Approximate entropy detects the effect of a secondary cognitive task on postural control in healthy young adults: a methodological report.

James T Cavanaugh,Nicholas Stergiou,Vicki S Mercer

doi:10.1186/1743-0003-4-42

Abstract

BackgroundBiomechanical measures of postural stability, while generally useful in neuroscience and physical rehabilitation research, may be limited in their ability to detect more subtle influences of attention on postural control. Approximate entropy (ApEn), a regularity statistic from nonlinear dynamics, recently has demonstrated relatively good measurement precision and shown promise for detecting subtle change in postural control after cerebral concussion. Our purpose was to further explore the responsiveness of ApEn by using it to evaluate the immediate, short-term effect of secondary cognitive task performance on postural control in healthy, young adults.MethodsThirty healthy, young adults performed a modified version of the Sensory Organization Test featuring single (posture only) and dual (posture plus cognitive) task trials. ApEn values, root mean square (RMS) displacement, and equilibrium scores (ES) were calculated from anterior-posterior (AP) and medial-lateral (ML) center of pressure (COP) component time series. For each sensory condition, we compared the ability of the postural control parameters to detect an effect of cognitive task performance.ResultsCOP AP time series generally became more random (higher ApEn value) during dual task performance, resulting in a main effect of cognitive task (p = 0.004). In contrast, there was no significant effect of cognitive task for ApEn values of COP ML time series, RMS displacement (AP or ML) or ES.ConclusionDuring dual task performance, ApEn revealed a change in the randomness of COP oscillations that occurred in a variety of sensory conditions, independent of changes in the amplitude of COP oscillations. The finding expands current support for the potential of ApEn to detect subtle changes in postural control. Implications for future studies of attention in neuroscience and physical rehabilitation are discussed.

Highlights

Over the last two decades, dual task studies examining the role of attention in postural control have become increasingly important in clinical neuroscience [1,2], engineering [3], and physical rehabilitation [4,5]
No significant interaction was found between cognitive task and sensory condition for Approximate entropy (ApEn)-AP and ApEn-ML values (Table 1)
Neither root mean square (RMS) displacement nor equilibrium scores (ES) revealed a significant interaction between cognitive task and sensory condition or a main effect of cognitive task

Summary

Introduction

Over the last two decades, dual task studies examining the role of attention in postural control have become increasingly important in clinical neuroscience [1,2], engineering [3], and physical rehabilitation [4,5]. Perhaps because of their relatively limited precision [16], have not consistently revealed changes in postural control during cognitive perturbations [7,10,12,15,17]. Biomechanical measures of postural stability, while generally useful in neuroscience and physical rehabilitation research, may be limited in their ability to detect more subtle influences of attention on postural control. Our purpose was to further explore the responsiveness of ApEn by using it to evaluate the immediate, short-term effect of secondary cognitive task performance on postural control in healthy, young adults

Methods

Results

Discussion

Conclusion