Neurophysiology and functional neuroanatomy of pain perception

The traditional view that the cerebral cortex is not involved in pain proce ssing has been abandoned during the past decades based on anatomic and phys iologic investigations in animals, and lesion, functional neuroimaging, and neurophysiologic studies in humans. These studies have revealed an extensi ve central network associated with nociception that consistently includes t he thalamus, the primary (SI) and secondary (SII) somatosensory cortices, t he insula, and the anterior cingulate cortex (ACC). Anatomic and electrophy siologic data show that these cortical regions receive direct nociceptive t halamic input. From the results of human studies there is growing evidence that these different cortical structures contribute to different dimensions of pain experience. The SI cortex appears to be mainly involved in sensory -discriminative aspects of pain. The SII cortex seems to have an important role in recognition, learning, and memory of painful events. The insula has been proposed to be involved in autonomic reactions to noxious stimuli and in affective aspects of pain-related learning and memory. The ACC is close ly related to pain unpleasantness and may subserve the integration of gener al affect, cognition, and response selection. The authors review the eviden ce on which the proposed relationship between cortical areas, pain-related neural activations, and components of pain perception is based.