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      Detection of functional connectivity using temporal correlations in MR images

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          Abstract

          Functional connectivity among brain regions has been investigated via an analysis of correlations between regional signal fluctuations recorded in magnetic resonance (MR) images obtained in a steady state. In comparison with studies of functional connectivity that utilize task manipulations, the analysis of correlations in steady state data is less susceptible to confounds arising when functionally unrelated brain regions respond in similar ways to changes in task. A new approach to identifying interregional correlations in steady state data makes use of two independent data sets. Regions of interest (ROIs) are defined and hypotheses regarding their connectivity are generated in one data set. The connectivity hypotheses are then evaluated in the remaining (independent) data set by analyzing low frequency temporal correlations between regions. The roles of the two data sets are then reversed and the process repeated, perhaps multiple times. This method was illustrated by application to the language system. The existence of a functional connection between Broca's area and Wernicke's area was confirmed in healthy subjects at rest. An increase in this functional connection when the language system was actively engaged (when subjects were continuously listening to narrative text) was also confirmed. In a second iteration of analyses, a correlation between Broca's area and a region in left premotor cortex was found to be significant at rest and to increase during continuous listening. These findings suggest that the proposed methodology can reveal the presence and strength of functional connections in high‐level cognitive systems. Hum. Brain Mapping 15:247–262, 2002. © 2002 Wiley‐Liss, Inc.

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          Most cited references32

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          Functional connectivity in single and multislice echoplanar imaging using resting-state fluctuations.

          A previous report of correlations in low-frequency resting-state fluctuations between right and left hemisphere motor cortices in rapidly sampled single-slice echoplanar data is confirmed using a whole-body echoplanar MRI scanner at 1.5 T. These correlations are extended to lower sampling rate multislice echoplanar acquisitions and other right/left hemisphere-symmetric functional cortices. The specificity of the correlations in the lower sampling-rate acquisitions is lower due to cardiac and respiratory-cycle effects which are aliased into the pass-band of the low-pass filter. Data are combined for three normal right-handed male subjects. Correlations to left hemisphere motor cortex, visual cortex, and amygdala are measured in long resting-state scans.
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            Sex differences in the functional organization of the brain for language.

            A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.
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              Modulation of connectivity in visual pathways by attention: cortical interactions evaluated with structural equation modelling and fMRI.

              Electrophysiological and neuroimaging studies have shown that attention to visual motion can increase the responsiveness of the motion-selective cortical area V5 and the posterior parietal cortex (PP). Increased or decreased activation in a cortical area is often attributed to attentional modulation of the cortical projections to that area. This leads to the notion that attention is associated with changes in connectivity. We have addressed attentional modulation of effective connectivity using functional magnetic resonance imaging (fMRI). Three subjects were scanned under identical stimulus conditions (visual motion) while varying only the attentional component of the task. Haemodynamic responses defined an occipito-parieto-frontal network, including the, primary visual cortex (V1), V5 and PR A structural equation model of the interactions among these dorsal visual pathway areas revealed increased connectivity between V5 and PP related to attention. On the basis of our analysis and the neuroanatomical pattern of projections from the prefrontal cortex to PP we attributed the source of modulatory influences, on the posterior visual pathway, to the prefrontal cortex (PFC). To test this hypothesis we included the PFC in our model as a 'modulator' of the pathway between V5 and PP, using interaction terms in the structural equation model. This analysis revealed a significant modulatory effect of prefrontal regions on V5 afferents to posterior parietal cortex.
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                Author and article information

                Contributors
                chell@boreas.med.yale.edu
                Journal
                Hum Brain Mapp
                Hum Brain Mapp
                10.1002/(ISSN)1097-0193
                HBM
                Human Brain Mapping
                Wiley Subscription Services, Inc., A Wiley Company (New York )
                1065-9471
                1097-0193
                23 January 2002
                April 2002
                : 15
                : 4 ( doiID: 10.1002/hbm.v15:4 )
                : 247-262
                Affiliations
                [ 1 ]Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut
                [ 2 ]Child Study Center, Yale University School of Medicine, New Haven, Connecticut
                Author notes
                [*] [* ]Department of Diagnostic Radiology, Yale University School of Medicine, 333 Cedar Street, Fitkin Basement, P. O. Box 208042, New Haven, Connecticut 06520‐8042
                Article
                PMC6872035 PMC6872035 6872035 HBM10022
                10.1002/hbm.10022
                6872035
                11835612
                407af20c-463b-4f64-83f3-00f47bde1e1e
                Copyright © 2002 Wiley‐Liss, Inc.
                History
                : 25 April 2001
                : 02 November 2001
                Page count
                Figures: 6, Tables: 2, References: 51, Pages: 16, Words: 10662
                Funding
                Funded by: National Institutes of Health
                Award ID: NS33332
                Award ID: MH01232
                Award ID: MH59139
                Award ID: MH18268
                Categories
                Article
                Articles
                Custom metadata
                2.0
                April 2002
                Converter:WILEY_ML3GV2_TO_JATSPMC version:5.7.2 mode:remove_FC converted:15.11.2019

                fMRI,method
                fMRI, method

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