Biomedical subjects

P F Van De Moortele

Publications and source records attributed to P F Van De Moortele.

6 recordsLinked to original sources

PubMed2001

Imaging brain function in humans at 7 Tesla.

This article describes experimental studies performed to demonstrate the feasibility of BOLD fMRI using echo-planar imaging (EPI) at 7 T and to characterize the BOLD response in humans at this ultrahigh magnetic field. Visual stimulation studies were performed in normal subjects using high-resolution multishot EPI sequences. Changes in R(*)(2) arising from visual stimulation were experimentally determined using fMRI measurements obtained at multiple echo times. The results obtained at 7 T were compared to those at 4 T. Experimental data indicate that fMRI can be reliably performed at 7 T and that at this field strength both the sensitivity and spatial specificity of the BOLD response are increased. This study suggests that ultrahigh field MR systems are advantageous for functional mapping in humans. Magn Reson Med 45:588-594, 2001.

Brain↗

PubMed2001

Elimination of k-space spikes in fMRI data.

The subtle signal changes in functional magnetic resonance imaging (fMRI) can be easily overwhelmed by noise of various origins. Spikes in the collected fMRI raw data often arise from high-duty usage of the scanner hardware and can introduce significant noise in the image and thereby in the image time series. Consequently, the spikes will corrupt the functional data and degrade the result of functional mapping. In this work, a simple method based on processing the time course of the k-space data are introduced and implemented to remove the spikes in the acquired data. Application of the method to experimental data shows that the methods are robust and effective for eliminating of spike-related noise in fMRI time series.

Algorithms↗

PubMed2000

Visual perception of motion and 3-D structure from motion: an fMRI study.

Functional magnetic resonance imaging was used to study the cortical bases of 3-D structure perception from visual motion in human. Nine subjects underwent three experiments designed to locate the areas involved in (i) motion processing (random motion versus static dots), (ii) coherent motion processing (expansion/ contraction versus random motion) and (iii) 3-D shape from motion reconstruction (3-D surface oscillating in depth versus random motion). Two control experiments tested the specific influence of speed distribution and surface curvature on the activation results. All stimuli consisted of random dots so that motion parallax was the only cue available for 3-D shape perception. As expected, random motion compared with static dots induced strong activity in areas V1/V2, V5+ and the superior occipital gyrus (SOG; presumptive V3/V3A). V1/V2 and V5+ showed no activity increase when comparing coherent motion (expansion or 3-D surface) with random motion. Conversely, V3/V3A and the dorsal parieto-occipital junction were highlighted in both comparisons and showed gradually increased activity for random motion, coherent motion and a curved surface rotating in depth, which suggests their involvement in the coding of 3-D shape from motion. Also, the ventral aspect of the left occipito-temporal junction was found to be equally responsive to random and coherent motion stimuli, but showed a specific sensitivity to curved 3-D surfaces compared with plane surfaces. As this region is already known to be involved in the coding of static object shape, our results suggest that it might integrate various cues for the perception of 3-D shape.

Adult↗

PubMed2000

Functional magnetic resonance imaging of mental strategy in a simulated aviation performance task.

BACKGROUND: The objective of this study was to analyze the sensory and cognitive functions associated with activated brain regions characterizing mental strategy relative to degree of expertise in aviation-related tasks. METHODS: We used echo-planar functional magnetic resonance imaging (fMRI) technique to examine brain activity in expert pilots (n = 6) compared with novice pilots (n = 6) during performance of a simulated aviation track-following task at 200 knots vs. 100 knots. RESULTS: Expert pilots showed reduced activity in visual and motor regions that contrasted with predominant activation within anterior structures including the frontal and prefrontal cortices; structures involved in visual working memory, planning, selective attention and decision making functions. Novice pilots showed widespread activation of anterior and posterior brain structures, with a rise in activity in the visual, parietal and motor cortices as task difficulty increased. CONCLUSIONS: A high level of performance in the track-following task related to a high degree of expertise in the aviation field. This corresponded to experts performing perceptual and mnemonic processing through a network of specialized functions from visual through multiple prefrontal areas. By contrast, the novice pilots predominantly show activity associated with non-specific perceptual processing and without subsequent representation of selective information in working memory.

Adult↗

PubMed1999

Human taste cortical areas studied with functional magnetic resonance imaging: evidence of functional lateralization related to handedness.

Whole-brain functional magnetic resonance imaging was used to detect local hemodynamic changes reflecting cortical activation in five left handed and five right handed human subjects during bilateral stimulation of the tongue with various tastes. Activation was found bilaterally in the insula and the perisylvian region. These regions correspond to the primary taste cortical areas identified with electrophysiological recordings in monkeys and suggested from former clinical observations in human subjects. Moreover, a unilateral projection was described for the first time in the inferior part of the insula of the dominant hemisphere, according to the subject's handedness.

Adult↗

PubMedDate not supplied

Investigation of the initial dip in fMRI at 7 Tesla.

In agreement with optical imaging studies, previous fMRI studies have reported an initial decrease (i.e. the initial dip) in the BOLD response, which is believed to arise from an increase in oxygen consumption and to be mostly microvascular. To date, experimental studies of the initial dip in humans have been performed at fields up to 4 T, with relatively low spatial resolution. Because the sensitivity to microvascular contribution is increased at high magnetic fields, the present study investigated the initial dip at 7 T. In addition, to reduce the partial volume effect, the study is conducted at a high spatial resolution. The initial dip was detected in all subjects studied and was found to reside mostly in the gray matter. The relative amplitude of the early response was found to be 0.6, higher than that at 4 T (0.3) and 1.5 T (0.11). In addition, based on the assumption that the initial dip is a result of increased oxygen utilization, the fractional change in oxygen utilization was estimated to be 40% of that of the fractional change in cerebral blood flow. These results are in agreement with the notion that the initial dip arises from an increase in oxygen consumption.

Adult↗