Mirror movements - A simple algorithm for mirror activity signal processing and normative values
José Castro1, Tomás Pedrosa2, Isabel de Castro1
1Instituto de Fisiologia, Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Department of Neurosciences and Mental Health, Centro Hospitalar Universitário de Lisboa Norte, Lisbon, Portugal.
Neuroscience Letters
|March 15, 2023
Summary
This study introduces a new, objective method to measure involuntary muscle activation, known as mirror activity, in healthy adults. The findings reveal correlations with age and limb dominance, establishing new normality limits for clinical use.
Area of Science:
- Neuroscience
- Human Physiology
- Biomedical Engineering
Background:
- Mirror activity is involuntary muscle activation observed during contralateral muscle contraction.
- Previously documented mainly in children and disease states, it's now recognized in healthy adults.
- Existing assessment methods lack standardization and objectivity.
Purpose of the Study:
- To develop and validate a simple, objective protocol for quantifying mirror activity.
- To establish normative values for mirror activity in healthy adults.
- To explore correlations between mirror activity and factors like age and limb dominance.
Main Methods:
- A custom algorithm was developed to analyze electromyography (EMG) signals during brief, maximal isometric contractions.
- Mirror activity was quantified in the Abductor digiti minimi (ADM) and Tibialis anterior (TA) muscles.
- Algorithm performance was validated against human operators using intraclass correlation and Bland-Altman analysis.
Main Results:
- The algorithm demonstrated excellent performance, comparable to human operators (ICC=0.998).
- Mirror activity showed significant positive correlations with contraction intensity and participant age.
- Left (non-dominant) limbs exhibited significantly higher mirror activity than right (dominant) limbs.
- Normative upper limits were established: 27.4% (right ADM), 15.4% (left ADM), 10.4% (right TA), 2.1% (left TA).
Conclusions:
- The proposed protocol provides a reliable and objective method for measuring mirror activity.
- Established normative values can aid in identifying potential neurological abnormalities.
- This technique holds promise for the investigation of various neurological disorders.
