Give me a pain that I am used to: distinct habituation patterns to painful and non-painful stimulation

Pain habituation is associated with a decrease of activation in brain areas related to pain perception. However, little is known about the specificity of these decreases to pain, as habituation has also been described for other responses like spinal reflexes and other sensory responses. Thus, it might be hypothesized that previously reported reductions in activation are not specifically related to pain habituation. For this reason, we performed a 3 T fMRI study using either painful or non-painful electrical stimulation via an electrode attached to the back of the left hand. Contrasting painful vs. non-painful stimulation revealed significant activation clusters in regions well-known to be related to pain processing, such as bilateral anterior and posterior insula, primary/secondary sensory cortices (S1/S2) and anterior midcingulate cortex (aMCC). Importantly, our results show distinct habituation patterns for painful (in aMCC) and non-painful (contralateral claustrum) stimulation, while similar habituation for both types of stimulation was identified in bilateral inferior frontal gyrus (IFG) and contralateral S2. Our findings thus distinguish a general habituation in somatosensory processing (S2) and reduced attention (IFG) from specific pain and non-pain related habituation effects where pain-specific habituation effects within the aMCC highlight a change in affective pain perception.

Give Me a Pain that I am used to: Distinct Habituation Patterns to Painful & Non-painful Stimulation

Pain habituation is associated with a decrease of activation in brain areas related to pain perception. However, little is known about the specificity of these decreases to pain, as habituation has also been described for other responses like spinal reflexes and other sensory responses. Thus, it might be hypothesized that previously reported reductions in activation are not specifically related to pain habituation. For this reason, we performed a 3T fMRI study using either painful or non-painful electrical stimulation via an electrode attached to the back of the left hand. Contrasting painful vs. non-painful stimulation revealed significant activation clusters in regions well-known to be related to pain processing, such as bilateral anterior and posterior insula, primary/secondary sensory cortices (S1/S2) and anterior midcingulate cortex (aMCC). Importantly, our results show distinct habituation patterns for painful (in aMCC) and non-painful (contralateral claustrum) stimulation, while similar habituation for both types of stimulation was identified in bilateral inferior frontal gyrus (IFG) and contralateral S2. Our findings thus distinguish a general habituation in somatosensory processing (S2) and reduced attention (IFG) from specific pain and non-pain related habituation effects where pain-specific habituation effects within the aMCC highlight a change in affective pain perception.

Time Course of Habituation After Repeated Ice-Bath Immersion of the Ankle

Context:Cryotherapy is initially uncomfortable, but habituation is thought to occur during treatment.Objective:To examine pain habituation to ice-bath immersion over 5 consecutive days.Design:Mean Borg ratings were analyzed by ANOVA.Setting:Athletic training laboratory.Intervention:Ankle immersion in a 1 °C ice bath for 20 min.Participants:28 healthy individuals.Main Outcome Measure:Level of discomfort was rated at immersion; during treatment at 1, 3, 5, 8, 11, 14, 17, and 20 min; and 1 min posttreatment.Results:Analysis revealed significant main effects for day and time and a Day × Time interaction. Day 1 had higher pain ratings than days 4 and 5. From min 1 to 11 there was a progressive decline in pain rating; after that there was no significant decline.Conclusions:Discomfort was greatest during the first 5 min, and perception of discomfort at initial immersion was consistent across 5 days. In addition, after 3 days of treatments habituation occurred. Taken together, this suggests that treatment habituation is not the result of change in receptor sensitivity.