Tonic heat pain stimulation resulted in lower central alpha1 and alpha2 activity and higher right-parietal and right-occipital delta power compared to non-painful heat stimulation.
Does tonic heat pain alter ongoing EEG patterns compared to non-painful heat in healthy subjects?
Tonic heat pain induces a specific EEG pattern characterized by lower central alpha and higher right-parietal/occipital delta power, independent of attention.
To confirm the existence of an ongoing electroencephalogram (EEG) pattern that is truly suggestive of pain, tonic heat pain was induced by small heat pulses at 1 °C above the pain threshold and compared to slightly less intense tonic non-painful heat pulses at 1 °C below the pain threshold. Twenty healthy subjects rated the sensation intensity during thermal stimulation. Possible confounding effects of attention were thoroughly controlled for by testing in four conditions: (1) focus of attention directed ipsilateral or (2) contralateral to the side of the stimulation, (3) control without a side preference, and (4) no control of attention at all. EEG was recorded via eight leads according to the 10/20 convention. Absolute power was computed for the frequency bands delta (0.5-4 Hz), theta (4-8 Hz), alpha1 (8-11 Hz), alpha2 (11-14 Hz), beta1 (14-25 Hz), and beta2 (25-35 Hz). Ratings were clearly distinct between the heat and pain conditions and suggestive for heat and pain sensations. Manipulation of attention proved to be successful by producing effects on the ratings and on the EEG activity (with lower ratings and lower EEG activity (theta, beta1, 2) over central areas for side-focused attention). During pain stimulation, lower central alpha1 and alpha2 activity and higher right-parietal and right-occipital delta power were observed compared to heat stimulation. This EEG pattern was not influenced by the manipulation of attention. Since the two types of stimuli (pain, heat) were subjectively felt differently although stimulation intensities were nearby, we conclude that this EEG pattern is clearly suggestive of pain.
Giehl et al. (Tue,) conducted a other in Healthy subjects (n=20). Tonic heat pain vs. Tonic non-painful heat pulses (1 °C below the pain threshold) was evaluated on EEG absolute power in frequency bands and sensation intensity ratings. Tonic heat pain stimulation resulted in lower central alpha1 and alpha2 activity and higher right-parietal and right-occipital delta power compared to non-painful heat stimulation.