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1 University of Toronto
2 Toronto Western Hospital
* To whom correspondence should be addressed. E-mail: kdavis{at}uhnres.utoronto.ca.
Acute and chronic pains are characterized by a particular constellation of pain qualities, such as burning, aching, stinging or sharp feelings. However, the temporal pattern of specific pain qualities and their relationship with pain and affect is not well understood. In addition, little is known about how the temperature time-course of the stimulus impacts the temporal dynamics of pain qualities and their inter-relationships. Therefore, we applied two types of stimuli to the feet of 10 healthy subjects, each calibrated to evoke a similar pain magnitude (50/100): static stimulus held at constant intensity and dynamic stimulus increased in intensity in small steps. Stimulus runs consisted of three 30s stimuli (either static or dynamic) with an interstimulus interval of 60s. Continuous online ratings of pain, burning, sharp, stinging, cutting and annoyance were obtained in separate runs and the evoked responses were characterized by within stimulus adaptation (early 15s peak vs. late 5s peak) and by their temporal properties (time to onset, peak and end). Sharp, stinging and cutting sensations attenuated in response to the static stimuli, but intensified along with pain and affect in response to the dynamic stimuli. Conversely, there was no attenuation in evoked profiles of pain, annoyance and burning quality; instead these qualities demonstrated a temporal summation-like association especially in response to static stimuli. These data demonstrate that specific pain qualities with known differences in underlying mechanisms have distinct temporal dynamics. Moreover, the relationship between pain qualities, pain and affect depends on stimulus intensity dynamics.
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