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1.
Invest Ophthalmol Vis Sci ; 64(13): 23, 2023 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-37847226

RESUMO

Purpose: Achromatopsia is a rare inherited disorder rendering retinal cone photoreceptors nonfunctional. As a consequence, the sizable foveal representation in the visual cortex is congenitally deprived of visual input, which prompts a fundamental question: is the cortical representation of the central visual field in patients with achromatopsia remapped to take up processing of paracentral inputs? Such remapping might interfere with gene therapeutic treatments aimed at restoring cone function. Methods: We conducted a multicenter study to explore the nature and plasticity of vision in the absence of functional cones in a cohort of 17 individuals affected by autosomal recessive achromatopsia and confirmed biallelic disease-causing CNGA3 or CNGB3 mutations. Specifically, we tested the hypothesis of foveal remapping in human achromatopsia. For this purpose, we applied two independent functional magnetic resonance imaging (fMRI)-based mapping approaches, i.e. conventional phase-encoded eccentricity and population receptive field mapping, to separate data sets. Results: Both fMRI approaches produced the same result in the group comparison of achromatopsia versus healthy controls: sizable remapping of the representation of the central visual field in the primary visual cortex was not apparent. Conclusions: Remapping of the cortical representation of the central visual field is not a general feature in achromatopsia. It is concluded that plasticity of the human primary visual cortex is less pronounced than previously assumed. A pretherapeutic imaging workup is proposed to optimize interventions.


Assuntos
Defeitos da Visão Cromática , Córtex Visual , Humanos , Células Fotorreceptoras Retinianas Cones/patologia , Canais de Cátion Regulados por Nucleotídeos Cíclicos/genética , Mutação
2.
World J Biol Psychiatry ; 24(1): 34-45, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-35332851

RESUMO

OBJECTIVES: Major Depression (MDD) and anxiety disorders are stress-related disorders that share pathophysiological mechanisms. There is evidence for alterations of glutamate-glutamine, N-acetylaspartate (NAA) and GABA in the anterior cingulate cortex (ACC), a stress-sensitive region affected by hypothalamic-pituitary-adrenal axis (HPA). The aim was to investigate metabolic alterations in the ACC and whether hair cortisol, current stress or early life adversity predict them. METHODS: We investigated 22 patients with MDD and comorbid anxiety disorder and 23 healthy controls. Proton magnetic resonance spectroscopy was performed with voxels placed in pregenual (pg) and dorsal (d) ACC in 3 T. Analysis of hair cortisol was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: The N-acetylaspartate/Creatin ratio (NAA/Cr) was reduced in patients in both pgACC (p = .040) and dACC (p = .016). A significant interactive effect of diagnosis and cortisol on both pg-NAA/Cr (F = 5.00, p = .033) and d-NAA/Cr (F = 7.86, p = .009) was detected, whereby in controls cortisol was positively correlated with d-NAA/Cr (r = 0.61, p = .004). CONCLUSIONS: Our results suggest a relationship between NAA metabolism in ACC and HPA axis activity as represented by long-term cortisol output.


Assuntos
Transtorno Depressivo Maior , Hidrocortisona , Humanos , Hidrocortisona/metabolismo , Sistema Hipotálamo-Hipofisário/metabolismo , Giro do Cíngulo/metabolismo , Cromatografia Líquida , Depressão , Sistema Hipófise-Suprarrenal/metabolismo , Espectrometria de Massas em Tandem , Transtorno Depressivo Maior/metabolismo , Ansiedade , Ácido Aspártico/metabolismo , Transtornos de Ansiedade
3.
Neuroimage Clin ; 33: 102925, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34959047

