Mapping the updating process: common and specific brain activations across different versions of the running span task.

Neuroimaging studies exploring the neural substrates of executive functioning have only rarely investigated whether the non-executive characteristics of the experimental executive tasks could contribute to the observed brain activations. The aim of this study was to determine cerebral activity in three different tasks involving the updating executive function. The experimental updating tasks required subjects to process strings of items (respectively letters, words, and sounds) of unknown lengths, and then to recall or identify a specific number of presented items.

Involvement of both prefrontal and inferior parietal cortex in dual-task performance.

This PET study explored the neural substrate of both dual-task management and integration task using single tasks that are known not to evoke any prefrontal activation. The paradigm included two simple (visual and auditory) discrimination tasks, a dual task and an integration task (requiring simultaneous visual and auditory discrimination), and baseline tasks (passive viewing and hearing). Data were analyzed using SPM99.

Exploring the unity and diversity of the neural substrates of executive functioning.

Previous studies exploring the neural substrates of executive functioning used task-specific analyses, which might not be the most appropriate approach due to the difficulty of precisely isolating executive functions. Consequently, the aim of this study was to use positron emission tomography (PET) to reexamine by conjunction and interaction paradigms the cerebral areas associated with three executive processes (updating, shifting, and inhibition). Three conjunction analyses allowed us to isolate the cerebral areas common to tasks selected to tap into the same executive process.

Modulation of brain activity during phonological familiarization.

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri.

Neural correlates of "hot" and "cold" emotional processing: a multilevel approach to the functional anatomy of emotion.

The neural correlates of two hypothesized emotional processing modes, i.e., schematic and propositional modes, were investigated with positron emission tomography.

A PET investigation of lexicality and phonotactic frequency in oral language processing.

Lexicality and phonotactic frequency effects are observed in many cognitive studies on language processing, but little is known about their underlying neural substrates, especially with regard to phonotactic frequency effects. Here, we conducted a positron emission tomography (PET) study in which 11 right-handed volunteers had either to repeat or to listen to lists of words, high phonotactic frequency nonwords, and low phonotactic frequency nonwords. The comparison of word versus nonword processing consistently confirmed previous findings of left temporal and prefrontal activations classically ascribed to lexicosemantic processing.

Contribution of lexico-semantic processes to verbal short-term memory tasks: a PET activation study.

Recent studies have demonstrated the intervention of long-term memory processes in verbal STM tasks and several cognitive models have been proposed to explain these effects. A PET study was performed in order to determine whether supplementary cerebral areas are involved when subjects have to execute short-term memory tasks for items having representations in long-term memory (in comparison to items without such representations: words vs non-words). Results indicate that verbal STM for words specifically involves the left middle temporal gyrus (BA 21) and temporo-parietal junction (BA 39).

Generation of rapid eye movements during paradoxical sleep in humans.

Although rapid eye movements (REMs) are a prominent feature of paradoxical sleep (PS), their origin and functional significance remain poorly understood in humans. In animals, including nonhuman primates, REMs during PS are closely related to the occurrence of the so-called PGO waves, i.e.

The functional anatomy of inhibition processes investigated with the Hayling task.

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition (response initiation), subjects had to complete sentences with a word clearly suggested by the context, whereas in the second condition (response inhibition), subjects had to produce a word that made no sense in the context of the sentence.

Striatum forever, despite sequence learning variability: a random effect analysis of PET data.

This PET study is concerned with the what, where, and how of implicit sequence learning. In contrast with previous studies imaging the serial reaction time (SRT) task, the sequence of successive locations was determined by a probabilistic finite-state grammar. The implicit acquisition of statistical relationships between serially ordered elements (i.

The role of lateral occipitotemporal junction and area MT/V5 in the visual analysis of upper-limb postures.

Humans, like numerous other species, strongly rely on the observation of gestures of other individuals in their everyday life. It is hypothesized that the visual processing of human gestures is sustained by a specific functional architecture, even at an early prelexical cognitive stage, different from that required for the processing of other visual entities. In the present PET study, the neural basis of visual gesture analysis was investigated with functional neuroimaging of brain activity during naming and orientation tasks performed on pictures of either static gestures (upper-limb postures) or tridimensional objects.

Neural mechanisms of antinociceptive effects of hypnosis.

Background: The neural mechanisms underlying the modulation of pain perception by hypnosis remain obscure. In this study, we used positron emission tomography in 11 healthy volunteers to identify the brain areas in which hypnosis modulates cerebral responses to a noxious stimulus.

Methods: The protocol used a factorial design with two factors: state (hypnotic state, resting state, mental imagery) and stimulation (warm non-noxious vs.

The neural correlates of updating information in verbal working memory.

The aim of the present study was to re-examine cerebral areas subserving the updating function of the central executive with a running span task requiring subjects to watch strings of consonants of unknown length and then to recall serially a specific number of recent items. In order to dissociate more precisely the updating process from the storage function, a four-item instead of a six-item memory load was used, contrary to our previous study (Salmon et al., 1996).

