Brain activation during human finger extension and flexion movements
ABSTRACT Corticospinal projections to the motor neuron pool of upper-limb extensor muscles have been reported to differ from those of the flexor muscles in humans and other primates. The influence of this difference on the central nervous system control for extension and flexion movements is unknown. Cortical activation during thumb extension and flexion movements of eight human volunteers was measured using functional magnetic resonance imaging (fMRI), which detects signal changes caused by an alteration in the local blood oxygenation level. Although the relative activity of the extensor and flexor muscles of the thumb was similar, the brain volume activated during extension was substantially larger than that during flexion. These fMRI results were confirmed by measurements of EEG-derived movement-related cortical potential. Higher brain activity during thumb extension movement may be a result of differential corticospinal, and possibly other pathway projections to the motoneuron pools of extensor and flexor muscles of upper the extremities.
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ABSTRACT: Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) despite lower muscle activation level associated with EC vs. CC in healthy, young individuals. It is unknown, however, whether elderly people exhibiting increased difficulties in performing EC than CC possess this unique cortical control mechanism for EC movements. To address this question, we examined functional magnetic resonance imaging (fMRI) data acquired during EC and CC of the first dorsal interosseous (FDI) muscle in 11 young (20-32 years) and 9 old (67-73 years) individuals. During the fMRI experiment, all subjects performed 20 CC and 20 EC of the right FDI with the same angular distance and velocity. The major findings from the behavioral and fMRI data analysis were that (1) movement stability was poorer in EC than CC in the old but not the young group; (2) similar to previous electrophysiological and fMRI reports, the EC resulted in significantly stronger activation in the motor control network consisting of primary, secondary and association motor cortices than CC in the young and old groups; (3) the biased stronger activation towards EC was significantly greater in the old than the young group especially in the secondary and association cortices such as supplementary and premotor motor areas and anterior cingulate cortex; and (4) in the primary motor and sensory cortices, the biased activation towards EC was significantly greater in the young than the old group. Greater activation in higher-order cortical fields for controlling EC movement by elderly adults may reflect activities in these regions to compensate for aging-related impairments in the ability to control complex EC movements. Our finding is useful for potentially guiding the development of targeted therapies to counteract age-related movement deficits and to prevent injury.Frontiers in Aging Neuroscience 05/2014; 6:86. DOI:10.3389/fnagi.2014.00086 · 2.84 Impact Factor
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ABSTRACT: Neuroergonomics is an emerging science that is defined as the study of the human brain in relation to performance at work and in everyday settings. This paper provides a critical review of the neuroergonomic approach to evaluating physical and cognitive work, particularly in mobile settings. Neuroergonomics research employing mobile and immobile brain imaging techniques are discussed in the following areas of physical and cognitive work: (1) physical work parameters; (2) physical fatigue; (3) vigilance and mental fatigue; (4) training and neuroadaptive systems; and (5) assessment of concurrent physical and cognitive work. Finally, the integration of brain and body measurements in investigating workload and fatigue, in the context of mobile brain/body imaging ("MoBI"), is discussed.Frontiers in Human Neuroscience 12/2013; 7:889. DOI:10.3389/fnhum.2013.00889 · 2.90 Impact Factor
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ABSTRACT: Regional brain alterations may be involved in the pathogenesis and adverse consequences of obstructive sleep apnea (OSA). The objectives for the current study were to (1) determine cerebrovascular reactivity in the motor areas that control upper airway musculature in patients with OSA, and (2) determine whether young patients with OSA have decreased cerebrovascular reactivity in response to breath holding. Case-control study. Academic center. Twelve subjects with OSA (age 24-42 y; apnea-hypopnea index 17; interquartile range [IQR] 9, 69 per hour) and control subjects (n = 10; age 29-44 y; AHI 2; IQR 1, 3 per hour). Subjects underwent blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) while awake, swallowing, and breath holding. In subjects with OSA, during swallowing, there was less activity in the brainstem than in controls (P = 0.03) that remained reduced after adjusting for cortical motor strip activity (P = 0.036). In OSA subjects, brain regions of increased cerebrovascular reactivity (38; IQR 17, 96 cm3) was smaller than that in controls (199; IQR 5, 423 cm3; P = 0.01). In OSA subjects, brain regions of decreased cerebrovascular reactivity during breath hold was greater (P = 0.01), and the ratio of increased-to-decreased brain regions was lower than that of controls (P = 0.006). Adjustment for cerebral volumes, body mass index, and white matter lesions did not change these results substantively. In patients with OSA, diminished change in brainstem activity during swallowing and reduced cerebrovascular reactivity may contribute to the etiopathogenesis and adverse cerebrovascular consequences, respectively. We speculate that decreased cerebral auto-regulation may be causative of gray matter loss in OSA. © 2014 Associated Professional Sleep Societies, LLC.Sleep 11/2014; · 5.06 Impact Factor