بهبود زمان واکنش ساده در سالمندان با تحریک شنیداری و ترکیبی گاما: شواهدی از عدم تأثیر بر زمان واکنش افتراقی و انتخابی

Introduction

The aging population is rapidly increasing worldwide, and this demographic shift has highlighted many health and social challenges related to older people, especially in countries like Iran. One of the significant issues in this age group is the decline in cognitive and motor functions, which significantly affects their quality of life. Among these functions, reaction time is a key indicator of the speed of information processing and decision-making in the nervous system. A decline in reaction time in the elderly can increase the risk of falls, mobility disorders, and reduced independence.

Recent studies have shown that non-invasive sensory stimulation techniques, such as binaural beats for auditory stimulation and rhythmic visual stimulation in the gamma band (40 Hz), can be novel approaches to enhance cognitive and motor functions in older adults. Although existing evidence supports the positive effects of these techniques on simple reaction time in elderly populations, there has been limited research on the combined effect of these two stimuli (auditory and visual) on reaction time.

Seeking to broaden the knowledge base regarding sensory stimulation’s influence on cognitive performance, specifically reaction time in aging populations, this research addresses a critical gap. Although prior work has confirmed the benefits of distinct auditory and visual stimuli on simple reaction time, this study offers the first comprehensive, simultaneous evaluation of combined auditory and visual stimulation at 40 Hz gamma frequency on simple, differential, and selective reaction times among older adults, generating novel evidence to fill this void

Methods

This quasi-experimental study used a pretest-posttest design with a control group. The study involved 40 elderly participants aged 60 and above, who were randomly assigned to one of four groups: auditory stimulation, visual stimulation, combined auditory and visual stimulation, and a control group. The intervention consisted of 40 Hz gamma stimulation for 20 minutes daily over two consecutive weeks.

In the auditory stimulation group, binaural beats at 400 Hz and 440 Hz were delivered to each ear, creating a 40 Hz frequency difference in the brain. In the visual stimulation group, 40 Hz rhythmic light stimuli were used. The combined group received both auditory and visual stimuli simultaneously.

Before the intervention, participants' reaction times—simple, differential, and selective—were measured using advanced reaction time software. These measurements were taken at both pre-test and post-test stages to evaluate any changes in reaction time after the intervention.

Results

The results showed that both auditory and combined (auditory + visual) stimulation significantly reduced simple reaction time compared to the control group (P ≤ 0.05). However, there was no significant difference in differential and selective reaction times between the groups (Table1). These findings suggest that 40 Hz gamma stimulation positively influences simple reaction time in elderly individuals, but for more complex reaction tasks, longer interventions or changes in training conditions may be necessary.

The intervention, comprising daily 20-minute sessions of 40 Hz gamma stimulation over two weeks, demonstrated varied outcomes among the study groups. Key findings from Tukey’s pairwise post-hoc comparisons (detailed in the table below) indicated a significant reduction in reaction times for both the auditory stimulation group and the combined auditory-visual stimulation group. Conversely, within-group analyses for the control group revealed no significant changes in reaction time during these two weeks, a finding possibly attributable to the ineffectiveness of the placebo condition or the lack of active intervention. Furthermore, visual stimulation administered alone did not significantly impact reaction time. This latter outcome might be attributed to the more complex nature of differential and selective reaction tasks, which necessitate higher cognitive processing.

Table 1: Mean Reaction Times (ms) ± Standard Deviation

Conclusion

The findings of this study indicate that 40 Hz gamma stimulation, particularly through auditory and combined auditory-visual stimulation, can improve simple reaction time in elderly individuals. This non-invasive, low-cost intervention can be an effective way to maintain motor function and reduce the risk of falls in elderly populations. However, its impact on more complex reaction tasks, such as differential and selective reaction time, was limited, highlighting the need for longer or more complex interventions to address these processes.

These findings pave the way for further research on the use of multisensory gamma stimulation to enhance cognitive and motor performance in older adults. Additionally, combining different stimulation techniques could offer a new strategy to improve the quality of life, particularly in the mental and physical aspects of elderly individuals.

Footnotes

Ethical approval

The code of ethics was received from the Research Ethics Committees at Faculty of Sport Sciences and Health University of Tehran, ID IR.UT.SPORT.REC.1404.003.

Funding

No funding has been provided for this  research

Authors’ contribution

1. Z. Sh: Initial drafting, data collection, methodology review, and editing. Sh. T.B (corresponding author): Methodology review and editing, research supervision, and project management. A: Editing, methodology review, and data analysis F.J: Editing, methodology review, platform management, and initial screening.

Acknowledgments

We are sincerely grateful to all esteemed clients whose active participation in implementing the intervention protocols and tests provided the foundation for the findings of this research. Special thanks and appreciation are extended to the respected personnel of Gohar Salamat Center who facilitated the necessary provisions for the successful execution of the field stages of this research through their administrative cooperation and support.