Attentional effects on the processing of noxious brief electric stimuli measured with EEG - Event-Related Potential (ERPs) testing.

Pain is an unpleasant sensory experience associated with actual or potential
tissue damage, or described in terms of such damage.
There is a difference between the terms nociception and pain; the first refers
to the physiological manifestations generated by noxious stimuli, whereas the
second involves the unpleasant experience of an aversive stimulus, which
requires the cognitive and affective processing of noxious stimuli.
Recently, MRI research has shown that chronic back pain can be associated with
decreased prefrontal and thalamic gray matter density. In addition, several
studies have reported that (chronic) pain affects cognitive functioning.
Vice versa, a number of studies have demonstrated that cognitive processes can
alter nociception.
Thus, we hypothesise that cognitive operations affect the processing of noxious
stimuli. Knowing more about cognitive aspects of nociception might lead to a
better understanding and treatment of chronic pain. ERP measurements are an
excellent method to examine cognitive processes.

- Measuring attentional effects central processing of somatosensory and
noxious, brief electric, stimuli.

Visual stimuli will be presented followed by brief, electric noxious stimuli.
Simultaneously the EEG will be recorded.
The experiment will comprise a S1-S2 paradigm. Each trial contains a S1 as S2
stimulus. Before each trial, a tone (1000 Hz, 100 ms) will be presented
together with a visual fixation cross on a computer screen. After 1 second, the
S1 will be presented for 400 milliseconds. S1 is a green/red diamond shape with
the green site pointing either left or right and the red site pointing either
left or right. Depending on the instructions, the participant has to attend to
either the red or green site of the diamond. Participants have to attend 50
trials to one colour (session 1) and 50 trials to the other colour (session 2).
The order of colours will be counterbalanced over participants.
One second after this visual S1 stimulus, the S2 stimulus will be presented.
The S2 stimulus is a brief electric stimulus wit either a high intensity (VAS 7
- 5 pulse; 50%) or a low intensity (1 pulse, 50%). The S2 is presented on the
hand of either the attended site (50%) or the unattended site (50%). So each
combination (attended/unattended vs high/low intensity) has a probability of
25%. Depending on the instructions, participants have to respond to only the
high or low intensity stimuli (counterbalanced over participants) to only the
attended hand.
Time between trials is 8 seconds variable. The duration of the experiment is 20
minutes.

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