Search PubMed⌕ Search

Biomedical subjects

Nathalie Tzourio-Mazoyer

Publications and source records attributed to Nathalie Tzourio-Mazoyer.

16 recordsLinked to original sources
PubMed2006

When a schizophrenic deficit becomes a reasoning advantage.

A deficit in context processing has been proposed to be one of the major deficiencies in schizophrenia. A demanding reasoning task, known to promote a very reproducible bias (i.e., a reasoning error) in healthy subjects, triggered by a misleading context, was administered in 26 schizophrenic patients and 26 healthy participants. Responses at random were checked by including an additional group of 11 schizophrenic patients who performed a control version of the task. We showed that patients presented a surprising imperviousness to the reasoning bias and had significantly better logical performances than their paired healthy participants. This finding demonstrates that there are some problem solving situations where disregarding contextual information, a cognitive deficit that usually impairs schizophrenic patients gives them a cognitive advantage over healthy controls.

Adult↗
PubMed2006

FMRI study of emotional speech comprehension.

Little is known about the neural correlates of affective prosody in the context of affective semantic discourse. We used functional magnetic resonance imaging to investigate this issue while subjects performed 1) affective classification of sentences having an affective semantic content and 2) grammatical classification of sentences with neutral semantic content. Sentences of each type were produced half by actors and half by a text-to-speech software lacking affective prosody. Compared with neutral sentences processing, sentences with affective semantic content--with or without affective prosody--led to an increase in activation of a left inferior frontal area involved in the retrieval of semantic knowledge. In addition, the posterior part of the left superior temporal sulcus (STS) together with the medial prefrontal cortex were recruited, although not activated by neutral sentences classification. Interestingly, these areas have been described as implicated during self-reflection or other's mental state inference that possibly occurred during the affective classification task. When affective prosody was present, additional rightward activations of the human-selective voice area and the posterior part of STS were observed, corresponding to the processing of speaker's voice emotional content. Accurate affective communication, central to social interactions, requires the cooperation of semantics, affective prosody, and mind-reading neural networks.

Adult↗
PubMed2006

Cognitive inhibition of number/length interference in a Piaget-like task in young adults: evidence from ERPs and fMRI.

We sought to determine whether the neural traces of a previous cognitive developmental stage could be evidenced in young adults. In order to do so, 12 young adults underwent two functional imaging acquisitions (EEG then fMRI). During each session, two experimental conditions were applied: a Piaget-like task with number/length interference (INT), and a reference task with number/length covariation (COV). To succeed at Piaget's numerical task, which children under the age of 7 years usually fail, the subjects had to inhibit a misleading strategy, namely, the visuospatial length-equals-number bias, a quantification heuristic that is often relevant and that continues to be used through adulthood. Behavioral data confirmed that although there was an automation in the young adult subjects as assessed by the very high number of accurate responses (>97%), the inhibition of the "length equals number strategy" had a cognitive cost, as the reaction times were significantly higher in INT than in COV (with a difference of 230 ms). The event-related potential results acquired during the first session showed electrophysiological markers of the cognitive inhibition of the number/length interference. Indeed, the frontal N2 was greater during INT than during COV, and a P3(late)/P6 was detected only during INT. During the fMRI session, a greater activation of unimodal areas (the right middle and superior occipital cortex) and in the ventral route (the left inferior temporal cortex) was observed in INT than in COV. These results seem to indicate that when fully automated in adults, inhibition processes might take place in unimodal areas.

Adult↗
PubMed2005

Hemispheric specialization for language: Brain volume matters.

Increasing brain volume may impose constraints, through longer information transfer delays, on the distributed networks supporting language. Here, we assessed the relative effects of brain volume and other putative predictors of the functional variability of perisylvian language areas, as probed with PET, during both a language comprehension and a language production task. In the case of language comprehension (story listening), a linear combination of planum temporale surface, brain volume and handedness could explain almost 60% of the functional asymmetry observed in the perisylvian area. Without brain volume, the goodness of fit was significantly decreased (39%, P < 0.05), and furthermore, the effect of handedness was not detected anymore. This was due to the fact that in our sample, left-handers (n = 12) had a significantly larger brain volume as compared to right-handers (n = 8, P = 0.03). As for language production (verb generation), brain volume and the planum temporale also played a role. However, in this case, the main predictor of functional variability was handedness, where a greater degree of right-handedness was associated with larger activation of left inferior frontal regions. Depending on the language component of interest, these results support different (yet compatible) theories on hemispheric specialization. Left specialization for comprehension could be attributed to the constraints of processing speech stimuli, while a gestural origin of language is mostly supported by the relation we observed between left specialization for production and right-handedness.

