The shape operator for differential analysis of images.

This work provides a new technique for surface oriented volumetric image analysis. The method makes no assumptions about topology, instead constructing a local neighborhood from image information, such as a segmentation or edge map, to define a surface patch. Neighborhood constructions using extrinsic and intrinsic distances are given.

Confrontation naming and morphometric analyses of structural MRI in frontotemporal dementia.

We studied the neural basis for confrontation naming difficulty in 29 patients with frontotemporal dementia (FTD) by correlating naming with voxel-based morphometric analyses of gray matter volume in structural MRI. We found that naming is significantly impaired in FTD, including patients with semantic dementia (SD), progressive nonfluent aphasia (PNFA), and nonaphasic patients (NON-APH) with a disorder of social and executive functioning. Significant cortical atrophy was found in the left anterior temporal cortex in all three FTD subgroups relative to healthy seniors.

Structural shape characterization via exploratory factor analysis.

Unlabelled: This article presents an exploratory factor analytic approach to morphometry in which a high-dimensional set of shape-related variables is examined with the purpose of finding clusters with strong correlation. This clustering can potentially identify regions that have anatomic significance and thus lend insight to knowledge discovery and morphometric investigations.

Methods: The information about regional shape is extracted by registering a reference image to a set of test images.

What's in a name: voxel-based morphometric analyses of MRI and naming difficulty in Alzheimer's disease, frontotemporal dementia and corticobasal degeneration.

Confrontation naming is impaired in neurodegenerative conditions like Alzheimer's disease (AD), frontotemporal dementia (FTD) and corticobasal degeneration (CBD). Some behavioural observations suggest a common source of impaired naming across these patient groups, while others find partially unique patterns of naming difficulty. We hypothesized that a large-scale neural network underlies naming, and that patterns of impaired naming in AD, FTD and CBD reflect cortical atrophy that interrupts this network in a manner that is partially shared and partially unique across these patient groups.

Alzheimer's disease and frontotemporal dementia exhibit distinct atrophy-behavior correlates: a computer-assisted imaging study.

Rationale And Objectives: The purpose of this study was to test the hypothesis that distinct patterns of gray matter atrophy are responsible for unique interruptions of the naming process in Alzheimer's disease (AD) and frontotemporal dementia (FTD).

Materials And Methods: Voxel-based morphometry (VBM) was performed to characterize at the voxel level the neuroanatomic changes that occur in AD and FTD based on high-resolution T1-weighted three-dimensional (3D) spoiled-gradient echo images of patients (AD, n = 12; FTD, n = 29) and healthy control subjects (n = 12). The cortical atrophy measurements were correlated with performance on behavioral measures of naming and related processes to identify brain regions that may contribute to this language function.

Characterization of regional pulmonary mechanics from serial magnetic resonance imaging data.

Rationale And Objectives: The aim of this study was to investigate a method for quantifying lung motion from the registration of successive images in serial magnetic resonance imaging acquisitions during normal respiration.

Materials And Methods: Estimates of pulmonary motion were obtained by summing the normalized cross-correlation over serially acquired lung images to identify corresponding locations between the images. The estimated motions were modeled as deformations of an elastic body and thus reflect to a first order approximation the true physical behavior of lung parenchyma.

Voxelwise mapping of magnetic resonance ventilation-perfusion ratio in a porcine model by multimodality registration: technical note.

Rationale And Objectives: The purpose of this study was to demonstrate the construction of voxelwise ventilation-perfusion (V/Q) ratio maps in a porcine model by nonrigidly aligning the respective ventilation and perfusion images using a multimodality registration algorithm.

Materials And Methods: The first-pass contrast agent technique for a blood flow map and 3He used for ventilation imaging were performed using a normal porcine model. The registered 3He-ventilation image was then aligned to the blood flow map using a multimodality registration algorithm.

Characterization of sexual dimorphism in the human corpus callosum.

