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The groundbreaking discovery of leptin in 1994 ignited the field of obesity research by providing the first direct evidence for a hormonal system primarily involved in body weight regulation. Advances in this field over the past 15 years have led to a detailed understanding of the central targets and mechanisms of leptin action. Although the arcuate(More)
Oscillatory activity in the beta frequency band has been shown to be modulated during the preparation and execution of voluntary movements at both cortical and subcortical levels. The exaggeration of beta activity in the basal ganglia of patients with Parkinson's disease has heightened interest in this phenomenon. However, the precise function, if any,(More)
The recent rapid increase in the prevalence of obesity across the world is undoubtedly due to changes in diet and lifestyle. However, it is also indisputable that different people react differently to this change in environment and this variation in response is likely to be genetically determined. While for the majority of people this effect is presumed to(More)
Movement is accompanied by changes in the degree to which neurons in corticobasal ganglia loops synchronize their activity within discrete frequency ranges. Although two principal frequency bands--beta (15-30 Hz) and gamma (60-90 Hz)--have been implicated in motor control, the precise functional correlates of their activities remain unclear. Local field(More)
Because the time to respond to a stimulus depend markedly on expectation, measurements of reaction time can, conversely, provide information about the brain's estimate of the probability of a stimulus. Previous studies have shown that the quantitative relationship between reaction time and static, long-term expectation or prior probability can be explained(More)
PURPOSE OF THE REVIEW Developments in functional neurosurgery for movement disorders and recent advances in electrophysiological techniques have allowed important insights into the role of oscillations in corticobasal ganglia circuits, both in health and in neurological disease states. Here we review recent developments in our understanding of how(More)
Functional neurosurgical techniques provide a unique opportunity to explore patterns of interaction between the cerebral cortex and basal ganglia in patients with Parkinson's disease (PD). Previous work using simultaneous magnetoencephalographic (MEG) and local field potential (LFP) recordings from the region of the subthalamic nucleus (STNr) has(More)
This technical note describes some Bayesian procedures for the analysis of group studies that use nonlinear models at the first (within-subject) level - e.g., dynamic causal models - and linear models at subsequent (between-subject) levels. Its focus is on using Bayesian model reduction to finesse the inversion of multiple models of a single dataset or a(More)
OBJECTIVE High-amplitude beta band oscillations within the subthalamic nucleus are frequently associated with Parkinson's disease but it is unclear how they might lead to motor impairments. Here we investigate a likely pathological coupling between the phase of beta band oscillations and the amplitude of high-frequency oscillations around 300 Hz. METHODS(More)
This technical paper offers a critical re-evaluation of (spectral) Granger causality measures in the analysis of biological timeseries. Using realistic (neural mass) models of coupled neuronal dynamics, we evaluate the robustness of parametric and nonparametric Granger causality. Starting from a broad class of generative (state-space) models of neuronal(More)