Differences In Brain Shape Research Articles

Morphometric Analysis of Brain Shape in Children With Nonsyndromic Cleft Lip and/or Palate

The purpose of this study was to test for differences in brain shape among children with cleft palate only (n = 22), children with cleft lip and palate (n = 35), and controls (n = 39) using Euclidean distance matrix analysis. Sixteen percent of interlandmark distances differed between children with cleft palate only and controls, 10% differed between children with cleft lip and palate and controls, and 10% differed between children with cleft palate only and children with cleft lip and palate. Major differences in brain shape associated with cleft lip and/or palate included posterior expansion of the occipital lobe, reorientation of the cerebellum, heightened callosal midbody, and posterior displacement of the caudate nucleus and thalamus. Differences in brain shape unique to cleft palate only and to cleft lip and palate were also identified. These results expand upon previous volumetric studies on brain morphology in individuals with cleft lip and/or palate and provide additional evidence that the primary defect in cleft lip and/or palate results in both facial and brain dysmorphology.

A pilot study of sexual dimorphism in the head morphology of domestic dogs

The dog (Canis lupus familiaris) displays more morphological diversity than any other species. It is a direct descendant of the gray wolf (Canis lupus), but shows remarkable behavioral and morphological differences. It has been suggested that differences in skull shape that relate to brain shape and retinal ganglion cell distribution may predict behavioral differences. The aim of this pilot study was to assess head morphology in common breeds for evidence of sexual dimorphism in head length, head width, and the ratio of the 2: cephalic index (CI). When males of 80 breeds studied were compared with females, sexual dimorphism (differences in a t-test at the level of P < 0.01) emerged for head length in 5 breeds, for head width in 10 breeds and in CI for 2 breeds. The 2 breeds that showed sexual dimorphism in CI showed no difference (at the level of P < 0.01) in either length or width. These results suggest that all 3 types of dimorphism in head morphometrics must be considered separately. Although the longer and wider heads in males may be predicted because, within a breed, they are expected to be generally bigger animals, the sexual dimorphism in CI is of interest. It may belie differences in brain shape and even predict differences in health, welfare, and behavior.

The developmental basis for jaw size variation in evolution and disease

Variation in jaw size was critical for the adaptive evolution of vertebrates, yet variation during development is often associated with disease. To test the hypothesis that NC progenitor number and proliferation rates contribute to variation in jaw size, we compared NC development in two birds with distinct jaw size, duck and quail. At stage HH10, duck and quail embryos have substantial differences in brain shape and expression of the brain regionalization genes, Pax6, Otx2, Fgf8, and Krox20. There is no significant difference in Pax7‐postive NC precursors in HH8 duck and quail embryos. But by HH13, duck embryos have nearly twice as many Dlx2‐positive NC in their jaw primordia as do quail, a ratio which is maintained in HH20 embryos. At HH20, quail NC divide 1.4 times faster than duck NC, however, quail embryos also develop 1.6 times faster during this developmental window. After reduction of NC precursors, post‐migratory NC compensate within the jaw primordia to produce a symmetric and relatively normally sized jaw. Importantly, while chick undergo complete compensation, ablated duck embryos form slightly smaller than normal jaws. Our results suggest that modification of multiple aspects of NC cell biology was important to the evolution of large jaw size. Further, our finding of compensatory mechanisms opens avenues for treatment of disease associated with NC progenitors loss.Grant Funding Source: none

A Morphometric Study of Phylogenetic and Ecologic Patterns in Procyonid (Mammalia: Carnivora) Endocasts

Brain size and shape have been linked to numerous evolutionary trends, with patterns of encephalization and variation well‐studied in Carnivora. Endocasts provide a proxy for brain morphology and access to potential suites of characters, but rarely are endocast characters used in cladistic analyses. We used three‐dimensional geometric morphometrics to examine phylogenetic and ecologic patterns in the endocasts of procyonids. Endocasts of seven ingroup taxa and four outgroup taxa were digitally rendered and 21 surface landmarks were collected. We tested correspondence of ‘brain shape’ with competing morphological and molecular phylogenies of Procyonidae. In analyses incorporating all taxa there was phylogenetic signal in brain shape for both topologies, but in analyses of ingroup taxa there was phylogenetic signal in the morphological topology only. Differences in brain shape suggest that procyonids emphasized areas associated with motor control, spatial perception, and balance relative to the basal musteloid, perhaps associated with increased arboreality. In Procyonidae, areas of the brain associated with arboreal behavior are also expanded in some taxa, but greater variation of brain shape occurs.Grant Funding Source: none

