Sabrina S. Burmeister - US grants

The goal of this research is to discover how social interactions are translated into functional changes in the brain. I proposed experiments that will identify neural pathways by which social interactions among male teleosts control gonadotropin releasing hormone (GnRH-I) neurons. Becoming socially dominant produces an 8-fold increase in their size of GnRH-I neurons while social descent causes those same neurons to shrink. It is not known, however, how social information reaches the brain regions that control GnRH-I. The specific aims are: 1) To identify functional circuits responsible for social regulation of reproduction using expression of the immediate early genes (IEG), c- FOS and erg-1 in appropriate social situations. Specifically, I will compare IEG induction of males in social transitions to males in stable social situations, to discover the time-course of activation, including when GnRH-I neurons are, themselves, activated. 2) I will map projections from sensory and motivational systems to GnRH-I neurons of the pre-optic area using a transsynaptic tracer, fragment C of tetnus toxin. By combining functional and neuroanatomical analyses with manipulation of the animal's social status, these experiments will add significantly to our understanding of how social information influences the brain. Regulation of reproduction by GnRH-I is highly conserved among vertebrates so that understanding the mechanisms by which social cues influence GnRH-I neurons is essential to a better understanding of numerous reproductive pathologies.

The decision to reproduce is one of the most important decision an animal makes. Females invest a large proportion of energy in reproduction and the timing of reproduction is therefore highly regulated. The timing of reproductive behavior is regulated through neural modulation by reproductive hormones, such as estradiol. The primary goal of the proposed research is to better understand how estradiol modulates neural systems to regulate the expression of reproductive behavior. An important component of reproductive behavior includes those behaviors that mediate a female's choice of a mate. Using túngara frogs, the researchers will investigate the effects of estradiol on the sensory systems that females use to respond to male mating signals. Female frogs choose mates based on their vocalizations, and they respond preferentially to vocalizations of their own species when their estradiol levels are high compared to when their estradiol levels are low. This research will test if estradiol influences activity in the auditory system through changes in neurochemicals in the brain. To measure neural activity, the researchers will assess changes in gene expression that are correlated with neural activity. They predict that estradiol causes females to respond selectively to male vocalizations because of its effects on catecholamines, a class of neurochemicals, in the auditory system. The results of this research will broaden our understanding of how brain function is modulated by hormones during critical behavioral decisions such as mate choice. The project will also provide training opportunities for graduate and undergraduate students.

Spatial memory is a specialized form of learned navigation characteristic of animals with large, complex brains. The underlying neural circuitry for the “brain’s GPS” has been identified but we lack a complete picture of how this ability evolves. The green-and-black poison frog is the only amphibian known to be capable of spatial memory, creating a unique opportunity to identify genes that enable the evolution of spatial memory by comparing species that vary in memory abilities. To this end, this award will allow the investigator to develop skills that they will use to discover the genetic mechanisms of spatial memory in poison frogs. By comparing species, they will determine the genes that confer the capacity to form spatial memories. In addition, the investigator will partner with the Museum of Life and Science in Durham NC to broaden participation in science and to increase public awareness of science. Together, the Museum and the investigator will host interactive sessions for museum visitors based on the proposed research and create an interpretive panel to accompany the Museum's Poison Frog Exhibit that highlights the cognitive abilities of poison frogs and gives insight into the underlying research process.

Despite an intense focus on genomics over the last 25 years, we still lack the ability to predict an organism's phenotype from knowledge of its genome and environment. This award will provide the investigator with a toolset in genomics that they will use to create a model for the functional genomics of spatial memory. By integrating genomics into her research, the investigator will leverage what is known about poison frog cognition to create a model for functional genomics of a complex cognitive trait. To do so, the investigator will partner with Dr. Erich Jarvis at Rockefeller University to acquire foundational skills in three areas: 1) sequencing and annotation of genomes of non-model organisms; 2) identifying gene networks activated by specific experiences; and 3) comparing gene networks across species. The investigator will use these skills to produce a high-quality, annotated genome of Dendrobates auratus, identify memory-associated gene networks expressed in the hippocampus of D. auratus, and test the link between spatial ecology and spatial memory-associated gene networks across species.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.