Figure 5.

Heterotopic effects of conditioning electrical stimuli on touch-evoked pain. A, B, Conditioning HFS induced a state in which these tactile, normally non-noxious stimuli became painful adjacent to the conditioning electrode (•) (allodynia) but not adjacent to the control electrode (○). Allodynia gradually developed after HFS and persisted throughout the 60 min observation period. C, Conditioning LFS at 10 × T elicited no allodynia. D, For conditioning LFS at 20 × T, one subject developed allodynia near the conditioning electrode but not the control electrode. Mean ± SEM values across eight subjects are shown. Each circle represents the normalized average of pain ratings across all three stimulus intensities over a 5 min time window. Asterisks indicate post hoc paired t tests; conditioned versus control site; p < 0.05.