Adult↗
PubMed2005

Handedness and cerebral anatomical asymmetries in young adult males.

Using voxel-based morphometry, we measured the cerebral anatomical asymmetries in a sample of 56 young right-handed males and then compared voxelwise asymmetry indices of these subjects to those of 56 young left-handed males. In the right-handed, the clusters of grey matter asymmetry corresponding to the leftward occipital petalia and planum temporale asymmetries were retrieved. Strong rightward temporo-parietal asymmetries were also observed, but the rightward grey matter asymmetry in the frontal lobe was less massive than previously described. Group comparisons of left- and right-handed subjects' asymmetry maps, performed at a statistical threshold not corrected for multiple comparisons, revealed significant effects of handedness on this pattern of anatomical asymmetry in frontal regions, notably in the lower central and precentral sulci, and also in the planum temporale, with right-handed subjects being more leftward asymmetric. Concerning white matter, although almost no focal differences between left- and right-handed subjects were detected, volumetric analyses at the hemispheric level revealed a leftward asymmetry, which happened to be significantly less marked in the left-handed. This latter result, together with the pattern of leftward white matter asymmetries, suggested that anatomical correlates of the left hemispheric specialization for language would exist in white matter. In the population we studied, differences in anatomical asymmetry between left- and right-handed subjects provided structural arguments for a greater functional ambilaterality in left-handed subjects.

Adolescent↗
PubMed2005

Effects of blood pressure lowering on cerebral white matter hyperintensities in patients with stroke: the PROGRESS (Perindopril Protection Against Recurrent Stroke Study) Magnetic Resonance Imaging Substudy.

BACKGROUND: The prevalence of white matter hyperintensities (WMHs) detected on cerebral MRI is associated with hypertension, but it is not known whether blood pressure lowering can arrest their progression. We report here the results of an MRI substudy of PROGRESS (Perindopril Protection Against Recurrent Stroke Study), a randomized trial of blood pressure lowering in subjects with cerebrovascular disease. METHODS AND RESULTS: The substudy comprised 192 participants who had a cerebral MRI both at baseline and after a mean follow-up time of 36 months (SD=6.0 months). At the first MRI, WMHs were graded with a visual rating scale from A (no WMH) to D (severe WMH). Participants were assigned to a combination of perindopril plus indapamide (or their placebos; 58%) or to single therapy with perindopril (or placebo). At the time of the second MRI, the blood pressure reduction in the active arm compared with the placebo arm was 11.2 mm Hg for systolic blood pressure and 4.3 mm Hg for diastolic blood pressure. Twenty-four subjects (12.5%) developed new WMHs at follow-up. The risk of new WMH was reduced by 43% (95% CI -7% to 89%) in the active treatment group compared with the placebo group (P=0.17). The mean total volume of new WMHs was significantly reduced in the active treatment group (0.4 mm3 [SE=0.8]) compared with the placebo group (2.0 mm3 [SE=0.7]; P=0.012). This difference was greatest for patients with severe WMH at entry, 0.0 mm3 (SE=0) in the active treatment group versus 7.6 mm3 (SE=1.0) in the placebo group (P<0.0001). CONCLUSIONS: These results indicate that an active blood pressure-lowering regimen stopped or delayed the progression of WMHs in patients with cerebrovascular disease.

Aged↗
PubMed2005

Atypical hemispheric specialization for language in right-handed schizophrenia patients.

BACKGROUND: The literature suggests that schizophrenia could be related to a failure in the setting up of left hemisphere dominance for language. We sought to determine hemispheric specialization for language in schizophrenic patients, using functional magnetic resonance imaging. METHODS: Twenty-one right-handed patients with DSM-IV schizophrenia and 21 right-handed control subjects matched by age, gender, and level of education were recruited. Fractional blood oxygen level dependent (BOLD) signal variations in anatomic regions of interest were compared between groups. Functional asymmetry indices (FAIs) were calculated in a region (LANG) resulting from the merging of activated regions showing a Group x Hemisphere interaction. The FAI difference between each patient and their matched control subject was computed. RESULTS: We found lower BOLD signal changes in patients as compared with their control subjects in a network comprising areas of the left middle temporal gyrus, the left angular gyrus, and the pars triangularis of the left inferior frontal gyrus, merged to constitute LANG. The intra-pair differences of FAIs in this area showed that 76% of the patients exhibited less leftward functional asymmetry than their matched control subjects, including six patients with a rightward asymmetry. CONCLUSIONS: These results demonstrated the existence of an anomaly in left hemisphere specialization for language in schizophrenic subjects.

