Handan UZUNÇAKMAK-UYANIK, Fatma Gökçem YILDIZ, Çağrı Mesut TEMUÇİN
Neurological Sciences and Neurophysiology - 2026;43(3):129-133
Background: Entrainment is a key feature in distinguishing between different tremor types but may be difficult to detect clinically. Electrophysiologic approaches, particularly electromyography (EMG)-based analyses, may provide objective insights. This study aimed to investigate whether burst duration of simulated tremors evolves over time under combined auditory-visual metronome guidance and to interpret this in the context of entrainment. Materials and Methods: Nineteen healthy right-handed volunteers performed 30-s tremor simulation tasks guided by a combined auditory-visual metronome (2 Hz). Surface EMG recordings were obtained, and burst durations were analyzed across early, middle, and late phases. Phase-dependent changes were assessed using the Friedman test. The linear mixed model (LMM) was used to evaluate time-dependent changes, and individual slope analyzes were performed to assess inter-individual variability (P < 0.05). Results: A significant phase-dependent modulation of burst duration was observed (P = 0.026), with gradual increases from early to late phases. However, no significant linear change over time was detected at the group level (P = 0.074). The LMM revealed significant inter-individual variability in temporal dynamics (P = 0.022). Individual analyses showed that all participants exhibited some degree of temporal evolution with heterogeneous patterns (increasing, decreasing, or near stable trends). Conclusion: Simulated tremor burst duration does not evolve uniformly at the group level but reflects heterogeneous, individual-specific temporal dynamics. These findings suggest that entrainment may present as individualized sensorimotor adaptation rather than a group-level phenomenon. Burst duration evolution analysis may serve as a complementary electrophysiologic approach for assessing entrainment in addition to conventional coherence methods.
