Relation between perceived stimulus intensity and exteroceptive reflex responses in the human masseter muscles.

The increase in ES1 and ES2 suppression seen in our study at increasing stimulus intensity is suggested to be mediated by activity in both nociceptive and non-nociceptive fibres converging onto central interneurones in the reflex circuits. We suggest that neither ISP nor PSP are reflex responses. It is unlikely that ES1, ES2, ISP and PSP evoked by electrical stimuli are directly linked to noxious activity.