Brain volume and shape in infants with deformational plagiocephaly

Infants with deformational plagiocephaly (DP) have been shown to exhibit developmental delays relative to unaffected infants. Although the mechanisms accounting for these delays are unknown, one hypothesis focuses on underlying differences in brain development. In this study, we used MRI to examine brain volume and shape in infants with and without DP. Participants included 20 infants with DP (mean age = 7.9 months, SD = 1.2; n = 12 male) and 21 controls (mean age = 7.9 months, SD = 1.3; n = 11 male). Measures included volumes of the total brain and cerebellum; midsagittal areas of the corpus callosum and cerebellar vermis; and linear distance measures used to quantify the shape of selected brain structures. We also evaluated the association between shape measures and developmental scores on the Bayley Scales of Infant and Toddler Development-III (BSID-III). Brain volume did not distinguish cases and controls (p = .214-.976). However, cases exhibited greater asymmetry and flattening of the posterior brain (p < .001-.002) and cerebellar vermis (p = .035), shortening of the corpus callosum (p = .012), and differences in the orientation of the corpus callosum (p = .005). Asymmetry and flattening of brain structures were associated with worse developmental outcomes on the BSID-III. Infants with DP show differences in brain shape, consistent with the skull deformity characteristic of this condition, and shape measures were associated with infant development. Longitudinal studies, beginning in the neonatal period, are needed to clarify whether developmental effects precede or follow brain deformation.

Three‐dimensional morphometric analysis of brain shape in nonsyndromic orofacial clefting

Previous studies report structural brain differences in individuals with nonsyndromic orofacial clefts (NSOFC) compared with healthy controls. These changes involve non-uniform shifts in tissue volume within the cerebral cortex and cerebellum, suggesting that the shape of the brain may be altered in cleft-affected individuals. To test this hypothesis, a landmark-based morphometric approach was utilized to quantify and compare brain shape in a sample of 31 adult males with cleft lip with or without cleft palate (CL/P), 14 adult males with cleft palate only (CPO) and 41 matched healthy controls. Fifteen midline and surface landmarks were collected from MRI brain scans and the resulting 3D coordinates were subjected to statistical shape analysis. First, a geometric morphometric analysis was performed in three steps: Procrustes superimposition of raw landmark coordinates, omnibus testing for group difference in shape, followed by canonical variates analysis (CVA) of shape coordinates. Secondly, Euclidean distance matrix analysis (EDMA) was carried out on scaled inter-landmark distances to identify localized shape differences throughout the brain. The geometric morphometric analysis revealed significant differences in brain shape among all three groups (P < 0.001). From CVA, the major brain shape changes associated with clefting included selective enlargement of the anterior cerebrum coupled with a relative reduction in posterior and/or inferior cerebral portions, changes in the medio-lateral position of the cerebral poles, posterior displacement of the corpus callosum, and reorientation of the cerebellum. EDMA revealed largely similar brain shape changes. Thus, compared with controls, major brain shape differences were present in adult males with CL/P and CPO. These results both confirm and expand previous findings from traditional volumetric studies of the brain in clefting and provide further evidence that the neuroanatomical phenotype in individuals with NSOFC is a primary manifestation of the defect and not a secondarily acquired characteristic.

Deformable registration of brain tumor images via a statistical model of tumor-induced deformation

An approach to the deformable registration of three-dimensional brain tumor images to a normal brain atlas is presented. The approach involves the integration of three components: a biomechanical model of tumor mass-effect, a statistical approach to estimate the model's parameters, and a deformable image registration method. Statistical properties of the sought deformation map from the atlas to the image of a tumor patient are first obtained through tumor mass-effect simulations on normal brain images. This map is decomposed into the sum of two components in orthogonal subspaces, one representing inter-individual differences in brain shape, and the other representing tumor-induced deformation. For a new tumor case, a partial observation of the sought deformation map is obtained via deformable image registration and is decomposed into the aforementioned spaces in order to estimate the mass-effect model parameters. Using this estimate, a simulation of tumor mass-effect is performed on the atlas image in order to generate an image that is similar to tumor patient's image, thereby facilitating the atlas registration process. Results for a real tumor case and a number of simulated tumor cases indicate significant reduction in the registration error due to the presented approach as compared to the direct use of deformable image registration.

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

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 © 2003 Lippincott Williams & Wilkins.

The detection of local shape changes via the geometry of Hotelling's $T^2$ fields

This paper is motivated by the problem of detecting local changes or differences in shape between two samples of objects via the nonlinear deformations required to map each object to an atlas standard. Local shape changes are then detected by high values of the random field of Hotelling’s $T^2$ statistics for detecting a change in mean of the vector deformations at each point in the object. To control the null probability of detecting a local shape change, we use the recent result of Adler that the probability that a random field crosses a high threshold is very accurately approximated by the expected Euler characteristic (EC) of the excursion set of the random field above the threshold. We give an exact expression for the expected EC of a Hotelling’s $T^2$ field, and we study the behavior of the field near local extrema. This extends previous results for Gaussian random fields by Adler and $\chi^2$, $t$ and $F$ fields by Worsley and Cao. For illustration, these results are applied to the detection of differences in brain shape between a sample of 29 males and 23 females.

Plastic Transformation of PET Images

A theory and technique are presented that allow nonlinear resampling of positron emission tomography data to remove nonlinear differences in brain shape. The resampling is determined empirically by a function relating the observed image and a desired template. The validity, reliability, and precision of the plastic transformation are compared with linear rescaling alone, within, and between subjects.