After baseline evaluation of light and pain sensitivity FM subjects and controls will undergo the PASAT task. This task consists of responding to a rapid presentation of numbers by ear phones. Subjects are asked to add each 2 consecutive numbers and provide a response each time the sum is equal to 13. This test will last several minutes and delivered at increasing speed.

Single and double digits are presented at intervals between 2 and 3 seconds and the participant must add each new digit to the one immediately prior to it. The participants will be asked to indicate by electronic button press whether the sum of the addition is 13 or not. The duration of the PASAT will be two 12-min tasks.

FM and control subjects will provide verbal ratings of experimental pain stimuli. For this purpose a numerical ratings scale (0-100) will be used ranging from "no sensation" to the "most intense sensation possible". All measures will be obtained in triplicates and the averages will be used for statistical comparisons.

FM and control subject will focus on a light source while VEPs are obtained. EEG tracings will be evaluated by special software to detect VEP. For intensity ratings of the flicker stimulus a numerical ratings scale (0-100) will be used ranging from "no sensation" to the "most intense sensation possible". All measures will be obtained in triplicates and the averages will be used for statistical comparisons.

FM and control subjects will complete the 2011 FM Questionnaire. The answers of this questionnaire will be added to obtain the wide-spread pain index and the somatic symptom score. The scores will be combined to obtain the final score. Scores of >12 fulfill the Criteria for Fibromyalgia