear to be important for quantative sensory testing (QSTing) because the authors used a ramp of 2°C or 4°C/sec.…”