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Peter Fox

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28 papers
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28

YNIMG Journal 2015 Journal Article

Evidence for an anterior–posterior differentiation in the human hippocampal formation revealed by meta-analytic parcellation of fMRI coordinate maps: Focus on the subiculum

  • Henry W. Chase
  • Mareike Clos
  • Sofia Dibble
  • Peter Fox
  • Anthony A. Grace
  • Mary L. Phillips
  • Simon B. Eickhoff

Previous studies, predominantly in experimental animals, have suggested the presence of a differentiation of function across the hippocampal formation. In rodents, ventral regions are thought to be involved in emotional behavior while dorsal regions mediate cognitive or spatial processes. Using a combination of modeling the co-occurrence of significant activations across thousands of neuroimaging experiments and subsequent data-driven clustering of these data we were able to provide evidence of distinct subregions within a region corresponding to the human subiculum, a critical hub within the hippocampal formation. This connectivity-based model consists of a bilateral anterior region, as well as separate posterior and intermediate regions on each hemisphere. Functional connectivity assessed both by meta-analytic and resting fMRI approaches revealed that more anterior regions were more strongly connected to the default mode network, and more posterior regions were more strongly connected to ‘task positive’ regions. In addition, our analysis revealed that the anterior subregion was functionally connected to the ventral striatum, midbrain and amygdala, a circuit that is central to models of stress and motivated behavior. Analysis of a behavioral taxonomy provided evidence for a role for each subregion in mnemonic processing, as well as implication of the anterior subregion in emotional and visual processing and the right posterior subregion in reward processing. These findings lend support to models which posit anterior–posterior differentiation of function within the human hippocampal formation and complement other early steps toward a comparative (cross-species) model of the region.

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YNIMG Journal 2015 Journal Article

Heritability of fractional anisotropy in human white matter: A comparison of Human Connectome Project and ENIGMA-DTI data

  • Peter Kochunov
  • Neda Jahanshad
  • Daniel Marcus
  • Anderson Winkler
  • Emma Sprooten
  • Thomas E. Nichols
  • Susan N. Wright
  • L. Elliot Hong

The degree to which genetic factors influence brain connectivity is beginning to be understood. Large-scale efforts are underway to map the profile of genetic effects in various brain regions. The NIH-funded Human Connectome Project (HCP) is providing data valuable for analyzing the degree of genetic influence underlying brain connectivity revealed by state-of-the-art neuroimaging methods. We calculated the heritability of the fractional anisotropy (FA) measure derived from diffusion tensor imaging (DTI) reconstruction in 481 HCP subjects (194/287 M/F) consisting of 57/60 pairs of mono- and dizygotic twins, and 246 siblings. FA measurements were derived using (Enhancing NeuroImaging Genetics through Meta-Analysis) ENIGMA DTI protocols and heritability estimates were calculated using the SOLAR-Eclipse imaging genetic analysis package. We compared heritability estimates derived from HCP data to those publicly available through the ENIGMA-DTI consortium, which were pooled together from five-family based studies across the US, Europe, and Australia. FA measurements from the HCP cohort for eleven major white matter tracts were highly heritable (h2 =0. 53–0. 90, p<10−5), and were significantly correlated with the joint-analytical estimates from the ENIGMA cohort on the tract and voxel-wise levels. The similarity in regional heritability suggests that the additive genetic contribution to white matter microstructure is consistent across populations and imaging acquisition parameters. It also suggests that the overarching genetic influence provides an opportunity to define a common genetic search space for future gene-discovery studies. Uniquely, the measurements of additive genetic contribution performed in this study can be repeated using online genetic analysis tools provided by the HCP ConnectomeDB web application.

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YNIMG Journal 2015 Journal Article

Multimodal connectivity of motor learning-related dorsal premotor cortex

  • Robert M. Hardwick
  • Elise Lesage
  • Claudia R. Eickhoff
  • Mareike Clos
  • Peter Fox
  • Simon B. Eickhoff

The dorsal premotor cortex (dPMC) is a key region for motor learning and sensorimotor integration, yet we have limited understanding of its functional interactions with other regions. Previous work has started to examine functional connectivity in several brain areas using resting state functional connectivity (RSFC) and meta-analytical connectivity modelling (MACM). More recently, structural covariance (SC) has been proposed as a technique that may also allow delineation of functional connectivity. Here, we applied these three approaches to provide a comprehensive characterization of functional connectivity with a seed in the left dPMC that a previous meta-analysis of functional neuroimaging studies has identified as playing a key role in motor learning. Using data from two sources (the Rockland sample, containing resting state data and anatomical scans from 132 participants, and the BrainMap database, which contains peak activation foci from over 10, 000 experiments), we conducted independent whole-brain functional connectivity mapping analyses of a dPMC seed. RSFC and MACM revealed similar connectivity maps spanning prefrontal, premotor, and parietal regions, while the SC map identified more widespread frontal regions. Analyses indicated a relatively consistent pattern of functional connectivity between RSFC and MACM that was distinct from that identified by SC. Notably, results indicate that the seed is functionally connected to areas involved in visuomotor control and executive functions, suggesting that the dPMC acts as an interface between motor control and cognition.

