The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Oscar M Aguilar - One of the best experts on this subject based on the ideXlab platform.
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dorsal and ventral visual stream contributions to preserved reading ability in patients with central alexia
Cortex, 2018Co-Authors: Jt Crinion, Oscar M Aguilar, Sheila J Kerry, Martina F Callaghan, Zoe Woodhead, Alexander P LeffAbstract:We investigated the role of the left temporo-parietal regions in supporting reading abilities of 23 patients with central alexia (CA). For the behavioural data, we employed principal components analysis (PCA), which identified two components: 'reading aloud' and 'reading for meaning'. Voxel-based morphometry of the PCA results showed an association between reading aloud and grey matter density in the left supramarginal gyrus, part of the dorsal visual stream. By contrast, reading for meaning was associated with a large cluster in the left ventral visual stream, from the Collateral Sulcus to the anterior temporal pole. Most of the peaks were within the group lesion map, indicating that sparing of these areas results in better preservation of reading ability. However, one white matter (WM) cluster in the medial occipitotemporal lobe was outside the lesioned area. A post-hoc test demonstrated that WM density here was equivalent to controls, suggesting that this was not driven by lesion effects. The two likeliest explanations for this correlation are: 1) that pre-morbid, inter-individual differences in brain structure mitigate the effects of CA; 2) that post-morbid practice-based with reading caused compensatory plasticity. We hope to adjudicate between these explanations with longitudinal therapy data collected in this cohort.
Michael Petrides - One of the best experts on this subject based on the ideXlab platform.
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Local morphology informs location of activation during navigation within the parahippocampal region of the human brain
Brain Structure and Function, 2017Co-Authors: Sonja C Huntgeburth, J.-k. Chen, A. Ptito, Michael PetridesAbstract:The relationship between the local morphological features that define the entorhinal and parahippocampal cortex in the medial temporal region of the human brain and activation as measured during a navigation task with functional magnetic resonance imaging was examined individually in healthy participants. Two functional activation clusters were identified one within the caudal end of the Collateral Sulcus proper and the other in the parahippocampal extension of the Collateral Sulcus, clearly establishing the activation in the posterior parahippocampal cortex. A third activation cluster was identified where the anterior segment of the Collateral Sulcus proper gives way to the posterior segment, demonstrating also activation within the middle parahippocampal cortex. No activation was observed in the entorhinal cortex that lies medial to the rhinal Sulcus or in the anterior part of the parahippocampal cortex along the anterior branch of the Collateral Sulcus proper. The activations could also be clearly differentiated from the cortex of the fusiform and lingual gyri that lie laterally and posteriorly. These findings demonstrated specific activation in the middle and posterior part of the parahippocampal cortex when information necessary for navigation was retrieved from a previously established cognitive map and demonstrate that the sulci that comprise the Collateral sulcal complex represent important landmarks that can provide an accurate localization of activation foci along the parahippocampal cortex and allow identification of subdivisions involved in the processing of spatial information.
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morphological patterns of the Collateral Sulcus in the human brain
European Journal of Neuroscience, 2012Co-Authors: Michael Petrides, Sonja C HuntgeburthAbstract:The Collateral sulcal complex is an important landmark on the medial surface of the temporal lobe. Anteriorly, it delineates the limbic regions of the parahippocampal gyrus from the visual-processing areas of the fusiform gyrus. Posteriorly, it continues into the occipital lobe, bearing no relationship to the memory-related limbic regions. Given the considerable extent of the Sulcus and functional heterogeneity of the surrounding cortex, an investigation of the morphology of this Sulcus was carried out to examine whether it is continuous or a series of sulcal parts, i.e. independent sulci classified together under the name Collateral Sulcus. We investigated the Collateral sulcal complex using magnetic resonance images taking into account the three-dimensional nature of the brain. Our examination demonstrated three separate sulcal segments: (i) an anterior segment, the rhinal Sulcus, delineating the uncus from the adjacent temporal neocortex, (ii) a middle segment, the Collateral Sulcus proper, forming the lateral border of the posterior parahippocampal cortex, and (iii) a caudal segment, the occipital extent of the Collateral Sulcus, within the occipital lobe. Three relationships exist between the rhinal Sulcus and Collateral Sulcus proper, only one being clearly identifiable from the surface. Posteriorly, the Collateral Sulcus proper and the occipital Collateral Sulcus, although appearing continuous on the brain surface, can be separated in the depth of the Sulcus in all cases. These results provide quantification of the location and variability within standard stereotaxic space for the three Collateral Sulcus segments that could be used to aid accurate identification of functional activation peaks derived from neuroimaging studies.
