Abstract
Information processing in the cerebral cortex involves interactions among distributed areas. Anatomical connectivity suggests that certain areas form local hierarchical relations such as within the visual system. Other connectivity patterns, particularly among association areas, suggest the presence of large-scale circuits without clear hierarchical relations. In this study the organization of networks in the human cerebrum was explored using resting-state functional connectivity MRI. Data from 1,000 subjects were registered using surface-based alignment. A clustering approach was employed to identify and replicate networks of functionally coupled regions across the cerebral cortex. The results revealed local networks confined to sensory and motor cortices as well as distributed networks of association regions. Within the sensory and motor cortices, functional connectivity followed topographic representations across adjacent areas. In association cortex, the connectivity patterns often showed abrupt transitions between network boundaries. Focused analyses were performed to better understand properties of network connectivity. A canonical sensory-motor pathway involving primary visual area, putative middle temporal area complex (MT+), lateral intraparietal area, and frontal eye field was analyzed to explore how interactions might arise within and between networks. Results showed that adjacent regions of the MT+ complex demonstrate differential connectivity consistent with a hierarchical pathway that spans networks. The functional connectivity of parietal and prefrontal association cortices was next explored. Distinct connectivity profiles of neighboring regions suggest they participate in distributed networks that, while showing evidence for interactions, are embedded within largely parallel, interdigitated circuits. We conclude by discussing the organization of these large-scale cerebral networks in relation to monkey anatomy and their potential evolutionary expansion in humans to support cognition.
complex behaviors are subserved by distributed systems of brain areas . The organization of these systems can be studied in nonhuman animals by using invasive techniques including histology, anatomical tract tracing, electrophysiology, and lesion methods. The organization of brain systems in the human has been inferred by comparing cytoarchitectonically defined homologies between species and by noting similarities in neuropsychological deficits following accidental brain injury to deficits present in animal ablation studies. General agreement has emerged from these comparisons that the basic organization of brain systems is similar across mammalian species. However, there is also evidence that the human cerebral cortex, particularly association cortex, is not simply a scaled version of other species.
The German anatomist Korbinian first emphasized that areas comprising the human inferior parietal lobule do not have clear homologs in the monkey, an observation that continues to motivate contemporary debates. Gross differences are also observed in the human brain when it is compared to those of our evolutionarily closest relatives. For example, the human brain is triple the size of modern great ape brains, but motor and visual cortices are about the same absolute size. This observation suggests that expansion of the human cerebrum disproportionately involves areas beyond those subserving basic sensory and motor functions. In a recent analysis of cortical expansion based on 23 homologous areas between the macaque and human, Van Essen and colleagues noted that the greatest growth occurs in regions distributed across frontal, parietal, and temporal association cortices. came to a similar conclusion in a detailed review of comparative anatomy. Thus, in addition to expecting the human brain to show broadly similar organizational properties with other well-studied species, expansion and perhaps elaboration of association networks is also expected.
In this article we report results of a comprehensive analysis of networks within the human cerebral cortex using intrinsic functional connectivity MRI (fcMRI). The analysis was based on 1,000 young adults who contributed uniformly collected MRI data. The data were brought into a common surface coordinate system to help preserve the surface topology of the cortical mantle. Analyses were motivated by two goals. First, we sought to provide reference maps that are a current best estimate of the organization of the human cerebral cortex as measured by functional connectivity. Second, we wanted to better understand how patterns of functional connectivity might give rise to the organizational properties that underlie distributed brain systems. Particular focus was placed on parietal and frontal association cortices. The foundations for the present work come from traditional anatomical studies of cortical organization.
Resource: http://www.ncbi.nlm.nih.gov
Resource: http://www.nutritionforest.com/
Information processing in the cerebral cortex involves interactions among distributed areas. Anatomical connectivity suggests that certain areas form local hierarchical relations such as within the visual system. Other connectivity patterns, particularly among association areas, suggest the presence of large-scale circuits without clear hierarchical relations. In this study the organization of networks in the human cerebrum was explored using resting-state functional connectivity MRI. Data from 1,000 subjects were registered using surface-based alignment. A clustering approach was employed to identify and replicate networks of functionally coupled regions across the cerebral cortex. The results revealed local networks confined to sensory and motor cortices as well as distributed networks of association regions. Within the sensory and motor cortices, functional connectivity followed topographic representations across adjacent areas. In association cortex, the connectivity patterns often showed abrupt transitions between network boundaries. Focused analyses were performed to better understand properties of network connectivity. A canonical sensory-motor pathway involving primary visual area, putative middle temporal area complex (MT+), lateral intraparietal area, and frontal eye field was analyzed to explore how interactions might arise within and between networks. Results showed that adjacent regions of the MT+ complex demonstrate differential connectivity consistent with a hierarchical pathway that spans networks. The functional connectivity of parietal and prefrontal association cortices was next explored. Distinct connectivity profiles of neighboring regions suggest they participate in distributed networks that, while showing evidence for interactions, are embedded within largely parallel, interdigitated circuits. We conclude by discussing the organization of these large-scale cerebral networks in relation to monkey anatomy and their potential evolutionary expansion in humans to support cognition.
complex behaviors are subserved by distributed systems of brain areas . The organization of these systems can be studied in nonhuman animals by using invasive techniques including histology, anatomical tract tracing, electrophysiology, and lesion methods. The organization of brain systems in the human has been inferred by comparing cytoarchitectonically defined homologies between species and by noting similarities in neuropsychological deficits following accidental brain injury to deficits present in animal ablation studies. General agreement has emerged from these comparisons that the basic organization of brain systems is similar across mammalian species. However, there is also evidence that the human cerebral cortex, particularly association cortex, is not simply a scaled version of other species.
The German anatomist Korbinian first emphasized that areas comprising the human inferior parietal lobule do not have clear homologs in the monkey, an observation that continues to motivate contemporary debates. Gross differences are also observed in the human brain when it is compared to those of our evolutionarily closest relatives. For example, the human brain is triple the size of modern great ape brains, but motor and visual cortices are about the same absolute size. This observation suggests that expansion of the human cerebrum disproportionately involves areas beyond those subserving basic sensory and motor functions. In a recent analysis of cortical expansion based on 23 homologous areas between the macaque and human, Van Essen and colleagues noted that the greatest growth occurs in regions distributed across frontal, parietal, and temporal association cortices. came to a similar conclusion in a detailed review of comparative anatomy. Thus, in addition to expecting the human brain to show broadly similar organizational properties with other well-studied species, expansion and perhaps elaboration of association networks is also expected.
In this article we report results of a comprehensive analysis of networks within the human cerebral cortex using intrinsic functional connectivity MRI (fcMRI). The analysis was based on 1,000 young adults who contributed uniformly collected MRI data. The data were brought into a common surface coordinate system to help preserve the surface topology of the cortical mantle. Analyses were motivated by two goals. First, we sought to provide reference maps that are a current best estimate of the organization of the human cerebral cortex as measured by functional connectivity. Second, we wanted to better understand how patterns of functional connectivity might give rise to the organizational properties that underlie distributed brain systems. Particular focus was placed on parietal and frontal association cortices. The foundations for the present work come from traditional anatomical studies of cortical organization.
Resource: http://www.ncbi.nlm.nih.gov
Resource: http://www.nutritionforest.com/
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