RESUMO

Autosomal recessive Achromatopsia (ACHM) is a rare inherited disorder associated with dysfunctional cone photoreceptors resulting in a congenital absence of cone input to visual cortex. This might lead to distinct changes in cortical architecture with a negative impact on the success of gene augmentation therapies. To investigate the status of the visual cortex in these patients, we performed a multi-centre study focusing on the cortical structure of regions that normally receive predominantly cone input. Using high-resolution T1-weighted MRI scans and surface-based morphometry, we compared cortical thickness, surface area and grey matter volume in foveal, parafoveal and paracentral representations of primary visual cortex in 15 individuals with ACHM and 42 normally sighted, healthy controls (HC). In ACHM, surface area was reduced in all tested representations, while thickening of the cortex was found highly localized to the most central representation. These results were comparable to more widespread changes in brain structure reported in congenitally blind individuals, suggesting similar developmental processes, i.e., irrespective of the underlying cause and extent of vision loss. The cortical differences we report here could limit the success of treatment of ACHM in adulthood. Interventions earlier in life when cortical structure is not different from normal would likely offer better visual outcomes for those with ACHM.


Assuntos
Defeitos da Visão Cromática , Córtex Visual , Adulto , Defeitos da Visão Cromática/congênito , Defeitos da Visão Cromática/diagnóstico por imagem , Defeitos da Visão Cromática/genética , Fóvea Central , Humanos , Córtex Visual Primário , Células Fotorreceptoras Retinianas Cones , Córtex Visual/diagnóstico por imagem
4.
Front Neurosci ; 15: 718958, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34720857

RESUMO

Most individuals with congenital achromatopsia (ACHM) carry mutations that affect the retinal phototransduction pathway of cone photoreceptors, fundamental to both high acuity vision and colour perception. As the central fovea is occupied solely by cones, achromats have an absence of retinal input to the visual cortex and a small central area of blindness. Additionally, those with complete ACHM have no colour perception, and colour processing regions of the ventral cortex also lack typical chromatic signals from the cones. This study examined the cortical morphology (grey matter volume, cortical thickness, and cortical surface area) of multiple visual cortical regions in ACHM (n = 15) compared to normally sighted controls (n = 42) to determine the cortical changes that are associated with the retinal characteristics of ACHM. Surface-based morphometry was applied to T1-weighted MRI in atlas-defined early, ventral and dorsal visual regions of interest. Reduced grey matter volume in V1, V2, V3, and V4 was found in ACHM compared to controls, driven by a reduction in cortical surface area as there was no significant reduction in cortical thickness. Cortical surface area (but not thickness) was reduced in a wide range of areas (V1, V2, V3, TO1, V4, and LO1). Reduction in early visual areas with large foveal representations (V1, V2, and V3) suggests that the lack of foveal input to the visual cortex was a major driving factor in morphological changes in ACHM. However, the significant reduction in ventral area V4 coupled with the lack of difference in dorsal areas V3a and V3b suggest that deprivation of chromatic signals to visual cortex in ACHM may also contribute to changes in cortical morphology. This research shows that the congenital lack of cone input to the visual cortex can lead to widespread structural changes across multiple visual areas.

5.
Neuroimage ; 222: 117250, 2020 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-32798683

RESUMO

Previous studies demonstrated that alterations in functional MRI derived receptive field (pRF) properties in cortical projection zones of retinal lesions can erroneously be mistaken for cortical large-scale reorganization in response to visual system pathologies. We tested, whether such confounds are also evident in the normal cortical projection zone of the fovea for simulated peripheral visual field defects. We applied fMRI-based visual field mapping of the central visual field at 3 T in eight controls to compare the pRF properties of the central visual field of a reference condition (stimulus radius: 14°) and two conditions with simulated peripheral visual field defect, i.e., with a peripheral gray mask, stimulating only the central 7° or 4° radius. We quantified, for the cortical representation of the actually stimulated visual field, the changes in the position and size of the pRFs associated with reduced peripheral stimulation using conventional and advanced pRF modeling. We found foveal pRF-positions (≤3°) to be significantly shifted towards the periphery (p<0.05, corrected). These pRF-shifts were largest for the 4° condition [visual area (mean eccentricity shift): V1 (0.9°), V2 (0.9°), V3 (1.0°)], but also evident for the 7° condition [V1 (0.5°), V2 (0.5°), V3 (0.9°)]. Further, an overall enlargement of pRF-sizes was observed. These findings indicate the dependence of foveal pRF parameters on the spatial extent of the stimulated visual field and are likely associated with methodological biases and/or physiological mechanisms. Consequently, our results imply that, previously reported similar findings in patients with actual peripheral scotomas need to be interpreted with caution and indicate the need for adequate control conditions in investigations of visual cortex reorganization.


