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104
Dynamic causal modelling of evoked potentials: a reproducibility study
- NeuroImage
, 2007
"... Dynamic causal modelling (DCM) has been applied recently to eventrelated responses (ERPs) measured with EEG/MEG. DCM attempts to explain ERPs using a network of interacting cortical sources and waveform differences in terms of coupling changes among sources. The aim of this work was to establish the ..."
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Cited by 33 (5 self)
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Dynamic causal modelling (DCM) has been applied recently to eventrelated responses (ERPs) measured with EEG/MEG. DCM attempts to explain ERPs using a network of interacting cortical sources and waveform differences in terms of coupling changes among sources. The aim of this work was to establish the validity of DCM by assessing its reproducibility across subjects. We used an oddball paradigm to elicit mismatch responses. Sources of cortical activity were modelled as equivalent current dipoles, using a biophysical informed spatiotemporal forward model that included connections among neuronal subpopulations in each source. Bayesian inversion provided estimates of changes in coupling among sources and the marginal likelihood of each model. By specifying different connectivity models we were able to evaluate three different hypotheses: differences in the ERPs to rare and frequent events are mediated by changes in forward connections (F-model), backward connections (B-model) or both (FB-model). The results were remarkably consistent over subjects. In all but one subject, the forward model was better than the backward model. This is an important result because these models have the same number of parameters (i.e., the complexity). Furthermore, the FB-model was significantly better than both, in 7 out of 11 subjects. This is another important result because it shows that a more complex model (that can fit the data more accurately) is not necessarily the most likely model. At the group level the FB-model supervened. We discuss these findings in terms of the validity and usefulness of DCM in characterising EEG/ MEG data and its ability to model ERPs in a mechanistic fashion. © 2007 Elsevier Inc. All rights reserved.
Brain structure predicts the learning of foreign speech sounds
- Cerebral Cortex
, 2007
"... Previous work has shown a relationship between parietal lobe anatomy and nonnative speech sound learning. We scanned a new group of phonetic learners using structural magnetic resonance imaging and diffusion tensor imaging. Voxel-based morphometry indicated higher white matter (WM) density in left H ..."
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Cited by 32 (0 self)
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Previous work has shown a relationship between parietal lobe anatomy and nonnative speech sound learning. We scanned a new group of phonetic learners using structural magnetic resonance imaging and diffusion tensor imaging. Voxel-based morphometry indicated higher white matter (WM) density in left Heschl’s gyrus (HG) in faster compared with slower learners, and manual segmentation of this structure confirmed that the WM volume of left HG is larger in the former compared with the latter group. This finding was replicated in a reanalysis of the original groups tested in Golestani and others (2002, Anatomical correlates of learning novel speech sounds. Neuron 35:997--1010). We also found that faster learners have a greater asymmetry (left> right) in parietal lobe volumes than slower learners and that the right insula and HG are more superiorly located in slower compared with faster learners. These results suggest that left auditory cortex WM anatomy, which likely reflects auditory processing efficiency, partly predicts individual differences in an aspect of language learning that relies on rapid temporal processing. It also appears that a global displacement of components of a right hemispheric language network, possibly reflecting individual differences in the functional anatomy and lateralization of language processing, is predictive of speech sound learning.
Fiber tracking in Q-ball fields using regularized particle trajectories
- Proc. of IPMI
, 2005
"... particle trajectories ..."
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Comparing the effects of auditory deprivation and sign language within the auditory and visual cortex
- J Cogn Neurosci
"... & To investigate neural plasticity resulting from early auditory deprivation and use of American Sign Language, we measured responses to visual stimuli in deaf signers, hearing signers, and hearing nonsigners using functional magnetic resonance imaging. We examined ‘‘compensatory hypertrophy’’ ( ..."
