Evaluation of EEG Oscillatory Patterns and Cognitive Process during Simple and Compound Limb Motor Imagery

PLOS ONE, Dec 2019

Motor imagery (MI), sharing similar neural representations to motor execution, is regarded as a window to investigate the cognitive motor processes. However, in comparison to simple limb motor imagery, significantly less work has been reported on brain oscillatory patterns induced by compound limb motor imagery which involves several parts of limbs. This study aims to investigate differences of the electroencephalogram (EEG) patterns as well as cognitive process between simple limb motor imagery and compound limb motor imagery. Ten subjects participated in the experiment involving three tasks of simple limb motor imagery (left hand, right hand, feet) and three tasks of compound limb motor imagery (both hands, left hand combined with right foot, right hand combined with left foot). Simultaneous imagination of different limbs contributes to the activation of larger cortical areas as well as two estimated sources located at corresponding motor areas within beta rhythm. Compared with simple limb motor imagery, compound limb motor imagery presents a network with more effective interactions overlying larger brain regions, additionally shows significantly larger causal flow over sensorimotor areas and larger causal density over both sensorimotor areas and neighboring regions. On the other hand, compound limb motor imagery also shows significantly larger 10–11 Hz alpha desynchronization at occipital areas and central theta synchronization. Furthermore, the phase-locking value (PLV) between central and occipital areas of left/right hand combined with contralateral foot imagery is significantly larger than that of simple limb motor imagery. All these findings imply that there exist apparent intrinsic distinctions of neural mechanism between simple and compound limb motor imagery, which presents a more complex effective connectivity network and may involve a more complex cognitive process during information processing.

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Evaluation of EEG Oscillatory Patterns and Cognitive Process during Simple and Compound Limb Motor Imagery

December Evaluation of EEG Oscillatory Patterns and Cognitive Process during Simple and Compound Limb Motor Imagery Weibo Yi 0 1 2 Shuang Qiu 0 1 2 Kun Wang 0 1 2 Hongzhi Qi 0 1 2 Lixin Zhang 0 1 2 Peng 2 Zhou 0 1 2 Feng He 0 1 2 Dong Ming 0 1 2 0 Department of Biomedical Engineering, Tianjin University , Tianjin , China, 1 Tianjin Key Laboratory of Biomedical Detecting Techniques and Instruments , Tianjin , China 2 Editor: Natasha M. Maurits, University Medical Center Groningen UMCG , Netherlands Motor imagery (MI), sharing similar neural representations to motor execution, is regarded as a window to investigate the cognitive motor processes. However, in comparison to simple limb motor imagery, significantly less work has been reported on brain oscillatory patterns induced by compound limb motor imagery which involves several parts of limbs. This study aims to investigate differences of the electroencephalogram (EEG) patterns as well as cognitive process between simple limb motor imagery and compound limb motor imagery. Ten subjects participated in the experiment involving three tasks of simple limb motor imagery (left hand, right hand, feet) and three tasks of compound limb motor imagery (both hands, left hand combined with right foot, right hand combined with left foot). Simultaneous imagination of different limbs contributes to the activation of larger cortical areas as well as two estimated sources located at corresponding motor areas within beta rhythm. Compared with simple limb motor imagery, compound limb motor imagery presents a network with more effective interactions overlying larger brain regions, additionally shows significantly larger causal flow over sensorimotor areas and larger causal density over both sensorimotor areas and neighboring regions. On the other hand, compound limb motor imagery also shows significantly larger 10-11 Hz alpha desynchronization at occipital areas and central theta synchronization. Furthermore, the phase-locking value (PLV) between central and occipital areas of left/right hand combined with contralateral foot imagery is significantly larger than that of simple limb motor imagery. All these findings imply that there exist apparent intrinsic distinctions of neural mechanism between simple and compound limb motor imagery, which presents a more complex effective connectivity network and may involve a more complex cognitive process during information processing. - Motor imagery (MI), defined as mental rehearsal of a motor act without any overt motor output, can modify the neuronal activity in the primary sensorimotor areas in a very similar way as motor execution [13]. In addition, motor imagery has also been demonstrated beneficial in motor rehabilitation in patients with movement disorders, and it plays a significantly important role in clinical and neuroscience studies [3]. Motor imagery can result in frequency specific changes of the ongoing EEG in forms of event-related desynchronization (ERD) or eventrelated synchronization (ERS), and the neural representations during mental tasks could be detected using spatial mapping of ERD/ERS. However, spatial mapping can not reveal the dynamic information flow between differently organized and specialized cortical regions [4]. Recently, there is a growing concern for interactions of the activated brain regions, typically in terms of effective connectivity [5]. Effective connectivity is a powerful method to analyze causal interaction among multiple neural regions in brain studies based on brain imaging techniques such as electroencephalogram (EEG). As a result, the mutual interactions between different channels overlying core regions recruited by motor imagery could be revealed through effective connectivity network. However, most research has been concentrated to investigate the effective connectivity network induced by simple limb motor imagery involving a single limb. The effective connectivity networks over sensorimotor areas during hand or foot movement execution and imagination have been estimated by different methods such as Directed Transfer Function (DTF) and phase-locking value (PLV) [4, 68]. In contrast, significantly less work has been reported about brain oscillatory patterns induced by compound limb movement imagination [9, 10]. In addition, the effective connectivity network induced by compound limb motor imagery is still not clear. With respect to simple limb motor imagery, several parts of limbs like hand (forearm, postbrachium) and foot (shank, thigh) are involved in compound limb movement imagination, which may activate the neurons oscillation in multiple functional areas of cerebral cortex, and involve a different cognitive motor process. The question is that whether the effective connectivity network of compound limb motor imagery is more complex than that of simple limb motor imagery, at the same time, what are the differences of EEG oscillatory patterns and cognitive process between simple limb (...truncated)


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Weibo Yi, Shuang Qiu, Kun Wang, Hongzhi Qi, Lixin Zhang, Peng Zhou, Feng He, Dong Ming. Evaluation of EEG Oscillatory Patterns and Cognitive Process during Simple and Compound Limb Motor Imagery, PLOS ONE, 2014, 12, DOI: 10.1371/journal.pone.0114853