Neuroanatomical limbic connections of the Locus coeruleus in the nonhuman primate

Abstract

The present doctoral dissertation concerns the neuroanatomical organization of the LC in the primate brain; and it is more specifically focused on the limbic connections of the HF, amygdala (Amy) and PFC with the LC in order to better understand the role that this nucleus may have in cognitive processes. Rodent functional studies indicate that LC is activated by novel salient stimuli and directly modulate memory processing. This modulation likely involves connections between LC and the HF, Amy and PFC, which have a crucial role in higher cognitive processes. Despite the functional evidence, anatomical data supporting the implication of LC in the “memory pathways” is still very limited, and whether and to what extent HF and PFC send direct ‘top-down’ input to LC remains unknown. The main goal of this project is to study the connections between LC and HF/Amy/PFC in the nonhuman primate that could undelie high cognitive processes. We use high-resolution MRI, neuronal tract tracing, histochemical and immunohistochemical methods to examine (1) whether there exist direct inputs from the HF to LC, (2) whether the PFC projects directly to LC, (3) which of the architectonic areas contribute to these projections, (4) whether there exist projections from the other amygdaloid nucleus beyond the central nucleus of the amygdala, and (5) the topography of these projections. This detailed mapping of the neuronal interconnections between LC, HF and PFC could provide a novel insight on the anatomy underlying the role of LC in the modulation of higher cognitive processes such as decision making and memory processing, and a key step for the understanding of the catecholamine-related disorders (depression, attention deficit- hyperactivity, and dementia in Alzheimer’s and Parkinson’s diseases), and towards the development of appropriate treatments.