Showing papers by "Daniela Perani published in 1997"

Brain activity during observation of actions. Influence of action content and subject's strategy.

Abstract: PET was used to map brain regions that are associated with the observation of meaningful and meaningless hand actions. Subjects were scanned under four conditions which consisted of visually presented actions. In each of the four experimental conditions, they were instructed to watch the actions with one of two aims: to be able to recognize or to imitate them later. We found that differences in the meaning of the action, irrespective of the strategy used during observation, lead to different patterns of brain activity and clear left/right asymmetries. Meaningful actions strongly engaged the left hemisphere in frontal and temporal regions while meaningless actions involved mainly the right occipitoparietal pathway. Observing with the intent to recognize activated memory-encoding structures. In contrast, observation with the intent to imitate was associated with activation in the regions involved in the planning and in the generation of actions. Thus, the pattern of brain activation during observation of actions is dependent both on the nature of the required executive processing and the type of the extrinsic properties of the action presented.

Anatomical variability in the cortical representation of first and second language

Abstract: Functional magnetic resonance imaging was used to assess inter-subject variability in the cortical representation of language comprehension processes. Moderately fluent French-English bilinguals were scanned while they listened to stories in their first language (L1 = French) or in a second language (L2 = English) acquired at school after the age of seven. In all subjects, listening to L1 always activated a similar set of areas in the left temporal lobe, clustered along the left superior temporal sulcus. Listening to L2, however, activated a highly variable network of left and right temporal and frontal areas, sometimes restricted only to right-hemispheric regions. These results support the hypothesis that first language acquisition relies on a dedicated left-hemispheric cerebral network, while late second language acquisition is not necessarily associated with a reproducible biological substrate. The postulated contribution of the right hemisphere to L2 comprehension is found to hold only on average, individual subjects varying from complete right lateralization to standard left lateralization for L2.

Functional heterogeneity of left inferior frontal cortex as revealed by fMRI.

Abstract: USING functional magnetic resonance imaging (fMRI), we mapped brain activity in six normal volunteers during two silent verbal fluency tasks, one with a phonemic (letter) cue and one with a semantic (category) cue. In comparison with resting state, both tasks activated the anterior triangular portion of the left inferior frontal gyrus (IFG or F3, for third frontal gyrus) and the left thalamus. There were also areas activated in one task but not in the other: the posterior opercular portion of the left IFG for phonemic fluency, and the left retrosplenial region for semantic fluency. Our findings concur with normal psychophysical data and neuropsychological observations to suggest the recruitment of two overlapping but dissociable systems for the two tasks, and demonstrate functional heterogeneity within the left 1FG (Broca's area), where the opercular portion is responsible for obtaining access to words through a phonemic/articulatory route.

Neural control of fast-regular saccades and antisaccades: an investigation using positron emission tomography

Abstract: Regional cerebral blood flow changes related to the performance of two oculomotor tasks and a central fixation task were compared in ten healthy human subjects. The tasks were: (a) performance of fast-regular saccades; (b) performance of voluntary antisaccades away from a peripheral cue; (c) passive maintenance of central visual fixation in the presence of irrelevant peripheral stimulation. The saccadic task was associated with a relative increase in activity in a number of occipitotemporal areas. Compared with both the fixation and the saccadic task, the performance of antisaccades activated a set of areas including: the superior and inferior parietal lobules, the precentral and prefrontal cortex, the cingulate cortex, and the supplementary motor area. The results of the present study suggest that: (a) compared with self-determined saccadic responses the performance of fast regular, reflexive saccades produces a limited activation of the frontal eye fields; (b) in the antisaccadic task the inferior parietal lobes subserve operations of sensory-motor integration dealing with attentional disengagement from the initial peripheral cue (appearing at an invalid spatial location) and with the recomputation of the antisaccadic vector on the basis of the wrong (e.g., spatially opposite) information provided by the same cue.

Cerebral metabolism in fatal familial insomnia: Relation to duration, neuropathology, and distribution of protease-resistent prion protein

Abstract: We used [ 18 F]-2-fluoro-2-deoxy-D-glucose (FDG) and PET to study regional cerebral glucose utilization in seven patients with fatal familial insomnia (FFI), an inherited prion disease with a mutation at codon 178 of the prion protein gene. Four patients were methionine/methionine homozygotes at codon 129 (symptom duration, 8.5 ± 1 months) and three were methionine/valine (MET/VAL 129 ) heterozygotes (symptom duration, 35± 11 months). A severely reduced glucose utilization of the thalamus and a mild hypometabolism of the cingulate cortex were found in all FFI patients. In six subjects the brain hypometabolism also affected the basal and lateral frontal cortex, the caudate nucleus, and the middle and inferior temporal cortex. Comparison between homozygous or heterozygous patients at codon 129 showed that the hypometabolism was more widespread in the MET/VAL 129 group, which had a significantly longer symptom duration at the time of [ 18 F] FDG PET study. Comparison between neuropathologic and [ 18 F] FDG PET findings in six patients showed that areas with neuronal loss were also hypometabolic. However, cerebral hypometabolism was more widespread than the histopathologic changes and significantly correlated with the presence of protease-resistent prion protein (PrP res ). Our findings indicate that hypometabolism of the thalamus and cingulate cortex is the hallmark of FFI, while the involvement of other brain regions depends on the duration of symptoms and some unknown factors specific to each patient. The present data also support the notion that PrP res formation is the cause of neuronal dysfunction in prion diseases.

Agrammatic speech production after a right cerebellar haemorrhage

Abstract: We report the case of a patient who developed a severe expressive agrammatic disorder, mainly characterized by the omission of function words, after a haemorrhagic stroke involving the right cerebellar hemisphere. A detailed analysis of syntactic and morphological abilities confirmed that the disorder was limited to spontaneous production, and was much less evident in recitation of well known dramatic pieces (the patient was a professional actor). The speech disorder recovered in about 2 months. The presence of crossed frontal diaschisis on a SPECT scan performed in the acute stage and its regression after recovery suggest that interference within a complex cerebellar basal ganglia-frontal cortex loop may be responsible for this unusual speech disorder.

PET study in subjects from two Italian FAD families with APP717 Val to Ileu mutation

Abstract: Cerebral glucose metabolism was investigated with 2-[18F]-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in seven members belonging to two Italian families with familial Alzheimer's disease (FAD) and APP717 Val to Ileu mutation. The aim of the study was to identify the pattern of cerebral hypometabolism in the affected patients and the possible occurrence of brain metabolic changes in the APP mutated subjects. The two patients with FAD, when compared with normal age matched controls, showed a severe bilateral hypometabolism in parietal and temporal regions, as well as in the prefrontal areas, which were more affected on the left side. Subcortical thalamic structures were also involved in one patient. In a comparison with a group of patients with sporadic AD, the most affected cerebral areas in the FAD patients were the prefrontal regions and the thalamus, bilaterally. One of the four mutated subjects, with an age close to the family age of disease onset, in a comparison with normals, showed metabolic reductions in the right thalamus, in the left dorsolateral frontal cortex and, bilaterally, in the frontal orbital regions. This regional brain hypometabolism was present in a preclinical phase, 1 year before the onset of dementia. In the three younger subjects carrying the mutation, a metabolic reduction was detected in the thalamus, bilaterally. These results demonstrate that a pattern of cerebral hypometabolism involving cortical and subcortical structures is present in FAD patients with APP717 Val to Ileu mutation. Cerebral hypometabolism may occur in pre-symptomatic and young asymptomatic APP717 mutated FAD subjects and it can be detected by a highly sensitive procedure such as PET.