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Baker V, Cruz L. Traveling Waves in Quasi-One-Dimensional Neuronal Minicolumns. Neural Comput 2021; 34:78-103. [PMID: 34758481 DOI: 10.1162/neco_a_01451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 07/03/2021] [Indexed: 11/04/2022]
Abstract
Traveling waves of neuronal activity in the cortex have been observed in vivo. These traveling waves have been correlated to various features of observed cortical dynamics, including spike timing variability and correlated fluctuations in neuron membrane potential. Although traveling waves are typically studied as either strictly one-dimensional or two-dimensional excitations, here we investigate the conditions for the existence of quasi-one-dimensional traveling waves that could be sustainable in parts of the brain containing cortical minicolumns. For that, we explore a quasi-one-dimensional network of heterogeneous neurons with a biologically influenced computational model of neuron dynamics and connectivity. We find that background stimulus reliably evokes traveling waves in networks with local connectivity between neurons. We also observe traveling waves in fully connected networks when a model for action potential propagation speed is incorporated. The biological properties of the neurons influence the generation and propagation of the traveling waves. Our quasi-one-dimensional model is not only useful for studying the basic properties of traveling waves in neuronal networks; it also provides a simplified representation of possible wave propagation in columnar or minicolumnar networks found in the cortex.
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Affiliation(s)
- Vincent Baker
- Department of Physics, Drexel University, Philadelphia, PA 19104, U.S.A.
| | - Luis Cruz
- Department of Physics, Drexel University, Philadelphia, PA 19104, U.S.A.
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2
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Comrie AE, Gray DT, Smith AC, Barnes CA. Different macaque models of cognitive aging exhibit task-dependent behavioral disparities. Behav Brain Res 2018; 344:110-119. [PMID: 29432794 PMCID: PMC5890935 DOI: 10.1016/j.bbr.2018.02.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 02/05/2018] [Accepted: 02/06/2018] [Indexed: 11/17/2022]
Abstract
Deficits in cognitive functions that rely on the integrity of the frontal and temporal lobes are characteristic of normative human aging. Due to similar aging phenotypes and homologous cortical organization between nonhuman primates and humans, several species of macaque monkeys are used as models to explore brain senescence. These macaque species are typically regarded as equivalent models of cognitive aging, yet no direct comparisons have been made to support this assumption. Here we used adult and aged rhesus and bonnet macaques (Macaca mulatta and Macaca radiata) to characterize the effect of age on acquisition and retention of information across delays in a battery of behavioral tasks that rely on prefrontal cortex and medial temporal lobe networks. The cognitive functions that were tested include visuospatial short-term memory, object recognition memory, and object-reward association memory. In general, bonnet macaques at all ages outperformed rhesus macaques on tasks thought to rely primarily on the prefrontal cortex, and were more resilient to age-related deficits in these behaviors. On the other hand, both species were comparably impaired by age on tasks thought to preferentially engage the medial temporal lobe. Together, these results suggest that rhesus and bonnet macaques are not equivalent models of cognitive aging and highlight the value of cross-species comparisons. These observations should enable improved design and interpretation of future experiments aimed at understanding changes in cognition across the lifespan.
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Affiliation(s)
- Alison E Comrie
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, 85724, USA; Division of Neural Systems, Memory & Aging, University of Arizona, Tucson, AZ, 85724, USA
| | - Daniel T Gray
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, 85724, USA; Division of Neural Systems, Memory & Aging, University of Arizona, Tucson, AZ, 85724, USA
| | - Anne C Smith
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, 85724, USA
| | - Carol A Barnes
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, 85724, USA; Division of Neural Systems, Memory & Aging, University of Arizona, Tucson, AZ, 85724, USA; Department of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ, 85724, USA.
