202 research outputs found
Relevance of Spectral Cues for Auditory Spatial Processing in the Occipital Cortex of the Blind
We have previously shown that some blind individuals can localize sounds more accurately than their sighted counterparts when one ear is obstructed, and that this ability is strongly associated with occipital cortex activity. Given that spectral cues are important for monaurally localizing sounds when one ear is obstructed, and that blind individuals are more sensitive to small spectral differences, we hypothesized that enhanced use of spectral cues via occipital cortex mechanisms could explain the better performance of blind individuals in monaural localization. Using positron-emission tomography (PET), we scanned blind and sighted persons as they discriminated between sounds originating from a single spatial position, but with different spectral profiles that simulated different spatial positions based on head-related transfer functions. We show here that a sub-group of early blind individuals showing superior monaural sound localization abilities performed significantly better than any other group on this spectral discrimination task. For all groups, performance was best for stimuli simulating peripheral positions, consistent with the notion that spectral cues are more helpful for discriminating peripheral sources. PET results showed that all blind groups showed cerebral blood flow increases in the occipital cortex; but this was also the case in the sighted group. A voxel-wise covariation analysis showed that more occipital recruitment was associated with better performance across all blind subjects but not the sighted. An inter-regional covariation analysis showed that the occipital activity in the blind covaried with that of several frontal and parietal regions known for their role in auditory spatial processing. Overall, these results support the notion that the superior ability of a sub-group of early-blind individuals to localize sounds is mediated by their superior ability to use spectral cues, and that this ability is subserved by cortical processing in the occipital cortex
Influence of the segmentation on the characterization of cerebral networks of structural damage for patients with disorders of consciousness
Disorders of consciousness (DOC) are a consequence of a variety of severe brain injuries. DOC commonly results in anatomical brain modifications, which can affect cortical and sub-cortical brain structures. Postmortem studies suggest that severity of brain damage correlates with level of impairment in DOC. In-vivo studies in neuroimaging mainly focus in alterations on single structures. Recent evidence suggests that rather than one, multiple brain regions can be simultaneously affected by this condition. In other words, DOC may be linked to an underlying cerebral network of structural damage. Recently, geometrical spatial relationships among key sub-cortical brain regions, such as left and right thalamus and brain stem, have been used for the characterization of this network. This approach is strongly supported on automatic segmentation processes, which aim to extract regions of interests without human intervention. Nevertheless, patients with DOC usually present massive structural brain changes. Therefore, segmentation methods may highly influence the characterization of the underlying cerebral network structure. In this work, we evaluate the level of characterization obtained by using the spatial relationships as descriptor of a sub-cortical cerebral network (left and right thalamus) in patients with DOC, when different segmentation approaches are used (FSL, Free-surfer and manual segmentation). Our results suggest that segmentation process may play a critical role for the construction of robust and reliable structural characterization of DOC conditions
Early Brain-Body Impact of Emotional Arousal
Current research in affective neuroscience suggests that the emotional content of visual stimuli activates brainâbody responses that could be critical to general health and physical disease. The aim of this study was to develop an integrated neurophysiological approach linking central and peripheral markers of nervous activity during the presentation of natural scenes in order to determine the temporal stages of brain processing related to the bodily impact of emotions. More specifically, whole head magnetoencephalogram (MEG) data and skin conductance response (SCR), a reliable autonomic marker of central activation, were recorded in healthy volunteers during the presentation of emotional (unpleasant and pleasant) and neutral pictures selected from the International Affective Picture System (IAPS). Analyses of event-related magnetic fields (ERFs) revealed greater activity at 180âms in an occipitotemporal component for emotional pictures than for neutral counterparts. More importantly, these early effects of emotional arousal on cerebral activity were significantly correlated with later increases in SCR magnitude. For the first time, a neuromagnetic cortical component linked to a well-documented marker of bodily arousal expression of emotion, namely, the SCR, was identified and located. This finding sheds light on the time course of the brainâbody interaction with emotional arousal and provides new insights into the neural bases of complex and reciprocal mindâbody links
Comprehension of concrete and abstract words in patients with selective anterior temporal lobe resection and in patients with selective amygdalo-hippocampectomy
The role of the anterior temporal lobe (ATL) in semantic memory is now firmly established.
There is still controversy, however, regarding the specific role of this region in processing
various types of concepts. There have been reports of patients suffering from semantic
dementia (SD), a neurodegenerative condition in which the ATL are damaged bilaterally, who
present with greater semantic impairment for concrete concepts than for abstract concepts, an
effect known as reversal of the concreteness effect. This effect has previously been interpreted
as reflecting degraded visual-perceptual features of objects due to damage to the inferior
temporal lobes such as is observed in SD. Temporal lobe atrophy in SD, however, is bilateral
even if it usually predominates to the left ATL, and it has been found to extend beyond the
ATL, throughout the temporal lobes including medial and posterior temporal lobe regions.
The question therefore remains whether greater impairment for concrete concepts results from
damage to the ATL or from damage to the visual association cortex, and if unilateral damage
can produce such a deficit.
