Friday, March 25, 2016

FWS Student Highlights: Maggie Greer

The Physiological and Behavioral Neuroscience in Juveniles Lab headed by Dr. Theodore Dumas at the Krasnow Institute aims to uncover brain mechanisms involved in learning and memory.  We focus on hippocampal-dependent processes in mice at the end of the third postnatal week, which is comparable to 2-4 years old in humans.  As an OSCAR rehire in Dr. Dumas’s lab, I have enjoyed opportunities to experience various branches of neuroscience research and I have developed skills that prepare me for a successful future in neuroscience. 

The project I currently work on utilizes various electrophysiological measures testing for neuroplasticity—long lasting functional changes due to experience—implicated in learning and memory.  Two molecular mechanisms found to play a substantial role in plasticity are NMDA and AMPA receptors that bind to glutamate, the brains main “excitatory” neurotransmitter.  When NMDA channels open, they allow calcium to flow into the post-synaptic cell; this causes depolarization and leads to long-term changes.  This means that NMDA receptors have a certain amount of control over information processing and form pathways that activate easier according to environmental stimulus.  Thus, we use transgenic mice with separate domains of NMDA receptors in order to regulate different aspects of spatial cognition distinctive in the hippocampus.  

Electrophysiology allows me to test plasticity in hippocampal neurons of adult vs. adolescent chimeric mice and compare responses to delineate specific mechanisms and their effect on learning and memory.  To obtain the necessary information, I meticulously place a tiny stimulating electrode on the axons of Schaffer collateral cells (pre-synaptic) in a slice of mouse hippocampus—the neurons are kept alive using artificial cerebral spinal fluid—that delivers a stimulus voltage to trigger depolarization via glutamate receptors.  A second hollow recording microelectrode is placed carefully at the cell bodies of CA1 (post-synaptic) cells and records the post-synaptic electrical response.  I also measure responses in “silenced” neurons encoded with fly allatostatin receptors.  When activated, these receptors keep the cell in a hyperpolarized state, thereby blocking all on-going activity.  This provides data relating specific neurons to aspects of hippocampal-dependent learning and memory function.  A majority of my time is spent analyzing the data from the abovementioned tests and making correlations relevant to the goals of our lab.