Showing papers by "A.D. (Bud) Craig published in 1994"

A thalamic nucleus specific for pain and temperature sensation

Abstract: THE existence of a posterolateral thalamic relay nucleus for pain and temperature sensation was postulated in 1911, on the basis of the stroke-induced analgesia and thermanaesthesia found paradox-ically in patients with thalamic pain syndrome1. Pain or tempera-ture sensations can be evoked in humans by electrical stimulation in a vaguely defined region of the posterolateral thalamus2'3. Here we use anterograde tracing and single unit recordings to demon-strate that there is a distinct nucleus in the posterior thalamus of the macaque monkey that receives a dense, topographic input from spinothalamic lamina I neurons and in which almost all neurons are nociceptive- or thermoreceptive-specific. Immunohistochemical staining showed that this nucleus is defined by a dense calbindin-positive fibre plexus in the macaque, so we applied the same stain-ing method to sections of human thalamus. We found a nearly identical fibre plexus localized within a distinct nucleus that is cytoarchitectonically homologous to the lamina I relay nucleus in the macaque thalamus. The stereotaxic coordinates of this nucleus and its location relative to the main somatosensory representation fit clinical descriptions of the pain-producing region in humans. We conclude that this is a specific thalamic nucleus for pain and temperature sensation in both monkey and human.

The thermal grill illusion: unmasking the burn of cold pain

Abstract: In Thunberg's thermal grill illusion, first demonstrated in 1896, a sensation of strong, often painful heat is elicited by touching interlaced warm and cool bars to the skin. Neurophysiological recordings from two classes of ascending spinothalamic tract neurons that are sensitive to innocuous or noxious cold showed differential responses to the grill. On the basis of these results, a simple model of central disinhibition, or unmasking, predicted a quantitative correspondence between grill-evoked pain and cold-evoked pain, which was verified psychophysically. This integration of pain and temperature can explain the thermal grill illusion and the burning sensation of cold pain and may also provide a basis for the cold-evoked, burning pain of the classic thalamic pain syndrome.