Functional anatomy of essential tremor: lessons from neuroimaging.

The neuropathogenetic processes underlying essential tremor appear to cause subtle morphologic changes in neural networks that include multiple brain structures, primarily the cerebellum, brain stem, frontal lobes, and thalamus. One of the main challenges of neuroimaging in essential tremor is differentiating disease-specific markers from the spectrum of structural changes that occur due to aging. This review discusses recent neuroimaging studies in the light of current knowledge of the neuropsychology and pathology of the disease. We suggest that the application of multiple macroscopic and microscopic neuroimaging modalities, combined with personalized information relative to cognitive and behavioral symptoms, is the prerequisite for a comprehensive classification and correct diagnosis of essential tremor.

Postmortem high-resolution 3-dimensional imaging of the primate brain: blockface imaging of perfusion stained tissue.

Modern anatomy of the brain is primarily concerned with visualizing contrast between tissue elements and with 3-dimensional (3-D) reconstruction. The first objective relies on specific neuroanatomical and imaging protocols, the latter on proper alignment of serial cross-sectional anatomy. We present a method that meets these goals at a resolution that allows for the structural delineation in the primate central nervous system. Methylene blue was administered by perfusion to the intact brain of three rhesus macaques thereby staining the neuropil in the cortex and gray nuclei of the brain in situ. Subsequent dissection and serial sectioning revealed excellent contrast in the tissue and showed clear boundaries between anatomical structures. We captured sequential images of the block surface of the brain before each serial section was cut from the specimen by means of a digital camera mounted directly over the microtome stage and the brain. We developed a suite of algorithms to automate the alignment, segmentation, normalization, and intensity correction for the series of blockface images. These digital images were the basis for 3-D reconstruction of the brains.

Localization of the human cortical visual area MT based on computer aided histological analysis.

We describe human area MT histologically based on the observer independent analysis of cortical myeloarchiteture, multiple complementary staining techniques and 3-D reconstruction. The topography of an architectonic field that presented constant structural characteristics across specimens was studied in relation to the sulcal geography of the occipito-temporal region. Objective and semi-automated analysis of local microstructure revealed a distinct cortical architecture and matched topographically the localization of MT derived from functional imaging. MT was localized by the histotopographic method in relation to definite macroscopic landmarks. This study demonstrates a new set of distinguishing architectonic features of human MT that permit localization on structural grounds and suggests that the characteristic laminar structure of this area may be related to its unique pattern of connections and to its role in visual perception.

A myelo-architectonic method for the structural classification of cortical areas.

We describe an automatic and reproducible method to analyze the histological design of the cerebral cortex as applied to brain sections stained to reveal myelinated fibers. The technique provides an evaluation of the distribution of myelination across the width of the cortical mantle in accordance with a model of its curvature and its intrinsic geometry. The profile lines along which the density of staining is measured are generated from the solution of a partial differential equation (PDE) that models the intermediate layers of the cortex. Cortical profiles are classified according to significant components that emerge from wavelet analysis. Intensity profiles belonging to each distinct class are normalized and averaged to produce area-specific templates of cortical myelo-architecture.