The modulation of pain by attention. Insights arising from neurophysiological studies

It is generally acknowledged that pain is a complex perceptive phenomenon that depends not only on the physical properties of the nociceptive stimulation but also on the subject's emotional and cognitive state. The central nervous system has its own resources to control pain and cope with external sources of danger. Among such internal abilities, attention plays a major role: taking attention away from the nociceptive signal and focusing it on other perceptive objects decreases nociceptive processing and resulting pain. Neurophysiological studies have succeeded in describing the spatio-temporal organisation in the human brain of the attentional processes involved in the modulation of pain. On the one hand, focusing attention on information from another sensory modality or on another body area can bias nociceptive processing by decreasing brain responses in somatosensory cortices (top-down attention). On the other hand, other attentional mechanisms controlled by the anterior cingulate area allow attention to be involuntarily attracted by the pain itself in order to process a potential source of danger (bottom-up attention). Pain control seems to depend on a fine balance between various attentional processes.