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spatial memory deficits in patients with lesions to the right hippocampus and to the right parahippocampal cortex
Neuropsychologia, 1998Co-Authors: Veronique D Bohbot, Miroslav Kalina, Katerina Stepankova, Natasa Spackova, Michael Petrides, Lynn NadelAbstract:Abstract Spatial memory tasks, performance of which is known to be sensitive to hippocampal lesions in the rat, or to medial temporal lesions in the human, were administered in order to investigate the effects of selective damage to medial temporal lobe structures of the human brain. The patients had undergone thermo-coagulation with a single electrode along the amygdalo-hippocampal axis in an attempt to alleviate their epilepsy. With this surgical technique, lesions to single medial temporal lobe structures can be carried out. The locations of the lesions were assessed by means of digital high-resolution magnetic resonance imaging and software allowing a 3-D reconstruction of the brain. A break in the Collateral Sulcus, dividing it into the anterior Collateral Sulcus and the posterior Collateral Sulcus is reported. This division may correspond to the end of the entorhinal\perirhinal cortex and the start of the parahippocampal cortex. The results confirmed the role of the right hippocampus in visuo–spatial memory tasks (object location, Rey–Osterrieth Figure with and without delay) and the left for verbal memory tasks (Rey Auditory Verbal Learning Task with delay). However, patients with lesions either to the right or to the left hippocampus were unimpaired on several memory tasks, including a spatial one, with a 30 min delay, designed to be analogous to the Morris water maze. Patients with lesions to the right parahippocampal cortex were impaired on this task with a 30 min delay, suggesting that the parahippocampal cortex itself may play an important role in spatial memory.
Zoe Woodhead - One of the best experts on this subject based on the ideXlab platform.
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dorsal and ventral visual stream contributions to preserved reading ability in patients with central alexia
Cortex, 2018Co-Authors: Jt Crinion, Oscar M Aguilar, Sheila J Kerry, Martina F Callaghan, Zoe Woodhead, Alexander P LeffAbstract:We investigated the role of the left temporo-parietal regions in supporting reading abilities of 23 patients with central alexia (CA). For the behavioural data, we employed principal components analysis (PCA), which identified two components: 'reading aloud' and 'reading for meaning'. Voxel-based morphometry of the PCA results showed an association between reading aloud and grey matter density in the left supramarginal gyrus, part of the dorsal visual stream. By contrast, reading for meaning was associated with a large cluster in the left ventral visual stream, from the Collateral Sulcus to the anterior temporal pole. Most of the peaks were within the group lesion map, indicating that sparing of these areas results in better preservation of reading ability. However, one white matter (WM) cluster in the medial occipitotemporal lobe was outside the lesioned area. A post-hoc test demonstrated that WM density here was equivalent to controls, suggesting that this was not driven by lesion effects. The two likeliest explanations for this correlation are: 1) that pre-morbid, inter-individual differences in brain structure mitigate the effects of CA; 2) that post-morbid practice-based with reading caused compensatory plasticity. We hope to adjudicate between these explanations with longitudinal therapy data collected in this cohort.
Sonja C Huntgeburth - One of the best experts on this subject based on the ideXlab platform.
