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An electrophysiology quesiton

Doktor DynaSoar targeting at OMCL.mil
Thu Feb 12 05:16:06 EST 2004

On Wed, 11 Feb 2004 16:20:53 +0000, Xiaoshen Li <xli6 at gmu.edu> wrote:

} Dear Everybody:
} My original post has become centered around what is voltage clamp and 
} what is current clamp and what is the purpose of each technique. Voltage 
} clamp and current clamp have been the only two choices for an 
} electrophysiologist. However recently I have heard that there is another 
} new clamping technique now. It is called "Dynamic clamp". It is said 
} that this techniqure provides some new information which V-clamp or 
} I-clamp cannot.
} Could anybody explain what dynamic clamp is and compare it with V-clamp 
} and I-clamp?

Here's a description. Although this paper is concerned with a method
of control of such devices, the description holds, and the references
can fill in anything this lacks.

(Please excuse the poor formatting. Google's PDF to HTML translation
misses spaces sometimes.)


Annals of Biomedical Engineering, Vol. 29, pp. 897–907, 2001

Real-Time Linux Dynamic Clamp: A Fast and Flexible Wayto Construct
Virtual Ion Channels in Living Cells


More recently, a third electrophysiological technique has been
developed.16,18,19In this technique, often calledt he ‘‘dynamic
clamp’’ method, the experimental systemcontrols membrane conductance
rather than transmem-brane current or potential. Because the dynamic
clampmethod allows one to mimic biological effects in theliving cells,
it allows the experimentalist to test newkinds of specific,
quantitative hypotheses directly in ex-periments. For example, dynamic
clamping has
beenusedtoverifythehypotheticaleffectsofneuromodulators;18show how
particular conductancescan account for changes in neural firing
modes,8,12spikewidths,14or spike timing;13search for input
study how particular parameters affectsynchronization properties in
‘‘virtual networks’’ consist-ing of one or more biological excitable
cells interactingwith each other, or with modeled counterparts, in
user-specified ways.3,4,20Dynamic clamp is fundamentally more
difficult toimplement than its forebears. Current clamp requiresonly a
high-quality current source. Voltage clamp re-quires a fast control
system that minimizes the differencebetween measured membrane
potential and a user-supplied ‘‘command’’ potential. A dynamic clamp
systemmust calculate the value of a time-varying artificial mem-brane
conductance. Often, this conductance comes fromthe real-time solution
to a set of nonlinear differentialequations that depend on time and
membrane potential.Next, the system must calculate and output the
amountof current that would have passed through this
virtualconductance. This calculation also depends on the
instan-taneous value of membrane potential, and thus must becalculated
in real time

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