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We investigated large-scale systems organization of the whole human brain using functional magnetic resonance imaging (fMRI) data acquired from healthy volunteers in a no-task or 'resting' state. Images were parcellated using a prior anatomical template, yielding regional mean time series for each of 90 regions (major cortical gyri and subcortical nuclei)(More)
The indirect catecholamine agonist methylphenidate (Ritalin) is the drug treatment of choice in attention deficit/hyperactivity disorder (AD/HD), one of the most common behavioral disorders of childhood (DSM-IV), although symptoms may persist into adulthood. Methylphenidate can enhance cognitive performance in adults and children diagnosed with AD/HD(More)
It is widely held that the frontal cortex plays a critical part in certain aspects of spatial and non-spatial working memory. One unresolved issue is whether there are functionally distinct subdivisions of the lateral frontal cortex that subserve different aspects of working memory. The present study used positron emission tomography (PET) to demonstrate(More)
BACKGROUND The differential diagnosis of disorders of consciousness is challenging. The rate of misdiagnosis is approximately 40%, and new methods are required to complement bedside testing, particularly if the patient's capacity to show behavioral signs of awareness is diminished. METHODS At two major referral centers in Cambridge, United Kingdom, and(More)
A diagnosis of vegetative state is made if a patient demonstrates no evidence of awareness of self or environment, no evidence of sustained, reproducible, purposeful or voluntary behavioural response to sensory stimuli and critically no evidence of language comprehension. For those patients who retain peripheral motor function, rigorous behavioural(More)
Diffusion tensor imaging (DTI) provides a unique insight into the cellular integrity of the brain. While conventional magnetic resonance imaging underestimates the extent of pathology following closed head injury, diffusion-weighted imaging has been shown to more accurately delineate the extent of cerebral damage. There have only been a few case studies of(More)
BACKGROUND Patients diagnosed as vegetative have periods of wakefulness, but seem to be unaware of themselves or their environment. Although functional MRI (fMRI) studies have shown that some of these patients are consciously aware, issues of expense and accessibility preclude the use of fMRI assessment in most of these individuals. We aimed to assess(More)
We analyzed the properties of the logarithm of the Rician distribution leading to a full characterization of the probability law of the errors in the linearized diffusion tensor model. An almost complete lack of bias, a simple relation between the variance and the signal-to-noise ratio in the original complex data, and a close approximation to normality(More)
The assessment of voluntary behavior in non-communicative brain injured patients is often challenging due to the existence of profound motor impairment. In the absence of a full understanding of the neural correlates of consciousness, even a normal activation in response to passive sensory stimulation cannot be considered as proof of the presence of(More)
OBJECTIVES Functional neuroimaging has shown that the absence of externally observable signs of consciousness and cognition in severely brain-injured patients does not necessarily indicate the true absence of such abilities. However, relative to traumatic brain injury, nontraumatic injury is known to be associated with a reduced likelihood of regaining(More)