Biomedical subjects

Muriel Roth

Publications and source records attributed to Muriel Roth.

8 recordsLinked to original sources

PubMed2005

Articulation in early and late bilinguals' two languages: evidence from functional magnetic resonance imaging.

The network of cortical and subcortical regions that contribute to articulation was examined in bilinguals using functional magnetic resonance imaging. Participants were all fluent in French and English: half were bilingual from birth and half were 'late bilinguals' who had learned French after the age of 12. Overt articulation resulted in the bilateral activation of the motor cortex, basal ganglia and cerebellum, and also the supplementary motor area, independent of the language spoken. Furthermore, the threshold and extent of the network involved in articulation was identical for the two bilingual groups with the exception of greater variation in the left putamen for the late bilinguals. These data challenge claims that age of acquisition results in fundamental differences in the neural substrates that subserve language in bilinguals.

Adult↗

PubMed2005

Premotor activations in response to visually presented single letters depend on the hand used to write: a study on left-handers.

In a previous fMRI study on right-handers (Rhrs), we reported that part of the left ventral premotor cortex (BA6) was activated when alphabetical characters were passively observed and that the same region was also involved in handwriting [Longcamp, M., Anton, J. L., Roth, M., & Velay, J. L. (2003). Visual presentation of single letters activates a premotor area involved in writing. NeuroImage, 19, 1492-1500]. We therefore suggested that letter-viewing may induce automatic involvement of handwriting movements. In the present study, in order to confirm this hypothesis, we carried out a similar fMRI experiment on a group of left-handed subjects (Lhrs). We reasoned that if the above assumption was correct, visual perception of letters by Lhrs might automatically activate cortical motor areas coding for left-handed writing movements, i.e., areas located in the right hemisphere. The visual stimuli used here were either single letters, single pseudoletters, or a control stimulus. The subjects were asked to watch these stimuli attentively, and no response was required. The results showed that a ventral premotor cortical area (BA6) in the right hemisphere was specifically activated when Lhrs looked at letters and not at pseudoletters. This right area was symmetrically located with respect to the left one activated under the same circumstances in Rhrs. This finding supports the hypothesis that visual perception of written language evokes covert motor processes. In addition, a bilateral area, also located in the premotor cortex (BA6), but more ventrally and medially, was found to be activated in response to both letters and pseudoletters. This premotor region, which was not activated correspondingly in Rhrs, might be involved in the processing of graphic stimuli, whatever their degree of familiarity.

Adult↗

PubMed2004

The role of human left superior parietal lobule in body part localization.

Electrophysiological data in primates suggest that the superior parietal lobule integrates the position of the limbs to construct complex representations of postures. Although in humans the neural basis of these mechanisms remains largely unknown, neuropsychological studies have implicated left superior parietal regions. We devised a simple functional magnetic resonance imaging paradigm aimed at exploring this hypothesis in healthy humans. Strong activation was obtained within the left but not the right superior parietal lobule, providing additional evidence that this structure may play a key role in body part localization processing.

Adult↗

PubMed2004

Awareness of muscular force during movement production: an fMRI study.

Awareness of the muscular forces we produce during voluntary movement must be distinguished from awareness of motor outcome itself. Indeed, there is no univocal relationship between produced muscle force and movement outcome because of external forces. In the present study, we performed a functional magnetic resonance imaging study to investigate the neural bases underlying the awareness we can have of the muscular forces we put into our voluntary movements. In reference conditions, subjects made rhythmical hand movements and knew they had to reproduce, in a subsequent condition in which the resistance to the movement was increased, either their muscular forces or their kinematics. The idea behind this (well established) reproduction paradigm is that, after an explicit verbal instruction, subjects can only reproduce what they are aware off. The main contrast, that is, between the condition during which the subjects had to gain awareness of their muscular forces and that during which they had to gain awareness of their kinematics (conditions in which the actual motor output was similar), shows that gaining awareness about muscular forces exerted during movement execution makes much higher demands on many brain structures, in particular posterior insula, primary sensorimotor areas and associative somatosensory areas. This indicates the important role of somesthetic information processing in awareness of produced muscular force. Therefore, the often-heard presumption that muscle force sense might be based on the outgoing motor command is not confirmed by the present results.

Adolescent↗

PubMed2003

Motor and parietal cortical areas both underlie kinaesthesia.