Adult↗
PubMed2005

Finger tapping, handedness and grey matter amount in the Rolando's genu area.

The morphology of the central sulcus (CS), at the level of the hand primary motor cortex, has been shown to be related to hand preference and skill. Differences in the cerebral functional organisation of left and right-handers have been described, notably with respect to hemispheric specialisation, which might cause the neural substrate of hand dominance or skill to differ between the two groups. Here, we further explored the relationship between the anatomical variability of the central sulcus and hand skill in two groups of young male subjects differing by handedness (n = 56 right-handers and n = 55 left-handers). Grey matter volume (GMV) in the upper region of the central sulcus was estimated with Voxel Based Morphometry, using a probabilistic region of interest approach, while hand motor skill was measured with the finger tapping test. No significant anatomical differences could be evidenced between the two hand preference groups, a rightward hemispheric asymmetry being observed in both samples. However, multiple regression analyses showed that, in the right-handed group, the maximum tapping rate of the right hand correlated positively with the left central sulcus GMV, but negatively with the right. Similar analyses showed that, in left-handers, the maximum tapping rate of the non-dominant right hand was strongly correlated with the GMV of the ipsilateral CS but not significantly with that of the contralateral CS. These results may be due to differences in the organisation of motor systems between these two groups, possibly concerning a left hemispheric specialisation for fast repetitive movements in right-handers, which would be different in left-handers.

Adult↗
PubMed2005

New insights into the anatomo-functional connectivity of the semantic system: a study using cortico-subcortical electrostimulations.

Despite a better understanding of the organization of the cortical network underlying the semantic system, very few data are currently available regarding its anatomo-functional connectivity. Here, we report on a series of 17 patients operated on under local anaesthesia for a cerebral low-grade glioma located within the dominant hemisphere. Prior to and during resection, intraoperative electrical stimulation was used to map sensorimotor and language structures so that permanent neurological deficits could be avoided. In a number of cases, cortical and subcortical stimulation caused semantic paraphasias. Using postoperative MRI, we correlated these functional findings with the anatomical locations of the sites where semantic errors were elicited by stimulation, especially at the subcortical level, with the aim of studying the connectivity underlying the semantic system. In temporal gliomas, cortical sites involved in semantic processing were found around the posterior part of the superior temporal sulcus, with subcortical pathways reproducibly located under the depth of this sulcus. In insular gliomas, although stimulation elicited no semantic disturbances at the cortical level, such semantic paraphasias were generated at the level of the anterior floor of the external capsule. In frontal tumours, cortical regions implicated in semantics were detected in the lateral orbitofrontal region and dorsolateral prefrontal cortex, with subcortical fibres located under the inferior frontal sulcus. All these eloquent structures were systematically preserved, thereby avoiding permanent postoperative deficits. Our results provide arguments in favour of the existence of a main ventral subcortical pathway underlying the semantic system, within the dominant hemisphere, joining the two essential cortical epicentres of this network: the posterior and superior temporal areas, and the orbitofrontal and dorsolateral prefontal regions. Such a ventral stream might anatomically partly correspond to the inferior fronto-occipital fasciculus.

Adolescent↗
PubMed2004

Hemispheric specialization for language.

Hemispheric specialization for language is one of the most robust findings of cognitive neuroscience. In this review, we first present the main hypotheses about the origins of this important aspect of brain organization. These theories are based in part on the main approaches to hemispheric specialization: studies of aphasia, anatomical asymmetries and, nowadays, neuroimaging. All these approaches uncovered a large inter-individual variability which became the bulk of research on hemispheric specialization. This is why, in a second part of the review, we present the main facts about inter-individual variability, trying to relate findings to the theories presented in the first part. This review focuses on neuroimaging as it has recently given important results, thanks to investigations of both anatomical and functional asymmetries in healthy subjects. Such investigations have confirmed that left-handers, especially "familial left-handers", are more likely to have an atypical pattern of hemispheric specialization for language. Differences between men and women seem less evident although a less marked hemispheric specialization for language was depicted in women. As for the supposed relationship between anatomical and functional asymmetries, it has been shown that the size of the left (not the right) planum temporale could explain part of the variability of left hemispheric specialization for language comprehension. Taken as a whole, findings seem to vary with language tasks and brain regions, therefore showing that hemispheric specialization for language is multi-dimensional. This is not accounted for in the existing models of hemispheric specialization.

