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Top-down and bottom-up modulation of pain-induced oscillations.

Hauck M, Domnick C, Lorenz J, Gerloff C, Engel AK - Front Hum Neurosci (2015)

Bottom Line: Top-down (attention) and bottom up (intensity) influences differed in their effects on oscillatory response components.Attention towards pain induced a decrease in alpha and an increase in gamma band power, localized in the insula.Our results indicate that bottom-up and top-down modes of processing exert different effects on pain-induced slow and fast oscillatory activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf Hamburg, Germany ; Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.

ABSTRACT
Attention is an important factor that is able to strongly modulate the experience of pain. In order to differentiate cortical mechanisms underlying subject-driven (i.e., top-down) and stimulus-driven (bottom-up) modes of attentional pain modulation, we recorded electric brain activity in healthy volunteers during painful laser stimulation while spatial attention and stimulus intensity were systematically varied. The subjects' task was to evaluate the pain intensity at the attended finger, while ignoring laser stimuli delivered to the other finger. Top-down (attention) and bottom up (intensity) influences differed in their effects on oscillatory response components. Attention towards pain induced a decrease in alpha and an increase in gamma band power, localized in the insula. Pain intensity modulated delta, alpha, beta and gamma band power. Source localization revealed stimulus driven modulation in the cingulate gyrus (CG) and somatosensory areas for gamma power changes. Our results indicate that bottom-up and top-down modes of processing exert different effects on pain-induced slow and fast oscillatory activities. Future studies may examine pain-induced oscillations using this paradigm to test for altered attentional pain control in patients with chronic pain.

No MeSH data available.


Related in: MedlinePlus

Experimental Design. Subjects were instructed to classify the stimulus intensity if the attended finger was stimulated and to ignore the other finger. Subjects’ report via button press was prompted by an acoustic signal 3 s after each laser stimulus. The experiment had a counterbalanced block design. Laser stimuli were delivered in eight blocks of different duration to the left index (i) and ring (a) finger. Block 2 is illustrated in more detail. Occurrence of low (1.5 × pain threshold = short vertical lines) and high (2 × pain threshold = long vertical lines) intensity stimuli was randomized as were the inter-stimulus interval (6–7 s) and the site of attention.
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Figure 1: Experimental Design. Subjects were instructed to classify the stimulus intensity if the attended finger was stimulated and to ignore the other finger. Subjects’ report via button press was prompted by an acoustic signal 3 s after each laser stimulus. The experiment had a counterbalanced block design. Laser stimuli were delivered in eight blocks of different duration to the left index (i) and ring (a) finger. Block 2 is illustrated in more detail. Occurrence of low (1.5 × pain threshold = short vertical lines) and high (2 × pain threshold = long vertical lines) intensity stimuli was randomized as were the inter-stimulus interval (6–7 s) and the site of attention.

Mentions: We delivered brief infrared laser stimuli of 1 ms duration and a beam diameter of 5 mm to the dorsum of the left ring and index finger using a Thulium YAG laser (wavelength 2 μm, StarMedTec, Starnberg, Germany). Prior to the experiment, participants were familiarized with the use of a pain rating scale ranging from zero (no sensation) to 100 (maximal pain). On this rating scale, a value of zero indicates no sensation at all and 30 indicates the threshold for a pain sensation. Sensation higher than zero and below 30 indicates non-painful warm, rarely tactile sensations, whereas sensation at pain threshold indicates the beginning of a painful hot and stinging pain. Individual pain threshold was tested by calculating the average intensity at which subjects reported first a rating value above 30 in three ascending stimulus series and, more- over, first a rating value below 30 in three descending series of laser stimuli using successive intensity increments of 20 mJ. During the experiment subjects were comfortably seated in an electrically shielded and sound-attenuated recording chamber with their eyes closed. The experiment consisted of eight blocks in total, comprising two blocks of 20, 50, 60 and 30 stimuli, respectively. The blocks were presented in counterbalanced order (see Figure 1). High-intensity stimuli (2-fold pain threshold) and low-intensity stimuli (1.5-fold pain threshold) were delivered during all blocks. The inter-stimulus interval varied between 6 or 7 s. Before each block, subjects were instructed to attend to the stimuli at one finger. The site of stimulation was randomized, providing that no more than two successive stimuli were delivered to the same finger. Three seconds after the laser stimulus, an acoustic event (2000-Hz tone) prompted a response. The subjects’ task was to respond after stimulation of the attended finger using two keys of a response-box with their right hand to classify the intensity of the stimulus (i.e., high or low). The stimuli delivered to the other finger had to be ignored and not to be classified. To control for differences between conditions due to finger movements a third button had to be pressed. Directed attention to one finger was counterbalanced over blocks. The assistant directing the laser beam onto the different fingers was instructed via earphones about the site of stimulation. Instructions and the acoustic prompt were controlled by the Presentation software (Neurobehavioral Systems, Albany, CA, USA).


