Figure 1.
Subjects were presented a white fixation point against black background. After 2000 ms a circular sine wave grating contracting towards its center was shown. After a pseudorandomly varied duration of 1200 to 2500 ms the contraction accelerated, signaling the subjects to press a button with their right hand as fast as possible. Visual feedback followed the response. In 50% of the trials painful stimuli were applied to the left hand (pain trials). Apart from the application of painful stimuli, pain and no pain trials were identical. Time of painful stimuli was varied with respect to the onset of visual stimulation to avoid predictability of painful stimuli. Subjects were instructed to complete the visual task without becoming distracted by the painful stimulation.
Figure 2.
A Single-subject reaction times for each group and condition. Please note that ascending lines connecting the no pain and pain conditions indicate a pain-induced prolongation of reaction times whereas descending lines indicate a reduction of reaction times. B Mean reaction times for each group and condition.
Figure 3.
Visual and pain-induced gamma oscillations.
The time-frequency-representations show group mean neuronal activity (% signal change) in pain trials used for neurophysiological analysis, averaged across central (Cz, C2) and occipital (POz, Oz, PO3/PO4, O1/O2) electrodes. Data are aligned to the onset of laser stimulation, which occurred 500 or 700 ms after onset of the visual stimulation, respectively. The topographic maps show the scalp distribution of gamma oscillations following visual (150–2500 ms after onset of visual stimulation, 48–54 Hz) and painful (575–700 ms after onset of visual stimulation, 75–200 ms after painful stimulation, 34–56 Hz) stimulation coded as % signal change as compared to baseline.
Figure 4.
Source localization of visual and pain-induced gamma oscillations.
Activations are maxima of mean activation maps superimposed on a normalized surface-rendered structural T1-weighted magnetic resonance image. Color-coded is the change of estimated activity in the target interval relative to the baseline in %.
Figure 5.
Relationship between pain-induced changes in visual gamma oscillations and pain-induced changes in visual task performance.
Displayed is the correlation between the signal change of visual gamma oscillations (signal changeno pain – signal changepain) at occipital electrodes, and the change of reaction times after painful laser stimulation (RTpain – RTno pain). Stronger pain-related modulations of visual gamma oscillations are associated with stronger pain-related modulations of reaction times.
Figure 6.
Relationship between pain-induced gamma oscillations and pain-induced changes in visual gamma oscillations.
Displayed is the correlation between the signal change of pain-induced gamma oscillations measured 75–200 ms after painful laser stimulation at central electrodes and the signal change of visual gamma oscillations measured 200–350 ms after painful laser stimulation at occipital electrodes (signal change occipitalno pain – signal change occipitalpain).