Assuntos
Escotoma/fisiopatologia , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Vias Visuais/fisiologia , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Estimulação Luminosa/métodos , Adulto Jovem
6.
Neuroimage ; 202: 116105, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31422172

RESUMO

In albinism, the pathological decussation of the temporal retinal afferents at the optic chiasm leads to superimposed representations of opposing hemifields in the visual cortex. Here, we assessed the equivalence of the two representations and the cortico-cortical connectivity of the early visual areas. Applying fMRI-based population receptive field (pRF)-mapping (both hemifield and bilateral mapping) and connective field (CF)-modeling, we investigated the early visual cortex in 6 albinotic participants and 4 controls. In albinism, superimposed retinotopic representations of the contra- and ipsilateral visual hemifield were observed on the hemisphere contralateral to the stimulated eye. This was confirmed by the observation of bilateral pRFs during bilateral mapping. Hemifield mapping revealed similar pRF-sizes for both hemifield representations throughout V1 to V3. The typical increase of V1-sampling extent for V3 compared to V2 was not found for the albinotic participants. The similarity of the pRF-sizes for opposing visual hemifield representations highlights the equivalence of the two maps in the early visual cortex. The altered V1-sampling extent in V3 might indicate the adaptation of cortico-cortical connections to visual pathway abnormalities in albinism. These findings thus suggest that conservative developmental mechanisms are complemented by alterations of the extrastriate cortico-cortical connectivity.


Assuntos
Albinismo/fisiopatologia , Córtex Visual/fisiopatologia , Vias Visuais/fisiopatologia , Adolescente , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
7.
Alzheimers Dement (Amst) ; 11: 281-285, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30976648

RESUMO

INTRODUCTION: This study aimed to assess how interindividual differences in locus coeruleus (LC) magnetic resonance imaging (MRI) contrast relate to cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD). METHODS: LC MRI contrast was quantified in 73 individuals from the DZNE Longitudinal Cognitive Impairment and Dementia Study (DELCODE) study comprising 25 healthy elderly adults and 21 individuals with subjective cognitive decline, 16 with mild cognitive impairment, and 11 participants with AD dementia using 3D T1-weighted fast low-angle shot (FLASH) imaging (0.75 mm isotropic resolution). Bootstrapped Pearson's correlations between LC contrast, CSF amyloid, and tau were performed in 44 individuals with CSF biomarker status. RESULTS: A significant regional decrease in LC MRI contrast was observed in patients with AD dementia but not mild cognitive impairment and subjective cognitive decline compared with healthy controls. A negative association between LC MRI contrast and levels of CSF amyloid but not with CSF tau was found. DISCUSSION: These results provide first evidence for a direct association between LC MRI contrast using in vivo T1-weighted FLASH imaging and AD pathology.

