Figure 1.
The Visual and Auditory Stroop Paradigms.
For the visual paradigm, the subjects were asked to name the color of the word in the color naming task and to read the name of the word in word reading task. Following the subject’s response and prior to the presentation of the next stimulus, a white fixation cross-hair was presented for 1000 msec. (A) Visual Stroop task. In the visual Stroop task, the subjects received a word that was either congruent, conflicting or neutral, and these types were presented in a constant ratio. The congruent stimulus is presented in the same color name of its own color, and the conflict stimulus is presented in a different color name of its own color. The neutral stimulus consists of four different words that are not related to the meaning of the color in which it is written. (B) Auditory Stroop task. The structure of the auditory Stroop task was similar to the visual Stroop task except for the stimulus condition. The word ‘left’ emanating from the left side speaker consisted of a congruent stimulus, while the word ‘left’ emanating from the right side speaker consisted of a conflict stimulus. Unlike the visual Stroop task, the fixation point was presented during both the stimulus and resting conditions to induce the subject’s eye fixation. (C) The structure of one set in the visual Stroop task. Each stimulus was presented until the subject’s response. The reaction time of all subjects was ranged from about 500 msec to 1,500 msec.
Figure 2.
Eyeblink rates (EBR) during the task.
The EBR had increased significantly during the task condition. The histogram shows the mean EBR in the resting state and Stroop task condition. In the resting condition, the subjects were required to fixate their eye on to the fixation point for 2 minutes, and the EBR was 20.7 ± 11.2 blinks/min. The EBR in the task condition was measured during the Stroop task and was 30.7 ± 13.0 blinks/min. (error bars denote standard error).
Figure 3.
A representative example of a subject from each subgroup.
We classified 28 subjects into 3 subgroups based on the position of the eyeblink peak location. The histogram (having 30 msec intervals) was drawn based on the time difference between the eyeblink and visual response for 240 trials per subject. (A) Subgroup I. The subjects who blinked mostly before the vocal response were classified as belonging to subgroup I. Of the 28 subjects, 17 belonged to this group. The mean number of eyeblinks was 1.1 ± 0.3 blinks/trial and the eyeblinks demonstrated a distribution of 210 ± 85 msec. (B) Subgroup II. The subjects who had a peak location after the vocal response were classified as belonging to subgroup II. Of the 28 subjects, 7 belonged to this group. The mean number of eyeblinks per a trial was 0.9 ± 0.4 blinks/trial and the peak location was 380 msec with standard deviation of 116 msec. (C) Subgroup III. The subjects who blinked both before and after the vocal response were classified as belonging to subgroup III. Of the 28 subjects, 4 belonged to this group. This bimodal distribution was drawn because the subject blinked before the response in one set, but blinked after the response in another set. Relative to subgroups I and II, subgroup III had a lower peak value due to its two different peak locations.
Figure 4.
Average peak location and standard deviation distribution for all subjects.
No significant differences were found between the stimulus type and condition. (A) For the 28 subjects, their peak locations were measured in each set, and the mean and standard deviation value across all of the subjects are presented. The total average peak location is the mean value of the subject’s entire set of peak values and is measured from the 30 msec interval histogram, which consists of 120 trials. The conflict and congruent average peak location is the subset of the total average peak location that is derived from each stimuli, which consists of 60 trials. The minus sign means that the peak was located before the response. As seen in the histogram, most subjects demonstrate a peak value near 250 msec before the response in subgroup I and 300 msec after the response in subgroup II. (B) The standard deviation distribution is the mean value of the standard deviation from the peak value in each subject with error bars showing the standard errors across all of the subjects.
Figure 5.
Eyeblink rates (EBR) during the task.
The histogram shows the mean EBR in the resting state and Stroop task condition (with error bars showing the standard errors). In addition, the EBR had increased significantly during the Stroop task condition. In the resting condition, the subjects were required to fixate their eye on to a fixation point for 2 minutes, and the EBR was 20.7 ± 11.2 blinks/min. The EBR in the task condition was measured during the Stroop task and was 35.0 ± 14.2 blinks/min. This EBR increase in the task condition relative to the resting state is consistent with the result of visual Stroop tasks. (Error bars denote standard errors).
Figure 6.
A representative example of a subject from each subgroup.
We classified the 28 subjects into 3 subgroups based on the position of eyeblink peak location. The histogram (having 30 msec intervals) was drawn based on the time difference between the eyeblink and visual response for 240 trials per subject. (A) Subgroup I. The subjects who blinked mostly before the vocal response were classified as belonging to subgroup I, and 20 of 28 subjects belonged to this subgroup. The mean number of eyeblinks was 1.2 ± 0.6 blinks/trial and had a distribution of 240 ± 95 msec. (B) Subgroup II. The subjects who had a peak location after the vocal response were classified as belonging to subgroup II, and 2 of 28 subjects belonged to this group. The mean number of eyeblinks per trial was 0.9 ± 0.5 blinks/trial and the peak location was 340 msec with a standard deviation of 98 msec. (C) Subgroup III. The subjects who blinked before and after the vocal response were classified as belonging to subgroup III, and 6 of 28 subjects belonged to this group. This bimodal distribution was drawn because the subject blinked before the response in one set but blinked after the response in another set. Relative to subgroup I and II, this subgroup had a lower peak value due to its two different peak locations.
Figure 7.
Average peak location and standard deviation distribution for all subjects.
No significant differences were found between the stimulus type and condition as in the visual Stroop task. (A) For the 28 subjects, peak locations were measured in each set, and the mean and standard deviation value across all of the subjects are presented. The total average peak location is the mean value of the subject’s entire set of peak values and is measured from the 30 msec interval histogram, which consists of 120 trials. The conflict and congruent average peak location is a subset of the total average peak location that is derived from each stimuli, which consists of 60 trials. (B) The standard deviation distribution is the mean value of the standard deviation from the peak value in each subject with error bars showing standard errors across all of the subjects.