1,721,139 research outputs found
Functional neuroanatomy of spatial perception, spatial processes and attention. In Handbook of Clinical Neuropsychology. (Oxford: Oxford University Press), pp. 697-723
No full textThe neural correlates of developmental dyslexia: a new meta-analysis of 48 neuroimaging studies
No full textOver the last two decades, developmental dyslexia has been the focus of much research using functional neuroimaging. A wide range of paradigms, tackling different neurocognitive domains, has been used to assess its neural correlates. The main trust of this work is that typical developmental dyslexics have dysfunction of the phonological and orthography to phonology conversion systems, normally housed in the left occipitotemporal cortex. It remains to be seen whether, besides this well replicated finding, there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories of dyslexia like, for example, the magnocellular one. To address this problem, we performed a meta-analysis based on an optimized hierarchical clustering algorithm (Cattinelli et al., 2012) which automatically grouped 1982 activation peaks, extracted from 48 neuroimaging studies (fMRI and PET), into clusters in which the activation peaks had minimized spatial variance. The data was based on the literature published up to December 2011 including experiments on reading but also on phonological awareness, motor control, visual motion perception and so forth.
The clustering analysis identified 82 clusters. The functional role of the clusters was assessed on the basis of statistical criteria. In particular, the binomial test was used to identify which clusters showed a specific activation effect for dyslexics rather than for controls.
The left inferior parietal lobule, the left middle temporal gyrus, the left fusiform gyrus and the left cerebellum showed a specific association with the normal control groups, not being active in the dyslexics; on the other hand early subdivisions of visual cortices, bilaterally, the left insula and the right opercular portion of the inferior frontal gyrus showed a specific association with the dyslexic subjects.
A qualitative analysis of each cluster was also performed to evaluate the distribution of the activations peaks in relation to the experimental task (e.g. reading, phonological awareness, motor learning, visual motion discrimination, etc.).
We found that the aforementioned difference in left fusiform gyrus was selectively due to a lack of commitment to reading in adult dyslexics while the same region showed occasional activation for more basic visual tasks. On the other hand, the specific activation of early visual cortices in dyslexics was associated with a variety of visual tasks with reading tasks playing a major role.
We conclude that the available literature demonstrates a specific lack of activation of the left occipitotemporal cortex in dyslexics that is specific for reading and for visuo-phonological tasks. The larger early occipital activations in dyslexics may represent a compensatory effort for the visual analysis of printed words in the absence of a higher-level visual-word form neural expertise.
References
Cattinelli I., Borghese A.N., Gallucci M., Paulesu E. (In Press) Reading the reading brain: a new meta-analysis of functional imaging data of reading. J. Neurolinguistic
The neural correlates of developmental dyslexia: a new meta-analysis of PET and fMRI activation studies
No full textINTRODUZIONE
Developmental dyslexia has been the focus of much functional anatomical research. The main trust of this work is that typical developmental dyslexics have a dysfunction of the phonological and orthography to phonology conversion systems, in which the left occipito-temporal cortex has a crucial role.
It remains to be seen whether there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories like, for example, the magnocellular/attentional or the motor/cerebellar ones, which postulate a more basic and anatomically distributed disorder in dyslexia.
METODO
We addressed this issue with a meta-analysis of all the imaging literature published until September 2013 using a combination of hierarchical clustering and activation likelihood estimates.
RISULTATI
The clustering analysis on 2360 peaks identified 193 clusters, 92 of which proved significant for spatial extent. Following binomial tests on the clusters, we found a normal-control specific (i.e. reduced involvement in dyslexics) left hemispheric network involving the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform region: these were specific for reading and the visual-to-phonology processes. There was also a more dorsal left fronto-parietal network: these clusters included peaks from tasks involving phonological manipulation, but also motoric or visuo-spatial perception/attention. No cluster was identified in area V5 for no task. No significant effects were found for cerebellar clusters either.