Despite decades of research, there is still no agreement over the presence of gender-based morphologic differences in the human corpus callosum. We approached the problem using a highly precise computational technique for shape comparison. Starting with a prospectively acquired sample of cranial MRIs of healthy volunteers (age ranges 18-84), the variations of individual callosa are quantified with respect to a reference callosum shape in the form of Jacobian determinant maps derived from the geometric transformations that map the reference callosum into anatomic alignment with the subject callosa.

Neural basis for sentence comprehension deficits in frontotemporal dementia.

Many patients with frontotemporal dementia (FTD) have impaired sentence comprehension. However, the pattern of comprehension difficulty appears to vary depending on the clinical subgroup. The purpose of this study was to elucidate the neural basis for these deficits in FTD.

Sexual dimorphism in the corpus callosum: a characterization of local size variations and a classification driven approach to morphometry.

We present two complementary quantitative approaches to the problem of characterizing morphometric variations between two distinct populations. The case presented focuses solely on local size variations, but the general method can easily be applied to other scalar morphometric quantities. The first method uses a statistical parametric map (SPM) to ascertain a P value, which indicates whether any statistically significant differences exist between the populations.

The neural basis for category-specific knowledge: an fMRI study.

Functional neuroimaging studies of healthy adults have associated different categories of knowledge with distinct activation patterns. The basis for these recruitment patterns has been controversial, due in part to the limited range of categories that has been studied. We used fMRI to monitor regional cortical recruitment patterns while subjects were exposed to printed names of Animals, Implements, and Abstract nouns.

Sentence processing strategies in healthy seniors with poor comprehension: an fMRI study.

We used fMRI to examine patterns of brain recruitment in 22 healthy seniors, half of whom had selective comprehension difficulty for grammatically complex sentences. We found significantly reduced recruitment of left posterolateral temporal [Brodmann area (BA) 22/21] and left inferior frontal (BA 44/6) cortex in poor comprehenders compared to the healthy seniors with good sentence comprehension, cortical regions previously associated with language comprehension and verbal working memory, respectively. The poor comprehenders demonstrated increased activation of left prefrontal (BA 9/46), right dorsal inferior frontal (BA 44/6), and left posterior cingulate (BA 31/23) cortices for the grammatically simpler sentences that they understood.

Neural representation of verb meaning: an fMRI study.

The neural basis for verb comprehension has proven elusive, in part because of the limited range of verb categories that have been assessed. In the present study, 16 healthy young adults were probed for the meaning associated with verbs of MOTION and verbs of COGNITION. We observed distinct patterns of activation for each verb subcategory: MOTION verbs are associated with recruitment of left ventral temporal-occipital cortex, bilateral prefrontal cortex and caudate, whereas COGNITION verbs are associated with left posterolateral temporal activation.

Neural basis for sentence comprehension: grammatical and short-term memory components.

We monitored regional cerebral activity with BOLD fMRI while subjects were presented written sentences differing in their grammatical structure (subject-relative or object-relative center-embedded clauses) and their short-term memory demands (short or long antecedent-gap linkages). A core region of left posterior superior temporal cortex was recruited during all sentence conditions in comparison to a pseudofont baseline, suggesting that this area plays a central role in sustaining comprehension that is common to all sentences. Right posterior superior temporal cortex was recruited during sentences with long compared to short antecedent-gap linkages regardless of grammatical structure, suggesting that this brain region supports passive short-term memory during sentence comprehension.

Age-related changes in working memory during sentence comprehension: an fMRI study.

Sentence comprehension declines with age, but the neural basis for this change is unclear. We monitored regional brain activity in 13 younger subjects and 11 healthy seniors matched for sentence comprehension accuracy while they answered a simple probe about written sentences. The sentences varied in their grammatical features (subject-relative vs object-relative subordinate clause) and their verbal working memory (WM) demands (short vs long antecedent noun-gap linkage).