Image Aquisition Order and Input Order of BOLD-fMRI Data for Slice Time Correction in fMRI Data Processing Tools

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Concurrent Cortical Representations of Function- and Size-Related Object Affordances: An fMRI Study

Previous work has shown that the perception of a graspable object may automatically potentiate actions that are tailored to specific action-related features of the object (e.g., its size) and may be related to its immediate grasping as well as to its long-term, functional use. We investigated the neural correlates of function-and size-related object affordances that may be concurrently potentiated by a graspable object. Participants were lying in a MR scanner holding a large switch in one hand and a small switch in the other hand. They passively attended a large or a small object with clearly separated functional and graspable end that was displayed centrally at an average angle of 45 degrees. Participants responded to the direction of an arrow that was overlaid on the object after a mean period of 1,000 ms after object onset and was pointing to the left or to the right with equal probability. Response times were shorter when the arrow pointed to the functional end of the object and when the responses were made with the switch that was congruent to the size of the perceived object. A clear distinction was found in the representation of function-and size-related affordances; the former was represented in the posterior parietal cortex and the latter in prefrontal, premotor, and primary sensorimotor cortices. We conclude that different aspects of object-directed actions may be automatically potentiated by individual object features and are represented in distinct brain areas

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

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

Objectives. The 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. Methods. Ten 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. Results. The 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. Conclusions. The 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

Absence of haemodynamic refractory effects in patients with migraine without aura -an interictal fMRI study

Abstract Background: In healthy controls, haemodynamic refractory effects are observed with blood-oxygenation-level dependent (BOLD) functional MRI (fMRI): the haemodynamic response function (HRF) to the second stimulus in a pair of stimuli with short interstimulus interval (ISI) shows a decreased amplitude and an increased time-to-peak. We hypothesize that there may be interictal haemodynamic abnormalities in migraineurs. Methods: An event-related fMRI design with paired face stimuli and varying ISIs was used to measure interictal HRFs in the face recognition area of patients with migraine without aura (MwoA) and controls. Net responses to the second stimulus in a pair were calculated and averaged per participant. Several characterizing parameters of the net responses were quantified and examined within each group. Results: Refractory effects were not observed in our patient group. There are no changes in the net responses compared with the reference situation in patients, irrespective of the ISI, whereas in controls all HRF parameters are decreased or delayed for an ISI of 1 second. Conclusion: This is the first fMRI study investigating the haemodynamic refractory effects in MwoA patients. Unlike in controls, these effects are not observed in migraineurs. Although currently unclear, it is tempting to speculate that this observation reflects the neurovascular correlate of lack of habituation measured with evoked potentials in migraineurs

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 3 T in 20 MwoA patients and 20 control subjects. Repetitive visual stimulation was applied using MR-compatible goggles with 8 Hz checkerboard stimulation during 12 min. 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 0.1–0.2 μmol/g at 3 T), 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

ExploreASL: an image processing pipeline for multi-center ASL perfusion MRI studies

Arterial spin labeling (ASL) has undergone significant development since its inception, with a focus on improving standardization and reproducibility of its acquisition and quantification. In a community-wide effort towards robust and reproducible clinical ASL image processing, we developed the software package ExploreASL, allowing standardized analyses across centers and scanners.The procedures used in ExploreASL capitalize on published image processing advancements and address the challenges of multi-center datasets with scanner-specific processing and artifact reduction to limit patient exclusion. ExploreASL is self-contained, written in MATLAB and based on Statistical Parameter Mapping (SPM) and runs on multiple operating systems. The toolbox adheres to previously defined international standards for data structure, provenance, and best analysis practice.ExploreASL was iteratively refined and tested in the analysis of >10,000 ASL scans using different pulse-sequences in a variety of clinical populations, resulting in four processing modules: Import, Structural, ASL, and Population that perform tasks, respectively, for data curation, structural and ASL image processing and quality control, and finally preparing the results for statistical analyses on both single-subject and group level. We illustrate ExploreASL processing results from three cohorts: perinatally HIV-infected children, healthy adults, and elderly at risk for neurodegenerative disease. We show the reproducibility for each cohort when processed at different centers with different operating systems and MATLAB versions, and its effects on the quantification of gray matter cerebral blood flow.ExploreASL facilitates the standardization of image processing and quality control, allowing the pooling of cohorts to increase statistical power and discover between-group perfusion differences. Ultimately, this workflow may advance ASL for wider adoption in clinical studies, trials, and practice