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3
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Tozzi A, Peters JF, Ori O. Cracking the barcode of fullerene-like cortical microcolumns. Neurosci Lett 2017; 644:100-106. [PMID: 28242327 DOI: 10.1016/j.neulet.2017.02.064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/05/2017] [Accepted: 02/22/2017] [Indexed: 11/27/2022]
Abstract
Artificial neural systems and nervous graph theoretical analysis rely upon the stance that the neural code is embodied in logic circuits, e.g., spatio-temporal sequences of ON/OFF spiking neurons. Nevertheless, this assumption does not fully explain complex brain functions. Here we show how nervous activity, other than logic circuits, could instead depend on topological transformations and symmetry constraints occurring at the micro-level of the cortical microcolumn, i.e., the embryological, anatomical and functional basic unit of the brain. Tubular microcolumns can be flattened in fullerene-like two-dimensional lattices, equipped with about 80 nodes standing for pyramidal neurons where neural computations take place. We show how the countless possible combinations of activated neurons embedded in the lattice resemble a barcode. Despite the fact that further experimental verification is required in order to validate our claim, different assemblies of firing neurons might have the appearance of diverse codes, each one responsible for a single mental activity. A two-dimensional fullerene-like lattice, grounded on simple topological changes standing for pyramidal neurons' activation, not just displays analogies with the real microcolumn's microcircuitry and the neural connectome, but also the potential for the manufacture of plastic, robust and fast artificial networks in robotic forms of full-fledged neural systems.
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Affiliation(s)
- Arturo Tozzi
- Center for Nonlinear Science, University of North Texas, 1155 Union Circle, #311427 Denton, TX 76203-5017, USA; Computational Intelligence Laboratory, University of Manitoba, Winnipeg, MB, R3T 5V6, Canada.
| | - James F Peters
- Department of Electrical and Computer Engineering, University of Manitoba, 75A Chancellor's Circle, Winnipeg, MB R3T 5V6, Canada; Department of Mathematics, Adıyaman University, 02040 Adıyaman, Turkey; Department of Mathematics, Faculty of Arts and Sciences, Adıyaman University 02040 Adıyaman, Turkey; Computational Intelligence Laboratory, University of Manitoba, Winnipeg, MB, R3T 5V6, Canada.
| | - Ottorino Ori
- Actinium Chemical Research, Via Casilina 1626/A, 00133 Rome, Italy.
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Rafati AH, Safavimanesh F, Dorph-Petersen KA, Rasmussen JG, Møller J, Nyengaard JR. Detection and spatial characterization of minicolumnarity in the human cerebral cortex. J Microsc 2016; 261:115-26. [PMID: 26575198 DOI: 10.1111/jmi.12321] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 08/01/2015] [Indexed: 01/16/2023]
Abstract
BACKGROUND Spatial characterization of vertical organization of neurons in human cerebral cortex, cortical columnarity or minicolumns, and its possible association with various psychiatric and neurological diseases has been investigated for many years. NEW METHOD In this study, we obtained 3D coordinates of disector sampled cells from layer III of Brodmann area 4 of the human cerebral cortex using light microscopy and 140-μm-thick glycolmethacrylate sections. A new analytical tool called cylindrical K-function was applied for spatial point pattern analysis of 3D datasets to see whether there is a spatially organized columnar structure. In order to demonstrate the behaviour of the cylindrical K-function, the result from brain tissues was compared with two models: A homogeneous Poisson process exhibiting complete spatial randomness, and a Poisson line cluster point process. The latter is a point process model in 3D space, which exhibits spatial structure of points similar to minicolumns. RESULTS The data show in three out of four samples nonrandom patterns in the 3D neuronal positions with the direction of minicolumns perpendicular to the pial surface of the brain - without a priori assuming the existence of minicolumns. COMPARISON WITH EXISTING METHODS Studies on columnarity are difficult and have mainly been based on two-dimensional images analysis of thin sections of the cerebral cortex with the a priori assumption that minicolumns existed. CONCLUSIONS A clear difference from complete spatial randomness in the data could be detected with the new tool, the cylindrical K-function, although classical functional summary statistics are less useful in this connection.
