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  • 1
    Online Resource
    Online Resource
    Information Exchange between Cortical Areas: The Visual System as a Model
    SAGE Publications ; 2023
    In:  The Neuroscientist Vol. 29, No. 3 ( 2023-06), p. 370-384
    Details
    In: The Neuroscientist, SAGE Publications, Vol. 29, No. 3 ( 2023-06), p. 370-384
    Abstract: As nearly all brain functions, perception, motion, and higher-order cognitive functions require coordinated neural information processing within distributed cortical networks. Over the past decades, new theories and techniques emerged that advanced our understanding of how information is transferred between cortical areas. This review surveys critical aspects of interareal information exchange. We begin by examining the brain’s structural connectivity, which provides the basic framework for interareal communication. We then illustrate information exchange between cortical areas using the visual system as an example. Next, well-studied and newly proposed theories that may underlie principles of neural communication are reviewed, highlighting recent work that offers new perspectives on interareal information exchange. We finally discuss open questions in the study of the neural mechanisms underlying interareal information exchange.
    Type of Medium: Online Resource
    ISSN: 1073-8584 , 1089-4098
    URL: Article
    DOI: 10.1177/10738584211069061
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2029471-2
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  • 2
    Online Resource
    Online Resource
    11 C-Methionine Positron Emission Tomographic Imaging of Biologic Activity of a Recurrent Glioblastoma Treated with Stereotaxy-Guided Laser-Induced Interstitial Thermotherapy
    SAGE Publications ; 2012
    In:  Molecular Imaging Vol. 11, No. 4 ( 2012-07-01), p. 7290.2011.00046-
    Details
    In: Molecular Imaging, SAGE Publications, Vol. 11, No. 4 ( 2012-07-01), p. 7290.2011.00046-
    Abstract: In patients with recurrent glioblastoma multiforme (GBM), local minimally invasive treatment modalities have gained increasing interest recently because they are associated with fewer side effects than open surgery. For example, local tumor coagulation by laser-induced interstitial thermotherapy (LITT) is such a minimally invasive technique. We monitored the metabolic effects of stereotaxy-guided LITT in a patient with a recurrent GBM using amino acid positron emission tomography (PET). Serial 11 C-methyl-L-methionine positron emission tomography (MET-PET) and contrast-enhanced computed tomography (CT) were performed using a hybrid PET/CT system in a patient with recurrent GBM before and after LITT. To monitor the biologic activity of the effects of stereotaxy-guided LITT, a threshold-based volume of interest analysis of the metabolically active tumor volume (MET uptake index of ≥ 1.3) was performed. A continuous decline in metabolically active tumor volume after LITT could be observed. MET-PET seems to be useful for monitoring the short-term therapeutic effects of LITT, especially when patients have been pretreated with a multistep therapeutic regimen. MET-PET seems to be an appropriate tool to monitor and guide experimental LITT regimens and should be studied in a larger patient group to confirm its clinical value.
    Type of Medium: Online Resource
    ISSN: 1536-0121 , 1536-0121
    URL: Article
    DOI: 10.2310/7290.2011.00046
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2012
    detail.hit.zdb_id: 2069848-3
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  • 3
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    Online Resource
    Interhemispheric Competition After Stroke: Brain Stimulation to Enhance Recovery of Function of the Affected Hand
    SAGE Publications ; 2009
    In:  Neurorehabilitation and Neural Repair Vol. 23, No. 7 ( 2009-09), p. 641-656
    Details
    In: Neurorehabilitation and Neural Repair, SAGE Publications, Vol. 23, No. 7 ( 2009-09), p. 641-656
    Abstract: Background and purpose. Within the concept of interhemispheric competition, technical modulation of the excitability of motor areas in the contralesional and ipsilesional hemisphere has been applied in an attempt to enhance recovery of hand function following stroke. This review critically summarizes the data supporting the use of novel electrophysiological concepts in the rehabilitation of hand function after stroke. Summary of review. Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are powerful tools to inhibit or facilitate cortical excitability. Modulation of cortical excitability may instantaneously induce plastic changes within the cortical network of sensorimotor areas, thereby improving motor function of the affected hand after stroke. No significant adverse effects have been noted when applying brain stimulation in stroke patients. To date, however, the clinical effects are small to moderate and short lived. Future work should elucidate whether repetitive administration of rTMS or tDCS over several days and the combination of these techniques with behavioral training (ie, physiotherapy) could result in an enhanced effectiveness. Conclusion. Brain stimulation is a safe and promising tool to induce plastic changes in the cortical sensorimotor network to improve motor behavior after stroke. However, several methodological issues remain to be answered to further improve the effectiveness of these new approaches.
