1,267 research outputs found

    Neurofeedback with fMRI: A Critical Systematic Review

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    Neurofeedback relying on functional magnetic resonance imaging (fMRI-nf) heralds new prospects for self-regulating brain and behavior. Here we provide the first comprehensive review of the fMRI-nf literature and the first systematic database of fMRI-nf findings. We synthesize information from 99 fMRI-nf experiments—the bulk of currently available data. The vast majority of fMRI-nf findings suggest that self-regulation of specific brain signatures seems viable; however, replication of concomitant behavioral outcomes remains sparse. To disentangle placebo influences and establish the specific effects of neurofeedback, we highlight the need for double-blind placebo-controlled studies alongside rigorous and standardized statistical analyses. Before fMRI-nf can join the clinical armamentarium, research must first confirm the sustainability, transferability, and feasibility of fMRI-nf in patients as well as in healthy individuals. Whereas modulating specific brain activity promises to mold cognition, emotion, thought, and action, reducing complex mental health issues to circumscribed brain regions may represent a tenuous goal. We can certainly change brain activity with fMRI-nf. However, it remains unclear whether such changes translate into meaningful behavioral improvements in the clinical domain

    A new empirical challenge for local theories of consciousness

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    Local theories of consciousness state that one is conscious of a feature if it is adequately represented and processed in sensory brain areas, given some background conditions. We challenge the core prediction of local theories based on recently discovered long-lasting postdictive effects demonstrating that features can be represented for hundreds of milliseconds in perceptual areas without being consciously perceived. Unlike previous empirical data aimed against local theories, proponents of local theories cannot explain these effects away by conjecturing that subjects are phenomenally conscious of features that they cannot report. Only a strong and counterintuitive version of this claim can account for long-lasting postdictive effects. Although possible, we argue that adopting this strong version of the “overflow hypothesis” would have the effect of nullifying the weight of the evidence taken to support local theories of consciousness in the first place. We also discuss several alternative explanations that proponents of local theories could offer

    Sensory Input Pathways and Mechanisms in Swallowing: A Review

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    Over the past 20 years, research on the physiology of swallowing has confirmed that the oropharyngeal swallowing process can be modulated, both volitionally and in response to different sensory stimuli. In this review we identify what is known regarding the sensory pathways and mechanisms that are now thought to influence swallowing motor control and evoke its response. By synthesizing the current state of research evidence and knowledge, we identify continuing gaps in our knowledge of these mechanisms and pose questions for future research

    Parkinson's disease dementia: a neural networks perspective.

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    In the long-term, with progression of the illness, Parkinson's disease dementia affects up to 90% of patients with Parkinson's disease. With increasing life expectancy in western countries, Parkinson's disease dementia is set to become even more prevalent in the future. However, current treatments only give modest symptomatic benefit at best. New treatments are slow in development because unlike the pathological processes underlying the motor deficits of Parkinson's disease, the neural mechanisms underlying the dementing process and its associated cognitive deficits are still poorly understood. Recent insights from neuroscience research have begun to unravel the heterogeneous involvement of several distinct neural networks underlying the cognitive deficits in Parkinson's disease dementia, and their modulation by both dopaminergic and non-dopaminergic transmitter systems in the brain. In this review we collate emerging evidence regarding these distinct brain networks to give a novel perspective on the pathological mechanisms underlying Parkinson's disease dementia, and discuss how this may offer new therapeutic opportunities

    Functional brain organization of preparatory attentional control in visual search

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    Looking for an object that may be present in a cluttered visual display requires an advanced specification of that object to be created and then matched against the incoming visual input. Here, fast event-related fMRI was used to identify the brain networks that are active when preparing to search for a visual target. By isolating the preparation phase of the task it has been possible to show that for an identical stimulus, different patterns of cortical activation occur depending on whether participants anticipate a 'feature' or a 'conjunction' search task. When anticipating a conjunction search task, there was more robust activation in ventral occipital areas, new activity in the transverse occipital sulci and right posterior intraparietal sulcus. In addition, preparing for either type of search activated ventral striatum and lateral cerebellum. These results suggest that when participants anticipate a demanding search task, they develop a different advanced representation of a visually identical target stimulus compared to when they anticipate a nondemanding search. © 2013 Elsevier B.V. All rights reserved

    Motor Cortex Plasticity during Unilateral Finger Movement with Mirror Visual Feedback

