Pieter Vandemaele

Developing a comprehensive presurgical functional MRI protocol for patients with intractable temporal lobe epilepsy: a pilot study

Our aim was to put together and test a comprehensive functional MRI (fMRI) protocol which could compete with the intracarotid amytal (IAT) or Wada test for the localisation of language and memory function in patients with intractable temporal lobe epilepsy. The protocol was designed to be performed in under 1xa0h on a standard 1.5xa0tesla imager. We used five paradigms to test nine healthy right-handed subjects: complex scene-encoding, picture-naming, reading, word-generation and semantic-decision tasks. The combination of these tasks generated two activation maps related to memory in the mesial temporal lobes, and three language-related maps of activation in a major part of the known language network. The functional maps from the encoding and naming tasks showed typical and symmetrical posterior mesial temporal lobe activation related to memory in all subjects. Only four of nine subjects also showed symmetrical anterior hippocampal activation. Language lateralisation was best with the word generation and reading paradigms and proved possible in all subjects. The reading paradigm enables localisation of language function in the left anterior temporal pole and middle temporal gyrus, areas typically resected during epilepsy surgery. The combined results of this comprehensive f MRI protocol are adequate for a comparative study with the IAT in patients with epilepsy being assessed for surgery.

MRI language dominance assessment in epilepsy patients at 1.0 T: region of interest analysis and comparison with intracarotid amytal testing

The primary goal of this study was to test the reliability of presurgical language lateralization in epilepsy patients with functional magnetic resonance imaging (fMRI) with a 1.0-T MR scanner using a simple word generation paradigm and conventional equipment. In addition, hemispherical fMRI language lateralization analysis and region of interest (ROI) analysis in the frontal and temporo-parietal regions were compared with the intracarotid amytal test (IAT). Twenty epilepsy patients under presurgical evaluation were prospectively examined by both fMRI and IAT. The fMRI experiment consisted of a word chain task (WCT) using the conventional headphone set and a sparse sequence. In 17 of the 20 patients, data were available for comparison between the two procedures. Fifteen of these 17 patients were categorized as left hemispheric dominant, and 2 patients demonstrated bilateral language representation by both fMRI and IAT. The highest reliability for lateralization was obtained using frontal ROI analysis. Hemispherical analysis was less powerful and reliable in all cases but one, while temporo-parietal ROI analysis was unreliable as a stand-alone analysis when compared with IAT. The effect of statistical threshold on language lateralization prompted for the use of t-value-dependent lateralization index plots. This study illustrates that fMRI-determined language lateralization can be performed reliably in a clinical MR setting operating at a low field strength of 1xa0T without expensive stimulus presentation systems.

Usefulness of language and memory testing during intracarotid amobarbital testing: observations from an fMRI study

Background – Several procedures for testing language lateralization and memory function exist during the intracarotid amobarbital test (IAT). The use of functional magnetic resonance imaging (fMRI) gives the opportunity to assess the validity of some of these procedures, or at least to inspect the neuronal correlates. A comprehensive fMRI protocol was tested, aimed at addressing aspects of lateralization of language, as well as testing memory in relation to activation of mesiotemporal regions. Here we report observations with possible consequences for the current IAT procedures.

Does visual cortex lactate increase following photic stimulation in migraine without aura patients? A functional 1H-MRS study

Proton magnetic resonance spectroscopy (1H-MRS) has been used in a number of studies to assess noninvasively the temporal changes of lactate (Lac) in the activated human brain. Migraine neurobiology involves lack of cortical habituation to repetitive stimuli and a mitochondrial component has been put forward. Our group has recently demonstrated a reduction in the high-energy phosphates adenosine triphosphate (ATP) and phosphocreatine (PCr) in the occipital lobe of migraine without aura (MwoA) patients, at least in a subgroup, in a phosphorus MRS (31P-MRS) study. In previous studies, basal Lac levels or photic stimulation (PS)-induced Lac levels were found to be increased in patients with migraine with aura (MwA) and migraine patients with visual symptoms and paraesthesia, paresia and/or dysphasia, respectively. The aim of this study was to perform functional 1H-MRS at 3xa0T in 20 MwoA patients and 20 control subjects. Repetitive visual stimulation was applied using MR-compatible goggles with 8xa0Hz checkerboard stimulation during 12xa0min. We did not observe any significant differences in signal integrals, ratios and absolute metabolite concentrations, including Lac, between MwoA patients and controls before PS. Lac also did not increase significantly during and following PS, both for MwoA patients and controls. Subtle Lac changes, smaller than the sensitivity threshold (i.e. estimated at 0.1–0.2xa0μmol/g at 3xa0T), cannot be detected by MRS. Our study does, however, argue against a significant switch to non-aerobic glucose metabolism during long-lasting PS of the visual cortex in MwoA patients.

Human Left Ventral Premotor Cortex Mediates Matching of Hand Posture to Object Use

Visuomotor transformations for grasping have been associated with a fronto-parietal network in the monkey brain. The human homologue of the parietal monkey region (AIP) has been identified as the anterior part of the intraparietal sulcus (aIPS), whereas the putative human equivalent of the monkey frontal region (F5) is located in the ventral part of the premotor cortex (vPMC). Results from animal studies suggest that monkey F5 is involved in the selection of appropriate hand postures relative to the constraints of the task. In humans, the functional roles of aIPS and vPMC appear to be more complex and the relative contribution of each region to grasp selection remains uncertain. The present study aimed to identify modulation in brain areas sensitive to the difficulty level of tool object - hand posture matching. Seventeen healthy right handed participants underwent fMRI while observing pictures of familiar tool objects followed by pictures of hand postures. The task was to decide whether the hand posture matched the functional use of the previously shown object. Conditions were manipulated for level of difficulty. Compared to a picture matching control task, the tool object – hand posture matching conditions conjointly showed increased modulation in several left hemispheric regions of the superior and inferior parietal lobules (including aIPS), the middle occipital gyrus, and the inferior temporal gyrus. Comparison of hard versus easy conditions selectively modulated the left inferior frontal gyrus with peak activity located in its opercular part (Brodmann area (BA) 44). We suggest that in the human brain, vPMC/BA44 is involved in the matching of hand posture configurations in accordance with visual and functional demands.

