Title: Cooling Reduces the Cutaneous Afferent Firing Response to Vibratory Stimuli in Corresponding Author

Skin on the foot sole plays an important role in postural control. Cooling the skin 23 of the foot is often used to induce anaesthesia to determine the role of skin in motor and 24 balance control. The effect of cooling on the four classes of mechanoreceptor in the skin is 25 largely unknown and thus the aim of the current study was to characterize the effects of 26 cooling on individual skin receptors in the foot sole. Such insight will better isolate 27 individual receptor contributions to balance control. Using microneurography, we recorded 28 39 single nerve afferents innervating mechanoreceptors in the skin of the foot sole in 29 humans. Afferents were identified as fastor slowly-adapting type I or II (FA I n=16, FA II 30 n=7, SA I n=6, SA II n=11). Receptor response to vibration was compared before and after 31 cooling the receptive field (2–20 min). Overall, firing response was abolished in 30% of all 32 receptors and this was equally distributed across receptor type (p=0.69). Longer cooling 33 times were more likely to reduce firing response below 50% of baseline however some 34 afferents responses were abolished with shorter cooling times (2-5 min.). Skin temperature 35 was not a reliable indicator of the level of receptor activation, and often became uncoupled 36 from receptor response levels, cautioning the use of this parameter as an indicator of 37 anesthesia. When cooled, receptors preferentially coded lower frequencies in response to 38 vibration. In response to a sustained indentation, SA receptors responded more like FA 39 receptors, primarily coding ‘on–off’ events. 40