Concurrent Changes of Brain Functional Connectivity and Motor Variability When Adapting to Task Constraints.

Grégoire Vergotte,Stéphane Perrey,Stefan Janaqi,Muthuraman Muthuraman,Kjerstin Torre

doi:10.3389/fphys.2018.00909

Abstract

In behavioral neuroscience, the adaptability of humans facing different constraints has been addressed on one side at the brain level, where a variety of functional networks dynamically support the same performance, and on the other side at the behavioral level, where fractal properties in sensorimotor variables have been considered as a hallmark of adaptability. To bridge the gap between the two levels of observation, we have jointly investigated the changes of network connectivity in the sensorimotor cortex assessed by modularity analysis and the properties of motor variability assessed by multifractal analysis during a prolonged tapping task. Four groups of participants had to produce the same tapping performance while being deprived from 0, 1, 2, or 3 sensory feedbacks simultaneously (auditory and/or visual and/or tactile). Whereas tapping performance was not statistically different across groups, the number of brain networks involved and the degree of multifractality of the inter-tap interval series were significantly correlated, increasing as a function of feedback deprivation. Our findings provide first evidence that concomitant changes in brain modularity and multifractal properties characterize adaptations underlying unchanged performance. We discuss implications of our findings with respect to the degeneracy properties of complex systems, and the entanglement of adaptability and effective adaptation.

Highlights

The huge ability of the brain to exploit its inherent plasticity to adapt to intrinsic or extrinsic constraints over different time scales is stunning and vital (Bassett et al, 2011; Fallani et al, 2014)
Our results are congruent with the literature (Aschersleben and Prinz, 1997), as we observed no significant differences between conditions of feedback deprivation in any of the three variables commonly characterizing tapping performance
Our present results show significant variations of multifractal properties as a function of feedback deprivation imposed to the system (Figure 5) without significant functional decrement (Figure 4), which does not appear directly relevant to the issue of adaptability

Summary

Introduction

The huge ability of the brain to exploit its inherent plasticity to adapt to intrinsic or extrinsic constraints over different time scales is stunning and vital (Bassett et al, 2011; Fallani et al, 2014). At a given observation scale, the brain network can be assessed as a modular organization, modules being defined as clusters that are densely connected within but weakly connected between them (Bullmore et al, 2009; Bassett and Gazzaniga, 2011; Sporns and Betzel, 2016). Complexity is increased by the dynamic properties of the functional connections within and between modules, which may compose and recompose depending on circumstances. Such connectivity scheme is closely related to degeneracy, a key property characterizing the structure-function relationship in the brain (Tononi et al, 1999; Noppeney et al, 2004). The variety of the dynamical states or network configurations involved to maintain a given function or performance, whether at rest (Deco et al, 2011) or during a task may basically reflect adaptation to changing conditions

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