Cognitive, Behavioral, and Systems NeuroscienceResearch PaperPerturbation-evoked cortical activity reflects both the context and consequence of postural instability
Section snippets
Subjects
Twelve subjects (six male, 29.3±6.4 years, 172.1±9.9 cm, 71.6±15.9 kg) agreed to participate in the study. All subjects were free of neuromuscular disorders and each provided written, informed consent prior to the onset of the study. The study was conducted with approval from the Research Ethics Board at the Toronto Rehabilitation Institute.
Electroencephalography
Electroencephalographic (EEG) signals were obtained using a 32 channel electrode cap (Quik-Cap, Neuroscan, El Paso, TX, USA) based on the International
Results
Following data analysis and subsequent removal of individual trials due to ocular artifact or anticipatory postural responses, a similar number of trials [F(3,11)=1.437, P>0.05] per subject for each of the task conditions was included in the statistical analysis (20±4, 20±4, 18±1 and 20±3 Block Unconstrained and Constrained, Random Unconstrained and Constrained respectively). Fig. 2 is a representative depiction of the EEG, EMG, and COP plots for a single participant, averaged across all trials.
Discussion
This study set out to determine the extent to which alterations in postural set modified the spatio-temporal characteristics of cortical potentials evoked by instability. Specifically, the current study explored the association between pre-perturbation (context) and post-perturbation (consequence) cortical activity associated with perturbations to upright stability. The main findings of this study were: (1) the magnitude of pre-perturbation cortical activity was scaled to perturbation amplitude
Conclusion
In summary, this study has demonstrated that pre-perturbation cortical activity tends to vary with the anticipated amplitude of perturbation. If the amplitude of imminent instability is unpredictable, the CNS sets a “default” setting to an increase in gain. These characteristics of cortical activity parallel previous observations based on muscle activity and provide additional support for the hypothesis that slow-wave potentials generated in advance of imminent instability are indicators of
Acknowledgments
The authors wish to thank H Cheung and R Lee for assistance with data collection. This work is supported by funding from the Heart and Stroke Foundation of Canada (GM, SB), the Canadian Stroke Network (SB), and the Natural Science and Engineering Research Council (WEM). We acknowledge the support of the Toronto Rehabilitation Institute who receives funding under the Provincial Rehabilitation Research Program from the Ministry of Health and Long Term Care in Ontario.
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2019, NeuroImageCitation Excerpt :The ERP in the midline central cluster showed the characteristics of perturbation-related potentials (Bolton, 2015; Varghese et al., 2017), i.e., a slow potential shift preceding the perturbation onset (around 1.2 s), followed by P1 (80 ms) and N1 (150 ms) potentials after the perturbation onset. Several previous EEG studies on balance control (Fujiwara et al., 2011; Jacobs et al., 2008; Mochizuki et al., 2008, 2010; Smith et al., 2012) have reported that expectation of an upcoming balance perturbation elicits a negative potential shift known as contingent negative variation (CNV), which is associated with cortical mechanisms of motor preparation (Neuper and Pfurtscheller, 2001; van Rijn et al., 2011). Noteworthy, the morphology of the CNV shown in Fig. 6 differs from previous reports due to the use of a higher cut-off frequency for the high-pass filter (0.5 Hz) during preprocessing.