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They are Larry Cohen, Chun X. Bleau
Brad Baker, Riota Homma and Lei Jin.
One reason the brain is difficult to study is that many
individual neurons or brain areas are active at once; conventional techniques
allow one to monitor only one or a few neurons or locations at a time. We have
worked on several variations of an optical method for measuring brain activity;
utilizing both voltage-sensitive dyes and calcium-sensitive dyes and either
a 464 element photodiode array (see photograph of array) or a 80x80 CCD camera. Both
systems are fast; frame rates >1.6kHz.
In the First variation (Population Signals, Larry Cohen), each pixel in the recording receives light from a large number of neurons and processes (e.g. from an area of brain 10µm x 10µm to 200µm x 200µm) and thus each signal represents the average of a population of neurons. There are several interesting aspects of vertebrate brain function where populations are involved. One example is the organization of visual cortex into modules such as ocular dominance columns. Another is the synchrony and oscillations that accompany sensory processing. A third is maps of the input to glomeruli in the olfactory bulb where 10,000 receptor neurons with identical olfactory receptor protein converge onto a single glomerulus. For studying phenomena of this type population recordings should be useful.
In the Second variation (Action Potential Signals), we use the dyes to follow the spike activity of individual neurons, and in favorable preparations about 500 individual neurons can be monitored simultaneously. In ganglia from sea slugs (opisthobranch molluscs, Aplysia), this number is a substantial fraction of the total number of neurons present. We hope that monitoring many neurons simultaneously will improve our understanding about how nervous systems are organized to generate behaviors.
The figure illustrates the voltage-sensitive dye signal (dots) and the action potential (smooth line) measured simultaneously from a squid giant axon. The two signals follow each other precisely providing one kind of evidence that this dye signal is potential dependent.
Ross, W.N., B.M. Salzberg, L.B. Cohen, A. Grinvald, H.V. Davila, A.S. Waggoner, and C.H. Wang (1977). Changes in absorption, fluorescence, dichroism, and birefringence in stained giant axons : optical measurement of membrane potential. J Membr Biol, 33, 141-183.
Ours is a small laboratory in the Department of Physiology.
One of the reasons for having a small laboratory is that the PI still enjoys
doing experiments and a large laboratory makes that impossible. In addition,
there are only two experimental set-ups. Thus, the planning, the experiments,
and the analysis have always been done in a very collaborative fashion with
everyone sharing their opinions and efforts.
You may
have noticed that all of the individuals are smiling. This must
mean that the experiments are easy.
(Left to Right)
Srdjan Antic: Department of Neuroscience, University of Connecticut
Health Center
Tsau Yang
Chris Hickie: University of Connecticut Medical School
Avrum Cohen's Homepage. Avrum was
a programmer at the lab off and on until his employment at Universal Imaging
Corporation in December of 1995
Fang Jing
Lam Ying-Wan: Department of Neurobiology, University
of Chicago
Michal Zochowski Department of
Physics, University of Michigan
Matt Wachowiak Department of Biology,
Boston University
Dejan Vucinic Stanford University
Maja Djurisic Department of Biology,
Stanford University
Stratos Kosmidis Aristotle University, Thessaloniki, 54 124, Greece
Dejan Zecevic Department of Cellular & Molecular Physiology, Yale University