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Affiliation(s)
- A H Rafati
- Stereology and Electron Microscopy Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark.,Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Risskov, Denmark
| | - F Safavimanesh
- Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark.,Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark
| | - K-A Dorph-Petersen
- Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark.,Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Risskov, Denmark.,Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A
| | - J G Rasmussen
- Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark.,Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark
| | - J Møller
- Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark.,Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark
| | - J R Nyengaard
- Stereology and Electron Microscopy Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Centre for Stochastic Geometry and Advanced Bioimaging (CSGB), Aarhus University, Aarhus, Denmark
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Chance SA. The cortical microstructural basis of lateralized cognition: a review. Front Psychol 2014; 5:820. [PMID: 25126082 PMCID: PMC4115615 DOI: 10.3389/fpsyg.2014.00820] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 07/10/2014] [Indexed: 01/19/2023] Open
Abstract
The presence of asymmetry in the human cerebral hemispheres is detectable at both the macroscopic and microscopic scales. The horizontal expansion of cortical surface during development (within individual brains), and across evolutionary time (between species), is largely due to the proliferation and spacing of the microscopic vertical columns of cells that form the cortex. In the asymmetric planum temporale (PT), minicolumn width asymmetry is associated with surface area asymmetry. Although the human minicolumn asymmetry is not large, it is estimated to account for a surface area asymmetry of approximately 9% of the region’s size. Critically, this asymmetry of minicolumns is absent in the equivalent areas of the brains of other apes. The left-hemisphere dominance for processing speech is thought to depend, partly, on a bias for higher resolution processing across widely spaced minicolumns with less overlapping dendritic fields, whereas dense minicolumn spacing in the right hemisphere is associated with more overlapping, lower resolution, holistic processing. This concept refines the simple notion that a larger brain area is associated with dominance for a function and offers an alternative explanation associated with “processing type.” This account is mechanistic in the sense that it offers a mechanism whereby asymmetrical components of structure are related to specific functional biases yielding testable predictions, rather than the generalization that “bigger is better” for any given function. Face processing provides a test case – it is the opposite of language, being dominant in the right hemisphere. Consistent with the bias for holistic, configural processing of faces, the minicolumns in the right-hemisphere fusiform gyrus are thinner than in the left hemisphere, which is associated with featural processing. Again, this asymmetry is not found in chimpanzees. The difference between hemispheres may also be seen in terms of processing speed, facilitated by asymmetric myelination of white matter tracts (Anderson et al., 1999 found that axons of the left posterior superior temporal lobe were more thickly myelinated). By cross-referencing the differences between the active fields of the two hemispheres, via tracts such as the corpus callosum, the relationship of local features to global features may be encoded. The emergent hierarchy of features within features is a recursive structure that may functionally contribute to generativity – the ability to perceive and express layers of structure and their relations to each other. The inference is that recursive generativity, an essential component of language, reflects an interaction between processing biases that may be traceable in the microstructure of the cerebral cortex. Minicolumn organization in the PT and the prefrontal cortex has been found to correlate with cognitive scores in humans. Altered minicolumn organization is also observed in neuropsychiatric disorders including autism and schizophrenia. Indeed, altered interhemispheric connections correlated with minicolumn asymmetry in schizophrenia may relate to language-processing anomalies that occur in the disorder. Schizophrenia is associated with over-interpretation of word meaning at the semantic level and over-interpretation of relevance at the level of pragmatic competence, whereas autism is associated with overly literal interpretation of word meaning and under-interpretation of social relevance at the pragmatic level. Both appear to emerge from a disruption of the ability to interpret layers of meaning and their relations to each other. This may be a consequence of disequilibrium in the processing of local and global features related to disorganization of minicolumnar units of processing.
