ANALYSIS OF THE LOCAL CONNECTIVITY AMONG AMYGDALA NUCLEI
The amygdala comprises at least 13 distinct nuclei, including the lateral (LA), basal (BA), basomedial (BMA) and central (CeA) nuclei. Amygdala is involved in numerous cognitive operations, such as fear memory processes. To understand how the amygdala fulfils its various functions, we need to reveal the organization principles of intra-amygdalar connectivity. Therefore, our aim was to examine the connectivity within the amygdala at the population and single cell levels. To this end, we used retrograde tracing corroborated by single cell reconstruction of neurons labelled in vivo using juxtacellular technique in the mouse brain. The former approach is a method for detecting the direct connection between brain areas, while the latter provides the possibility of revealing the dendritic and axonal processes in the intact brain. Together, these methods are ideal for mapping the connections between small and closely related brain regions. In accord with previous results, we confirmed the reciprocal connectivity between the LA and BMA and the directionality within the amygdala networks. Notably, we identified a reciprocal connection between the BA and BMA. Moreover, based on its relationship with the CeA, two regions can be distinguished within the BA: the lateral-Posterior part projecting to the CeA, while the medial-anterior part does not.We conclude that the BA comprises of functionally distinct subregions. The presence of a medial area unrelated to the CeA function suggests a new information flow pathway within the amygdala. These results support the hypothesis that parallel and serial information processing co-exist within the amygdala circuits.