Functional neuroanatomy of hypnotic state.

Background: The aim of the present study was to describe the distribution of regional cerebral blood flow during the hypnotic state (HS) in humans, using positron-emission tomography (PET) and statistical parametric mapping.

Methods: The hypnotic state relied on revivification of pleasant autobiographical memories and was compared to imaging autobiographical material in "normal alertness." A group of 9 subjects under polygraphic monitoring received six H215O infusions and was scanned in the following order: alert-HS-HS-HS with color hallucination-HS with color hallucination-alert.

Regional brain activity during tasks devoted to the central executive of working memory.

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed.

Functional neuroanatomy of human slow wave sleep.

The distribution of regional cerebral blood flow (rCBF) was estimated during sleep and wakefulness by using H215O positron emission tomography (PET) and statistical parametric mapping. A group analysis on 11 good sleepers (8 with steady slow wave sleep, SWS) showed a significant negative correlation between the occurrence of SWS and rCBF in dorsal pons and mesencephalon, thalami, basal ganglia, basal forebrain/hypothalamus, orbitofrontal cortex, anterior cingulate cortex, precuneus, and, on the right side, in a region that follows the medial aspect of the temporal lobe. Given the known decrease in global cerebral blood flow levels during SWS, these negative correlations suggest that rCBF is decreased significantly more in these cerebral areas than in the rest of the brain.

Regional brain activity during working memory tasks.

The first aim of our PET study was to replicate previous findings concerning the brain areas activated by a verbal working memory task. The second aim was to specify the neural basis of the central executive, using a task of working memory updating. Our data confirm that the lower left supramarginal gyrus and premotor area are the key regions subserving short-term verbal memory processes.

Functional neuroanatomy of human rapid-eye-movement sleep and dreaming.

Rapid-eye-movement (REM) sleep is associated with intense neuronal activity, ocular saccades, muscular atonia and dreaming. The function of REM sleep remains elusive and its neural correlates have not been characterized precisely in man. Here we use positron emission tomography and statistical parametric mapping to study the brain state associated with REM sleep in humans.

Combined study of cerebral glucose metabolism and [11C]methionine accumulation in probable Alzheimer's disease using positron emission tomography.

There is a characteristic decrease in glucose metabolism in associative frontal and temporo-parietal cortices of patients suffering from Alzheimer's disease (AD). The decrease in metabolism might result from local neuronal loss or from a decrease of synaptic activity. We measured in vivo [11C]methionine accumulation into proteins with positron emission tomography (PET) to assess cortical tissue loss in AD.

Brain activation induced by estimation of duration: a PET study.

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative H215O infusions, and statistical parametric mapping, we investigated the neural correlates of time processing. Nine normal subjects underwent six serial rCBF.

[Study of cerebral metabolism and blood flow in partial complex epilepsy and status epilepticus in man using positron emission tomography].

Positron Emission Tomography (PET) with the oxygen-15 steady state inhalation technique was used to provide quantitative values of regional cerebral blood flow (CBF), oxygen consumption (CMRO2) and oxygen extraction ratio (OER) in 25 patients with partial complex seizures during the interictal state, in 1 patient with recurrent temporal seizures and in 3 patients whose EEGs were characterized by periodic lateralized epileptiform discharges (PLEDs). Interictal scans showed temporal zone(s) of hypoperfusion and hypometabolism in 80% of patients with normal X-ray CT Scan. In all cases, ictal scans revealed a focal or multifocal increase in CBF and CMRO2.

Myocardial blood flow and glucose uptake after myocardial infarction.

Position emission tomography can picture the distribution of flow tracers as well as of metabolic substrates or analogs. Studies of the distribution of these tracers allow to infer information about regional myocardial clearance (flow X extraction) and substrate utilization. In a study of 32 patients after myocardial infarction, we have contrasted flow and substrate utilization to demonstrate ischemic but viable myocardium in the arterial territory of the infarct in a number of patients also specially after fibrinolytic reperfusion.

Regional cerebral blood flow and metabolic rates in human focal epilepsy and status epilepticus.

Positron emission tomography with the oxygen-15 steady state or bolus inhalation technique was used to provide quantitative values of regional cerebral blood flow (CBF), oxygen extraction ratio (OER) and oxygen consumption (CMRO2) in 25 patients with partial complex seizures during the interictal state and in 5 patients during status epilepticus. Glucose utilization (CMRglu) was also studied in one case of status epilepticus with the 18F-fluorodeoxyglucose technique (18FDG). Interictal scans showed zone(s) of hypoperfusion and hypometabolism without significant variation of the OER in approximately 80% of patients.

Radiocardiographic evaluation of left ventricular function after inhalation of C15O2.

Inhalation of C15O2 delivers a bolus of labelled water into the pulmonary veins and the left atrium; analysis of the left ventricular curve provides an easy method for the evaluation of left ventricular function. the patient was seated before six collimated probes positioned toward the lungs. An additional probe was directed toward the heart in a modified 15 to 20 degrees left anterior oblique projection.