8.
J Neurosci ; 38(30): 6779-6786, 2018 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-29954849

RESUMO

Alterations in motivated behavior are a hallmark of attention-deficit/hyperactivity disorder (ADHD), one of the most common psychiatric disorders in children and adolescents. The orbitofrontal cortex (OFC) plays a key role in controlling goal-directed behavior, but the link between OFC dysfunction and behavioral deficits in ADHD, particularly in adolescence, remains poorly understood. Here we used advanced high-resolution functional magnetic resonance imaging (fMRI) of the human OFC in adolescents with ADHD and typically developing (TD) controls (N = 39, age 12-16, all male except for one female per group) to study reward-related OFC responses and how they relate to behavioral dysfunction in ADHD. During fMRI data acquisition, participants performed a simple decision-making task, allowing us to image expectation-related responses to small and large monetary outcomes. Across all participants, we observed significant signal increases to large versus small expected rewards in the OFC. These responses were significantly enhanced in ADHD relative to TD participants. Moreover, stronger reward-related activity was correlated with individual differences in hyperactive/impulsive symptoms in the ADHD group, whereas high cognitive ability was associated with normalized OFC responses. These results provide evidence for the importance of OFC dysfunctions in the neuropathology of ADHD, highlighting the role of OFC-dependent goal-directed control mechanisms in this disorder.SIGNIFICANCE STATEMENT Attention-deficit/hyperactivity disorder (ADHD) is characterized by alterations in motivated behavior which can be understood as diminished goal-directed control. The orbitofrontal cortex (OFC) plays a key role in controlling goal-directed behavior, but its potential contribution to ADHD symptomatology remains poorly understood. Using high-resolution fMRI, we show that adolescent ADHD patients display enhanced OFC signaling of future rewards and that these increased reward-related responses are correlated with the severity of hyperactivity/impulsivity. These findings suggest that an inability to adequately evaluate future outcomes may translate into maladaptive behavior in ADHD patients. They also challenge the idea that dysfunctions in dopaminergic brain areas are the sole contributor to reward-related symptoms in ADHD and point to a central contribution of goal-directed control circuits in hyperactivity.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Adolescente , Encéfalo/fisiopatologia , Criança , Feminino , Humanos , Comportamento Impulsivo/fisiologia , Imageamento por Ressonância Magnética , Masculino , Motivação/fisiologia , Recompensa , Transdução de Sinais/fisiologia
9.
Proc Natl Acad Sci U S A ; 115(9): 2228-2233, 2018 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-29440429

RESUMO

The locus coeruleus (LC) is the principal origin of noradrenaline in the brain. LC integrity varies considerably across healthy older individuals, and is suggested to contribute to altered cognitive functions in aging. Here we test this hypothesis using an incidental memory task that is known to be susceptible to noradrenergic modulation. We used MRI neuromelanin (NM) imaging to assess LC structural integrity and pupillometry as a putative index of LC activation in both younger and older adults. We show that older adults with reduced structural LC integrity show poorer subsequent memory. This effect is more pronounced for emotionally negative events, in accord with a greater role for noradrenergic modulation in encoding salient or aversive events. In addition, we found that salient stimuli led to greater pupil diameters, consistent with increased LC activation during the encoding of such events. Our study presents novel evidence that a decrement in noradrenergic modulation impacts on specific components of cognition in healthy older adults. The findings provide a strong motivation for further investigation of the effects of altered LC integrity in pathological aging.


Assuntos
Envelhecimento/fisiologia , Locus Cerúleo/fisiologia , Memória , Adulto , Idoso , Idoso de 80 Anos ou mais , Humanos , Imageamento por Ressonância Magnética , Adulto Jovem
10.
Neuroimage ; 163: 150-159, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28943414

RESUMO

The locus coeruleus (LC), a major origin of noradrenergic projections in the central nervous system (CNS), may serve a critical role in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). As such, there is considerable interest to develop magnetic resonance imaging (MRI) techniques to assess the integrity of the LC in vivo. The high neuromelanin content of the LC serves as an endogenous contrast for MRI but existing protocols suffer from low spatial resolution along the rostrocaudal axis of the LC rendering it difficult to differentiate its integrity in caudal and rostral portions. This study presents a novel approach to investigate the human LC in vivo using T1-weighted Fast Low Angle Shot (FLASH) MRI at 3 T (T). Using high-resolution isotropic imaging to minimise the effect of low spatial resolution in the slice direction, this study aimed to characterise the rostrocaudal distribution of LC signal intensity attributed to neuromelanin from 25 young (22-30) and 57 older (61-80) adults. We found a significant age-related increase in maximum but not median signal intensity, indicating age-related differences were not homogenous. Instead, they were confined to the rostral third of the LC with relative sparing of the caudal portion. The findings presented demonstrate in vivo T1-weighted FLASH imaging may be used to characterise signal intensity changes across the entire rostrocaudal length of the LC (a corresponding standardised LC map is available for download), which may help to identify how the human LC is differentially affected in aging and neurodegenerative disease.


