Amygdala communication across sgACC and pgACC networks

About This Grant

The anterior cingulate cortex (ACC) is a heterogenous structure that is strongly connected with the amygdala. Its subdivisions are critical for unique limbic and cognitive functions. The subgenual ACC (sgACC, Brodmann area 25/14c), implicated in major depression in humans, is a key node of the salience network and is important for arousal state modulation and valuation of sensory information. In contrast, the perigenual ACC (pgACC, Brodmann area 32/24b) is dorsal to the sgACC, and is important for cognitive functions including decision-making and conflict monitoring. Despite known functional differences in sgACC and pgACC, the main cortical and thalamic drivers of the ACC subregions are not fully understood in higher species. My preliminary data using paired injections in the same hemisphere indicates that sgACC afferent networks involve midline thalamic nuclei, insula, and medial wall inputs. In contrast, pgACC receives unique inputs from mediodorsal (MD) thalamus, orbital, and lateral PFC inputs (9/46) that carry information important for spatial and temporal localization of salient stimuli. These data indicate specific functional hubs in sgACC and pgACC. Despite evidence for discrete afferent networks to the sgACC and pgACC, the amygdala projects broadly to both. sgACC and pgACC inputs to the amygdala converge onto glutamatergic ‘hot spots’ in the basal and accessory basal nuclei, which in turn project back to the sgACC and pgACC. New molecular evidence indicates diverse glutamatergic neuronal phenotypes in the basal and accessory basal nucleus. We hypothesis a unique subtype comprises both the sgACC and pgACC projection. Recent preliminary evidence suggests that despite an apparently broad projection to the sgACC and pgACC, specialized glutamatergic neurons in specific amygdala subregions may be important in regulating these two regions. Aim 1 analyzes paired retrograde tracer injections in sgACC and pgACC in the same animal, and uses standard correlation and also unsupervised cluster analysis to identify cortical and thalamic afferent ensembles across the sgACC-pgACC trajectory. Aim 2A will define transcriptome shifts in neuron populations along the basal and accessory basal amygdala, beginning broadly and then focusing on glutamatergic neuron signatures using single-nucleus RNA sequencing. Spatially defined localizations of specific glutamatergic subtypes will be validated with in situ hybridization (RNAScope). Aim 2B will determine the molecular features of amygdala- sgACC and amygdala-pgACC projection neurons, following injections in Aim 1. These results will then be integrated with the results of cortical-thalamic input networks for comprehensive analysis of sgACC and pgACC connectivity. This research is part of a comprehensive training plan with direct mentorship in experimental design, techniques, field knowledge, scientific writing and career development, supported by my Sponsors, my Collaborator, and their respective institutions (URMC, Emory, and Wake Forest).