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Local morphology informs location of activation during navigation within the parahippocampal region of the human brain
Brain Structure and Function, 2017Co-Authors: Sonja C Huntgeburth, J.-k. Chen, A. Ptito, Michael PetridesAbstract:The relationship between the local morphological features that define the entorhinal and parahippocampal cortex in the medial temporal region of the human brain and activation as measured during a navigation task with functional magnetic resonance imaging was examined individually in healthy participants. Two functional activation clusters were identified one within the caudal end of the Collateral Sulcus proper and the other in the parahippocampal extension of the Collateral Sulcus, clearly establishing the activation in the posterior parahippocampal cortex. A third activation cluster was identified where the anterior segment of the Collateral Sulcus proper gives way to the posterior segment, demonstrating also activation within the middle parahippocampal cortex. No activation was observed in the entorhinal cortex that lies medial to the rhinal Sulcus or in the anterior part of the parahippocampal cortex along the anterior branch of the Collateral Sulcus proper. The activations could also be clearly differentiated from the cortex of the fusiform and lingual gyri that lie laterally and posteriorly. These findings demonstrated specific activation in the middle and posterior part of the parahippocampal cortex when information necessary for navigation was retrieved from a previously established cognitive map and demonstrate that the sulci that comprise the Collateral sulcal complex represent important landmarks that can provide an accurate localization of activation foci along the parahippocampal cortex and allow identification of subdivisions involved in the processing of spatial information.
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morphological patterns of the Collateral Sulcus in the human brain
European Journal of Neuroscience, 2012Co-Authors: Michael Petrides, Sonja C HuntgeburthAbstract:The Collateral sulcal complex is an important landmark on the medial surface of the temporal lobe. Anteriorly, it delineates the limbic regions of the parahippocampal gyrus from the visual-processing areas of the fusiform gyrus. Posteriorly, it continues into the occipital lobe, bearing no relationship to the memory-related limbic regions. Given the considerable extent of the Sulcus and functional heterogeneity of the surrounding cortex, an investigation of the morphology of this Sulcus was carried out to examine whether it is continuous or a series of sulcal parts, i.e. independent sulci classified together under the name Collateral Sulcus. We investigated the Collateral sulcal complex using magnetic resonance images taking into account the three-dimensional nature of the brain. Our examination demonstrated three separate sulcal segments: (i) an anterior segment, the rhinal Sulcus, delineating the uncus from the adjacent temporal neocortex, (ii) a middle segment, the Collateral Sulcus proper, forming the lateral border of the posterior parahippocampal cortex, and (iii) a caudal segment, the occipital extent of the Collateral Sulcus, within the occipital lobe. Three relationships exist between the rhinal Sulcus and Collateral Sulcus proper, only one being clearly identifiable from the surface. Posteriorly, the Collateral Sulcus proper and the occipital Collateral Sulcus, although appearing continuous on the brain surface, can be separated in the depth of the Sulcus in all cases. These results provide quantification of the location and variability within standard stereotaxic space for the three Collateral Sulcus segments that could be used to aid accurate identification of functional activation peaks derived from neuroimaging studies.
Alexander P Leff - One of the best experts on this subject based on the ideXlab platform.
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dorsal and ventral visual stream contributions to preserved reading ability in patients with central alexia
Cortex, 2018Co-Authors: Jt Crinion, Oscar M Aguilar, Sheila J Kerry, Martina F Callaghan, Zoe Woodhead, Alexander P LeffAbstract:We investigated the role of the left temporo-parietal regions in supporting reading abilities of 23 patients with central alexia (CA). For the behavioural data, we employed principal components analysis (PCA), which identified two components: 'reading aloud' and 'reading for meaning'. Voxel-based morphometry of the PCA results showed an association between reading aloud and grey matter density in the left supramarginal gyrus, part of the dorsal visual stream. By contrast, reading for meaning was associated with a large cluster in the left ventral visual stream, from the Collateral Sulcus to the anterior temporal pole. Most of the peaks were within the group lesion map, indicating that sparing of these areas results in better preservation of reading ability. However, one white matter (WM) cluster in the medial occipitotemporal lobe was outside the lesioned area. A post-hoc test demonstrated that WM density here was equivalent to controls, suggesting that this was not driven by lesion effects. The two likeliest explanations for this correlation are: 1) that pre-morbid, inter-individual differences in brain structure mitigate the effects of CA; 2) that post-morbid practice-based with reading caused compensatory plasticity. We hope to adjudicate between these explanations with longitudinal therapy data collected in this cohort.