Fear and pain slow the brain

Abstract

N europhysiological signals detected noninvasively at the scalp using techniques such as EEG/MEG contain rhythms (oscillatory activity) occurring at distinct frequency bands. The predominant rhythm in healthy humans occurs between the bandwidth of 8 to 14 Hz and is commonly referred to as the alpha rhythm. The frequency within the alpha band where power is maximal is called the peak alpha frequency (PAF) or individual alpha frequency. Peak alpha frequency varies considerably between individuals, 9,14 and this variability is believed to play a role in the individual differences in perceptual ability and temporal binding of sensory information. 1,8,21,23 The relationship of PAF to both acute and chronic pain is an exciting area currently under investigation by multiple laboratories. Patients with chronic pain often exhibit changes in alpha rhythms, particularly slower PAF, when compared with control subjects, 26 and the degree of PAF slowing has been found to correlate with chronic pain duration. 3 One interpretation of this PAF slowing is that it reflects brain processes that actively maintain chronic pain, such as excess "inhibition or disfacilitation" brought about by ongoing pain. 16 An alternative interpretation is that slower PAF reflects processes related to higher pain sensitivity and an increased disposition to develop chronic pain that predate disease onset. This latter interpretation is supported by a series of studies of acute pain in healthy subjects, which found that an individual's PAF recorded during a pain-free rest period was negatively correlated with the intensity of a future pain event. [5][6][7] This work has undergone initial clinical validation: In a cohort of patients undergoing thoracotomy, PAF collected before surgery was able to predict the severity of postsurgery pain. 20 Thus, PAF has been suggested as a biomarker of pain sensitivity, which has been hypothesized to be a key factor in the transition from acute to chronic pain. 10 Precisely how PAF fits into the myriad of biological, social, and psychological factors involved in the transition from acute to chronic pain has remained unexplored. One of these factors is the fear of movement, which has been demonstrated to be a significant predictor of the transition from acute low back pain to chronic low back pain (CLBP). 19,25