Using LabVIEW to Implement Virtual Instrumentation in Vestibular Research

Author(s):
Randell Riggs - University of Texas Medical Branch at Galveston
Adrian A.. Perachio - University of Texas Medical Branch at Galveston

Industry:
University/Education, Life Science

Products:
LabVIEW,

The Challenge:
Developing a flexible system that provides the necessary experimental control and data acquisition and analysis capabilities needed to perform vestibular physiology experiments.

The Solution:
Using National Instruments LabVIEW software and data acquisition hardware to develop a flexible computer-based system to conduct biomedical research.

Performing Vestibular Physiology Experiments
Balance and movement require the coordination of sensory and motor information. We study how this occurs in the perception of balance and how the sense of balance changes during motor learning and recovery from damage. Our efforts reveal that the balance and other sensory-motor systems in the brain work together to resolve the problems that impair the sense of balance.

Developing a Flexible, Computer-Based System Using LabVIEW and Data Acquisition Hardware
We constructed an easy-to-maintain, high-performance, and scalable system using commodity PCs as a platform for LabVIEW and NI data acquisition and output generation hardware. By configuring a flexible, distributed solution, experimental control and data acquisition systems can produce motion output or graphical representation for the experimenter, while other systems in our solution monitor the appropriateness of the experimental subject’s response to stimuli. After the experiment, we can process data through a suite of analysis VIs for further interpretation.

By keeping the system compartmentalized in separate software modules, we can easily and inexpensively add functionality or perform minor modifications by upgrading specific modules with a patch. Because we maintain relatively small modules with limited functional roles, we can generate initial programs more quickly and maintain a more stable architecture. We can isolate upgrades of these VI modules with the readily transposable NI hardware and some basic distributed programming. Moreover, if we need new features that we cannot easily incorporate into current programs, we can build and add a new module to the experiment system in a short time. Given the nature of LabVIEW programming, we can easily customize and repair programs without breaking current programs in the process. This localization is inherent to the ease of programming with LabVIEW and the conceptual independence of the core modules. This provides a versatile system architecture by reducing the time and effort required in customization. We then integrate the new function into our data acquisition or storage structure without destroying access to input signals or previous data.

Creating Virtual Instruments for Experimental Research Using LabVIEW
We utilize virtual instruments using LabVIEW for online experimental control, data acquisition, and data analysis to avoid compatibility issues between programs. The VIs are specific to a task, and we generally implement them in a stepwise process. We run the VIs on PCs equipped with E Series data acquisition cards for data input, and the NI-PXI-6711 analog output cards for output control to take advantage of our investments in legacy servo-controllers. Our VIs include: ProtocolController, DataStore, Reward, DataView, ViewEvents, and UnitRates. The ProtocolController VI coordinates servomotors and galvanometers to move experimental subjects in a horizontal plane and present the servomotors and galvanometers with a controlled visual environment. The DataStore VI acquires and records feedback from those motors along with the physiological signals from the experimental subject, including neurophysiologic and eye-movement signals. We use the Reward VI for training experimental subjects by comparing feedback from the motors to the eye-movement signals. We can analyze this feedback online to reward to control juice pumps that reward subjects for on-task responses. We use the DataView VI to review experiments and to process the recorded eye and neuronal firing signals for further analysis with the ViewEvents and UnitRates VIs. Using the ViewEvents and UnitRates VIs, we can perform detailed analysis of eye movement and brain cell activity data, as they relate to the visual and motion stimuli used.

We use the National Instruments products to run these applications on any number of hardware configurations. For instance, we run DataStore and ProtocolController VIs on separate PCs in one lab to accommodate for the performance requirements of the data acquisition rates used and graphical presentation of that data. However, with little modification, we can run these two programs from a single computer in another lab with a much lower data rate. Because each lab has specific needs, we do not use all of the modules in every lab to perform experiments.

Saving Time and Resources with Flexible Solution
With the VI modules, each lab creates a working system from building blocks without having to reinvest in programming or specialized hardware. We estimate that modification of core modules for re-use cost. By modifying core modules for re-use, we estimate saving 75 percent of the time and resources needed to originally develop that module. Repetitive re-use results in savings of development costs, as well as a reduction in subsequent startup time for new or re-engineered systems.

By designing each VI program module to perform specific core functions, we can customize programs for individual laboratories based on the modules we include. We used this customization in designing the signal processing and calibration procedures that are specific to each lab. To properly adjust the output from the ProtocolController VI, or the data needed to assess behavior in the Reward VI, or even the graphical representations presented by the Datastore VI, the physical constraints of the experimental systems across laboratories requires that we dynamically adjust some signals in relation to the feedback from other signals. To perform customized online signal processing using the ProtocolController VI, we use the incoming position feedback signal from the positioning motors to adjust the output signal to the galvanometers. By doing this, we can control the position of the laser relative to the position of the subject or the subject’s eyes.

A suite of analysis programs processes the data we acquire in experiments. These programs, principally composed of ViewEvents and UnitRates VIs, process the data stored in a standardized and optimized structure and process the data in two separate analysis paths. We use the ViewEvents VI to evaluate eye movement data to determine the suitability of the subject’s behavior to their environment. We designed the UnitRates VI to explore the activity of brain cells, so we can link the activity of the brain to the interpretation of the environment or to the production of behavior. On each analysis path, the steps to analyze data build on the processing from a previous step and provide user interpretable information and the output for further analysis. We use these integrated analysis programs across our vestibular research laboratories to answer a variety of experimental questions.

For more information, contact:
Adrian Perachio
University of Texas Medical Branch at Galveston
Tel: 409-747-3770
E-Mail: aperachi@utmb.edu

Browse All Case Studies »