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IS Journal 2009 Journal Article

The Emerging Field of Semantic Scientific Knowledge Integration

  • Deborah L. McGuinness
  • Peter Fox
  • Boyan Brodaric
  • Elisa Kendall

Interest in and requirements for the next generation of information technology for science are expanding. e-Science has become a growing subject of discussion covering topics such as grid computing for science as well as knowledge-enhanced scientific data retrieval. The demand for deep integration of scientific data and knowledge within and among disciplines is also growing, as larger and broader science questions are becoming more common. Concurrent with the growing demand for next generation information technology for science is a commensurate growth in semantic technologies. We seek to explore the general space of semantic e-Science while focusing on the support and potential for deep data and knowledge integration.

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YNIMG Journal 2007 Journal Article

Complex spatio-temporal dynamics of fMRI BOLD: A study of motor learning

  • Eugene Duff
  • Jinhu Xiong
  • Binquan Wang
  • Ross Cunnington
  • Peter Fox
  • Gary Egan

Many studies have investigated the temporal properties of BOLD signal responses to task performance in regions of interest, often noting significant departures from the conventionally modelled response shape, and significant variation between regions. However, these investigations are rarely extended across the whole brain nor incorporated into the routine analysis of fMRI studies. As a result, little is known about the range of response shapes generated in the brain by common paradigms. The present study finds such temporal dynamics can be complex. We made a detailed investigation of BOLD signal responses across the whole brain during a two minute motor-sequence task, and tracked changes due to learning. The multi-component OSORU (Onset, Sustained, Offset, Ramp, Undershoot) linear model, developed by Harms and Melcher (J. Neurophysiology, 2003), was extended to characterise responses. In many regions, signal transients persisted for over thirty seconds, with large signal spikes at onset often followed by a dip in signal below the final sustained level of activation. Training altered certain features of the response shape, suggesting that different features of the response may reflect different aspects of neuro-vascular dynamics. Unmodelled, this may give rise to inconsistent results across paradigms of varying task durations. Few of the observed effects have been thoroughly addressed in physiological models of the BOLD response. The complex, extended dynamics generated by this simple, often employed task, suggests characterisation and modelling of temporal aspects of BOLD responses needs to be carried out routinely, informing experimental design and analysis, and physiological modelling.

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YNIMG Journal 2003 Journal Article

Positron emission tomography during transcranial magnetic stimulation does not require μ-metal shielding

  • Jae Sung Lee
  • Shalini Narayana
  • Jack Lancaster
  • Paul Jerabek
  • Dong Soo Lee
  • Peter Fox

Recording brain activity using positron emission tomography (PET) during the stimulation of different parts of the brain by transcranial magnetic stimulation (TMS) permits the mapping of neural connections in the living human brain. However, controversy remains regarding the need for μ-metal shielding of the PET scanner during magnetic stimulation. The aim of this study was to test the effects of magnetic fields generated by TMS on PET data acquisition. With TMS-on and -off in the PET field of view, transmission scans with a 68Ge/68Ga pin source and emission scans with an uniform phantom filled with water and 18F were acquired. The frequency and intensity of stimulation were set at 3–5 Hz and 70–80% of the maximum output of the stimulator, respectively. The TMS coil was placed at several locations inside the PET gantry, and the main field direction of the TMS coil was varied between parallel and perpendicular orientation to the scanner's axis. Qualitative and quantitative evaluation of the sinograms of transmission PET scans and reconstructed emission images indicated no measurable differences between TMS-on and -off and post-TMS conditions for any position or orientation. The long distance between the TMS coil and the detector block in the PET scanner, as well as the rapid reduction of the magnetic field with distance (3% of maximum field at 10 cm, in air), could explain the lack of TMS interference. The brief duration (∼250 μs) of the TMS pulses relative to the total PET acquisition time would also explain the lack of TMS effects. The lack of TMS effects on the PET scanner, as well as PET imaging without any shielding, has been reported by other laboratories.

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