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Jack Lancaster

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20 papers
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20

YNICL Journal 2015 Journal Article

Thalamic functional connectivity predicts seizure laterality in individual TLE patients: Application of a biomarker development strategy

  • Daniel S. Barron
  • Peter T. Fox
  • Heath Pardoe
  • Jack Lancaster
  • Larry R. Price
  • Karen Blackmon
  • Kristen Berry
  • Jose E. Cavazos

Noninvasive markers of brain function could yield biomarkers in many neurological disorders. Disease models constrained by coordinate-based meta-analysis are likely to increase this yield. Here, we evaluate a thalamic model of temporal lobe epilepsy that we proposed in a coordinate-based meta-analysis and extended in a diffusion tractography study of an independent patient population. Specifically, we evaluated whether thalamic functional connectivity (resting-state fMRI-BOLD) with temporal lobe areas can predict seizure onset laterality, as established with intracranial EEG. Twenty-four lesional and non-lesional temporal lobe epilepsy patients were studied. No significant differences in functional connection strength in patient and control groups were observed with Mann-Whitney Tests (corrected for multiple comparisons). Notwithstanding the lack of group differences, individual patient difference scores (from control mean connection strength) successfully predicted seizure onset zone as shown in ROC curves: discriminant analysis (two-dimensional) predicted seizure onset zone with 85% sensitivity and 91% specificity; logistic regression (four-dimensional) achieved 86% sensitivity and 100% specificity. The strongest markers in both analyses were left thalamo-hippocampal and right thalamo-entorhinal cortex functional connection strength. Thus, this study shows that thalamic functional connections are sensitive and specific markers of seizure onset laterality in individual temporal lobe epilepsy patients. This study also advances an overall strategy for the programmatic development of neuroimaging biomarkers in clinical and genetic populations: a disease model informed by coordinate-based meta-analysis was used to anatomically constrain individual patient analyses.

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YNIMG Journal 2010 Journal Article

On the genetic architecture of cortical folding and brain volume in primates

  • Jeffrey Rogers
  • Peter Kochunov
  • Karl Zilles
  • Wendy Shelledy
  • Jack Lancaster
  • Paul Thompson
  • Ravindranath Duggirala
  • John Blangero

Understanding the evolutionary forces that produced the human brain is a central problem in neuroscience and human biology. Comparisons across primate species show that both brain volume and gyrification (the degree of folding in the cerebral cortex) have progressively increased during primate evolution and there is a strong positive correlation between these two traits across primate species. The human brain is exceptional among primates in both total volume and gyrification, and therefore understanding the genetic mechanisms influencing variation in these traits will improve our understanding of a landmark feature of our species. Here we show that individual variation in gyrification is significantly heritable in both humans and an Old World monkey (baboons, Papio hamadryas). Furthermore, contrary to expectations based on the positive phenotypic correlation across species, the genetic correlation between cerebral volume and gyrification within both humans and baboons is estimated as negative. These results suggest that the positive relationship between cerebral volume and cortical folding across species cannot be explained by one set of selective pressures or genetic changes. Our data suggest that one set of selective pressures favored the progressive increase in brain volume documented in the primate fossil record, and that a second independent selective process, possibly related to parturition and neonatal brain size, may have favored brains with progressively greater cortical folding. Without a second separate selective pressure, natural selection favoring increased brain volume would be expected to produce less folded, more lissencephalic brains. These results provide initial evidence for the heritability of gyrification, and possibly a new perspective on the evolutionary mechanisms underlying long-term changes in the nonhuman primate and human brain.

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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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YNIMG Journal 2000 Journal Article

Intersubject Variability in Cortical Activations during a Complex Language Task

  • Jinhu Xiong
  • Shobini Rao
  • Paul Jerabek
  • Frank Zamarripa
  • Marty Woldorff
  • Jack Lancaster
  • Peter T. Fox

Intersubject variability in the functional organization of the human brain has theoretical and practical importance for basic and clinical neuroscience. In the present study, positron emission tomography (PET) and anatomical magnetic resonance imaging (MRI) were used to study the functional anatomy of language processes. Intersubject variability in task-induced activations in six brain regions was assessed in 20 normal subjects (10 men and 10 women) for frequency of occurrence, location, intensity, and extent. A complex, but well-studied task (overt verb generation) was compared to a simple baseline (visual fixation) to induce activations in brain areas serving perceptual, motoric, and cognitive functions. The frequency of occurrence was high for all selected brain areas (80–95%). The variability in response location in Talairach space, expressed as the standard deviation along each axis (x, y, z), ranged from 5. 2 to 9. 9 mm. This variability appears to be uniformly distributed across the brain, uninfluenced by regional differences in the complexity of gyral anatomy or mediated behavior. The variability in response location, expressed as the average Euclidean distances (averaged across subjects) about mean locations of activations, varied from 9. 40 to 13. 36 mm and had no significant differences by region (P > 0. 05, β = 0. 20). Intensity variability was also relatively small and homogenous across brain regions. In contrast, response extent was much more variable both across subjects and across brain regions (0. 79 to 1. 77, coefficient of variation). These findings are in good agreement with previous PET studies of intersubject variability and bode well for the possibility of using functional neuroimaging to study neural plasticity subsequent to congenital and acquired brain lesions.

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