DYSAUTONOMIA IN FATAL FAMILIAL INSOMNIA AS AN INDICATOR OF THE POTENTIAL ROLE OF THE THALAMUS IN AUTONOMIC CONTROL

Fatal familiar insomnia (FFI) is characterized by insomnia, dysautonom ia, disruption of circadian rhythms, and motor dysfunction. The typica l neuropathological findings in FFI are severe neuronal depletion in t he mediodorsal (MD) and anteroventral nuclei of the thalamus, The inte raction between the thalamus and central autonomic control mechanisms is poorly understood. The central autonomic areas include the anterior cingulate and insular cortices; amygdala, paraventricular nucleus, do rsomedial nucleus, and lateral hypothalamic area; periaqueductal gray; parabrachial nucleus; ventrolateral medulla; and nucleus of the solit ary tract, Several nuclei of the thalamus have connections with areas of the central autonomic network, The paraventricular nucleus (PVT) pr ojects to the medial prefrontal cortex, and receives multimodal viscer al and somatosensory inputs, The MD nucleus is connected with several ''limbic'' areas involved in autonomic control, The autonomic manifest ations of FFI are exaggerated sympathetic activation with preserved pa rasympathetic drive to the cardiovascular system, This reflects an exa ggerated sympathetic drive from supramedullary structures. Bicuculline , administered into the MD, elicits an increase in arterial pressure a nd heart rate, The medial portion of the MD may share with the PVT a r elay function for circuits controlling autonomic responses, MD involve ment in FFI suggests a role of the thalamus in central autonomic and o ther integrative functions.