Subject: painfully loud sound From: jan schnupp <jan.schnupp(at)PHYSIOL.OX.AC.UK> Date: Wed, 10 Nov 2004 00:56:20 +0000Dear List, while teaching medical students some basic Neuroscience (including nociceptive pathways and pain) I wondered: what determines whether we would consider a particular sound to be painfully loud? Does the cochlea contain specific nociceptive fibres? Or are painfully loud sounds so intense that they can activate pain fibres in the middle ear? As I understand it, many people suspect now that one may not need specific "pain fibre" activation to elicit pain (I guess phantom limb pain kind of illustrates this possibility quite nicely). Instead, particular patterns of activation of other types of afferents might also be able to trigger painful sensations. I wonder whether painfully loud sounds (or painfully bright lights) might be examples of this. Have the experts on middle and inner ear histology among you observed lots of nociceptive fibres in places that would make them likely to be sensitive to intense acoustic stimulation? What about people with extensive damage to hair cells: if pain responses to very loud sounds are triggered by separate nociceptors, rather than by overstimulation of hair cells, then patients with profound deafness due to hair cell loss should still find exposure to 140 dB plus noise levels painful, even though they can't hear them. Is that the case? Or do pain thresholds invariably go up as hearing sensitivity goes down? Regards, Jan -- Dr Jan Schnupp University Laboratory of Physiology Parks Road - Oxford OX1 3PT Tel +44-1865-272513 email: jan(at)physiol.ox.ac.uk http://www.physiol.ox.ac.uk/~jan/