Record an I/V Curve

This tutorial describes a typical procedure for measuring the current/voltage relationship of a neuron using the Task Runner. This tutorial is run from the example configuration, using a simulated patch clamp amplifier and neuron.

  1. Start ACQ4, then from the module list in the Manager window, select “Task Runner” and click Load Module.

  2. In the Task Runner, check the box next to “Clamp1” under Devices. The task interface for the simulated clamp device will appear. Notice the tas at the bottom of the window; the DAQ configuration including the sample rate can be accessed here.

  3. At the top-left of the newly created dock, click on vc, then select ic from the list.

  4. In the task settings dock, just beneath the device list, click Test. A noisy recording should appear; you have just recorded 200 ms of current-clamp data from a Hodgkin-Huxley neuron.

  5. In the same dock, change Duration to 400 ms.

  6. Now we will create a square-pulse waveform to stimulate the cell:
    1. In the function generator for the clamp device, click Add Stimulus, then Pulse.

    2. Change the pulse amplitude to 50 pA, then click Update. A square-pulse waveform appears, colored red.

    3. Check Auto adjacent to the Update button; this will make the stimulus waveform automatically update as we adjust it.

    4. Change start to 50 ms and length to 200 ms; verify that the square-pulse waveform has changed accordingly.

    5. Click Test again, just for fun.

  7. Next, we will create a sequence of pulses at different amplitudes:
    1. Expand the amplitude parameter by clicking the arrow (or +) immediately to its left.

    2. Change the sequence parameter to range.

    3. Make the start value -100 pA, and the stop value 100 pA.

    4. Check that a sequence of pulses is now visible in the waveform plot. Sequence waveforms are plotted in grey.

    5. Check that an item called “Clamp1 command.Pulse_amplitude” has appeared in the Sequence Parameters list.

    6. Just below the Sequence Parameters list, click Test.

    7. The entire sequence executes, plotting each result one at a time. Note this will run a bit slow because it is simulating the neuron; a real experiment would be much faster.