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Affiliation(s)
- Steven A Chance
- Neuropathology, Nuffield Department of Clinical Neurosciences, Neuroanatomy and Cognition Group, University of Oxford Oxford, UK
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Henderson M, Urbanc B, Cruz L. A computational model for the loss of neuronal organization in microcolumns. Biophys J 2014; 106:2233-42. [PMID: 24853752 DOI: 10.1016/j.bpj.2014.04.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 03/13/2014] [Accepted: 04/04/2014] [Indexed: 10/25/2022] Open
Abstract
A population of neurons in the cerebral cortex of humans and other mammals organize themselves into vertical microcolumns perpendicular to the pial surface. Anatomical changes to these microcolumns have been correlated with neurological diseases and normal aging; in particular, in area 46 of the rhesus monkey brain, the strength of microcolumns was shown to decrease with age. These changes can be caused by alterations in the spatial distribution of the neurons in microcolumns and/or neuronal loss. Using a three-dimensional computational model of neuronal arrangements derived from thin tissue sections and validated in brain tissue from rhesus monkeys, we show that neuronal loss is inconsistent with the findings in aged individuals. In contrast, a model of simple random neuronal displacements, constrained in magnitude by restorative harmonic forces, is consistent with observed changes and provides mechanistic insights into the age-induced loss of microcolumnar structure. Connection of the model to normal aging and disease are discussed.
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Affiliation(s)
- Maxwell Henderson
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
| | - Luis Cruz
- Department of Physics, Drexel University, Philadelphia, Pennsylvania.
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7
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Statistical physics approach to quantifying differences in myelinated nerve fibers. Sci Rep 2014; 4:4511. [PMID: 24676146 PMCID: PMC3968487 DOI: 10.1038/srep04511] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 03/12/2014] [Indexed: 11/08/2022] Open
Abstract
We present a new method to quantify differences in myelinated nerve fibers. These differences range from morphologic characteristics of individual fibers to differences in macroscopic properties of collections of fibers. Our method uses statistical physics tools to improve on traditional measures, such as fiber size and packing density. As a case study, we analyze cross–sectional electron micrographs from the fornix of young and old rhesus monkeys using a semi-automatic detection algorithm to identify and characterize myelinated axons. We then apply a feature selection approach to identify the features that best distinguish between the young and old age groups, achieving a maximum accuracy of 94% when assigning samples to their age groups. This analysis shows that the best discrimination is obtained using the combination of two features: the fraction of occupied axon area and the effective local density. The latter is a modified calculation of axon density, which reflects how closely axons are packed. Our feature analysis approach can be applied to characterize differences that result from biological processes such as aging, damage from trauma or disease or developmental differences, as well as differences between anatomical regions such as the fornix and the cingulum bundle or corpus callosum.
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8
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Hemispheric asymmetry in the fusiform gyrus distinguishes Homo sapiens from chimpanzees. Brain Struct Funct 2012; 218:1391-405. [DOI: 10.1007/s00429-012-0464-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 10/06/2012] [Indexed: 12/24/2022]
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Peters A, Kemper T. A review of the structural alterations in the cerebral hemispheres of the aging rhesus monkey. Neurobiol Aging 2012; 33:2357-72. [PMID: 22192242 PMCID: PMC3337968 DOI: 10.1016/j.neurobiolaging.2011.11.015] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 11/02/2011] [Accepted: 11/10/2011] [Indexed: 02/07/2023]
Abstract
Like humans, rhesus monkeys show cognitive decline and this review considers what structural age-related changes underlie this decline. Some structural measures do not alter significantly with age. These include brain weight, overall cortical thickness; numbers of cortical neurons; and numbers of astrocytes and microglial cells. Other structural measures change with age, but the change does not correlate with cognitive decline. These changes include nerve fiber loss from some fiber tracts, degeneration, and regeneration of myelin sheaths, and increase in the frequency of oligodendrocytes. Among the structural measures that increase in frequency with age and also correlate with cognitive decline are the increased frequency of degenerating myelin sheaths and a loss of nerve fibers from some fiber tracts; and the loss of synapses and dendritic spines from upper layers of prefrontal cortex. Consequently, the existing data suggest that cognitive decline correlates with changes in myelinated nerve fibers and with disconnections between and within cortical areas, as reflected by the age-related loss of synapses and of dendritic spines from some cortical areas.
