Jack L. Lancaster

Automated labeling of the human brain: a preliminary report on the development and evaluation of a forward-transform method.

A forward‐transform method for retrieving brain labels from the 1988 Talairach Atlas using x‐y‐z coordinates is presented. A hierarchical volume‐occupancy labeling scheme was created to simplify the organization of atlas labels using volume and subvolumetric components. Segmentation rules were developed to define boundaries that were not given explicitly in the atlas. The labeling scheme and segmentation rules guided the segmentation and labeling of 160 contiguous regions within the atlas. A unique three‐dimensional (3‐D) database label server called the Talairach Daemon (http://ric.uthscsa.edu/projects) was developed for serving labels keyed to the Talairach coordinate system. Given an x‐y‐z Talairach coordinate, a corresponding hierarchical listing of labels is returned by the server. The accuracy and precision of the forward‐transform labeling method is now under evaluation. Hum. Brain Mapping 5:238–242, 1997.

Magnetic Resonance Imaging Demonstrates Incomplete Myelination in 18q- Syndrome: Evidence for Myelin Basic Protein Haploinsufficiency

Magnetic resonance imaging (MRI) and MRI relaxometry were used to investigate disturbed brain myelination in 18q- syndrome, a disorder characterized by mental retardation, dysmorphic features, and growth failure. T1-weighted and dual spin-echo T2-weighted MR images were obtained, and T1 and T2 parametric image maps were created for 20 patients and 12 controls. MRI demonstrated abnormal brain white matter in all patients. White matter T1 and T2 relaxation times were significantly prolonged in patients compared to controls at all ages studied, suggesting incomplete myelination. Chromosome analysis using fluorescence in situ hybridization techniques showed that all patients with abnormal MRI scans and prolonged white matter T1 and T2 relaxation times were missing one copy of the myelin basic protein (MBP) gene. The one patient with normal-appearing white matter and normal white matter T1 and T2 relaxation times possessed two copies of the MBP gene. MRI and molecular genetic data suggest that incomplete cerebral myelination in 18q- is associated with haploinsufficiency of the gene for MBP.

Localized morphological brain differences between English-speaking Caucasians and Chinese-speaking Asians: new evidence of anatomical plasticity.

&NA; Deformation field morphometry was applied to magnetic resonance images to detect differences in brain shape between English‐speaking Caucasians and Chinese‐speaking Asians. Anatomical differences between these two groups were limited to gyri in the frontal, temporal and parietal lobes, which are known (through functional imaging studies) to differentiate Chinese speakers from English speakers. We interpret these anatomical differences as evidence of neural plasticity shaped by the process of language acquisition during childhood.While anatomical plasticity due to manual skill acquisition (e.g. in musicians) has been established, to our knowledge this is the first report of a brain anatomical difference attributable to a learned cognitive strategy. NeuroReport 14:961–964

Positron emission tomography scanning in essential blepharospasm

PURPOSE To localize in the brain using positron emission tomography neuroimaging with (18)fluorodeoxyglucose [PET ((18)FDG)] differences in glucose metabolism between patients with essential blepharospasm (EB) and controls. DESIGN Prospective case-control study. METHODS Positron emission tomography neuroimaging with (18)fluorodeoxyglucose was performed in 11 patients with EB and 11 controls matched for age and gender. Global analysis of images was used to localize differences in glucose metabolism between groups. RESULTS Multiple cortical and subcortical abnormalities were observed in EB patients in comparison with controls. Cortical areas with the largest and most significant clusters of increased glucose uptake were the inferior frontal gyri, right posterior cingulate gyrus, left middle occipital gyrus, fusiform gyrus of the right temporal lobe, and left anterior cingulate gyrus. Cortical areas with the largest and most significant clusters of decreased glucose uptake were the inferior frontal gyri, ventral to the area of increased glucose metabolism. Subcortical abnormalities, consisting of increased glucose uptake, involved the right caudate and consisting of decreased glucose uptake, involved the left inferior cerebellar hemisphere and thalamus. CONCLUSIONS Global analysis of positron emission tomography neuroimaging with (18)fluorodeoxyglucose neuroimaging in EB patients in comparison with controls demonstrates a pattern of abnormalities involving several cortical and subcortical areas that control blinking, including the inferior frontal lobe, caudate, thalamus, and cerebellum.