Top-down and bottom-up modulation of pain-induced oscillations.

Hauck M, Domnick C, Lorenz J, Gerloff C, Engel AK - Front Hum Neurosci (2015)

Experimental Design. Subjects were instructed to classify the stimulus intensity if the attended finger was stimulated and to ignore the other finger. Subjects’ report via button press was prompted by an acoustic signal 3 s after each laser stimulus. The experiment had a counterbalanced block design. Laser stimuli were delivered in eight blocks of different duration to the left index (i) and ring (a) finger. Block 2 is illustrated in more detail. Occurrence of low (1.5 × pain threshold = short vertical lines) and high (2 × pain threshold = long vertical lines) intensity stimuli was randomized as were the inter-stimulus interval (6–7 s) and the site of attention.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488623&req=5

Figure 1: Experimental Design. Subjects were instructed to classify the stimulus intensity if the attended finger was stimulated and to ignore the other finger. Subjects’ report via button press was prompted by an acoustic signal 3 s after each laser stimulus. The experiment had a counterbalanced block design. Laser stimuli were delivered in eight blocks of different duration to the left index (i) and ring (a) finger. Block 2 is illustrated in more detail. Occurrence of low (1.5 × pain threshold = short vertical lines) and high (2 × pain threshold = long vertical lines) intensity stimuli was randomized as were the inter-stimulus interval (6–7 s) and the site of attention.
Mentions: We delivered brief infrared laser stimuli of 1 ms duration and a beam diameter of 5 mm to the dorsum of the left ring and index finger using a Thulium YAG laser (wavelength 2 μm, StarMedTec, Starnberg, Germany). Prior to the experiment, participants were familiarized with the use of a pain rating scale ranging from zero (no sensation) to 100 (maximal pain). On this rating scale, a value of zero indicates no sensation at all and 30 indicates the threshold for a pain sensation. Sensation higher than zero and below 30 indicates non-painful warm, rarely tactile sensations, whereas sensation at pain threshold indicates the beginning of a painful hot and stinging pain. Individual pain threshold was tested by calculating the average intensity at which subjects reported first a rating value above 30 in three ascending stimulus series and, more- over, first a rating value below 30 in three descending series of laser stimuli using successive intensity increments of 20 mJ. During the experiment subjects were comfortably seated in an electrically shielded and sound-attenuated recording chamber with their eyes closed. The experiment consisted of eight blocks in total, comprising two blocks of 20, 50, 60 and 30 stimuli, respectively. The blocks were presented in counterbalanced order (see Figure 1). High-intensity stimuli (2-fold pain threshold) and low-intensity stimuli (1.5-fold pain threshold) were delivered during all blocks. The inter-stimulus interval varied between 6 or 7 s. Before each block, subjects were instructed to attend to the stimuli at one finger. The site of stimulation was randomized, providing that no more than two successive stimuli were delivered to the same finger. Three seconds after the laser stimulus, an acoustic event (2000-Hz tone) prompted a response. The subjects’ task was to respond after stimulation of the attended finger using two keys of a response-box with their right hand to classify the intensity of the stimulus (i.e., high or low). The stimuli delivered to the other finger had to be ignored and not to be classified. To control for differences between conditions due to finger movements a third button had to be pressed. Directed attention to one finger was counterbalanced over blocks. The assistant directing the laser beam onto the different fingers was instructed via earphones about the site of stimulation. Instructions and the acoustic prompt were controlled by the Presentation software (Neurobehavioral Systems, Albany, CA, USA).

Bottom Line: Top-down (attention) and bottom up (intensity) influences differed in their effects on oscillatory response components.Attention towards pain induced a decrease in alpha and an increase in gamma band power, localized in the insula.Our results indicate that bottom-up and top-down modes of processing exert different effects on pain-induced slow and fast oscillatory activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf Hamburg, Germany ; Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.

ABSTRACT
Attention is an important factor that is able to strongly modulate the experience of pain. In order to differentiate cortical mechanisms underlying subject-driven (i.e., top-down) and stimulus-driven (bottom-up) modes of attentional pain modulation, we recorded electric brain activity in healthy volunteers during painful laser stimulation while spatial attention and stimulus intensity were systematically varied. The subjects' task was to evaluate the pain intensity at the attended finger, while ignoring laser stimuli delivered to the other finger. Top-down (attention) and bottom up (intensity) influences differed in their effects on oscillatory response components. Attention towards pain induced a decrease in alpha and an increase in gamma band power, localized in the insula. Pain intensity modulated delta, alpha, beta and gamma band power. Source localization revealed stimulus driven modulation in the cingulate gyrus (CG) and somatosensory areas for gamma power changes. Our results indicate that bottom-up and top-down modes of processing exert different effects on pain-induced slow and fast oscillatory activities. Future studies may examine pain-induced oscillations using this paradigm to test for altered attentional pain control in patients with chronic pain.

No MeSH data available.


Related in: MedlinePlus