A Computerized Stroop Test for the Evaluation of Psychotropic Drugs in Healthy Participants

Article excerpt

Byline: Raveendranadh. Pilli, MUR. Naidu, Usha. Pingali, J. Shobha, A. Reddy

Background: The Stroop paradigm evaluates susceptibility to interference and is sensitive to dysfunction in frontal lobes and drug effects. The aim of the present study was to establish a simple and reliable computerized version of Stroop color-word test, which can be used for screening of various psychotropic drugs. Materials and Methods: The standardized method was followed in all cases, by recording the reaction time (RT) in msec in 24 healthy participants using computerized version of Stroop color-word test. Reproducibility of the test procedure was evaluated by recording the RTs by a single experimenter on two sessions (interday reproducibility). Validity of the model was further tested by evaluating the psychotropic effect of Zolpidem 5 mg, Caffeine 500 mg, or Placebo on 24 healthy subjects in a randomized, double blind three-way crossover design. Results: The method was found to produce low variability with coefficient of variation less than 10%. Interday reproducibility was very good as shown by Bland-Altman plot with most of the values within [+ or -]2SD. There was a significant increase in RTs in Stroop performance with Zolpidem at 1 hr and 2 hrs; in contrast, caffeine significantly decreased RTs in Stroop performance at 1 hr only compared to placebo. Conclusion: The Stroop color-word recording and analysis system is simple, sensitive to centrally acting drug effects, and has potential for future experimental psychomotor assessment studies.

Introduction

"Everyone knows what attention is." wrote William James in 1890. "It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. It implies withdrawal from some things in order to deal effectively with others". [sup][1]Attention is of great importance in human performance, as the ability to select information from the environment and to sustain efficient input is often a major constraint. It refers to a variety of components: (a) initiation or focusing; (b) sustaining attention or vigilance; (c) inhibiting responses to irrelevant stimuli or selective attention; and (d) shifting attention. Psychotropic drugs, especially antidepressants and antipsychotics, may give rise to some concern in clinical practice because of their known ability to induce changes in attention and documentation of such changes is an important part of assessing the deleterious effects of such drugs. The optimum profile of a psychotropic drug should include no detrimental effect on cognitive and psychomotor functions.

A range of tests are used to measure attention. For example, some tests use faint stimuli close to the threshold of perception, while others use briefly presented stimuli that are easily detected by the alert subject; some use auditory stimuli while others are visual; and some use concentrated attention while others use divided attention or introduce distracters. Although these various measures have been used in many psychological investigations, they have seldom been directly compared and so it is difficult to assess the relative sensitivities of the different types of measure. Tests to analyze attention processes, such as the Gottschaldt Shuffled Figures Test, the Odd Man Out Test, and Stroops color-word procedure, have been related more specifically to selective attention.

The Stroop color-word interference task is one of the most widely used experimental tasks in all of cognitive psychology and is used as a measure of selective attention and inhibitory control. [sup][2] It is a quick and easy test to administer and may be regarded as reflecting different levels of central processing. The Stroop interference effect refers to the increase in response latency observed when an individual is required to identify the color of a color-word when these aspects of the stimulus are incongruent (e. …