Tendon vibration has long been known to evoke perception of illusory movements through activation of muscle spindle primary endings. Few studies, however, have dealt with the cortical processes resulting in these kinaesthetic illusions. We conceived an fMRI experiment to investigate the cortical structures taking part in these illusory perceptions. Since muscle spindle afferents project onto different cortical areas involved in motor control it was necessary to discriminate between activation related to sensory processes and activation related to perceptual processes. To this end, we designed and compared different conditions. In two illusion conditions, covibration at different frequencies of the tendons of the right wrist flexor and extensor muscle groups evoked perception of slow or fast illusory movements. In a no illusion condition, covibration at the same frequency of the tendons of these antagonist muscle groups did not evoke a sensation of movement. Results showed activation of most cortical areas involved in sensorimotor control in both illusion conditions. However, in most areas, activation tended to be larger when the movement perceived was faster. In the no illusion condition, motor and premotor areas were little or not activated. Specific contrasts showed that perception of an illusory movement was specifically related to activation in the left premotor, sensorimotor, and parietal cortices as well as in bilateral supplementary motor and cingulate motor areas. We conclude that activation in motor as well as in parietal areas is necessary for a kinaesthetic sensation to arise.

Adult↗

PubMed2003

Visual presentation of single letters activates a premotor area involved in writing.

In the present fMRI study, we addressed the question as to whether motor-perceptual interactions might be involved in reading. Recognizing the letters encountered when reading is generally assumed to be a purely visual process, yet because we know how to write, we also possess a sensorimotor representation of the letters. Does simply viewing a letter suffice to activate the corresponding motor representation? To answer this question, we asked right-handed subjects first to look at and then to copy single letters or pseudoletters. We established that the visual presentation of letters activated a part of the left premotor cortex (BA6) that was also activated when the letters were being written by the subjects. This premotor zone resembles Exner's area, which is thought to contain the motor programs necessary for producing letters. Visually presented pseudoletters, which had never been written before by the subjects, did not activate this region. These results indicate that the writing motor processes are implicitly evoked when passively observing letters. The cerebral representation of letters is therefore presumably not strictly visual, but based on a multicomponent neural network built up while learning concomitantly to read and write. One of the components might be a sensorimotor one associated with handwriting. This finding shows the existence of close functional relations between the reading and writing processes, and suggests that our reading abilities might be somehow dependent on the way we write.

Adult↗

PubMed2003

Retrospective intra-scan motion correction.

This paper analyzes the effects of intra-scan motion and demonstrates the possibility of correcting them directly in k-space with a new automatic retrospective method. The method is presented for series of 2D acquisitions with Cartesian sampling. Using a reference k-space acquisition (corrected for translations) within the series, intra-scan motion parameters are accurately estimated for each trajectory in k-space of each data set in the series resulting in pseudo-random sample positions. The images are reconstructed with a Bayesian estimator that can handle sparse arbitrary sampling in k-space and reduces intra-scan rotation artefacts to the noise level. The method has been assessed by means of a Monte Carlo study on axial brain images for different signal-to-noise ratios. The accuracy of motion estimates is better than 0.1 degrees for rotation, and 0.1 and 0.05 pixel, respectively, for translation along the read and phase directions for signal-to-noise ratios higher than 6 of the signals on each trajectory. An example of reconstruction from experimental data corrupted by head motion is also given.

Algorithms↗

PubMed2002

An fMRI study of music sight-reading.

The brain areas involved in music reading were investigated using fMRI. In order to evaluate the specificity of these areas we compared reading music notation to reading verbal and number notations in a task that required professional pianists to play the notes (in musical and verbal notations) and the numbers displayed on a 5-key keyboard. Overall, the three tasks revealed a similar pattern of activated brain areas. However, direct contrasts between the music notation and the verbal or the numerical notation tasks also revealed specific major foci of activation in the right occipito-temporal junction, superior parietal lobule and the intraparietal sulcus. We interpret the right occipito-temporal difference as due to differences at the encoding level between notes, words and numbers. This area might be analogous to one described for words, called the visual word form area. The parietal activations are discussed in terms of visuo-motor transcoding pathways that differ for the three types of notations used. Finally, we present a model of music reading that can possibly explain our findings.

Auditory Perception↗