Neuroscience
-
Some models of motivation distinguish between intrinsic and extrinsic motivation. While past work has examined the neural and cognitive correlates of extrinsic motivation, research on intrinsic motivation has relied primarily on behavioral measures of performance and learning. In particular, no past work has examined the neural and cognitive correlates of social performance expectancy, which is linked to intrinsic motivation. ⋯ EEG was used to examine motor-action preparation as measured by suppression of beta band activity over the motor cortex and feedback processing as measured by the Reward Positivity (RewP). Results revealed expectancy of difficult (vs. easy) trials narrowed attentional scope, reduced beta activity over the motor cortex, and enhanced RewP amplitudes to win feedback. These findings suggest that enhancing intrinsic motivation through expectancies of positive social comparison engages similar neural and cognitive correlates as extrinsic motivators high in motivational intensity.
-
Intracranial hypertension (IH) is a medical or surgical emergency that can be the common ending of various neurological disorders, such as traumatic brain injury, cerebral vascular diseases and brain tumors. However, the molecular mechanisms underlying IH-induced neuronal apoptosis have not been fully determined, and the treatments are symptomatic, insufficient and complicated by side-effects. In this study, a cellular model induced by compressed gas treatment in primary cultured rat cortical neurons was performed to mimic IH-induced neuronal injury in vitro. ⋯ Furthermore, the results using inhibitors of each signaling pathway demonstrated that ROS mediated the compression-induced ER stress and mitochondrial dysfunction in cortical neurons. In conclusion, our results demonstrated that compression induced apoptosis in primary cultured cortical neurons, which was associated with ROS mediated ER stress and mitochondrial dysfunction. Pharmacological compounds or agents targeting mitochondrial dysfunction and ER stress associated oxidative stress might be ideal candidates for the treatment of IH-related neurological diseases.
-
Impaired finger motor function in post-stroke hemiplegia is a debilitating condition with no evidence-based or accessible treatments. Here, we evaluated the neurophysiological effectiveness of direct brain control of robotic exoskeleton that provides movement support contingent with brain activity. To elucidate the mechanisms underlying the neurofeedback intervention, we assessed resting-state functional connectivity with functional magnetic resonance imaging (rsfcMRI) between the ipsilesional sensory and motor cortices before and after a single 1-h intervention. ⋯ Although the neurofeedback intervention delivered fewer total sensorimotor stimulations compared to the sham-control, rsfcMRI in the ipsilesional sensorimotor cortices was increased during the neurofeedback intervention compared to the sham-control. Higher coactivation of the sensory and motor cortices during neurofeedback intervention enhanced rsfcMRI in the ipsilesional sensorimotor cortices. This study showed neurophysiological evidence that EEG-contingent neurofeedback is a promising strategy to induce intrinsic ipsilesional sensorimotor reorganization, supporting the importance of integrating closed-loop sensorimotor processing at a neurophysiological level.
-
The glare illusion enhances the perceived brightness of a central white area surrounded by a luminance gradient, without any actual change in light intensity. In this study, we measured the varied brightness and neurophysiological responses of electroencephalography (EEG) and pupil size with the several luminance contrast patterns of the glare illusion to address the question of whether the illusory brightness changes to the glare illusion process in the early visual cortex. We hypothesized that if the illusory brightness enhancement was created in the early stages of visual processing, the neural response would be similar to how it processes an actual change in light intensity. ⋯ We found the SSVEP amplitude was lower in the glare illusion than in the control condition, especially under high luminance contrast conditions. Furthermore, we found the probable mechanisms of the inhibited SSVEP amplitude to the high luminance contrast of glare illusion based on the greater pupil constriction, thereby decreasing the amount of light entering the pupil. Thus, the brightness enhancement in the glare illusion is already represented at the primary stage of visual processing linked to the larger pupil constriction.
-
Response inhibition - the suppression of prepotent behaviours when they are inappropriate - has been thought to rely on executive control. Against this received wisdom, it has been argued that external cues repeatedly associated with response inhibition can come to trigger response inhibition automatically without top-down command. The current project endeavoured to provide evidence for associatively-mediated motor inhibition. ⋯ Once trained, the subjects received transcranial magnetic stimulation applied over their primary motor cortex during passive observation of either the stop signal (i.e. without any need to stop a response) or an equally familiar control stimulus never associated with stopping. Analysis of motor-evoked potentials showed that corticospinal excitability was reduced during exposure to the stop signal, which likely involved stimulus-driven activation of intracortical GABAergic interneurons. This result provides evidence that, through associative learning, stop-associated stimuli can engage local inhibitory processes at the level of the motor cortex.