تأثیر دست‌کاری بینایی بر نوسان امواج مغزی سالمندان در شرایط کنترل قامت ایستا

Extended Abstract
Background and Purpose
Maintaining posture is a complex motor task that becomes increasingly challenging for elderly individuals due to the integration demands of various sensory inputs. The ability to sustain equilibrium in static postures relies on the central nervous system’s capability to regulate movements and postural adjustments, ensuring that the body's center of mass (COM) remains within the base of support as represented by the center of pressure (COP). The inverted pendulum model, described by Choi and Kim (2008), serves as a fundamental framework for conceptualizing human postural control. Within this paradigm, the COM oscillates forward while the COP generates a compensatory inward force that re-centers the COM over the support base. This study aimed to explore how vision manipulation influences posture control and cerebral cortical activity in older adults.
 
Methods
Sixty healthy elderly volunteers aged 65 to 74 years—equally divided between men and women to enhance external validity—participated in this study. During static postural control tasks, participants stood on a stationary Biodex Balance System platform, instructed to maintain posture without using hand or upper body muscle contractions. The protocol comprised two trials: eyes open and eyes closed, each lasting 60 seconds.
Electroencephalogram (EEG) data were collected using a portable, wireless system (mBrainTrain®, Belgrade, Serbia). Following the international 10-20 system, Ag/AgCl electrodes were placed on the scalp at positions including Fp1, Fp2, AFz, F3, Fz, F4, T7, C3, Cz, C4, T8, CPz, P7, P3, Pz, P4, P8, POz, O1, O2, M1, and M2, with FPz as the ground and FCz as the reference.
Preprocessing used the EEGLab toolbox and included visual artifact detection, bandpass filtering (0.1–50 Hz), and independent component analysis (ICA) implemented via MATLAB R2022b scripts. ICA facilitated removal of artifacts such as eye blinks and muscle activity. EEG signals were filtered into five frequency bands: delta (1–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta
(13–30 Hz), and gamma (30–50 Hz).
Statistical analysis employed custom MATLAB scripts enabling spectral power density computation and inferential testing.
 Results
A mixed ANOVA assessed absolute power spectral density across conditions, channels (24), and frequency bands, revealing significant effects (F (2.66,276) = 3.71, p = 0.0001, η² = 0.26). Dependent t-tests comparing brain regions identified distinct topographical variations.




 



 
Note: EO= eye open, EC=eye closed
 
There are no differences in the Delta band between the control condition and static postural control with eyes open or closed.
 Conclusion
The sensorimotor cortex, parietal cortex, left occipital, temporal, central-parietal, and parietal-occipital regions collectively contribute to static postural regulation. During static balance control, the parietal cortex exhibited oscillations across theta, alpha, beta, and gamma bands regardless of visual manipulation context.
A particularly notable finding was the significant increase of gamma band activity in the parietal lobe (P3) and frontal lobe (F7) when contrasting eyes-open and eyes-closed conditions. This supports the hypothesis that gamma oscillations in these cortical areas facilitate preparatory motor responses necessary for balance maintenance.
Consistent with these results, Slobounov et al. (2005) documented heightened gamma activity at 40 Hz in frontal and central regions preceding compensatory postural adjustments during impaired balance conditions.
Keywords: Somatosensory, Parietal Cortex, Frontal Lobe, Aging
 Article Message
This study highlights the critical role of cortical oscillations in sustaining static posture in older adults, especially under visual input manipulation. Parietal, sensorimotor, frontal, and occipital cortices prominently contribute, reflecting a shift toward cortical conscious control mechanisms rather than automatic subcortical processes. This adaptive neurophysiological strategy likely compensates for age-related sensory and neuromuscular declines. Understanding these mechanisms underscores the necessity for brain-centered rehabilitation and balance training designs aimed at fall risk reduction and functional independence enhancement in the elderly.
 
Ethical Considerations
This investigation was approved by the Shahid Beheshti University Ethics Committee (Code: IR.SBU.REC.1400.103).
Authors’ Contributions
Conceptualization: Saeed Alboghebeish, Mahin Aghdaei, Reza Khosrowabadi, Alireza Farsi
Data Collection: Saeed Alboghebeish, Alireza Farsi
Data Analysis: Saeed Alboghebeish, Reza Khosrowabadi, Alireza Farsi
Manuscript Writing: Saeed Alboghebeish, Mahin Aghdaei, Reza Khosrowabadi, Alireza Farsi
Review and Editing: Saeed Alboghebeish, Mahin Aghdaei, Reza Khosrowabadi, Alireza Farsi
Funding Responsibility: Saeed Alboghebeish, Alireza Farsi
Literature Review: Saeed Alboghebeish, Mahin Aghdaei, Reza Khosrowabadi, Alireza Farsi
Project Management: Saeed Alboghebeish, Alireza Farsi
Conflict of Interest
The authors declare no conflicts of interest.
 
Acknowledgments
The authors gratefully acknowledge all participants who contributed to this research.