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    Altres ajuts: This work was supported in part by grants from Foundation La Marato TV3 PI110932 to Hatice Kumru.Plasticity is one of the most important physiological mechanisms underlying motor recovery from brain lesions. Rehabilitation methods, such as mirror visual feedback therapy, which are based on multisensory integration of motor, cognitive, and perceptual processes, are considered effective methods to induce cortical reorganization. The present study investigated 3 different types of visual feedback (direct, mirrored, and blocked visual feedback: DVF, MVF, and BVF, resp.) on M1 cortex excitability and intracortical inhibition/facilitation at rest and during phasic unimanual motor task in 11 healthy individuals. The excitability of the ipsilateral M1 cortex and the intracortical facilitation increased during motor task performance in the DVF and MVF but not in the BVF condition. In addition, MVF induced cortical disinhibition of the ipsilateral hemisphere to the index finger performing the motor task, which was greater when compared to the BVF and restricted to the homologue first dorsal interosseous muscle. The visual feedback is relevant to M1 cortex excitability modulation but the MVF plays a crucial role in promoting changes in intracortical inhibition in comparison to BVF. Altogether, it can be concluded that a combination of motor training with MVF therapy may induce more robust neuroplastic changes through multisensory integration that is relevant to motor rehabilitation

    Keeping the breath in mind: Respiration, neural oscillations, and the free energy principle

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    Scientific interest in the brain and body interactions has been surging in recent years. One fundamental yet underexplored aspect of brain and body interactions is the link between the respiratory and the nervous systems. In this article, we give an overview of the emerging literature on how respiration modulates neural, cognitive and emotional processes. Moreover, we present a perspective linking respiration to the free-energy principle. We frame volitional modulation of the breath as an active inference mechanism in which sensory evidence is recontextualized to alter interoceptive models. We further propose that respiration-entrained gamma oscillations may reflect the propagation of prediction errors from the sensory level up to cortical regions in order to alter higher level predictions. Accordingly, controlled breathing emerges as an easily accessible tool for emotional, cognitive, and physiological regulation

    The neural basis of the sense of fatigue

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    Evidence suggests that the genesis and regulation of the sense of exertional fatigue is rooted within the same neural networks responsible for processing affective responses. One key mechanism proposed to be involved in the sense of exertional fatigue is the interaction between the cognitive inhibitory processes of the dorsolateral prefrontal cortex (DLPFC) and the interoceptive inputs to the amygdala. The primary purpose of this dissertation is to examine the development and progression of exertional fatigue during exercise by examining the interactions between the level of bodily perturbations evoked by the exercise, the activity of the DLPFC (Tissue Oxygenation Index [TOI] percentage), the amygdala (indexed by the acoustic startle eyeblink response [ASER] amplitude), and affective responses (Empirical Valence Scale [EVS] score). The secondary purpose is to modulate the interaction between the DLPFC TOI, the EVS scores, and the ASER amplitudes using transcranial direct current stimulation (tDCS), to explore its potential as a treatment for attenuating the sense of fatigue during physical exertion. Individual differences were also examined. Thirty healthy university students—12 women and 18 men—exercised on a cycle ergometer for up to 20 minutes or until volitional termination at (1) heavy-intensity exercise while receiving sham tDCS on the right and left DLPFC (H-Sham), (2) heavy-intensity exercise while receiving active tDCS (H-Active), (3) severe-intensity exercise while receiving sham tDCS (S-Sham), and (4) severe-intensity exercise while receiving active tDCS (S-Active). The rate of decline in EVS scores was significantly greater during severe-intensity exercise compared to heavy-intensity exercise. The decline in the right and left DLPFC TOI percentages was significantly greater during severe-intensity exercise compared to heavy-intensity exercise, and this decline was larger in the right DLPFC compared to the left DLPFC. During both exercise intensities, the strength of the correlations between EVS scores and the right and left DLPFC TOI percentages increased as the interoceptive cues intensified. tDCS significantly increased DLPFC TOI percentages and the pattern of the ASER amplitudes. In conjunction with the decline in EVS scores, the drop in TOI was most prominent during severe-intensity exercise when, on average, the right DLPFC TOI dropped below baseline and, therefore, the DLPFC entered a hypometabolic state. Individuals with a higher level of tolerance demonstrated a greater activation of the right DLPFC during the heavy-intensity exercise compared to individuals with lower tolerance. The findings of this dissertation suggest that affective responses during exercise were a function of both the severity of homeostatic perturbations and the level of inhibitory control exerted by the right DLPFC. These results support the model for hemispheric specialization of the right PFC in the cognitive inhibition of displeasure. The regulation of the sense of exertional fatigue is, therefore, likely controlled by the right DLPFC. Exertional fatigue emerged at a defined threshold. Accordingly, the physiological response pattern entered a non-steady-state, accompanied by feelings of greater displeasure (or less pleasure) and high perceived activation. Proximal to the point of termination, the hypometabolic state of the DLPFC and the decline in affective responses were not reversed with active tDCS. As such, near one’s physiological limits, if the deactivation of the DLPFC and the corresponding displeasure serve to protect the body from reaching dangerous levels of perturbation, then this mechanism appears to be immutable. Future work should evaluate the potential of therapies that target the modulation of DLPFC inhibitory control (top–down) or interoceptive sensitivity (bottom–up) networks in relation to types of fatigue (e.g., clinical)
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