Funded by: The Leverhulme Trust
In recent years the electrophysiological study of human skin sensory receptors has led to the identification and characterisation of a class of nerve fibres named CT afferents. These unmyelinated, low threshold mechanosensitive nerves, found only in hairy skin, respond optimally to low force/velocity stroking touch, which is typically perceived as pleasant. Coupling microneurography recordings with psychophysical ratings from healthy human volunteers, during CT stimulation with a soft brush, has determined that the speed and force of stroking is crucial to perceived pleasantness. CTs response to dynamic touch during microneurography recordings is described by an inverted U-shaped function, firing optimally to a stimulus moving ~5cm/second, the speed which also produces the highest subjective ratings of pleasantness when measured psychophysically. Their response characteristics appear to make CTs ideally suited to form the first stage of encoding socially relevant and rewarding tactile information resulting from affiliative behaviours, suggesting they may have an evolutionarily conserved function in the formation and maintenance of social bonds.
We are investigating the role of CT afferents in the modulation of neural, neurochemical & behavioural responses to social stimuli. By combining behavioural, psychophysical, pharmacological and neuroimaging techniques, we aim to determine; i) how trait differences in sociability affect ratings of pleasant and unpleasant touch as mediated by CT afferents; ii) explore whether exposure to affective social touch modulates social cognitions and behaviours; iii) establish whether 5-HT differentially modulates perceptual, cognitive and behavioural responses to affective touch; iv) establish the neural basis of trait and state responses to affective touch.