Throbbing Pain not Connected to Heartbeat

A new study indicates that the experience of throbbing pain is linked to how the brain works, and not to the pulsations of blood at the location of the pain.

Researchers at the University of Florida (UFL; Gainesville, USA) reported a case study of a woman with a history of daily headache consistent with the diagnosis of chronic migraine, but in whom throbbing pain persisted long after the resolution of the headache. To examine the neurophysiological correlate, the researchers simultaneously documented the subjective report of the throbbing rhythm, arterial pulse, and recorded a high-density electroencephalogram (EEG). They found that the subjective throbbing rate (48±1.7 beats per minute) and heart rate (68±2 beats per minute) were distinct, and thus unrelated.

Spectral analysis of the EEG revealed that the overall amount of activity in the alpha range (8–12 Hz), increased in association with greater throbbing intensity. In addition, the rhythmic oscillations of overall alpha brain waves—the so-called modulations of alpha power—coincided with the timing of the throbbing rhythm, and the synchrony was proportional to the subjective intensity of the throbbing quality. The study was published in the July 2013 issue of the journal Pain.

“Aristotle linked throbbing pain to heart rhythm 2,300 years ago. It took two millennia to discover that his presumption was wrong,” said senior author neurologist Andrew Ahn, MD. “We understand very little about alpha waves, but they appear to have an important role in attention and how we experience the world. In addition, by analogy to how a radio works, alpha waves may also act as a carrier signal that allows different parts of the brain to communicate with itself.”

Alpha waves arise from synchronous and coherent (in phase or constructive) electrical activity of thalamic pacemaker cells, and predominantly originate from the occipital lobe during wakeful relaxation with closed eyes; they are reduced with open eyes, drowsiness, and sleep. Historically, they were thought to represent the activity of the visual cortex in an idle state, but recent papers have argued that they inhibit areas of the cortex not in use, or alternatively play an active role in network coordination and communication.

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