Distribution of cardiovascular related cells within the human thalamus.

Representation of cardiovascular function has not been investigated in the human thalamus. In the rat, the insular cortex is the principal forebrain site of cardiovascular representation whose afferents originate from a circumscribed thalamic area (nucleus ventralis posterolateralis-parvicellular portion, VPLpc). We therefore evaluated 4481 thalamic cells for phasic cardiovascular activity using extracellular recording techniques in 60 unanesthetized patients undergoing neurosurgical procedures. We identified 26 cells with phasic activity strongly related to the cardiac cycle in 10 patients. These cells clustered within the ventrocaudal nucleus of the thalamus (the principal sensory nucleus analogous to the ventral posterior thalamic group in the rat and monkey) and were equally distributed between the right and left sides. The majority of these cells (17/26) showed peaks of phasic neuronal activity within 50 ms of the peak systolic pressure; 35% had peripheral cutaneous fields in areas to which cardiac pain is often referred. We suggest that these cells may be involved in the integration of afferent baroreceptor information; may possibly be concerned with the generation and/or processing of central cardiac pain in humans; and that their derangement may possibly contribute to the lethal cardiovascular disturbances which occur in fatal familial insomnia.