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Universal positive correlations between different cognitive tests motivate the concept of "general intelligence" or Spearman's g. Here the neural basis for g is investigated by means of positron emission tomography. Spatial, verbal, and perceptuo-motor tasks with high-g involvement are compared with matched low-g control tasks. In contrast to the common(More)
It is often proposed that prefrontal cortex is important in organization and control of working memory contents. In some cases, effective reorganization can decrease task difficulty, implying a dissociation between frontal activity and basic memory demand. In a spatial working memory task, we studied the improvement of performance that occurs when materials(More)
The lateral prefrontal cortex is critical for the control and organization of information in working memory. In certain situations, effective reorganization can attenuate task difficulty, suggesting a dissociation between lateral prefrontal activity and basic memory demand. In a verbal working memory task, we investigated the enhancement of performance that(More)
Previous studies have indicated that the lateral prefrontal cortex (LPFC) is closely involved in strategic recoding, even when such processes lessen task demands. For example, 2 studies presented, in the spatial and verbal domains, sequences of stimuli for participants to retain during a short interval and then retrieve. Stimuli were either randomly(More)
In human functional magnetic resonance imaging (fMRI), a characteristic pattern of frontal and parietal activity is produced by many different cognitive demands. Although frontoparietal cortex has been shown to represent a variety of task features in different contexts, little is known about detailed representation of different task features within and(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)
While the importance of the prefrontal cortex for "higher-order" cognitive functions is largely undisputed, no consensus has been reached regarding the fractionation of functions within this region. Several recent functional neuroimaging studies have suggested that the mid-ventrolateral frontal cortex may play an important role in various aspects of human(More)
UNLABELLED SINGLE CASE: DT is a savant with exceptional abilities in numerical memory and mathematical calculations. DT also has an elaborate form of synaesthesia for visually presented digits. Further more, DT also has Asperger syndrome (AS). We carried out two preliminary investigations to establish whether these conditions may contribute to his savant(More)
Despite converging agreement about the definition of persistent vegetative state, recent reports have raised concerns about the accuracy of diagnosis in some patients, and the extent to which, in a selection of cases, residual cognitive functions may remain undetected. Objective assessment of residual cognitive function can be extremely difficult as motor(More)