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Author

Dirk Van Roost

Other affiliations: University Hospital Bonn
Bio: Dirk Van Roost is an academic researcher from University of Bonn. The author has contributed to research in topics: Temporal lobe & Epilepsy. The author has an hindex of 14, co-authored 21 publications receiving 1245 citations. Previous affiliations of Dirk Van Roost include University Hospital Bonn.

Papers
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Journal ArticleDOI
03 Sep 1999-Science
TL;DR: It is suggested that declarative memory formation is dissociable into subprocesses and sequentially organized within the MTL, as well as within the rhinal cortex and the hippocampus.
Abstract: A fundamental question about human memory is which brain structures are involved, and when, in transforming experiences into memories. This experiment sought to identify neural correlates of memory formation with the use of intracerebral electrodes implanted in the brains of patients with temporal lobe epilepsy. Event-related potentials (ERPs) were recorded directly from the medial temporal lobe (MTL) as the patients studied single words. ERPs elicited by words subsequently recalled in a memory test were contrasted with ERPs elicited by unrecalled words. Memory formation was associated with distinct but interrelated ERP differences within the rhinal cortex and the hippocampus, which arose after about 300 and 500 milliseconds, respectively. These findings suggest that declarative memory formation is dissociable into subprocesses and sequentially organized within the MTL.

301 citations

Journal ArticleDOI
01 Mar 2004-Blood
TL;DR: Aberrant somatic hypermutations at high frequency in the PIM1, PAX5, RhoH/TTF, and c-MYC genes in most PCNSLs may indicate a pathogenic role for aberrant somatics hypermutation inPCNSL development.

164 citations

Journal ArticleDOI
TL;DR: Data suggest that PCNSLs are derived from highly mutated germinal-center B cells, and the frequent usage of the V4-34 gene and the presence of a shared replacement mutation may indicate that the tumor precursors recognized a shared (super) antigen.
Abstract: Primary central nervous system lymphomas (PCNSLs) have recently received considerable clinical attention due to their increasing incidence. To clarify the histogenetic origin of these intriguing neoplasms, PCNSLs from 10 HIV-negative patients were analyzed for immunoglobulin (Ig) gene rearrangements. All tumors exhibited clonal IgH gene rearrangements. Of the 10 cases, 5 used the V4–34 gene segment, and all of these lymphomas shared an amino acid exchange from glycine to aspartate due to a mutation in the first codon of the complementarity-determining region 1. No preferential usage of D H , J H , V κ , J κ , V λ , or J λ gene segments was observed. All potentially functional rearrangements exhibited somatic mutations. The pattern of somatic mutations indicated selection of the tumor cells (or their precursors) for expression of a functional antibody. Mean mutation frequencies of 13.2% and 8.3% were detected for the heavy and light chains, respectively, thereby exceeding other lymphoma entities. Cloning experiments of three tumors showed ongoing mutation in at least one case. These data suggest that PCNSLs are derived from highly mutated germinal-center B cells. The frequent usage of the V4–34 gene and the presence of a shared replacement mutation may indicate that the tumor precursors recognized a shared (super) antigen.

160 citations

Journal ArticleDOI
TL;DR: Intacranial recordings indicated that different electrophysiological responses in different temporal lobe structures were linked to memory scores from specific neuropsychological tests.

156 citations

Journal ArticleDOI
TL;DR: This computed tomography-based protocol proved to be reliable and hence can be considered as an adequate alternative to MRI-based stereotactic implantation if MRI is not available or if a single MRI-like set-up is unreliable because of intolerable distortions.
Abstract: OBJECTIVE: An individualized computed tomography-based stereotactic technique for the longitudinal insertion of intrahippocampal electrodes is presented and its accuracy described. METHODS: The technique makes use of one well reproducible target in the hippocampal head and of the approximate inclination of the anteroposterior length axis of the hippocampus, for which the orbital floor is taken as an auxiliary landmark. It was used in 141 patients with medically intractable complex partial seizures. In 106 patients, magnetic resonance imaging (MRI) was available for assessment of implantation accuracy. Each of the 212 electrodes was plotted on topographic drawings and its goodness of fit rated. RESULTS: Whereas hippocampal head and body were hit by 97 and 96% of the electrodes, respectively, the amygdala was hit by only 75% of the electrodes and mainly at its basal margin. For 93% of the electrodes, the inclination in a sagittal plane corresponded exactly to that of the hippocampus. The implantation morbidity amounted to 5.7%, whereas permanent neurological deficit occurred in one (0.7%) of the 141 patients. CONCLUSION: This computed tomography-based protocol proved to be reliable and hence can be considered as an adequate alternative to MRI-based stereotactic implantation if MRI is not available or ii a single MRI-based stereotactic set-up is unreliable because of intolerable distortions.

116 citations


Cited by
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Journal ArticleDOI
TL;DR: Findings using an electrophysiological brain component, the N400, that reveal the nature and timing of semantic memory use during language comprehension support a view of memory in which world knowledge is distributed across multiple, plastic-yet-structured, largely modality-specific processing areas, and in which meaning is an emergent, temporally extended process.

1,924 citations

Journal ArticleDOI
01 Apr 2000-Neuron
TL;DR: A technique that combines structural and functional MRI with magnetoencephalography (MEG) to obtain spatiotemporal maps of human brain activity with millisecond temporal resolution was used to obtain dynamic statistical parametric maps of cortical activity during semantic processing of visually presented words.

1,618 citations

Journal ArticleDOI
TL;DR: This work focuses on the central issue in this dispute — the relative contributions of the hippocampus and the perirhinal cortex to recognition memory.
Abstract: The hallmark of medial temporal lobe amnesia is a loss of episodic memory such that patients fail to remember new events that are set in an autobiographical context (an episode). A further symptom is a loss of recognition memory. The relationship between these two features has recently become contentious. Here, we focus on the central issue in this dispute — the relative contributions of the hippocampus and the perirhinal cortex to recognition memory. A resolution is vital not only for uncovering the neural substrates of these key aspects of memory, but also for understanding the processes disrupted in medial temporal lobe amnesia and the validity of animal models of this syndrome.

1,560 citations

Journal ArticleDOI
TL;DR: It is shown that evidence bearing on where the N400 response is generated provides key insights into what it reflects, and this has important consequences for neural models of language comprehension.
Abstract: Measuring event-related potentials (ERPs) has been fundamental to our understanding of how language is encoded in the brain. One particular ERP response, the N400 response, has been especially influential as an index of lexical and semantic processing. However, there remains a lack of consensus on the interpretation of this component. Resolving this issue has important consequences for neural models of language comprehension. Here we show that evidence bearing on where the N400 response is generated provides key insights into what it reflects. A neuroanatomical model of semantic processing is used as a guide to interpret the pattern of activated regions in functional MRI, magnetoencephalography and intracranial recordings that are associated with contextual semantic manipulations that lead to N400 effects.

1,392 citations

Journal ArticleDOI
TL;DR: In this paper, the authors apply the concept of phase synchronization of chaotic and/or noisy systems and the statistical distribution of the relative instantaneous phases to electroencephalograms (EEGs) recorded from patients with temporal lobe epilepsy.

1,232 citations