Abstract
Children with Down's syndrome (DS) might exhibit disrupted brain functional connectivity in the motor and prefrontal cortex. To inspect the alterations in brain activation and functional connectivity for children with DS, the functional near-infrared spectroscopy (fNIRS) method was applied to examine the brain activation difference in the motor and prefrontal cortex between the DS and typically developing (TD) groups during a fine motor task. In addition, small-world analysis based on graph theory was also carried out to characterize the topological organization of functional brain networks. Interestingly, behavior data demonstrated that the DS group showed significantly long reaction time and low accuracy as compared to the TD group (p < 0.05). More importantly, significantly reduced brain activations in the frontopolar area, the pre-motor, and the supplementary motor cortex (p < 0.05) were identified in the DS group compared with the TD group. Meanwhile, significantly high global efficiency (Eg) and short average path length (Lp) were also detected for the DS group. This pilot study illustrated that the disrupted connectivity of frontopolar area, pre-motor, and supplementary motor cortex might be one of the core mechanisms associated with motor and cognitive impairments for children with DS. Therefore, the combination of the fNIRS technique with functional network analysis may pave a new avenue for improving our understanding of the neural mechanisms of DS.
Highlights
Down’s syndrome (DS) resulting from an extra 21st chromosome was first described in 1866 by John Langdon Down (Lott and Dierssen, 2010)
The small-world analysis combined with functional near-infrared spectroscopy (fNIRS) recordings was conducted to inspect the differences in brain activation and networks along the motor and prefrontal cortex between the typically developing (TD) and DS children, which involves both the motor and cognitive functions, the executive function (EF)
We discovered that the TD group exhibited significantly higher brain activation in the dorsolateral prefrontal cortex (DLPFC) and premotor cortex (PMC) as compared to the DS group during a fine motor task (Figure 5)
Summary
Down’s syndrome (DS) resulting from an extra 21st chromosome was first described in 1866 by John Langdon Down (Lott and Dierssen, 2010). Children who suffered from DS might exhibit disabled executive function (EF), impaired language comprehension (Martin et al, 2009), and poor learning ability and working memory (Jarrold and Baddeley, 2001). Brain Connectivity in Down’s Syndrome Children of executive functioning, such as response selection/inhibition, working memory and attention (Traverso et al, 2015). EF is denoted as a set of higher-order functions that organize and regulate goal-driven behavior, which involves several brain regions including the prefrontal cortex (PFC; Diamond, 2013). Recent studies have illustrated that the motor performance shows a significant relationship with EF in children with atypical development (Piek et al, 2004; Wassenberg et al, 2005; Hartman et al, 2010; Cao et al, 2015; Yennu et al, 2016). The motor cortex including premotor cortex (PMC), supplementary motor area (SMA) and primary motor cortex, and the somatosensory cortex (SMC), as well as the PFC (Seitz et al, 1990; Deiber et al, 1991; Shibasaki et al, 1993; Grafton et al, 1998; Nakamura et al, 1998; Li et al, 2001; Robertson et al, 2001; O’connor et al, 2004), play an essential role in motor and executive functions (Miyachi et al, 1997; Bloedel, 2004)
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