Cerebral metabolism during vegetative state and after recovery to consciousness

peer reviewe

Restoration of thalamocortical connectivity after recovery from persistent vegetative state

Moreover, the performance on these factors is correlated to different anterior and posterio

Impaired effective cortical connectivity in vegetative state: preliminary investigation using PET.

Vegetative state (VS) is a condition of abolished awareness with persistence of arousal. Awareness is part of consciousness, which itself is thought to represent an emergent property of cerebral neural networks. Our hypothesis was that part of the neural correlate underlying VS is an altered connectivity, especially between the associative cortices. We assessed regional cerebral glucose metabolism (rCMRGlu) and effective cortical connectivity in four patients in VS by means of statistical parametric mapping and [18F]fluorodeoxyglucose-positron emission tomography. Our data showed a common pattern of impaired rCMRGlu in the prefrontal, premotor, and parietotemporal association areas and posterior cingulate cortex/precuneus in VS. In a next step, we demonstrated that in VS patients various prefrontal and premotor areas have in common that they are less tightly connected with the posterior cingulate cortex than in normal controls. These results provide a strong argument for an alteration of cortical connectivity in VS patients.Case ReportsJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

.Human Brain Mapping 10:179-194(2000). Striatum Forever, Despite Sequence Learning Variability: A Random Effect Analysis of PET Data

Abstract: This PET study is concemed with the what, where, and how of implicit sequence leaming. 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.e., what) was studied scan by scan, aiming to evidence the brain areas (i.e., where) specifically involved in the implicit processing of this core component of sequential higher-order knowledge. As behavioural results demonstrate between- and within-subjects variability in the implicit acquisition of sequential knowledge through practice, functional PET data were modelled using a random-effect model analysis (i.e., how) to account for both sources of behavioural variability.First, two mean condition images were created per subject depending on the presence or not of implicit sequential knowledge at the time of each of the 12 scans. Next, direct comparison of these mean condition images provided the brain areas involved in sequential knowledge processing. Using this approach, we have shown that the striatum is involved in more than simple pairwise associations and that it has the capacity to process higher-order knowledge. We suggest that the striatum is not only involved in the implicit automatization of serial information through prefrontal cortex-caudate nucleus networks, but also that it plays a significant role for the selection of the most appropriate responses in the context created by both the current and previous stimuli, thus contributing to better efficiency and faster response preparation in the SRT task. Hum. Brain Mapping 10:179-194,2000. @ 2000 Wiley-Liss, Inc

Serotonin 5HT2 receptor imaging in the human brain using positron emission tomography and a new radioligand, [18F]altanserin: results in young normal controls.

Changes in serotonin-2 receptors have been demonstrated in brain autopsy material from patients with various neurodegenerative and affective disorders. It would be desirable to locate a ligand for the study of these receptors in vivo with positron emission tomography (PET). Altanserin is a 4-benzoylpiperidine derivative with a high affinity and selectivity for S2 receptors in vitro. Dynamic PET studies were carried out in nine normal volunteers with high-specific activity (376-1,680 mCi/mumol) [18F]altanserin. Arterial blood samples were obtained and the plasma time-activity curves were corrected for the presence of labeled metabolites. Thirty minutes after injection, selective retention of the radioligand was observed in cortical areas, while the cerebellum, caudate, and thalamus had low radioactivity levels. Specific binding reached a plateau between 30 and 65 min postinjection at 1.8% of the injected dose/L of brain and then decreased, indicating the reversibility of the binding. The total/nonspecific binding ratio reached 2.6 for times between 50 and 70 min postinjection. The graphical analysis proposed by Logan et al. allowed us to estimate the binding potential (Bmax/KD). Pretreatment with ketanserin was given to three volunteers and brain activity remained uniformly low. An additional study in one volunteer showed that [18F]altanserin can be displaced from the receptors by large doses of ketanserin. At the end of the study, unchanged altanserin was 57% of the total plasma activity. These results suggest that [18F]altanserin is selective for S2 receptors in vivo as it is in vitro. They indicate that [18F]altanserin is suitable for imaging and quantifying S2 receptors with PET in humans

Zerebrale Funktionen bei hirngeschädigten Patienten. Was bedeuten Koma,

Comatose, vegetative, minimally conscious or locked-in patients represent a problem in terms of diagnosis, prognosis, treatment and everyday management at the intensive care unit. The evaluation of possible cognitive functions in these patients is difficult because voluntary movements may be very small, inconsistent and easily exhausted. Functional neuroimaging cannot replace the clinical assessment of patients with altered states of consciousness. Nevertheless, it can describe objectively how deviant from normal the cerebral activity is and its regional distribution at rest and under various conditions of stimulation. The quantification of brain activity differentiates patients who sometimes only differ by a brief and incomplete blink of an eye. In the present paper, we will first try to define consciousness as it can be assessed at the patient's bedside. We then review the major clinical entities of altered states of consciousness encountered in the intensive care unit. Finally, we discuss the functional neuroanatomy of these conditions as assessed by positron emission tomography (PET) scanning.English AbstractJournal ArticleReviewinfo:eu-repo/semantics/publishe