Assuntos
Envelhecimento/patologia , Mapeamento Encefálico/métodos , Locus Cerúleo/diagnóstico por imagem , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Locus Cerúleo/patologia , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
11.
Hum Brain Mapp ; 35(10): 5093-105, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24771411

RESUMO

Congenital malformations of the optic chiasm, such as enhanced and reduced crossing of the optic nerve fibers, are evident in albinism and achiasma, respectively. In early visual cortex the resulting additional visual input from the ipsilateral visual hemifield is superimposed onto the normal retinotopic representation of the contralateral visual field, which is likely due to conservative geniculo-striate projections. Counterintuitively, this organization in early visual cortex does not have profound consequences on visual function. Here we ask, whether higher stages of visual processing provide a correction to the abnormal representation allowing for largely normal perception. To this end we assessed the organization patterns of early and ventral visual cortex in five albinotic, one achiasmic, and five control participants. In albinism and achiasma the mirror-symmetrical superposition of the ipsilateral and contalateral visual fields was evident not only in early visual cortex, but also in the higher areas of the ventral processing stream. Specifically, in the visual areas VO1/2 and PHC1/2 no differences in the extent, the degree of superposition, and the magnitude of the responses were evident in comparison to the early visual areas. Consequently, the highly atypical organization of the primary visual cortex was propagated downstream to highly specialized processing stages in an undiminished and unchanged manner. This indicates largely unaltered cortico-cortical connections in both types of misrouting, i.e., enhanced and reduced crossing of the optic nerves. It is concluded that main aspects of visual function are preserved despite sizable representation abnormalities in the ventral visual processing stream.


Assuntos
Mapeamento Encefálico , Quiasma Óptico/patologia , Doenças do Nervo Óptico/patologia , Córtex Visual/patologia , Adulto , Análise de Variância , Feminino , Lateralidade Funcional/fisiologia , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Quiasma Óptico/irrigação sanguínea , Oxigênio/sangue , Estimulação Luminosa , Fatores de Tempo , Córtex Visual/irrigação sanguínea , Adulto Jovem
12.
Stereotact Funct Neurosurg ; 92(1): 25-30, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24216749

RESUMO

BACKGROUND: The thalamic anteroventral nucleus (AV) is a promising target structure for deep brain stimulation (DBS) in patients suffering from refractory epilepsy. Direct visualization of the AV would improve spatial accuracy in functional stereotactic neurosurgery for treatment of this disease. METHODS: On 3-tesla magnetic resonance imaging (MRI), acquisition parameters were adjusted for optimal demarcation of the AV in 1 healthy subject. Reliability of AV visualization was then evaluated in 5 healthy individuals and 3 patients with refractory epilepsy. RESULTS: In all individuals, an adjusted T1-weighted sequence allowed for demarcation of the AV. It was clearly distinguishable from hyperintense myelin-rich lamellae surrounding it ventrally and laterally and appeared hypo-intense compared to the adjacent thalamic nuclei. Image resolution and contrast facilitated direct stereotactic targeting of the AV prior to DBS surgery in all 3 patients. CONCLUSIONS: Direct targeting of the AV can be achieved, which has immediate implications for the accuracy of MRI-guided DBS in patients with refractory epilepsy.


