Social experience dependent cellular plasticity of brain circuits - Summary Social animals often compete for dominance through agonistic interactions to form social hierarchies. As social relationships mature, the behavior patterns of members diverge according to social rank. Although we know that the behavioral differences that emerge between dominant and subordinate animals are rooted in physiological adaptions, our understanding of the morphological and functional plasticity the nervous system undergoes remains poorly understood. This proposal tackles this issue by investigating the neural bases of social dominance and its impact on behavior using zebrafish as a model organism. We focus on two brain nuclei involved in social regulation: The diencephalic dopaminergic posterior tuberculum nucleus (PTN) regulates motivation, aggression, and spinal motor circuits, and secondly, the thalamic parathyroid nucleus which regulates prosocial behavior and processing of visual information. Our objective is to examine the cellular mechanisms of how social dominance induces morphological and functional plasticity of the PTN and how status affects the thalamic parathyroid system and its regulation of visual information. We will leverage the technical biological advantages zebrafish provides to address the following aims: In aim 1, we will examine how social dominance affects the morphological architecture of the PTN and its synaptic interconnectivity during social rise and fall. In aim 2, we will examine how social dominance induces status-dependent functional differences in PTN electrical excitability, calcium dynamics and biochemical activities. In aim 3, we will examine how social status affects the morphological and functional architecture of the parathyroid nucleus, its morphological interactions with the visual system and modulation of motor behavior. Results from this study will improve our understanding of how social dominance influences decision-making networks and their regulation of motivation and aggression, the principles of which may be applicable to other social species.