    Type of Medium: Online Resource
    ISSN: 1545-9683 , 1552-6844
    URL: Article
    DOI: 10.1177/1545968309336661
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
    detail.hit.zdb_id: 2100545-X
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  • 4
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    Online Resource
    Neuroinflammation Extends Brain Tissue at Risk to Vital Peri-Infarct Tissue: A Double Tracer [ 11 C]PK11195- and [ 18 F]FDG-PET Study
    SAGE Publications ; 2009
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 29, No. 6 ( 2009-06), p. 1216-1225
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 29, No. 6 ( 2009-06), p. 1216-1225
    Abstract: Focal cerebral ischemia elicits strong inflammatory responses involving activation of resident microglia and recruitment of monocytes/macrophages. These cells express peripheral benzodiazepine receptors (PBRs) and can be visualized by positron emission tomography (PET) using [ 11 C]PK11195 that selectively binds to PBRs. Earlier research suggests that transient ischemia in rats induces increased [ 11 C]PK11195 binding within the infarct core. In this study, we investigated the expression of PBRs during permanent ischemia in rats. Permanent cerebral ischemia was induced by injection of macrospheres into the middle cerebral artery. Multimodal imaging 7 days after ischemia comprised (1) magnetic resonance imaging that assessed the extent of infarcts; (2) [ 18 F]-2-fluoro-2-deoxy-d-glucose ([ 18 F]FDG)-PET characterizing cerebral glucose transport and metabolism; and (3) [ 11 C]PK11195-PET detecting neuroinflammation. Immunohistochemistry verified ischemic damage and neuroinflammatory processes. Contrasting with earlier data for transient ischemia, no [ 11 C]PK11195 binding was found in the infarct core. Rather, permanent ischemia caused increased [ 11 C]PK11195 binding in the normoperfused peri-infarct zone (mean standard uptake value (SUV): 1.93 ± 0.49), colocalizing with a 60% increase in the [ 18 F]FDG metabolic rate constant with accumulated activated microglia and macrophages. These results suggest that after permanent focal ischemia, neuroinflammation occurring in the normoperfused peri-infarct zone goes along with increased energy demand, therefore extending the tissue at risk to areas adjacent to the infarct.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1038/jcbfm.2009.36
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
    detail.hit.zdb_id: 2039456-1
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  • 5
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    Online Resource
    Dorsal and Ventral Attention Systems : Distinct Neural Circuits but Collaborative Roles
    SAGE Publications ; 2014
    In:  The Neuroscientist Vol. 20, No. 2 ( 2014-04), p. 150-159
    Details
    In: The Neuroscientist, SAGE Publications, Vol. 20, No. 2 ( 2014-04), p. 150-159
    Abstract: The idea of two separate attention networks in the human brain for the voluntary deployment of attention and the reorientation to unexpected events, respectively, has inspired an enormous amount of research over the past years. In this review, we will reconcile these theoretical ideas on the dorsal and ventral attentional system with recent empirical findings from human neuroimaging experiments and studies in stroke patients. We will highlight how novel methods—such as the analysis of effective connectivity or the combination of neurostimulation with functional magnetic resonance imaging—have contributed to our understanding of the functionality and interaction of the two systems. We conclude that neither of the two networks controls attentional processes in isolation and that the flexible interaction between both systems enables the dynamic control of attention in relation to top-down goals and bottom-up sensory stimulation. We discuss which brain regions potentially govern this interaction according to current task demands.
    Type of Medium: Online Resource
    ISSN: 1073-8584 , 1089-4098
    URL: Article
    DOI: 10.1177/1073858413494269
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2029471-2
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  • 6
    Online Resource
    Online Resource
    Volumetry of [ 11 C]-Methionine Positron Emission Tomographic Uptake as a Prognostic Marker before Treatment of Patients with Malignant Glioma
    SAGE Publications ; 2012
    In:  Molecular Imaging Vol. 11, No. 6 ( 2012-11), p. 7290.2012.00022-
    Details
    In: Molecular Imaging, SAGE Publications, Vol. 11, No. 6 ( 2012-11), p. 7290.2012.00022-
    Type of Medium: Online Resource
    ISSN: 1536-0121 , 1536-0121
    URL: Article
    DOI: 10.2310/7290.2012.00022
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2012
    detail.hit.zdb_id: 2069848-3
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  • 7
    Online Resource
    Online Resource
    Imaging of Non— or Very Subtle Contrast-Enhancing Malignant Gliomas with [ 11 C]-Methionine Positron Emission Tomography
    SAGE Publications ; 2011
    In:  Molecular Imaging Vol. 10, No. 6 ( 2011-11-01), p. 7290.2011.00014-
    Details
    In: Molecular Imaging, SAGE Publications, Vol. 10, No. 6 ( 2011-11-01), p. 7290.2011.00014-
    Abstract: In patients with World Health Organization (WHO) grade III glioma with a lack of or minimal ( 〈 1 cm 3 ) magnetic resonance imaging (MRI) contrast enhancement, the volume of the metabolically active part of the tumor was assessed by [ 11 C]-methionine positron emission tomography (MET-PET). Eleven patients with WHO grade III gliomas underwent MET-PET and MRI (contrast-enhanced T 1 -and T 2 -weighted images). To calculate the volumes in cubic centimeters, threshold-based volume of interest analyses of the metabolically active tumor (MET uptake index ≥ 1.3), contrast enhancement, and the T 2 lesion were performed after coregistration of all images. In all patients, the metabolically active tumor volume was larger than the volume of gadolinium–diethylenetriamine pentaacetic acid (Gd-DTPA) enhancement (20.8 ± 18.8 vs 0.29 ± 0.25 cm 3 ; p 〈 .001). With the exception of one patient, the volumes of contrast enhancement were located within the metabolically active tumor volume. In contrast, in the majority of patients, MET uptake overlapped with the T 〈 sb 〉 2 lesion and reached beyond it (in 10 of 12 MRIs/MET-PET scans). The present data suggest that in patients with WHO grade III glioma with minimal or a lack of contrast enhancement, MET-PET delineates metabolically active tumor tissue. These findings support the use of combined PET-MRI with radiolabeled amino acids (eg, MET) for the delineating of the true extent of active tumor in the diagnosis and treatment planning of patients with gliomas.