The aim of the present study was to investigate the processing of concrete and abstract
words in rare patients who underwent a selective ATL surgical resection, and to compare their
performance with that of patients with selective medial temporal lobe damage sparing the
ATL region. Seven patients with a selective unilateral anterior temporal resection (ATL), 15
patients with a selective unilateral amygdalo-hippocampectomy (SeAH), and 15 healthy ageand education-matched controls underwent detailed neuropsychological assessment and
carried out a semantic similarity judgement task evaluating their comprehension of concrete
and abstract words. Results showed that both ATL and SeAH groups were significantly
impaired on the semantic task relative to the control group. Within the patient groups,
however, comprehension of concrete words was significantly more impaired than that of
abstract words in the ATL group, while comprehension of abstract and concrete words was equally affected in the SeAH group. Results of this study suggest that the ATL region may
play a critical role in processing concrete concepts, and that the reversal of the concreteness
effect observed in ATL patients may result from damage to a categorical organization
underlying the representation of concrete concepts
Des connections du cerveau qui se redessinent
Affiche prĂ©sentĂ©e dans le cadre du Colloque de l'ARC, «Pour que la formation de la relĂšve scientifique soit sur toutes les lĂšvres», dans le cadre du 87e CongrĂšs de l'Acfas, UniversitĂ© du QuĂ©bec en Outaouais (UQO), Gatineau, le 28 mai 2019.Quand un sens est inopĂ©rant de façon prolongĂ©e en raison dâune pathologie, la section du cerveau qui lui serait normalement dĂ©diĂ©e est plutĂŽt utilisĂ©e pour traiter les stimuli provenant dâautres sens. Ceci donne probablement lieu Ă une rĂ©organisation des connections complexes entre les structures du cerveau. Câest ce que nous cherchons Ă mettre en Ă©vidence. Nous comparons Ă cette fin la connectivitĂ© structurelle de cerveaux sourds Ă celle de cerveaux percevant les stimuli auditifs, en particulier lĂ oĂč il y a traitement auditif, langagier, somatosensoriel et visuel. Pour ce faire, nous avons analysĂ© les images de diffusion en rĂ©sonance magnĂ©tique (DW-IRM) de deux groupes : 17 personnes non entendantes et 17 personnes entendantes. Nous avons dâabord appliquĂ© une mĂ©thode standard qui consiste Ă comparer lâanisotropie fractionnelle (AF) des fibres principales des deux groupes. Une AF de 0 indique un milieu de diffusion isotrope alors quâune AF prĂšs de 1 indique un milieu oĂč la diffusion est restreinte Ă une dimension. Nous avons obtenu des rĂ©sultats prĂ©liminaires prometteurs, mais insuffisants pour indiquer une diffĂ©rence significative entre les deux groupes. Nous avons donc poussĂ© plus loin et tracĂ© le trajet des fibres reliant des structures cĂ©rĂ©brales clĂ©s en utilisant des outils plus sophistiquĂ©s. Nous appliquons maintenant des mĂ©thodes statistiques puissantes pouvant dĂ©tecter des diffĂ©rences subtiles de connectivitĂ© entre nos deux groupes cibles
Early childhood development of visual texture segregation in full-term and preterm children
AbstractTo date, very little is known about the normal development trajectory of visual texture segregation, or how it is affected by preterm birth. The goal of this study was to characterize the development of visual texture segregation using texture segregation visual evoked potentials (tsVEPs) in children born full-term and children born preterm without major neurological impairment. Forty-five full-term and 43 preterm children were tested at either 12, 24 or 36months of age (corrected age for prematurity at 12 and 24months old). VEPs were obtained using two lower-level stimuli defined by orientation (oriVEP) and two higher-level stimuli defined by texture (texVEP). TsVEP was obtained by dividing by two the subtraction of oriVEP from texVEP. Results show a clear maturation of the processes underlying visual texture segregation in the full-term group, with a significant N2 latency reduction between 12 and 36months of age for all conditions. Significant N2 amplitude reduction was observed for oriVEP between 12 and 24months, as well as for texVEP between 12 and 24months, and 12 and 36months. Comparison between full-term and preterm children indicated significantly lower N2 amplitude for the preterm group at 12months for oriVEP and texVEP. These differences were no longer apparent at 24months of age, suggesting that children born preterm catch up with their full-term counterparts somewhere between 12 and 24months of age. Our results appear to reflect a maturational delay in preterm children in both lower-level and higher-level visual processing during, at least, early childhood
Clinical effectiveness of different natalizumab interval dosing schedules in a large Italian population of patients with multiple sclerosis
Introduction Natalizumab (NTZ) is one of the most
effective treatment options for multiple sclerosis (MS)
treatment. Our study aimed to evaluate the effectiveness
of NTZ when administered according to the extended
dosing strategy compared with standard 4-weekly
administration in a large Italian MS population.
Materials and methods This retrospective multicentre
study included patients with relapsing-remitting
MS
(RR-MS)
who received NTZ administrations between the
1 June 2012 and the 15 May 2018 and were followed
by the âItalian MS Registerâ. All patients with MS were
stratified into two groups based on NTZ administration
schedule: standard interval dosing (SID) patients who
received infusions on average from 28 to 32 days
(median 30) and extended interval dosing (EID) including
patients who have been infused with interval between
33 and 49 days (median 43). Clinical data were assessed
at baseline (before starting NTZ), after 12 (T1) and 24
months (T2) of treatment.
