The present study was done on 50 healthy subjects
(32 males and 18 females, Mean age = 22.78±3.90
years and BMI 24.82±3.59 kg/m2). Institutional ethics
committee approval was obtained and written informed
consent was obtained from all participants after
explaining the study protocol. Subjects with known
acute or chronic medical illness, chronic smokers,
and alcoholics were excluded from the study. All the
recordings were done in between 9 AM-11 AM after
2-3 hrs of light breakfast. Subjects were not allowed
to have caffeinated foods and drinks on the day of
recording since that may have influenced the
parameters under observation. Estimation of VRT and
ART were done in PC 1000 Hz and Biopac® MP 36
separately for minimum of 3 trials each. Of these
three readings, best one was chosen as an estimate
of reaction time.
Audacity
Audacity®, open source software, was used in
the study for recording and displaying the RT
estimates in real time (14). Using the software
installed on a computer obviates the need of
a separate external analog to digital converter
and microprocessor. Also, the software can display
real time signals with parameters of time and
amplitude.
PC 1000 Hertz Reaction Timer:
The device was built in-house by the investigators
for determination of auditory and visual reaction time.
It had a soft key for start and stop function with
1000 Hz square wave oscillator. It consisted of two
components - E&S - connected to each other. The
start button in the first component (E) was controlled
by the examiners and was out of the view of the
subjects.
The subjects operated the second component (S)
which had a stop button. Red LED light was used
for visual stimulus as it persists for a long time in
retina. 1000 hertz tone delivered through head phone
was used for the auditory stimulus. Both component
E & S were connected to a personal computer running
Audacity® software. Audacity® software recorded the
reaction time in wave format (accuracy in the range
of 0.001 sec).
Visual Reaction Time (VRT) Recording:
Examiner provided the visual stimulus by pressing
the START button in first component (E) which was
out of the view of the subject. As soon as subject
saw red light in the instrument, he/she had to press the STOP button in second component (S). VRT was
thus recorded in Audacity® software in wave format.
Auditory Reaction Time (ART) Recording:
Examiner provided the auditory stimulus by pressing
the START button in first component (E) which was
out of the view of the subject. The subject was
instructed to press the stop button (S) as soon as
he/she heard the sound (1000 Hertz tone) through
the headphone connected to it. ART time was
estimated in Audacity® software.
A minimum of three trials were given for both VRT
and ART measurement. The graphical representation
for VRT and ART is shown in Figure 3.
Statistical analysis
Normality of data was tested using Kolmogrov-F Smirnov test. A p value of > 0.05 indicated normal
Gaussian distribution. The data presented with mean
and standard deviations. Independent t test was used
to compare the reaction time values obtained by the
both devices. Association between values of the two
devices was made using Pearson correlation (r) test
for parametric distribution. r > 0.75 was considered
as strong correlation, r value between 0.5 to 0.75
was considered as moderate correlation and r < 0.5
was a weak correlation. P<0.05 was the significance
level for all tests. R statistical software version 3.1.2
was used for the statistical analysis.
