Starodubtseva, N. M. | Search bioRxiv

bioRxiv2025

Modulatory Effects of the Motor Imagery and Jendrassik Maneuver upon the Forearm H-Reflex and Electroencephalographic Activity

While the Jendrassik maneuver (JM) is commonly used in neurology to enhance monosynaptic reflexes such as the knee-jerk reflex, its interaction with cognitive processes like motor imagery (MI) remains unclear. In this study, we examined the effects of JM, MI, and their combination on the left flexor carpi radialis (FCR) H-reflex and cortical electroencephalographic (EEG) activity. Twenty healthy participants completed four tasks: resting, MI (imagining squeezing a tennis ball with the left hand), JM (squeezing a tennis ball with the right hand), and JM combined with MI (JM&MI). The FCR H-reflex was elicited with median nerve stimulation, and EEG changes were analyzed through event-related potentials and modulations of the mu rhythm. Surprisingly, JM performed with the right hand did not affect the contralateral H-reflex. MI of the left hand decreased the H-reflex in the right FCR. JM and MI significantly modulated cortical activity. Event-related desynchronization (ERD) of the mu-rhythm occurred during both JM and MI, and it was contralateral to the physical contraction or imagery. Bilateral ERD was observed during JM&MI. Cortical responses to nerve stimulation (P100, N100 and P300 components) varied by task, and during JM the P100 and P300 components correlated with strength of mu-rhythm ERD.

neuroscience↗

bioRxiv2025

Beyond Traditional Poincare Analysis: Second-Order Plots Reveal Respiratory Effects in Heart Rate Variability

Heart rate variability (HRV) is a non-invasive biomarker of autonomic nervous system activity, commonly analyzed using a Poincare plot. This plot visualizes correlations between successive heartbeats (RRi vs. RRi+1) and quantifies autonomic regulation through SD1 and SD2 parameters. We introduce a second-order Poincare plot, a natural extension that clarifies serial dependencies by plotting successive differences in RR intervals ({Delta}RRi vs. {Delta}RRi+1). Applied to a PhysioNet dataset of 20 healthy individuals, this technique filtered out the slow HRV baseline of traditional elliptical plots to reveal distinct higher-order dynamics. These included ring-shaped structures indicating cardiorespiratory synchronization. A coupled-oscillator model, developed to simulate respiratory modulation, confirmed that these patterns are dictated by the respiratory frequency to heart rate ratio: slower breathing produces positive serial correlations in {Delta}RR, while faster breathing induces negative ones. By visualizing serial dependencies that conventional HRV metrics miss, the second-order Poincare plot extends the classical analysis framework. This tool provides a refined method for uncovering subtle dynamical features in HRV across diverse physiological and clinical states. HighlightsO_LISecond-order Poincare plots, plotting successive differences of RR intervals ({Delta}RRi vs. {Delta}RRi+1), extend traditional Poincare analysis to reveal rapid HRV dynamics. C_LIO_LIIn a dataset of 20 healthy individuals, second-order plots filtered out slow HRV components, highlighting respiratory modulation. C_LIO_LIRing-shaped patterns in some participants indicated strong cardiorespiratory coupling, while others showed positive or negative serial correlations linked to breathing rate. C_LIO_LIA coupled-oscillator model confirmed that the ratio of respiratory to heart rate frequency determines serial correlation patterns. C_LIO_LIThis method offers a novel tool for analyzing HRV dynamics, with potential applications in physiological and clinical research. C_LI

physiology↗