Biomedical subjects

Nathalie Marie

Publications and source records attributed to Nathalie Marie.

5 recordsLinked to original sources

PubMed2005

Subcortical aphasia: a longitudinal PET study.

BACKGROUND AND PURPOSE: Very few neuroimaging studies have focused on follow-up of subcortical aphasia. Here, overt language production tasks were used to correlate regional cerebral blood flow (rCBF) changes and language performance in patients with vascular subcortical lesions. METHODS: Seven aphasic patients were scanned twice with positron emission tomography (PET) at 1-year interval during a word-generation task. Using SPM2, Language-Rest contrast at PET1 was correlated to language performance and to time-lag from stroke. The same contrast was performed at PET2 and session effect (PET2-PET1) was correlated with performance improvement. RESULTS: At PET1, correlation between rCBF and delay from stroke involved mainly ventral regions of the left temporal cortex and mesial frontal cortex. Correlations between rCBF and performance showed predominantly left dorsal regions in the frontal, temporal, and parietal lobes, but also the left ventral temporal cortex. One year apart, language performance improved and rCBF increased in perisylvian regions bilaterally. Best performers at PET2 showed an increase of activity in left ventral temporal cortex as well as in right middle temporal gyrus. CONCLUSIONS: On follow-up, expected language improvement and increase of activation in the classical language areas and their counterparts were observed. Moreover, all correlational analyses both at PET1 and on follow-up implicated the anterior part of the left inferior temporal gyrus, suggesting a disconnection between the superior and inferior parts of the left temporal cortex and a specific role for this region in lexical semantic processing.

Adult↗

PubMed2004

Lexical learning of the English language: a PET study in healthy French subjects.

To investigate the neural correlates of word learning in adults, 10 right-handed French subjects who had learned English without mastering it performed an English and a French naming task during two PET sessions, one before (PET1) and the second after (PET2) a 4-week lexical training in English. Behavioral performance was collected during the two PET exams and 2 months after (T3). At T2, performance on English naming increased in all subjects; this improvement persisted at T3, with no correlation between English performance at T2 and T3. Cerebral activation during French naming mainly showed a left frontal temporal network. The pattern specifically associated with English lexical learning included, in addition to the anterior cingulate cortex involved in attentional processing and BAs 4/6 reflecting speech output, the right cerebellum and the left insular cortex that are linked to speech gesture learning, and the right medial temporal regions, likely to reflect the involvement of episodic memory during verbal learning. Correlations between English T2/T1 performance and English T2/T1 rCBF changes reinforced the hypothesis of intervention of episodic memory since they interested right frontal, hippocampal, and lateral temporal regions. 'Predictive' correlations between English T3/T2 performance and English T2/T1 rCBF changes showed, in good reminders, increased activities in the left posterior superior temporal sulcus and middle temporal cortex probably related to efficient semantic storage of learned words.

Adult↗

PubMed2003

Behavioral and neurofunctional changes over time in healthy and aphasic subjects: a PET Language Activation Study.

BACKGROUND AND PURPOSE: Follow-up neuroimaging studies of aphasia never addressed a comparison between aphasic and healthy subjects. Investigation of changes over time in healthy subjects during language tasks seems a prerequisite before interpretation of longitudinal changes in aphasic patients. METHODS: Six healthy subjects and 8 aphasic patients were PET scanned twice (PET1 and PET2) at a 1-year interval during a word generation task. Using SPM99, language-rest main effect was compared at PET1 and PET2 in each group, whereas group effect was assessed at each session. Correlations were analyzed in each group between performance indexes and changes in regional cerebral flood flow (rCBF) between the 2 sessions. RESULTS: Language performances were improved in both groups. rCBF decreased from PET1 to PET2 in the healthy group and increased in the aphasic group in perisylvian regions bilaterally. Correlations between performance and rCBF changes across sessions were similar in the 2 groups; positive correlations involved superior temporal cortexes bilaterally, and negative correlations concerned superior frontal and medial temporal regions. CONCLUSIONS: Increased perisylvian activation over time probably reflects improved performance at the expenses of cognitive effort in aphasic patients. Decreased activation in different neural systems suggests a familiarization effect with reduced emotional load.

Adult↗

PubMed2003

Neural substrates of impaired categorical perception of phonemes in adult dyslexics: an fMRI study.

Phonological developmental dyslexics remain impaired in phonetic categorical perception (CP) even in adulthood. We studied the brain correlates of CP in dyslexics and controls using a block design fMRI protocol and stimuli from an phonetic continuum between natural /Pa/ and /Ta/ syllables. Subjects performed a pseudo-passive listening task which does not imply voluntary categorical judgment. In the control group, categorical deviant stimuli elicited specific activations in the left angular gyrus, the right inferior frontal gyrus and the right superior cingulate cortex. These regions were not activated in the dyslexic group in which activation was observed for acoustic but not phonetic changes in stimuli. Failures to activate key regions for language perception and auditory attention in dyslexic might account for persistent deficits in phonological awareness and reading tasks.

Adult↗

PubMed2002

Enhanced response of the left frontal cortex to slowed down speech in dyslexia: an fMRI study.

Language difficulties of dyslexic subjects may result partly from a basic deficit in processing rapidly changing sensory inputs. In this fMRI study, we compared brain activities in adult dyslexics and controls during implicit categorical perception of phonemes with normal and slowed down stimuli. Perception of phonemic contrasts activated a frontal parietal network (Broca's area and the left supramarginal gyrus) in which the frontal component was down-regulated by slowed speech in controls and enhanced in dyslexic subjects. No modulation by speech rate was observed in the left supra-marginal gyrus. Enhancement of activity in Broca's area for slowed speech in dyslexic subjects might represent a neural basis of the improvement of performance that has been observed after remediation using this type of stimuli.

Adult↗