Annalisa Scimemi, Department of Biology, SUNY Albany, USA
A circadian clock for hippocampal plasticity and cognitive processing
Most animal species operate according to a 24-h period set by the suprachiasmatic nucleus (SCN) of the hypothalamus. The rhythmic activity of the SCNmodulates hippocampal-dependent memory, but the molecular and cellular mechanisms that account for this effect remain largely unknown. Here, we identify cell-type specific structural and functional changes that occur with circadian rhythmicity in neurons and astrocytes in hippocampal area CA1. Pyramidal neurons change the surface expression of NMDA receptors. Astrocytes change their proximity to synapses. Together, these phenomena alter glutamate clearance, receptor activation, and integration of temporally clustered excitatory synaptic inputs, ultimately shaping hippocampal-dependent learning in vivo. We identify corticosterone as a key contributor to changes in synaptic strength. These findings highlight important mechanisms through which neurons and astrocytes modify the molecular composition and structure of the synaptic environment, contribute to the local storage of information in the hippocampus, and alter the temporal dynamics of cognitive processing.
The brain regulates every aspect of our daily life, yet many of the fundamental mechanisms underlying its function remain unclear. How do neurons in the brain exchange information among each other? How is their activity conveyed across neurons in different brain regions and how is it shaped by astrocytes?nbsp;In our lab, we are interested in understanding the functional properties of central synapses, the specialized structures that convert the electrical activity of a neuron into a chemical signal for its target cells. We want to understand how individual molecules are distributed within the synapse and how their spatial arrangement influences the properties of neurotransmitter release. We want to know how neurotransmitters diffuse outside of the synapse and generate long-distance signals to different cells. Our ultimate goal is to gain insights into the functional consequences of changes in synaptic function associated with the onset of different neuropsychiatric and neurodegenerative disorders. To perform our studies, we use a combination of experimental and theoretical approaches, including electrophysiology, optogenetics, two-photon imaging and reaction-diffusion computer simulations. We are also eager to learn and develop novel experimental approaches and research tools.
Dr. Scimemi got her PhD in Biophysics from the International School of Advanced Studies (SISSA/ISAS) working with John Nicholls and Enrico Cherubini. She continued her postdoctoral studies with Dr. Dimitri Kullmann (UCL) and Jeff Diamond (NIH). She got her faculty position at SUNY Albany in 2013 and is currently an Associate Professor in the Department of Biology.