MR pulse wave velocity increases with age faster in the thoracic aorta than in the abdominal aorta

To assess the difference between thoracic and abdominal aortic pulse wave velocity (PWV) in apparently healthy subjects including young adults to elderly subjects.

Acoustic features of palilalia : A case study

While a number of authors have suggested that patients with palilalia typically show a tendency to repeat words or phrases with an increasing rate, others maintain that an accelerating speech rate is not essential. The present paper reports the results of an instrumental analysis of the reiterations in a 60-year-old man with palilalia. Results indicate that there is not necessarily an increasing rapidity in palilalia. Duration of the repetition trains, duration of the pauses between the trains, and average number and average duration of the components within a train were variable but did not show a pattern indicative of a systematically increasing rate. The variation in the reiterations suggests that novel or varying motor processes are deployed to produce the elements in a sequence rather than an invariant motor program.

Functional Magnetic Resonance Imaging Study of Brain Activity Associated With Pitch Adaptation During Phonation in Healthy Women Without Voice Disorders.

OBJECTIVESnThis functional magnetic resonance imaging (fMRI) study investigated the brain activity associated with pitch adaptation during phonation in healthy women without voice disorders.nnnSTUDY DESIGNnThis is an interventional prospective study.nnnMETHODSnSixteen healthy women (mean age: 24.3 years) participated in a blocked design fMRI experiment involving two phonation (comfortable phonation and high-pitched phonation) and exhalation (prolonged exhalation) tasks. BrainVoyager QX Version 2.4 software was used for group-level general linear model analysis (q[FDR]u2009<u20090.05).nnnRESULTSnAnalyses showed a significant main effect of phonation with pitch adaptation compared with rest period in the bilateral precentral gyrus, superior frontal gyrus, posterior cingulate gyrus, superior and middle temporal gyrus, insula and cerebellum, left middle and inferior frontal gyrus, right lingual gyrus, cingulate gyrus, and thalamus. Statistical results also identified a significant main effect of exhalation compared with rest period in the bilateral precentral gyrus, cerebellum, right lingual gyrus, thalamus, and left supramarginal gyrus. In addition, a significant main effect of phonation was found in the bilateral superior temporal gyrus and right insula, as well as in the left midbrain periaqueductal gray for high-pitched phonation only.nnnCONCLUSIONSnWe demonstrated that a blocked design fMRI is sensitive enough to define a widespread network of activation associated with phonation involving pitch variation. The results of this study will be implemented in our future research on phonation and its disorders.

Healthy brain ageing assessed with 18F-FDG PET and age-dependent recovery factors after partial volume effect correction

Context and purpose: The mechanisms of ageing of the healthy brain are not entirely clarified to date. In recent years several authors have tried to elucidate this topic by using F-18-FDG positron emission tomography. However, when correcting for partial volume effects (PVE), divergent results were reported. Therefore, it is necessary to evaluate these methods in the presence of atrophy due to ageing. In this paper we first evaluate the performance of two PVE correction techniques with a phantom study: the Rousset method and iterative deconvolution. We show that the ability of the latter method to recover the true activity in a small region decreases with increasing age due to brain atrophy. Next, we have calculated age-dependent recovery factors to correct for this incomplete recovery. These factors were applied to PVE-corrected F-18-FDG PET scans of healthy subjects for mapping the age-dependent metabolism in the brain. nResults: Many regions in the brain show a reduced metabolism with ageing, especially in grey matter in the frontal and temporal lobe. An increased metabolism is found in grey matter of the cerebellum and thalamus. nConclusion: Our study resulted in age-dependent recovery factors which can be applied following standard PVE correction methods. Cancelling the effect of atrophy, we found regional changes in F-18-FDG metabolism with ageing. A decreasing trend is found in the frontal and temporal lobe, whereas an increasing metabolism with ageing is observed in the thalamus and cerebellum.

Brain activity during phonation in women with muscle tension dysphonia : an fMRI study

OBJECTIVESnThe main objectives of this functional magnetic resonance imaging (fMRI) study are (1) to investigate brain activity during phonation in women with muscle tension dysphonia (MTD) in comparison with healthy controls; and (2) to explain the neurophysiological mechanism of laryngeal hyperfunction/tension during phonation in patients with MTD.nnnMETHODSnTen women with MTD and fifteen healthy women participated in this study. The fMRI experiment was carried out using a block design paradigm. Brain activation during phonation and exhalation was analyzed using BrainVoyager software.nnnRESULTSnThe statistical analysis of fMRI data has demonstrated that MTD patients control phonation by use of the auditory, motor, frontal, parietal, and subcortical areas similar to phonation control by healthy people. Comparison of phonation tasks in the two groups revealed higher brain activities in the precentral gyrus, inferior, middle and superior frontal gyrus, lingual gyrus, insula, cerebellum, midbrain, and brainstem as well as lower brain activities in the cingulate gyrus, superior and middle temporal gyrus, and inferior parietal lobe in the MTD group. No differences were found between the two groups regarding exhalation control.nnnCONCLUSIONSnThe findings in this study provide insight into phonation and exhalation control in patients with MTD. The imaging results demonstrated that in patients with MTD, altered (higher/lower) brain activities may result in laryngeal tension and vocal hyperfunction.