Animals↗
PubMed2003

Left planum temporale: an anatomical marker of left hemispheric specialization for language comprehension.

We report on a study aimed at investigating the relationships between handedness, anatomical data and functional data related to speech processing. Twenty subjects with variable handedness (Edinburgh score ranging from -100 to 100) underwent both anatomical magnetic resonance imaging (MRI) and Positron Emission Tomography (PET) during story listening and rest. The surface areas of the left and right planum temporale (PT) were measured on each subject's MRI scan. A multiple regression analysis of PET data was conducted using these PT surface areas as well as handedness scores as predictors. The surface of the left PT explained a significant part of the functional variability. We observed that subjects who had the larger left PT were likely to show a larger leftward functional asymmetry of several perisylvian areas, namely the inferior parietal lobule outside the supra-marginal gyrus (the angular gyrus and the cortex above), Heschl's gyrus, the rolandic operculum, and the temporal pole. The size of the right PT explained only a little part of functional variability and we found no evidence that the anatomical asymmetry of the PT explained functional variability. In addition, we could not evidence any relationship between handedness and functional data. These results, which confirm previous work, argue for a perceptive origin of hemispheric specialization for language comprehension as has been suggested by others.

Adult↗
PubMed2002

Distinguishing visuospatial working memory and complex mental calculation areas within the parietal lobes.

The present study was aimed at differentiate, within the parietal cortex, the areas underlying visuospatial working memory/attentionnal processes and those devoted to arithmetic processing. We compared, using positron emission tomography, the cerebral networks activated in two groups of subjects, one solving two-by-two digit numbers multiplications and the other performing a visuospatial non-numerical N-Back task. Both tasks were compared to a resting state and a control condition. During both tasks, activation was observed, bilaterally, in superior parietal areas reflecting visuospatial working memory and attentionnal processes shared by both tasks. The calculation task elicited more activation in the left inferior parietal lobule and the left precuneus. These areas could subtend numerical representation, numbers storage and retrieval processes. These results added some strong support for a special role of the left inferior parietal areas in arithmetic processing.

Adult↗
PubMed2002

Comparison of spatial normalization procedures and their impact on functional maps.

The alignment accuracy and impact on functional maps of four spatial normalization procedures have been compared using a set of high resolution brain MRIs and functional PET volumes acquired in 20 subjects. Simple affine (AFF), fifth order polynomial warp (WRP), discrete cosine basis functions (SPM), and a movement model based on full multi grid (FMG) approaches were applied on the same dataset for warping individual volumes onto the Human Brain Atlas (HBA) template. Intersubject averaged structural volumes and tissue probability maps were compared across normalization methods and to the standard brain. Thanks to the large number of degrees of freedom of the technique, FMG was found to provide enhanced alignment accuracy as compared to the other three methods, both for the grey and white matter tissues; WRP and SPM exhibited very similar performances whereas AFF had the lowest registration accuracy. SPM, however, was found to perform better than the other methods for the intra-cerebral cerebrospinal fluid (mainly in the ventricular compartments). Limited differences in terms of activation morphology and detection sensitivity were found between low resolution functional maps (FWHM approximately 10 mm) spatially normalized with the four methods, which overlapped in 42.8% of the total activation volume. These findings suggest that the functional variability is much larger than the anatomical one and that precise alignment of anatomical features has low influence on the resulting intersubject functional maps. When increasing the spatial resolution to approximately 6 mm, however, differences in localization of activated areas appear as a consequence of the different spatial normalization procedure used, restricting the overlap of the normalized activated volumes to only 6.2%.

Adult↗
PubMed2002

Neural correlates of woman face processing by 2-month-old infants.

The age of 2 months marks a turn in the development of face processing in humans with the emergence of recognition based on internal feature configuration. We studied the neural bases of this early cognitive expertise, critical for adaptive behavior in the social world, by mapping with positron emission tomography the brain activity of 2-month-old alert infants while looking at unknown woman faces. We observed the activation of a distributed network of cortical areas that largely overlapped the adult face-processing network, including the so-called fusiform face area. We also evidenced the activation of left superior temporal and inferior frontal gyri, regions associated, in adults, with language processing. These findings demonstrates that cognitive development proceeds early in functionally active interconnected cortical areas despite the fact they have not all yet reached full metabolic maturation.

Brain↗