Using NI Software and Hardware to Develop an Automated System for Neuroscience Research

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" With LabVIEW, we were able to easily build and test functional algorithms, then gradually integrate them as sub-VIs into the overall system. LabVIEW provides not only a full palette of standard programming functionality, but also a robust set of user interface elements. "

- 楠 杨, Lucent Technologies Qingdao Communication Equipment Co., Ltd.

The Challenge:
Supporting neuroscience drug discovery efforts by automating the generation of synaptic physiology data from multiple brain slices.

The Solution:
Using NI software and hardware to develop a flexible, powerful, yet easy-to-use system to facilitate the design, execution, and analysis of stimulus-evoked field potential experiments in in vitro brain slices.

Author(s):
楠 杨 - Lucent Technologies Qingdao Communication Equipment Co., Ltd.

Many current pharmaceutical research efforts target the therapeutic modulation of neuronal synapses, the electrochemical junctions brain cells use to communicate. Brief electrical pulses applied to in vitro slices of rat or mouse brain evoke very characteristic and reproducible voltage patterns, which can be recorded and analyzed for clues to disordered neuronal function. Such so-called brain slice field potential recordings are a widely used experimental paradigm for the study of synaptic physiology. A variety of standard synaptic tests have been extensively characterized, each elucidating particular aspects of synaptic function, including synaptic plasticity, the physiological basis of learning and memory. In essence, all synaptic tests consist of a series of stimulus-response events. In this case, the stimulus is an electric current delivered to a neuronal fiber bundle either as a single square pulse or as a series of pulses with a specific temporal pattern. The response is the resulting waveform recorded from downstream populations of neurons. Within this general framework exists a virtually unlimited range of experimental possibilities.

Unable to identify a commercial product with all the necessary flexibility and power, we explored the development of a custom instrument of our own design. This instrument would require the following features:

  • A user-friendly interface for the easy set-up of complex synaptic physiology experimental designs
  • Control over all stimulation parameters, including µA resolution of stimulus pulse intensity and µsec resolution of plasticity-inducing temporal patterns
  • Ability to record from multiple slices simultaneously and in an automated fashion
  • Ability to switch automatically between multiple perfusion solutions
  • Detailed analysis of acquired waveform data online during the experimental run with quick exportation to spreadsheet format upon completion
  • Design from inexpensive off-the-shelf components

Given its range of software and hardware options, the National Instruments product line was identified early on as an obvious platform for developing our system, Synaptic Explorer.

Instrument Design

Because the sampling requirements of brain slice field recordings are relatively modest (20 kS/s for 10 to 50 ms every 20 to 60 seconds), the low-cost NI M series data acquisition cards were an ideal choice. Another consideration was that each brain slice required a devoted pair of analog output (AO, for stimulus generation) and analog input (AI, for response recording) channels. Onboard triggering would then provide an ideal means of coordinating stimulus-response events. Finally, digital I/O would be required to control pinch valve arrays for drug solution exchanges. The NI PCI-6229 data acquisition board, in a Dell Precision 340 running Windows XP, provided a powerful, yet remarkably cost-effective basis for our instrument.

While the NI hardware component of the equation was more than adequate to the task, it was the synergy of that hardware with the NI LabVIEW Developer Suite that truly offered a complete solution platform. With LabVIEW, we were able to easily build and test functional algorithms, then gradually integrate them as sub-VIs into the overall system. LabVIEW provides not only a full palette of standard programming functionality, but also a robust set of user interface elements.

System Operation and Functionality

Synaptic Explorer’s user interface is organized as a full-screen tab control container, its four tabs sequentially arranged to match the functional order of a typical field recording experiment. All tabs are similarly organized as four horizontally-arranged groupings of interface elements, corresponding to each of four available recording channels. These tabs are as follows:

  • Setup: Users design automated experiments by setting a series of parameters distributed across separate tab controls for each recording channel. Four XY graphs provide a user event-driven representation of the overall experimental designs for each channel. Over fifty parameters can be individually set for each slice; saved to the disk; and then reloaded for easy setup of recurrent designs.
  • Test: This section provides for the manual stimulation-recordings of brain slice fields. The most recent field potentials recorded from each slice are graphed while accumulating analysis results are charted. This tab represents the brief manual phase of a typical experiment during which the user carefully optimizes electrode placement and monitors slice stability.
  • Run: Selecting this tab initiates the execution of the experimental design configured in the SETUP tab. A dialog box present a selection of channels to activate, after which the experiment runs through to completion, typically freeing the investigator for several hours. Additional tab controls for each recording channel present a series of charts with continuously updating analysis results.
  • Review: Here, fields are analyzed and normalized results plotted according to the SETUP parameters. Individual fields are viewed by dragging a cursor across an analysis graph. Experiments can be saved as LabVIEW files, which include both the SETUP parameters as well as all related field recordings. Additionally, analysis results can be exported in spreadsheet format, as can individual field recording waveforms.

Synaptic Explorer, our LabVIEW and NI-DAQmx solution for automated, multislice field recording, represents a significant breakthrough in our ability to provide synaptic physiology data to the Wyeth neuroscience drug discovery efforts. While scaling up significantly the number of daily recordings, the precision with which experiments are carried out and the ease with which data is collected and stored have also improved the overall quality of our data over that obtained by previous, manual systems.

Author Information:
楠 杨
Lucent Technologies Qingdao Communication Equipment Co., Ltd.

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