PSAAL - A LabVIEW Program for Psychophysiological Research

Author(s):
Alessandro Angrilli - University of Padova Italy

Industry:
Life Science

Products:
LabVIEW,

The Challenge:
Devising an integrated group of programs suited for most short-epochs psychophysiological experiments that includes both acquisition and analysis routines. In addition, the programs must be flexible and easy to use for both beginners in psychophysiological research and psychology students.

The Solution:
Using a PC-based virtual instrumentation system with DAQ hardware controlled by LabVIEW.

Physiological Signals Acquisition and Analysis in the LabVIEW Language (PSAAL) consists of a group of seven pro-grams that perform acquisition, display, reduction, and analysis of physiological data. Compared to most psychophysiological applications, it is very easy to set up programs with PSAAL, verify the signals, and follow the various steps from acquisition to data analysis. All these features make it a convenient starting point set for conducting experiments in psychophysiology.

The Acquisition program performs acquisition and display of physiological responses with 12 or 16-bit resolution, according to the A/D board used. Analysis programs include conversion of electrocardiogram into heart rate, elaboration of the main parameters of skin conductance responses, integrated electromyogram, startle reflex, averaging of evoked potentials, or other event-related physiological responses under different experimental conditions. The Reduction program transforms raw data into a few summary data (bins) and converts their amplitude into the original values (e.g., microvolts, millivolts, beats per minute, etc.) according to the physiological function recorded. With the Reduction program, users can reduce physiological functions into 0.5 or 1 sec bins before statistical analysis.

The Display Red program permits the reorganization of reduced data under different experimental conditions and the correction of artifacts. This program makes it possible to associate a different set of conditions with the same data. The 1CH-Analysis program performs specific analysis on one selected channel, including the averaging of evoked responses under different conditions. The selection of a time window makes it possible to calculate, for each trial and for each experimental condition, several parameters (maximum amplitude, peak latency, area, etc). Using two programs, To Statistic and Build Within, the user saves time by organizing data in a spreadsheet ready for most statistical packages (ANOVA - ANalysis Of VAriance statistics) without using other spreadsheet applications. Every step, from acquisition to statistic reorganization of the data, is performed by creating ASCII files that the user can read and modify with any text editor or spreadsheet program.

LabVIEW in the PSAAL
LabVIEW, a general-purpose programming system, includes libraries of functions designed specifically for data acquisitionand instrument control. Some researchers are now beginning to use LabVIEW either to analyze specific parameters of certain physiological functions or to control and handle complex tasks or routines. In many cases, LabVIEW is comparable to commercial turnkey systems, which not only are more expensive, but often lack flexibility. Small labs that need custom programs but cannot afford professional programmers can take advantage of the ease and flexibility of LabVIEW.

With its object-oriented capabilities, any researcher can quickly learn to modify or build a program without mastering professional knowledge of computer languages. In addition, the easy graphical interface, rich library of virtual instruments (VIs), and variety of functions available are impressive and represent a powerful instrument for psychophysiological research.

Flexibility and Portability
Thanks to the flexibility and portability of LabVIEW, PSAAL can handle several different platforms (Mac OS, Windows, Sun, HP-UX) and can run on many different kinds of National Instruments DAQ boards, including the low-cost ones. PSAAL Programs
The seven PSAAL programs include:

• Acquisition
• One-Channel Analysis
• Reduction
• One-Channel Grand Averaging
• Display Red
• To Statistic
• Build Within
  

The programs are freely available upon personal request to the author.

For more information, contact:

Dr. Alessandro Angrilli

Università di Padova

Dipartimento di Psicologia Generale

Via Venezia 8, 35131 Padova, Italy

E-mail: angrilli@psico.unipd.it

Alessandro.Angrilli@uni-konstanz.de

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