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Affiliation(s)
- Alan Peters
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
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10
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¿Existe la enfermedad de Alzheimer en todos los primates? Afección de Alzheimer en primates no humanos y sus implicaciones fisiopatológicas (I). Neurologia 2012; 27:354-69. [DOI: 10.1016/j.nrl.2011.05.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 05/19/2011] [Indexed: 11/17/2022] Open
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Toledano A, Álvarez M, López-Rodríguez A, Toledano-Díaz A, Fernández-Verdecia C. Does Alzheimer's disease exist in all primates? Alzheimer pathology in non-human primates and its pathophysiological implications (I). NEUROLOGÍA (ENGLISH EDITION) 2012. [DOI: 10.1016/j.nrleng.2012.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Picq JL, Aujard F, Volk A, Dhenain M. Age-related cerebral atrophy in nonhuman primates predicts cognitive impairments. Neurobiol Aging 2012; 33:1096-109. [PMID: 20970891 PMCID: PMC3381737 DOI: 10.1016/j.neurobiolaging.2010.09.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 09/01/2010] [Accepted: 09/10/2010] [Indexed: 11/24/2022]
Abstract
In humans, but not in nonhuman primates, a clear relationship has been established between age-associated cognitive decline and atrophy of specific brain regions. We evaluated age-related cerebral atrophy and cognitive alterations in mouse lemur primates. Cerebral atrophy was evaluated by in vivo magnetic resonance imaging in 34 animals aged from 1.9 to 11.8 years. The caudate and splenium were atrophied in most older animals, whereas shrinkage of the hippocampus, entorhinal cortex, and septal region was identified in a subgroup of the older animals. The temporal and cingulate cortex also exhibited a severe atrophy, whereas frontal and parietal areas were spared. Measures of cognitive ability in 16 animals studied by magnetic resonance imaging (MRI) showed that both executive functions and spatial memory declined with aging. Impairment of executive functions in older animals was associated with atrophy of the septal region while spatial memory performance was related to atrophy of the hippocampus and entorhinal cortex. Mouse lemurs are the first nonhuman primates in which a clear relationship is established between age-associated cognitive alteration and cerebral atrophy.
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Affiliation(s)
- Jean-Luc Picq
- Laboratoire de psychopathologie et de neuropsychologie, E.A. 2027, Université Paris 8, 2 rue de la liberté, 93000 St Denis, France
- CNRS UMR 7179, MNHN, 4 Av du Petit Château, 91800 Brunoy, France
| | - Fabienne Aujard
- CNRS UMR 7179, MNHN, 4 Av du Petit Château, 91800 Brunoy, France
| | - Andreas Volk
- Institut Curie, Research Center, 91405 Orsay Cedex, France
- U759 INSERM, Centre Universitaire, Labo 112, 91405 Orsay Cedex, France
| | - Marc Dhenain
- CEA, DSV, I2BM, MIRCen, URA CEA CNRS 2210, 18 route du panorama 92 265 Fontenay-aux-Roses cedex, France
- CNRS, URA 2210, 18 route du panorama 92 265 Fontenay-aux-Roses cedex, France
- CEA, DSV, I2BM, NeuroSpin, Centre CEA de Saclay, Bât. 145, 91191 Gif sur Yvette, France
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van Veluw SJ, Sawyer EK, Clover L, Cousijn H, De Jager C, Esiri MM, Chance SA. Prefrontal cortex cytoarchitecture in normal aging and Alzheimer's disease: a relationship with IQ. Brain Struct Funct 2012; 217:797-808. [PMID: 22302432 DOI: 10.1007/s00429-012-0381-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 01/07/2012] [Indexed: 12/24/2022]
Abstract
We have previously shown that the minicolumnar spacing of neurons in the cerebral cortex relates to cognitive ability, and that minicolumn thinning occurs in old age. The present study examines further the relationship between cognitive ability and cortical fine structure(minicolumn organization and neuropathology) in the dorsolateral prefrontal cortex (dlPFC) and the parahippocampal gyrus (PHG) in mild cognitive impairment (MCI)and Alzheimer's disease (AD). Premortem neuropsychological scores were related to postmortem microanatomy in 58 adults (20 normal controls, 18 MCI, and 20 confirmed AD patients). We found a correspondence between minicolumn thinning in the dlPFC and IQ decline in dementia.In mild impairment, IQ remained stable, as did dlPFC minicolumn width and dlPFC plaque load. IQ only declined as dlPFC minicolumn thinning occurred and dlPFC plaque load increased in more severe dementia. By contrast, plaque load increased and minicolumns became steadily thinner in the PHG, where minicolumn width correlated with declining mini-mental state examination score across both MCI and severe dementia. By including a further 14 younger control subjects, we found that in normal healthy aging, minicolumn width decreased in the dlPFC, whereas PHG minicolumn width did not change.AD patients in our dataset with higher IQ were older at time of death and had less pathology, which supports a neural basis for the cognitive reserve hypothesis.