Evaluation of octree regional spatial normalization method for regional anatomical matching

The goal of regional spatial normalization is to remove anatomical differences between individual three‐dimensional (3D) brain images by warping them to match features of a standard brain atlas. Processing to fit features at the limiting resolution of a 3D MR image volume is computationally intensive, limiting the broad use of full‐resolution regional spatial normalization. In Kochunov et al. (1999: NeuroImage 10:724–737), we proposed a regional spatial normalization algorithm called octree spatial normalization (OSN) that reduces processing time to minutes while targeting the accuracy of previous methods. In the current study, modifications of the OSN algorithm for use in human brain images are described and tested. An automated brain tissue segmentation procedure was adopted to create anatomical templates to drive feature matching in white matter, gray matter, and cerebral‐spinal fluid. Three similarity measurement functions (fast‐cross correlation (CC), sum‐square error, and centroid) were evaluated in a group of six subjects. A combination of fast‐CC and centroid was found to provide the best feature matching and speed. Multiple iterations and multiple applications of the OSN algorithm were evaluated to improve fit quality. Two applications of the OSN algorithm with two iterations per application were found to significantly reduce volumetric mismatch (up to six times for lateral ventricle) while keeping processing time under 30 min. The refined version of OSN was tested with anatomical landmarks from several major sulci in a group of nine subjects. Anatomical variability was appreciably reduced for every sulcus investigated, and mean sulcal tracings accurately followed sulcal tracings in the target brain. Hum. Brain Mapping 11:193–206, 2000.

Comparison of navigator echo and centroid corrections of image displacement induced by static magnetic field drift on echo planar functional MRI

Image displacement caused by static magnetic field drift may result in serious edge artifacts in echo‐planar functional magnetic resonance imaging (MRI). We compared navigator echo and centroid methods for correcting the artifacts for phantom and in vivo studies. A motor‐stimulation fMRI study was performed to demonstrate the possible effects due to the displacement. The navigator echo method was shown to be the superior technique for the correction of image displacement by effectively eliminating edge artifacts, resulting in improved functional maps. J. Magn. Reson. Imaging 2001;13:308–312.

Improvement in variability of the horizontal meridian of the primary visual area following high-resolution spatial normalization

We investigated the decrease in intersubject functional variability in the horizontal meridian (HM) of the primary visual area (V1) before and after individual anatomical variability was significantly reduced using a high‐resolution spatial normalization (HRSN) method. The analyzed dataset consisted of 10 normal, right‐handed volunteers who had undergone both an O‐15 PET study, which localized retinotopic visual area (V1), and a high‐resolution anatomical MRI. Individual occipital lobes were manually segmented from anatomical images and transformed into a common space using an in‐house high‐resolution regional spatial normalization method called OSN. Individual anatomical and functional variability was quantified before and after HRSN processing. The reduction of individual anatomical variability was judged by the reduction in gray matter (GM) mismatch and by the improvement in overlap frequency between individual calcarine sulci. The reduction in intersubject functional variability of HM was determined by measurements of the overlap frequency between individual HM areas and by improvement in intersubject Z‐score maps. The HRSN processing significantly reduced the individual anatomical variability: GM mismatch was reduced by a factor of two and the mean calcarine sulcus overlap frequency was improved from 37 to 68%. The reduction in functional variability was more subtle. However, both HM mean overlap (increased from 18 to 28%) and the average Z‐score (increased from 2.2 to 2.55) were significantly improved. Although, functional registration was significantly improved by matching sulci, there was still residual variability. This is believed to be the variability of individual areas within the calcarine sulcus, and cannot be resolved by sulcal match. Thus, the proposed methodology provides an efficient, unbiased, and automated way to study structure‐functional relationship in human brain. Hum. Brain Mapping 18:123–134, 2003.