Assuntos
Núcleos Anteriores do Tálamo/patologia , Estimulação Encefálica Profunda/métodos , Epilepsia/terapia , Imageamento por Ressonância Magnética/métodos , Adulto , Feminino , Humanos , Masculino , Procedimentos Neurocirúrgicos , Reprodutibilidade dos Testes , Técnicas Estereotáxicas
13.
Neuron ; 75(3): 393-401, 2012 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-22884323

RESUMO

The absence of the optic chiasm is an extraordinary and extreme abnormality in the nervous system. The abnormality produces highly atypical functional responses in the cortex, including overlapping hemifield representations and bilateral population receptive fields in both striate and extrastriate visual cortex. Even in the presence of these large functional abnormalities, the effect on visual perception and daily life is not easily detected. Here, we demonstrate that in two achiasmic humans the gross topography of the geniculostriate and occipital callosal connections remains largely unaltered. We conclude that visual function is preserved by reorganization of intracortical connections instead of large-scale reorganizations of the visual cortex. Thus, developmental mechanisms of local wiring within cortical maps compensate for the improper gross wiring to preserve function in human achiasma.


Assuntos
Quiasma Óptico/anormalidades , Vias Visuais/anatomia & histologia , Humanos , Imageamento por Ressonância Magnética , Plasticidade Neuronal
14.
Psychophysiology ; 49(2): 261-70, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22092224

RESUMO

Severe and chronic stress affects the hippocampus, especially during development. However, studies concerning structural alterations of the hippocampus yielded a rather inconsistent picture. Moreover, further anxiety-relevant brain regions, such as the insula, might be implicated in the pathophysiology of posttraumatic stress disorder (PTSD). We combined magnetic resonance (MR) volumetric and spectroscopic analyses of hippocampus and insula in highly traumatized refugees without a history of alcohol/substance abuse or other comorbid diseases. No PTSD-related difference was apparent in the volumes or neurometabolite levels of bilateral hippocampus or insula. However, an association between left hippocampal N-acetyl-aspartate (NAA) and adverse childhood experiences indicated a potential detrimental effect of the early environment on hippocampal integrity. Our results add to increasing evidence that PTSD-related, morphological alterations in the hippocampus are a consequence of early adversity or may result from other factors, such as extensive use of alcohol.


Assuntos
Córtex Cerebral/patologia , Hipocampo/patologia , Transtornos de Estresse Pós-Traumáticos/patologia , Estresse Psicológico/patologia , Adulto , Estudos de Casos e Controles , Humanos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Refugiados/psicologia
15.
Cereb Cortex ; 21(6): 1435-42, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21071619

RESUMO

Recent evidence indicates experience-dependent brain volume changes in humans, but the functional and histological nature of such changes is unknown. Here, we report that adult men performing a cognitively demanding spatial navigation task every other day over 4 months display increases in hippocampal N-acetylaspartate (NAA) as measured with magnetic resonance spectroscopy. Unlike measures of brain volume, changes in NAA are sensitive to metabolic and functional aspects of neural and glia tissue and unlikely to reflect changes in microvasculature. Training-induced changes in NAA were, however, absent in carriers of the Met substitution in the brain-derived neurotrophic factor (BDNF) gene, which is known to reduce activity-dependent secretion of BDNF. Among BDNF Val homozygotes, increases in NAA were strongly related to the degree of practice-related improvement in navigation performance and normalized to pretraining levels 4 months after the last training session. We conclude that changes in demands on spatial navigation can alter hippocampal NAA concentrations, confirming epidemiological studies suggesting that mental experience may have direct effects on neural integrity and cognitive performance. BDNF genotype moderates these plastic changes, in line with the contention that gene-context interactions shape the ontogeny of complex phenotypes.


Assuntos
Ácido Aspártico/análogos & derivados , Fator Neurotrófico Derivado do Encéfalo/genética , Hipocampo/metabolismo , Polimorfismo de Nucleotídeo Único/genética , Comportamento Espacial/fisiologia , Ensino/métodos , Valina/genética , Adulto , Análise de Variância , Ácido Aspártico/metabolismo , Mapeamento Encefálico , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Feminino , Lateralidade Funcional , Genótipo , Homozigoto , Humanos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Fatores Sexuais , Adulto Jovem
16.
Neuropsychologia ; 48(13): 3834-45, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20863844

