Lempel-Ziv complexity changes and physiological mental fatigue level during different mental fatigue state with spontaneous EEG

Lian-Yi Zhang,Chong-Xun Zheng

doi:10.4236/health.2009.11007

Abstract

The objective was to study changes in EEG time-domain Kolmogorov complexity under different mental fatigue state and to evaluate mental fatigue using Lempel-Ziv complexity analysis of spontaneous EEG in healthy human subjects. EEG data for healthy subjects were acquired using a net of 2 electrodes (Fp1 and Fp2) at PM 4:00, AM 12:00 and AM 3:00 in the 24 hours sleep-deprived mental fatigue experiments. It was presented that initial results for eight subjects examined in three different mental fa-tigue state with 2-channel EEG time-domain Lempel-Ziv complexity computations. It was found that the value of mean Lempel-Ziv com-plexity corresponding to a special mental state fluctuates within the special range and the value of C(n) increases with mental fatigue increasing for the total frequency spectrum. The result in-dicates that the value of C(n) is strongly cor-relative with the mental fatigue state. These re-sults suggest that it may be possible to nonin-vasively differentiate different mental fatigue level according to the value of C(n) for particular mental state from scalp spontaneous EEG data. This method may be useful in further research and efforts to evaluate mental fatigue level ob-jectively. It may also provide a basis for the study of effects of mental fatigue on central neural system.

Highlights

Mental fatigue has been a recurrent topic in medicine and psychology and has recently been attracting much attention
Working on cognitively demanding tasks for a considerable time often leads to mental fatigue, which can impact task performance [2]
It was found that the value of mean Lempel-Ziv complexity corresponding to a special mental state fluctuates within the special range and the value of C(n) increases with mental fatigue increasing for the total frequency spectrum

Summary

Introduction

Working on cognitively demanding tasks for a considerable time often leads to mental fatigue, which can impact task performance [2]. D. van der Linden et al [2] defined mental fatigue as a change in psychophysiological state due to sustained performance This change in psychophysiological state has subjective and objective manifestation, which include an increased resistance against further effort, an increased propensity towards less analytic information processing, and changes in mood. Sustained performance, in this definition, does not necessarily involve the same task but can extend over different tasks that require mental effort, such as fatigue because of a day in the office. The study was conducted to provide some additional insights into mental fatigue and its underlying processes

Objectives

Methods

Results