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Cited by 26 (1 self)
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& To investigate neural plasticity resulting from early auditory deprivation and use of American Sign Language, we measured responses to visual stimuli in deaf signers, hearing signers, and hearing nonsigners using functional magnetic resonance imaging. We examined ‘‘compensatory hypertrophy’’ (changes in the responsivity/size of visual cortical areas) and ‘‘cross-modal plasticity’ ’ (changes in auditory cortex responses to visual stimuli). We measured the volume of early visual areas (V1, V2, V3, V4, and MT+). We also measured the amplitude of responses within these areas, and within the auditory cortex, to a peripheral visual motion stimulus that was attended or ignored. We found no major differences between deaf and hearing subjects in the size or responsivity of early visual areas. In contrast, within the auditory cortex, motion stimuli evoked significant responses in deaf subjects, but not in hearing subjects, in a region of the right auditory cortex corresponding to Brodmann’s areas 41, 42, and 22. This hemispheric selectivity may be due to a predisposition for the right auditory cortex to process motion; earlier studies report a right hemisphere bias for auditory motion in hearing subjects. Visual responses within the auditory cortex of deaf subjects were stronger for attended than ignored stimuli, suggesting top-down processes. Hearing signers did not show visual responses in the auditory cortex, indicating that cross-modal plasticity can be attributed to auditory deprivation rather than sign language experience. The largest effects of auditory deprivation occurred within the auditory cortex rather than the visual cortex, suggesting that the absence of normal input is necessary for large-scale cortical reorganization to occur. &
Sulcal Pattern and Morphology of the Superior Temporal Sulcus
, 2004
"... this paper, we demonstrated the possibility performing structural morphometry using automatic image analysis tools to extract the cortical folds (Mangin et al., 1995a,b). The fold labeling according to the sulcus nomenclature, however, was performed manually by a neurosurgeon. We have recently devel ..."
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Cited by 25 (1 self)
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this paper, we demonstrated the possibility performing structural morphometry using automatic image analysis tools to extract the cortical folds (Mangin et al., 1995a,b). The fold labeling according to the sulcus nomenclature, however, was performed manually by a neurosurgeon. We have recently developed a system to perform this labeling automatically, using a set of 500 neural networks trained on a manually labeled database (Riviere et al., 2002). Each neural network is in charge of a local anatomical feature. This opens the door to automatic "Structural Based Morphometry" (SBM), that is to say a large-scale morphometric study similar to those performed with a voxel-based approach. We have also reported the advent of new visualization tools dedicated to the 3D shape of the folding that can be used to improve the current understanding of the folding patterns. These tools can be used to study the variability of the buried gyri (pli de passage) which often interrupt the usual sulci. Future work consists of the validation and automatic recognition of the foetal sulcal root patterns, which would improve the reliability of the morphometric attributes used for the automatic studies. This work will rely on longitudinal studies of the folding process and new mathematical methods to infer the buried gyri localization for the curvature of the cortical surface (Cachia et al., 2001)
The song system of the human brain.
- Cogn. Brain Res.,
, 2004
"... Abstract: Although sophisticated insights have been gained into the neurobiology of singing in songbirds, little comparable knowledge exists for humans, the most complex singers in nature. Human song complexity is evidenced by the capacity to generate both richly structured melodies and coordinated ..."
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Cited by 25 (4 self)
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Abstract: Although sophisticated insights have been gained into the neurobiology of singing in songbirds, little comparable knowledge exists for humans, the most complex singers in nature. Human song complexity is evidenced by the capacity to generate both richly structured melodies and coordinated multi-part harmonizations. The present study aimed to elucidate this multi-faceted vocal system by using 15O-water positron emission tomography to scan -listen and respond‖ performances of amateur musicians either singing repetitions of novel melodies, singing harmonizations with novel melodies, or vocalizing monotonically. Overall, major blood flow increases were seen in the primary and secondary auditory cortices, primary motor cortex, frontal operculum, supplementary motor area, insula, posterior cerebellum, and basal ganglia. Melody repetition and harmonization produced highly similar patterns of activation. However, whereas all three tasks activated secondary auditory cortex (posterior Brodmann Area 22), only melody repetition and harmonization activated the planum polare (BA 38). This result implies that BA 38 is responsible for an even higher level of musical processing than BA 22. Finally, all three of these -listen and respond‖ tasks activated the frontal operculum (Broca's area), a region involved in cognitive/motor sequence production and imitation, thereby implicating it in musical imitation and vocal learning. Author Keywords: Singing; Song system; Brain; Music; Melody; Harmony, Motor Systems and Sensorimotor Integration, Cortex Article: Singing is a specialized class of vocal behavior found in a limited number of animal taxa, including humans, gibbons, humpback whales, and about half of the nine thousand species of bird. Various functions have been attributed to singing, including territorial defense, mate attraction, pair bonding, coalition signaling, and group cohesion [5, 25, 46 and 76]. Song production is mediated by a specialized system of brain areas and neural pathways known as the song system. This system is also responsible for song learning, as most singing species acquire their songs via social learning during development [30 and 31]. In some species, known as -age-limited learners‖, song learning occurs once during a critical period; in -open-ended learners‖, song learning occurs throughout much of the life span (e.g., Although humans are by far the most complex singers in nature, the neurobiology of human song is much less well understood. A deeper understanding of singing may benefit from a comparative approach, as human singers show features that are both shared with, and distinct from, birds and other singers in nature
Surface-based approaches to spatial localization and registration in primate cerebral cortex.