CONCLUSIONI
We conclude that the available literature demonstrates a specific lack of activation of the left occipitotemporal cortex in dyslexics that is specific for reading and reading-like behaviours and for visuo-phonological tasks. Additional deficits may be associated with dorsal fronto-parietal deficits
Central neural contribution to the perception of chest pain in cardiac syndrome X
No full textObjective: To investigate the central neural contribution to chest pain perception in cardiac syndrome X (angina-like pain, ECG changes during stress, angiographically normal coronary arteriogram). Subjects: Eight syndrome X patients and eight healthy volunteers. Methods: Dobutamine stress using echocordiography to assess myocardial function, and positron emission tomography to measure changes in regional cerebral blood flow, as an index of neuronal activity. Results: During similar doses of dobutamine, syndrome X patients and controls showed comparable regional cerebral blood flow changes in the hypothalamus, thalami, right orbito-frontal cortex, and anterior temporal poles, associated with the sensation of a fast or powerful heart beat. In patients, but not controls, the stress also generated severe chest pain associated with increased activity in the right anterior insula/frontal operculum junction. There were ischaemia-like ECG changes in the syndrome X patients, but no left ventricular dysfunction on echocardiography. Activation of the right insula during chest pain clearly distinguished the syndrome X patients from a group of patients with known coronary disease. Conclusions: Chest pain and ECG changes were not accompanied by demonstrable myocardial dysfunction in syndrome X patients, but altered central neural handling of afferent signals may contribute to the abnormal pain perception in these patients
Building the bodily self-awareness: Evidence for the convergence between interoceptive and exteroceptive information in a multilevel kernel density analysis study
No full textExteroceptive and interoceptive signals shape and sustain the bodily self-awareness. The existence of a set of brain areas, supporting the integration of information coming from the inside and the outside of the body in building the sense of bodily self-awareness has been postulated, yet the evidence remains limited, a matter of discussion never assessed quantitatively. With the aim of unrevealing where in the brain interoceptive and exteroceptive signals may converge, we performed a meta-analysis on imaging studies of the sense of body ownership, modulated by external visuotactile stimulation, and studies on interoception, which involves the self-awareness for internal bodily sensations. Using a multilevel kernel density analysis, we found that processing of stimuli of the two domains converges primarily in the supramarginal gyrus bilaterally. Furthermore, we found a right-lateralized set of areas, including the precentral and postcentral, and superior temporal gyri. We discuss these results and propose this set of areas as ideal candidates to match multiple body-related signals contributing to the creation of a multidimensional representation of the bodily self
A place for nouns and a place for verbs? A critical review of neurocognitive data on grammatical-class effects
No full textIt is generally held that noun processing is specifically sub‐served by temporal areas, while the neural underpinnings of verb processing are located in the frontal lobe. However, this view is now challenged by a significant body of evidence accumulated over the years. Moreover, the results obtained so far on the neural implementation of noun and verb processing appear to be quite inconsistent. The present review briefly describes and critically re‐considers the anatomo‐correlative, neuroimaging, MEG, TMS and cortical stimulation studies on nouns and verbs with the aim of assessing the consistency of their results, particularly within technique. The paper also addresses the question as to whether the inconsistency of the data could be due to the variety of the tasks used. However, it emerged that neither the different investigation techniques used nor the different cognitive tasks employed fully explain the variability of the data. In the final section we thus suggest that the main reason for the emergence of inconsistent data in this field is that the cerebral circuits underlying noun and verb processing are not spatially segregated, at least for the spatial resolution currently used in most neuroimaging studies
Reading the dyslexic brain: Multiple dysfunctional routes revealed by a new meta-analysis of PET and fMRI activation studies
No full textDevelopmental dyslexia has been the focus of much functional anatomical research. The main trust of this work is that typical developmental dyslexics have a dysfunction of the phonological and orthography to phonology conversion systems, in which the left occipito-temporal cortex has a crucial role. It remains to be seen whether there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories like, for example, the magnocellular/attentional or the motor/cerebellar ones, which postulate a more basic and anatomically distributed disorder in dyslexia. We addressed this issue with a meta-analysis of all the imaging literature published until September 2013 using a combination of hierarchical clustering and activation likelihood estimation methods. The clustering analysis on 2360 peaks identified 193 clusters, 92 of which proved spatially significant. Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.e., of reduced involvement in dyslexics) including the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform regions: these were preferentially associated with reading and the visual-to-phonology processes. There was also a more dorsal left fronto-parietal network: these clusters included peaks from tasks involving phonological manipulation, but also motoric or visuo-spatial perception/attention. No cluster was identified in area V5 for no task, nor cerebellar clusters showed a reduced association with dyslexics. We conclude that the examined literature demonstrates a specific lack of activation of the left occipito-temporal cortex in dyslexia particularly for reading and reading-like behaviors and for visuo-phonological tasks. Additional deficits of motor and attentional systems relevant for reading may be associated with altered functionality of dorsal left fronto-parietal corte
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