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Affiliation(s)
- Susanne J van Veluw
- Nutfield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Morcom AM, Friston KJ. Decoding episodic memory in ageing: a Bayesian analysis of activity patterns predicting memory. Neuroimage 2012; 59:1772-82. [PMID: 21907810 PMCID: PMC3236995 DOI: 10.1016/j.neuroimage.2011.08.071] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 07/08/2011] [Accepted: 08/21/2011] [Indexed: 11/23/2022] Open
Abstract
Normal ageing is associated with a decline in episodic memory, and neuroimaging studies in older adults have shown reduced activity in prefrontal cortex and other regions critical for memory function in the young. However, older adults also activate additional regions, suggesting a degree of functional reorganisation that has been attributed variously to detrimental and adaptive changes. Evaluation of these competing hypotheses depends critically upon inferences about the relative location and distribution of activity that are not well supported by current univariate or multivariate analyses. Here, we employed a recently developed model-based multivariate 'decoding' approach (Friston et al., 2008) to re-analyse a rich episodic encoding dataset and examine directly how the patterns of activity change in ageing. We assessed which spatial activity patterns, within lateral prefrontal cortex, best predict successful memory formation. Bayesian model comparison showed that the older adults had more distributed and bilateral (fragmented) predictive patterns of activity in anterior inferior frontal gyrus and middle frontal gyrus. With this direct multivariate test for changes in patterns of activity, we replicate and extend earlier findings of reduced prefrontal lateralisation in ageing. These findings extend conclusions based on conventional analyses, and support the notion that ageing alters the spatial deployment of neuronal activity, to render it less spatially coherent and regionally specific. This greater distribution of activity in older adults was also linked to poorer individual memory performance, suggesting that it reflects neural ageing, rather than adaptive compensatory responses.
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Affiliation(s)
- Alexa M Morcom
- Psychology and Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK.
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15
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Voytko ML, Murray R, Higgs CJ. Executive function and attention are preserved in older surgically menopausal monkeys receiving estrogen or estrogen plus progesterone. J Neurosci 2009; 29:10362-70. [PMID: 19692611 PMCID: PMC2744632 DOI: 10.1523/jneurosci.1591-09.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 06/17/2009] [Accepted: 07/22/2009] [Indexed: 11/21/2022] Open
Abstract
Animal models of menopause have been used to further define the cognitive processes that respond to hormone therapy and to investigate parameters that may influence the cognitive effects of estrogen. Many investigations in animals have focused on memory; however, the effects of hormone therapy on executive function and attention processes have not been well studied. Thus, the purpose of this set of investigations was to assess the effects of estrogen therapy alone or with progesterone on executive and attention processes in middle-aged ovariectomized monkeys. Monkeys were preoperatively trained on a modified version of the Wisconsin card sort task and on a visual cued reaction time task. Hormone therapy was initiated at the time of ovariectomy and cognitive function was reassessed at 2, 12, and 24 weeks postoperatively. Relative to monkeys receiving either of the estrogen therapies, monkeys receiving placebo were impaired in their ability to shift a cognitive set in the Wisconsin card sort task and were impaired in shifting visuospatial attention in the visual cued reaction time task. Our findings are consistent with clinical studies that indicate that hormone therapy can improve executive function and attention processes in postmenopausal women.
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Affiliation(s)
- Mary Lou Voytko
- Department of Neurobiology and Anatomy and Interdisciplinary Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
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