- Neuroimage,
, 2004
"... Explicit surface reconstructions provide invaluable substrates for visualizing and analyzing the complex convolutions of cerebral cortex. This report illustrates the utility of surface-based atlases of human and macaque monkey for representing many aspects of cortical organization and function. The ..."
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Cited by 23 (1 self)
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Explicit surface reconstructions provide invaluable substrates for visualizing and analyzing the complex convolutions of cerebral cortex. This report illustrates the utility of surface-based atlases of human and macaque monkey for representing many aspects of cortical organization and function. These include a variety of cortical partitioning schemes plus an open-ended collection of complex activation patterns obtained from fMRI studies. Surface-based registration from one hemisphere to an atlas provides powerful approach to (i) objectively and quantitatively representing both the consistencies and the variability of the pattern of convolutions and the patterns of functional activation from any given task; and (ii) making comparisons across species and evaluating candidate homologies between cortical areas or functionally delineated regions. D 2004 Elsevier Inc. All rights reserved.
Multiple movement representations in the human brain: an event-related fMRI study
- J. Cogn. Neurosci
, 2002
"... & Neurovascular correlates of response preparation have been investigated in human neuroimaging studies. However, conventional neuroimaging cannot distinguish, within the same trial, between areas involved in response selection and/ or response execution and areas specifically involved in respon ..."
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Cited by 21 (5 self)
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& Neurovascular correlates of response preparation have been investigated in human neuroimaging studies. However, conventional neuroimaging cannot distinguish, within the same trial, between areas involved in response selection and/ or response execution and areas specifically involved in response preparation. The specific contribution of parietal and frontal areas to motor preparation has been explored in electrophysiological studies in monkey. However, the asso-ciative nature of sensorimotor tasks calls for the additional contributions of other cortical regions. In this article, we have investigated the functional anatomy of movement represen-tations in the context of an associative visuomotor task with instructed delays. Neural correlates of movement representa-tions have been assessed by isolating preparatory activity that
Multisensory integration sites identified by perception of spatial wavelet filtered visual speech gesture information
- J. Cogn. Neurosci
, 2004
"... & Perception of speech is improved when presentation of the audio signal is accompanied by concordant visual speech gesture information. This enhancement is most prevalent when the audio signal is degraded. One potential means by which the brain affords perceptual enhancement is thought to be th ..."
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Cited by 14 (0 self)
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& Perception of speech is improved when presentation of the audio signal is accompanied by concordant visual speech gesture information. This enhancement is most prevalent when the audio signal is degraded. One potential means by which the brain affords perceptual enhancement is thought to be through the integration of concordant information from multiple sensory channels in a common site of convergence, multisensory integration (MSI) sites. Some studies have iden-tified potential sites in the superior temporal gyrus/sulcus (STG/S) that are responsive to multisensory information from the auditory speech signal and visual speech movement. One limitation of these studies is that they do not control for activity resulting from attentional modulation cued by such things as visual information signaling the onsets and offsets of
G.: Structural asymmetries in the infant language and sensori-motor networks. Cerebral Cortex 19(2
, 2008
"... Both language capacity and strongly lateralized hand preference are among the most intriguing particularities of the human species. They are associated in the adult brain with functional and anatomical hemispheric asymmetries in the speech perception-production network and in the sensori-motor syste ..."
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Cited by 14 (0 self)
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Both language capacity and strongly lateralized hand preference are among the most intriguing particularities of the human species. They are associated in the adult brain with functional and anatomical hemispheric asymmetries in the speech perception-production network and in the sensori-motor system. Only studies in early life can help us to understand how such asymmetries arise during brain development, and to which point structural left--right differences are the source or the consequence of functional lateralization. In this study, we aimed to provide new in vivo structural markers of hemispheric asymmetries in infants from 1 to 4 months of age, with diffusion tensor imaging. We used 3 complementary analysis methods based on local diffusion indices and spatial localizations of tracts. After a prospective approach over the whole brain, we demonstrated early leftward asymmetries in the arcuate fasciculus and in the cortico-spinal tract. These results suggest that the early macroscopic geometry, microscopic organization, and maturation of these white matter bundles are related to the development of later functional lateralization.
