Age Effects on Spatiotemporal Dynamics of Response Inhibition: An MEG Study

Inhibition, the ability to suppress irrelevant information, thoughts or movements, is crucial for humans to perform context-appropriate behaviors. It was suggested that declined cognitive performance in older adults might be attributed to inhibitory deficiencies. Although previous studies have shown an age-associated reduction in inhibitory ability, the understanding regarding its cortical spatiotemporal maps remained limited. Thus, we used a whole-head magnetoencephalography (MEG) to elucidate the age effects on response inhibition, and to explore the brain activation differences in high- and low-performing seniors. We recruited 22 younger and 22 older adults to participate in the visual Go/No-go task. Both behavioral performance and neuromagnetic responses to No-go stimuli were analyzed. The behavioral results showed that the older adults made more false alarm (FA) errors than the younger adults did. The MEG results showed that the seniors exhibited declined cortical activities in middle temporal gyrus (MTG) and delayed activation in MTG, prefrontal cortex (PFC) and pre-supplementary motor area (pre-SMA). Furthermore, among the older adults, more recruitment of the left PFC was found in the high-performers than in the lower-performers. In conclusion, age-related deficiencies in response inhibition were observed in both behavioral performance and neurophysiological measurement. Our results also suggested that frontal recruitment plays a compensatory role in successful inhibition

Reduced motor cortex deactivation in individuals who suffer from writer's cramp.

This study investigated the neuromagnetic activities of self-paced finger lifting task and electrical median nerve stimulation in ten writer's cramp patients and fourteen control subjects. The event-related de/synchronizations (ERD/ERS) of beta-band activity levels were evaluated and the somatosensory cortical activity levels were analyzed using equivalent-current dipole modeling. No significant difference between the patients and control subjects was found in the electrical stimulation-induced beta ERS and electrical evoked somatosensory cortical responses. Movement-related beta ERD did not differ between controls and patients. Notably, the amplitude of the beta ERS after termination of finger movement was significantly lower in the patients than in the control subjects. The reduced movement-related beta ERS might reflect an impairment of motor cortex deactivation. In conclusion, a motor dependent dysregulation of the sensorimotor network seems to be involved in the functional impairment of patients with writer's cramp

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Clinical profiles of the ten writer's cramp patients.

<p>Patient 2 received botox injection 3 months before MEG measurement.</p

Movement-related and electrical-induced beta synchronization.

<p><b>A</b>. The relative changes of movement-related beta power for controls (hollow circle) and patients with writer's cramp (solid circle) during the time interval from −3.5 to 2 s relative to movement offset. The horizontal line represents the reference period (3.5 to 2.5 s before the EMG offset). <b>B</b>. The relative changes of electrical-induced beta power for controls (hollow circle) and patients with writer's cramp (solid circle) during the time interval from −0.5 to 1.5 s relative to movement onset. The horizontal line represents the reference period (0.5 to 0.1 s before the electrical stimulation). Time zero indicates electrical trigger onset. Each scatter and error bar illustrates the mean (±SEM). The asterisk (*) denotes a <i>p</i> value of <0.05.</p

Movement-related beta desynchronization.

<p>The relative changes of movement-related beta power in controls (hollow circle) and patients with writer's cramp (solid circle) during the time interval from −3.5 to 2 s relative to movement onset. The horizontal line represents the reference period (3.5 to 2.5 s before the EMG onset). Each scatter and error bar illustrates the mean (±SEM).</p

Somatosensory evoked neuromagnetic activities in response to right median nerve stimulation.

<p><b>A</b>. Typical waveforms and cortical generators of the left hemispheric SEFs in one healthy subject and one patient. Upper panel: the responses were evoked after the stimulus onset (vertical lines). Lower panel: the ECD localization of N20m (black dots) and P35m (white dots) components superimposed on the subject's own MR images. N20m and P35m have opposite orientations. <b>B</b>. The mean dipole strength and peak latency of the N20m and P35m responses in fourteen control subjects and ten patients with WC. Error bars indicate the standard error of the mean (SEM). The arrow indicates the location of the central sulcus. R, right; L, left; WC, writer's cramp.</p