Results Out of 5231 patients with RR-MS
screened,
2092 (mean age 43.2±12.0, 60.6% women) were
enrolled. A total of 1254 (59.9%) received NTZ
according to SID, and 838 (40.1%) according to EID. At
12 and 24 months, no differences in terms of annualised
relapse rate and disability status were found between the
two groups. Progression index and confirmed disability
worsening were similar between the two groups.
Discussion The use of NTZ with an extended interval
schedule showed similar effectiveness compared with
SID. Unchanged clinical efficacy of EID schedule may
raise the question of a possible advantage in terms of
tolerability and safety
Progression independent of relapse activity in relapsing multiple sclerosis: impact and relationship with secondary progression
Objectives: We investigated the occurrence and relative contribution of relapse-associated worsening (RAW) and progression independent of relapse activity (PIRA) to confirmed disability accrual (CDA) and transition to secondary progression (SP) in relapsing multiple sclerosis (MS). Methods: Relapsing-onset MS patients with follow-up > / = 5 years (16,130) were extracted from the Italian MS Registry. CDA was a 6-month confirmed increase in Expanded Disability Status Scale (EDSS) score. Sustained disability accumulation (SDA) was a CDA with no EDSS improvement in all subsequent visits. Predictors of PIRA and RAW and the association between final EDSS score and type of CDA were assessed using logistic multivariable regression and multivariable ordinal regression models, respectively. Results: Over 11.8 ± 5.4 years, 16,731 CDA events occurred in 8998 (55.8%) patients. PIRA (12,175) accounted for 72.3% of CDA. SDA occurred in 8912 (73.2%) PIRA and 2583 (56.7%) RAW (p < 0.001). 4453 (27.6%) patients transitioned to SPMS, 4010 (73.2%) out of 5476 patients with sustained PIRA and 443 (24.8%) out of 1790 patients with non-sustained PIRA. In the multivariable ordinal regression analysis, higher final EDSS score was associated with PIRA (estimated coefficient 0.349, 95% CI 0.120-0.577, p = 0.003). Discussion: In this real-world relapsing-onset MS cohort, PIRA was the main driver of disability accumulation and was associated with higher disability in the long term. Sustained PIRA was linked to transition to SP and could represent a more accurate PIRA definition and a criterion to mark the putative onset of the progressive phase
Risk of Getting COVID-19 in People With Multiple Sclerosis
Background and Objectives
Several studies have assessed risk factors associated with the severity of COVID-19 outcomes in
people with multiple sclerosis (PwMS). The potential role of disease-modifying therapies
(DMTs) and demographic and clinical factors on the risk of acquiring SARS-CoV-2 infection
has not been evaluated so far. The objective of this study was to assess risk factors of contracting
SARS-CoV-2 infection in PwMS by using data collected in the Italian MS Register (IMSR).
Methods
Acase-control (1:2) studywas set up. Cases included PwMSwith a confirmed diagnosis ofCOVID-19,
and controls included PwMS without a confirmed diagnosis of COVID-19. Both groups were propensity
scoreâmatched by the date of COVID-19 diagnosis, the date of last visit, and the region of
residence. No healthy controls were included in this study. COVID-19 risk was estimated by multivariable
logistic regression models including demographic and clinical covariates. The impact of DMTs
was assessed in 3 independent logistic regression models including one of the following covariates: last
administeredDMT, previousDMTsequences, or the place where the last treatment was administered.
Results
A total of 779 PwMS with confirmed COVID-19 (cases) were matched to 1,558 PwMS without
COVID-19 (controls). In all 3 models, comorbidities, female sex, and a younger age were significantly
associated (p < 0.02)with a higher risk of contractingCOVID-19. Patients receiving natalizumab as last
DMT(OR[95%CI]: 2.38 [1.66â3.42], p < 0.0001) and those who underwent an escalation treatment
strategy (1.57 [1.16â2.13], p = 0.003) were at significantly higher COVID-19 risk. Moreover, PwMS receiving their last DMT requiring
hospital access (1.65 [1.34â2.04], p < 0.0001) showed a significant higher risk than those taking self-administered DMTs at home.
Discussion
This case-control study embedded in the IMSR showed that PwMS at higher COVID-19 risk are younger, more frequently
female individuals, and with comorbidities. Long-lasting escalation approach and last therapies that expose patients to the
hospital environment seem to significantly increase the risk of SARS-CoV2 infection in PwMS.
Classification of Evidence
This study provides Class III evidence that among patients with MS, younger age, being female individuals, having more
comorbidities, receiving natalizumab, undergoing an escalating treatment strategy, or receiving treatment at a hospital were
associated with being infected with COVID-19. Among patients with MS who were infected with COVID-19, a severe course
was associated with increasing age and having a progressive form of MS, whereas not being on treatment or receiving an
interferon beta agent was protective
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