    Type of Medium: Online Resource
    ISSN: 1536-0121 , 1536-0121
    URL: Article
    DOI: 10.2310/7290.2011.00014
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2011
    detail.hit.zdb_id: 2069848-3
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  • 8
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    Online Resource
    Spatial and sustained attention in relation to smoking status: behavioural performance and brain activation patterns
    SAGE Publications ; 2011
    In:  Journal of Psychopharmacology Vol. 25, No. 11 ( 2011-11), p. 1485-1495
    Details
    In: Journal of Psychopharmacology, SAGE Publications, Vol. 25, No. 11 ( 2011-11), p. 1485-1495
    Abstract: Nicotine enhances attentional functions. Since chronic nicotine exposure through smoking induces neuroadaptive changes in the brain at a structural and molecular level, the present functional MRI (fMRI) study aimed at investigating the neural mechanisms underlying visuospatial and sustained attention in smokers and non-smokers. Visuospatial attention was assessed with a location-cueing paradigm, while sustained attention was measured by changes in response speed over time. During invalid trials, neural activity within the basal forebrain was selectively enhanced in smokers and higher basal forebrain activity was associated with increased parietal cortex activation. Moreover, higher levels of expired carbon monoxide in smokers before scanning were associated with higher parietal cortex activation and faster responses to invalidly cued targets. Smokers showed a slowing of responses and additionally recruited an area within the right supramarginal gyrus with increasing time on task. Activity decreases over time were observed in visual areas in smokers. The data provide evidence for altered attentional functions in smokers as compared with non-smokers, which were partly modulated by residual nicotine levels and were observed at a behavioural level for sustained and at a neural level for spatial and sustained attention.
    Type of Medium: Online Resource
    ISSN: 0269-8811 , 1461-7285
    URL: Article
    DOI: 10.1177/0269881110391830
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2011
    detail.hit.zdb_id: 2028926-1
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  • 9
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    Online Resource
    Impact of Aphasia on Consciousness Assessment : A Cross-Sectional Study
    SAGE Publications ; 2015
    In:  Neurorehabilitation and Neural Repair Vol. 29, No. 1 ( 2015-01), p. 41-47
    Details
    In: Neurorehabilitation and Neural Repair, SAGE Publications, Vol. 29, No. 1 ( 2015-01), p. 41-47
    Abstract: Background. Previous findings suggest that language disorders may occur in severely brain-injured patients and could interfere with behavioral assessments of consciousness. However, no study investigated to what extent language impairment could affect patients’ behavioral responses. Objective. To estimate the impact of receptive and/or productive language impairments on consciousness assessment. Methods. Twenty-four acute and subacute stroke patients with different types of aphasia (global, n = 11; Broca, n = 4; Wernicke, n = 3; anomic, n = 4; mixed, n = 2) were recruited in neurology and neurosurgery units as well as in rehabilitation centers. The Coma Recovery Scale–Revised (CRS-R) was administered. Results. We observed that 25% (6 out of 24) of stroke patients with a diagnosis of aphasia and 54% (6 out of 11) of patients with a diagnosis of global aphasia did not reach the maximal CRS-R total score of 23. An underestimation of the consciousness level was observed in 3 patients with global aphasia who could have been misdiagnosed as being in a minimally conscious state, even in the absence of any documented period of coma. More precisely, lower subscores were observed on the communication, motor, oromotor, and arousal subscales. Conclusion. Consciousness assessment may be complicated by the co-occurrence of severe language deficits. This stresses the importance of developing new tools or identifying items in existing scales, which may allow the detection of language impairment in severely brain-injured patients.
    Type of Medium: Online Resource
    ISSN: 1545-9683 , 1552-6844
    URL: Article
    DOI: 10.1177/1545968314528067
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2015
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