RESUMO

Due to an abnormal projection of the temporal retina the albinotic primary visual cortex receives substantial input from the ipsilateral visual field. To test whether representation abnormalities are also evident in higher tier visual, and in motor and somatosensory cortices, brain activity was measured with fMRI in 14 subjects with albinism performing a visuo-motor task. During central fixation, a blue or red target embedded in a distractor array was presented for 250 ms in the left or right visual hemifield. After a delay, the subjects were prompted to indicate with left or right thumb button presses the target presence in the upper or lower hemifield. The fMRI responses were evaluated for different regions of interest concerned with visual, motor and somatosensory processing and compared to previously acquired data from 14 controls. The following results were obtained: (1) in albinism the hit rates in the visuo-motor task were indistinguishable from normal. (2) In area MT and the intraparietal sulcus there was an indication of abnormal lateralisation patterns. (3) Largely normal lateralisation patterns were evident in motor and somatosensory cortices. It is concluded that in human albinism, the abnormal visual field representation is made available for visuo-motor processing with a motor cortex that comprises an essentially normal lateralisation. Consequently, specific adaptations of the mechanisms mediating visuo-motor integration are required in albinism.


Assuntos
Albinismo/fisiopatologia , Córtex Motor/fisiopatologia , Córtex Visual/fisiopatologia , Vias Visuais/fisiopatologia , Adulto , Análise de Variância , Mapeamento Encefálico , Feminino , Fixação Ocular , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa , Desempenho Psicomotor/fisiologia , Campos Visuais
17.
Oper Neurosurg (Hagerstown) ; 66(suppl_1): ons-E121-ons-E123, 2010 03.
Artigo em Inglês | MEDLINE | ID: mdl-20173580

RESUMO

OBJECTIVE: To demonstrate that proton density weighted magnetic resonance imaging (MRI) at 3 T accomplishes delineation of the centre median (CM) complex from surrounding thalamic tissue and may improve targeting accuracy in stereotactic neurosurgery. METHODS: Five healthy subjects (1 man, 4 women; age range 22-35 years) underwent high-resolution MRI at 3 T with different imaging parameters in order to optimize the direct visualization of the CM. RESULTS: In healthy subjects, the CM complex of the thalamus can be reliably contrasted on axially oriented slices by means of proton density weighted turbo-spin-echo MRI. An in-plane resolution of at least 0.6 x 0.6 mm2 is crucial at a slice thickness between 2 and 3 mm. Effective suppression of head motion is essential. CONCLUSION: MRI-based delineation of the CM could have therapeutic potential to facilitate target determination for neuromodulation in stereotactic neurosurgery.


Assuntos
Mapeamento Encefálico/métodos , Núcleos Intralaminares do Tálamo/anatomia & histologia , Imageamento por Ressonância Magnética/métodos , Tálamo/anatomia & histologia , Adulto , Feminino , Humanos , Núcleos Intralaminares do Tálamo/cirurgia , Masculino , Neuronavegação/métodos , Cuidados Pré-Operatórios/métodos , Técnicas Estereotáxicas , Tálamo/cirurgia , Adulto Jovem
18.
J Neuroimaging ; 20(2): 148-156, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19453831

RESUMO

BACKGROUND AND PURPOSE: The goal of this study was to explore the structural correlates of functional language dominance by directly comparing the brain morphology of healthy subjects with left- and right-hemisphere language dominance. METHODS: Twenty participants were selected based on their language dominance from a cohort of subjects with known language lateralization. Structural differences between both groups were assessed by voxel-based morphometry, a technique that automatically identifies differences in the local gray matter volume between groups using high-resolution T1-weighted magnetic resonance images. RESULTS: The main findings can be summarized as follows: (1) Subjects with right-hemisphere language dominance had significantly larger gray matter volume in the right hippocampus than subjects with left-hemisphere language dominance. (2) Leftward structural asymmetries in the posterior superior temporal cortex, including the planum temporale (PT), were observed in both groups. CONCLUSIONS: Our study does not support the still prevalent view that asymmetries of the PT are related in a direct way to functional language lateralization. The structural differences found in the hippocampus underline the importance of the medial temporal lobe in the neural language network. They are discussed in the context of recent findings attributing a critical role of the hippocampus in the development of language lateralization.


