Datensatz

Zusammenfassung

Neuroanatomical and functional evidence indicates that pain and temperature are represented with numerous other interoceptive sensory inputs in a phylogenetically novel spinothalamocortical pathway in primates (for review, see Craig, TINS 2003 26:303-307). Prior tract-tracing studies in the monkey demonstrated that nociceptive and thermoreceptive spinothalamic tract neurons in spinal lamina I primarily project to the posterior part of the ventromedial nucleus of the thalamus (VMpo; a nucleus specific to primates) and that nociceptive and thermoreceptive thalamocortical tract neurons in VMpo project to the dorsal posterior insular cortex. Electrophysiological recordings in spinal lamina I and VMpo in the anesthetized monkey revealed precise encoding of the grading of thermal and pain stimuli. Functional imaging in humans and EEG in monkeys indicated that the dorsal posterior insula is strongly activated by graded cooling of the skin. In the present study, we examined the activation of the insular cortex using high-resolution functional magnetic resonance imaging (4.7T) with thermal stimulation of the skin in two anesthetized cynomolgus monkeys. A graded cooling of the palmar surface of the foot from a baseline temperature of 35°C to a target temperature of 15°C (0.5°C/sec) followed by a re-warming to baseline (0.5°C/sec) produced highly significant (p < 0.001) BOLD signal exclusively in the dorsal mid-posterior portion of the contralateral insular cortex. No or poorly significant (p < 0.05) BOLD signal occurred in primary and secondary somatosensory cortices. These results support prior evidence that the insula in primates encodes ongoing interoceptive activity necessary to maintain homeostatic balance (e.g. thermoregulation). Neuroanatomical tract-tracers were injected in the insular regions displaying significant BOLD signal; mapping of anterograde and retrograde labeling from these injections will be presented.