Altered cortical connectivity after experimentally induced long-term potentiation like pain amplification
Authors
Jørgensen, Lea Tøttrup ; Poulsen, Aida Hejlskov
Term
4. term
Publication year
2017
Submitted on
2017-06-06
Pages
93
Abstract
Langtidspotentiering (LTP) er en vedvarende styrkelse af synaptiske forbindelser. I smertesystemet menes det at bidrage til kroniske smerter ved at øge følsomheden (sensibilisering). LTP-lignende smerte kan fremkaldes hos mennesker med betinget elektrisk stimulation (CES) og vurderes med smerterating og elektroencefalografi (EEG). Dette studie undersøgte, om induceret LTP-lignende smerte ændrer kortikal konnektivitet (hvordan hjerneområder kommunikerer), målt som EEG-koherens efter kilde-rekonstruktion med sLORETA (en metode til at estimere, hvor i hjernen signalerne opstår). Deltagerne modtog en 10 Hz elektrisk stimulation bestående af eksponentielt aftagende pulser, der tiltog over 50 sekunder. Vi indsamlede psykofysiske vurderinger til mekaniske pinprick-stimuli og registrerede EEG i hvile og under kontinuerlig pinprick-stimulation. Derefter beregnede vi koherens mellem kortikale kilder. Vi fandt ingen signifikante ændringer i smerteopfattelse og ingen ændringer i koherens under pinprick-stimulation. I hvile-EEG sås der derimod en signifikant interaktion mellem tid og specifikke forbindelser i delta- (p=0.019), theta- (p=0.0030) og alfa-båndet (p=0.0080). En mindsket alfa-koherens mellem parietalområdet og den orbitofrontale cortex var forbundet med øget smerteopfattelse. Kun hvile-EEG viste en effekt af CES, hvilket kan hænge sammen med det lille sample (n=11) og utilstrækkelig standardisering af stimulusintensitet, da ikke alle deltagere oplevede CES som smertefuld.
Long-term potentiation (LTP) is a lasting strengthening of synaptic connections. In pain pathways, it is thought to contribute to chronic pain by increasing sensitivity (sensitization). LTP-like pain can be induced in humans with conditional electrical stimulation (CES) and assessed with pain ratings and electroencephalography (EEG). This study examined whether induced LTP-like pain changes cortical connectivity (how brain areas communicate), measured as EEG coherence after source reconstruction with sLORETA (a method that estimates where in the brain EEG signals arise). Participants received a 10 Hz electrical stimulation using exponentially decaying pulses that increased over 50 seconds. We collected psychophysical ratings to mechanical pinprick stimuli and recorded EEG at rest and during continuous pinprick stimulation. We then computed coherence between cortical sources. We found no significant changes in pain perception and no changes in coherence during pinprick stimulation. In resting EEG, however, there was a significant interaction between time and specific connections in the delta (p=0.019), theta (p=0.0030) and alpha (p=0.0080) bands. Notably, a decrease in alpha-band coherence between the parietal area and the orbitofrontal cortex correlated with increased pain perception. Only resting EEG showed an effect of CES, which may reflect the small sample (n=11) and insufficient standardization of stimulus intensity, as not all participants perceived CES as painful.
[This abstract was generated with the help of AI]
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