Assuntos
Encéfalo/citologia , Encéfalo/fisiologia , Dominância Cerebral/fisiologia , Idioma , Imageamento por Ressonância Magnética/métodos , Neurônios/citologia , Neurônios/fisiologia , Adulto , Feminino , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estatística como Assunto
19.
Neuropsychologia ; 47(5): 1313-22, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19428395

RESUMO

PURPOSE: We assessed response and functional connectivity patterns of different parts of the visual and motor cortices during visuo-motor integration with particular focus on the intraparietal sulcus (IPS). METHODS: Brain activity was measured during a visuo-motor task in 14 subjects using event-related fMRI. During central fixation, a blue or red target embedded in an array of grey distractors was presented for 250 ms in either the left or right visual hemifield. After a delay, the subjects were prompted to press the upper or lower response button for targets in the upper and lower hemifield with the left or right thumb for blue and red targets, respectively. The fMRI responses were evaluated for different regions of interests (ROIs), and the functional connectivity of the IPS subregions with these ROIs was quantified. RESULTS: In an anterior IPS region and a region in the anterior premotor cortex, presumably the frontal eye fields (FEF), visually driven responses were dominant contralateral to both visual stimulus and effector. Thus, the anterior IPS combines, in contrast to the posterior IPS and the occipital cortex, response properties of cortex activated by visual input and by motor output. Further, functional connectivity with the motor areas was stronger for the anterior than for the posterior IPS regions. DISCUSSION: Anterior IPS and FEF appear to be of major relevance for relating visual and effector information during visuo-motor integration. Patient studies with the devised paradigm are expected to uncover the impact of pathophysiologies and plasticity on the observed cortical lateralisation patterns.


Assuntos
Lateralidade Funcional/fisiologia , Córtex Motor/fisiologia , Vias Neurais/fisiologia , Desempenho Psicomotor/fisiologia , Córtex Visual/fisiologia , Adulto , Mapeamento Encefálico , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Estimulação Luminosa
20.
Clin Neurophysiol ; 120(1): 108-16, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19071059

RESUMO

OBJECTIVE: fMRI-based retinotopic mapping data obtained at a magnetic field strength of 7T are evaluated and compared to 3T acquisitions. METHODS: With established techniques retinotopic mapping data were obtained in four subjects for 25 slices parallel to the calcarine sulcus at 7 and 3T for three voxel sizes (2.5(3), 1.4(3), and 1.1(3)mm(3)) and in two subjects for 49 slices at 7T for 2.5(3)mm(3) voxels. The data were projected to the flattened representation of T1 weighted images acquired at 3T. RESULTS: The obtained retinotopic maps allowed for the identification of visual areas in the occipito-parietal cortex. The mean coherence increased with magnetic field strength and with voxel size. At 7T, the occipital cortex could be sampled with high sensitivity in a short single session at high resolution. Alternatively, at lower resolution simultaneous mapping of a great expanse of occipito-parietal cortex was possible. CONCLUSION: Retinotopic mapping at 7T aids a detailed description of the visual areas. Here, recent findings of multiple stimulus-driven retinotopic maps along the intraparietal sulcus are supported. SIGNIFICANCE: Retinotopic mapping at 7T opens the possibility to detail our understanding of the cortical visual field representations in general and of their plasticity in visual system pathologies.


Assuntos
Mapeamento Encefálico , Retina/fisiologia , Córtex Visual/fisiologia , Adulto , Feminino , Lateralidade Funcional , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Masculino , Oxigênio/sangue , Reconhecimento Visual de Modelos , Estimulação Luminosa/métodos , Tempo de Reação , Córtex Visual/irrigação sanguínea , Campos Visuais , Vias Visuais/irrigação sanguínea , Vias Visuais/fisiologia , Adulto Jovem
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