Seminar on
Modern Optics and Spectroscopy


Mriganka Sur, MIT

Imaging cells synapses, and molecules in the live brain

March 27, 2007

12:00 noon - 1:00 p.m. Grier Room 34-401


Abstract:

Neuroscience is being transformed by optical tools, particularly those that combine high resolution cellular imaging with novel reporters of cell structure and function. Recent studies from our laboratory demonstrate the power of these approaches for revealing mechanisms of plasticity in neurons and networks of the mammalian cerebral cortex. Cortical neurons receive excitatory synapses at trillions of tiny protrusions, termed spines. Spines change their structure dynamically. By combining structural two-photon imaging of GFP-labeled neurons and functional intrinsic signal optical imaging in visual cortex in vivo, we have shown that functional plasticity in cortical networks is anchored by structural changes in identified spines. As the basis for spine dynamics, we have used a virally packaged CFP/YFP FRET probe to reveal real-time changes in CaMKIIα autophosphorylation within spines and dendrites in vivo. Synaptic plasticity is known to require precise spatial and temporal cellular expression of molecules such as Arc. By using mice genetically engineered to express GFP in response to Arc activation, we have demonstrated the physiological role of Arc in cortical information processing.  Finally, using functional two-photon imaging of calcium signals in vivo combined with cell-specific markers, we have revealed the function of astrocytes – which constitute half of all cortical cells but whose function was hitherto unknown. Individual neurons and adjacent astrocytes in visual cortex have matched spatial receptive fields and similarly tuned responses. Astrocytes mediate structural plasticity at spines as well as cortical hemodynamic responses, which couple neuronal activity to vascular signals that underlie noninvasive brain imaging.

TUESDAYS, 12:00-1:00, GRIER ROOM (34-401)
Refreshments served following the seminar

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Co-sponsored by the George R. Harrison Spectroscopy Laboratory,
the Department of Electrical Engineering and Computer Science and
the School of Science, Massachusetts Institute of Technology.