Extended dynamic clamp: controlling up to four neurons using a single desktop computer and interface

The dynamic clamp protocol allows an experimenter to simulate the presence of membrane conductances in, and synaptic connections between, biological n eurons. Existing protocols and commercial ADC/DAC boards provide ready cont rol in and between less than or equal to2 neurons. Control at >2 sites is d esirable when studying neural circuits with serial or ring connectivity. He re, we describe how to extend dynamic clamp control to four neurons and the ir associated synaptic interactions, using a single IBM-compatible PC, an A DC/DAC interface with two analog outputs, and an additional demultiplexing circuit. A specific C++ program, DYNCLAMP4, implements these procedures in a Windows environment, allowing one to change parameters while the dynamic clamp is running. Computational efficiency is increased by varying the dura tion of the input-output cycle. The program simulates less than or equal to 8 Hodgkin-Huxley-type conductances and less than or equal to 18 (chemical a nd/or electrical) synapses in less than or equal to4 neurons and runs at a minimum update rate of 5 kHz on a 450 MHz CPU. (Increased speed is possible in a two-neuron version that does not need auxiliary circuitry). Using ide ntified neurons of the crustacean stomatogastric ganglion, we illustrate on -line parameter modification and the construction of three-member synaptic rings. (C) 2001 Elsevier Science B.V. All rights reserved.