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Functional
organization of single neurons as revealed by voltage imaging
Understanding the biophysical properties of single neurons and how they process information is fundamental to understanding how brain works. Brain function depends critically on how exactly are signals integrated by individual nerve cells functioning as complex operational units. The principles of information processing in single neurons can only be determined by studying specific neuronal types in different experimental models. Studying the functional organization of a neuron requires monitoring of the activity of different parts of the same cell simultaneously. Consequently, a major experimental leap forward in this field was achieved by the development of a recording method that allowed simultaneous monitoring of voltage transients from two locations on a single neuron (double-patch recording in brain slices; Stuart and Sakmann, 1994). However, pair-wise recording is a limited tool for assessing rapidly changing spatio-temporal patterns of signal initiation and propagation in complex dendritic structures. Thus, most of the uncertainties in the interpretation of double-patch electrical recordings were due to the insufficient spatial resolution of the measurements. It is necessary to complement the patch-electrode approach with technologies that permit a massive parallel recording from the neuron. We achieve this goal by using high-resolution multi-site monitoring of membrane potential signals with intracellular voltage-sensitive dyes (voltage-imaging; Zecevic, 1996; Antic et al., 1999; 2000; Djurisic et al, 2004) and combine this approach with standard patch-clamp recording and Ca 2+-imaging. The long term objective of our research is to develop a full understanding of the computational task and functional organization of two classes of vertebrate neurons: mitral and tufted cells of the olfactory bulb and hippocampal CA1 pyramidal neurons. The functional characterization obtained by experimental measurements is linked to numerical simulations (multi-compartmental computer models). These models reflect our current understanding of the interactions between many functional parameters that control the behavior and the input-output transforms carried out by individual neurons.
Figure caption:
Sequential voltage-imaging and Ca2+-imaging from the same neuron reveal spatial aspects of the interaction between membrane potential changes, synaptically activated Ca2+ signals, and Ca2+ signals associated with the back-propagating spikes during pairing protocols shown to result in associative synaptic plasticity. The experiments were carried out on CA1 hippocampal pyramidal neurons loaded with the voltage-sensitive dye JPW 3028 and a Ca2+-indicator bis-fura-2. Supra-linear Ca2+-signal in response to EPSP - bAP pairing was restricted to a single oblique dendrite and did not always correlate with bAP boosting.
Recent
publications:
Popovic M., Djurisic M. and Zecevic D. (2005). Determinants of low EPSP attenuation in primary dendrites of mitral cells. Ann. NY Acad. Sci., 1048: 344-349.
Djurisic M., Antic S., and Zecevic D. (2004) Dendritic voltage imaging. In: Imaging in Neuroscience and Development; Laboratory Manual. Ed.: R. Yuste and A. Konnerth. Cold Spring Harbor Laboratory Press. pp 457-463.
Djurisic M., S. Antic, W. Chen, and D. Zecevic (2004). Functional organisation of mitral cell: a voltage-imaging study. J. Neurosci. 24:6703– 6714 .
Djurisic, M. R., Zochowski, M., Wachowiak, M., Falk, C.X., Cohen, L.B., and Zecevic, D. (2003) Optical Monitoring of Neural Activity Using Voltage-Sensitive Dyes, In Methods In Enzymology, ed. by G. Marriott and I. Parker, 361: 423-451.
Antic S, Wuskell JP, Loew L, Zecevic D. Functional
profile of the giant metacerebral neuron of Helix aspersa: temporal and spatial
dynamics of electrical activity in situ. J Physiol. 2000 Aug 15;527 Pt 1:55-69.
Zecevic D. Multiple
spike-initiation zones in single neurons revealed by voltage-sensitive dyes. Nature. 1996 May 23;381(6580):322-5.
dejan.zecevic@yale.edu http://info.med.yale.edu/cmphysiol/cohen/redshirtdiaries.html
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