Stria Of Gennari Research Articles

Laminar imaging of positive and negative BOLD in human visual cortex at 7 T

Deciphering the direction of information flow is critical to understand the brain. Data from non-human primate histology shows that connections between lower to higher areas (e.g. retina→V1), and between higher to lower areas (e.g. V1←V2) can be dissociated based upon the distribution of afferent synapses at the laminar level. Ultra-high field scanners opened up the possibility to image brain structure and function at an unprecedented level of detail. Taking advantage of the increased spatial resolution available, it could theoretically be possible to disentangle activity from different cortical depths from human cerebral cortex, separately studying different compartments across depth.Here we use half-millimeter human functional and structural magnetic resonance imaging (fMRI, MRI) to derive laminar profiles in early visual cortex using a paradigm known to elicit two separate responses originating from an excitatory and a suppressive source, avoiding any contamination due to blood-stealing. We report the shape of laminar blood level oxygenation level dependent (BOLD) profiles from the excitatory and suppressive conditions. We analyse positive and negative %BOLD laminar profiles with respect to the dominating linear trend towards the pial surface, a confounding feature of gradient echo BOLD fMRI, and examine the correspondence with the anatomical landmark of input-related signals in primary visual cortex, the stria of Gennari.

Characterizing the contrast of white matter and grey matter in high-resolution phase difference enhanced imaging of human brain at 3.0 T.

The purpose of this study was to address the feasibility of characterizing the contrast both between and within grey matter and white matter using the phase difference enhanced (PADRE) technique. PADRE imaging was performed in 33 healthy volunteers. Vessel enhancement (VE), tissue enhancement (TE), and PADRE images were reconstructed from source images and were evaluated with regard to differentiation of grey-to-white matter interface, the stria of Gennari, and the two layers, internal sagittal stratum (ISS) and external sagittal stratum (ESS), of optic radiation. White matter regions showed decreased signal intensity compared to grey matter regions. Discrimination was sharper between white matter and cortical grey matter in TE images than in PADRE images, but was poorly displayed in VE images. The stria of Gennari was observed on all three image sets. Low-signal-intensity bands displayed in VE images representing the optic radiation were delineated as two layers of different signal intensities in TE and PADRE images. Statistically significant differences in phase shifts were found between frontal grey and white matter, as well as between ISS and ESS (p < 0.01). The PADRE technique is capable of identifying grey-to-white matter interface, the stria of Gennari, and ISS and ESS, with improved contrast in PADRE and TE images compared to VE images. • Phase difference enhanced (PADRE) imaging can yield diverse contrasts between tissues • The PADRE technique utilizes the inherent variety of magnetic susceptibilities • PADRE MR imaging provides better visualization of certain cerebral anatomy in vivo • PADRE imaging is able to delineate the stria of Gennari in the primary visual cortex • PADRE imaging is able to identify the two optic radiation layers.

Layer-specific diffusion weighted imaging in human primary visual cortex in vitro

One of the most prominent characteristics of the human neocortex is its laminated structure. The first person to observe this was Francesco Gennari in the second half the 18th century: in the middle of the depth of primary visual cortex, myelinated fibres are so abundant that he could observe them with bare eyes as a white line. Because of its saliency, the stria of Gennari has a rich history in cyto- and myeloarchitectural research as well as in magnetic resonance (MR) microscopy. In the present paper we show for the first time the layered structure of the human neocortex with ex vivo diffusion weighted imaging (DWI). To achieve the necessary spatial and angular resolution, primary visual cortex samples were scanned on an 11.7 T small-animal MR system to characterize the diffusion properties of the cortical laminae and the stria of Gennari in particular. The results demonstrated that fractional anisotropy varied over cortical depth, showing reduced anisotropy in the stria of Gennari, the inner band of Baillarger and the deepest layer of the cortex. Orientation density functions showed multiple components in the stria of Gennari and deeper layers of the cortex. Potential applications of layer-specific diffusion imaging include characterization of clinical abnormalities, cortical mapping and (intra)cortical tractography. We conclude that future high-resolution in vivo cortical DWI investigations should take into account the layer-specificity of the diffusion properties.

Delineation of Optic Radiation and Stria of Gennari on High-resolution Phase Difference Enhanced Imaging

Phase difference enhanced (PADRE) imaging technique can selectively enhanced the phase difference between the target and surrounding tissue. Our purpose is to assess the delineations of the optic radiation and primary visual cortex (stria of Gennari) using PADRE. The subjects were 6 healthy volunteers. Axial and coronal high-spatial resolution PADRE images were acquired covering the entire optic radiation using a 3T magnetic resonance system. Two radiologists evaluated the PADRE and susceptibility-weighted imaging (SWI)-like images for the delineation of four layers at the optic radiation (tapetum, internal sagittal stratum, external sagittal stratum, and adjacent white matter) on the basis of the anatomic appearances of the cadaveric specimens stained with Bodian's method and Kluver-Barrera method. The radiologists also assessed the delineations of the stria of Gennari on PADRE and SWI-like images. In all 6 healthy subjects, the PADRE images clearly identified the four layers at the optic radiation, as well as the stria of Gennari, which were difficult to appreciate in SWI-like images. The anatomic appearances of the optic radiation on PADRE images were more similar to those seen in the specimens stained with Kluver-Barrera method than with Bodian's method. The PADRE technique can delineate the four layers at the optic radiation and the stria of Gennari; the differences in myelin densities can also be enhanced. The PADRE technique may have the potential to reinforce the clinical utility of MRI in the diagnosis of diseases that affect the optic radiation and primary visual cortex.

Accurate prediction of V1 location from cortical folds in a surface coordinate system

Previous studies demonstrated substantial variability of the location of primary visual cortex (V1) in stereotaxic coordinates when linear volume-based registration is used to match volumetric image intensities [Amunts, K., Malikovic, A., Mohlberg, H., Schormann, T., and Zilles, K. (2000). Brodmann’s areas 17 and 18 brought into stereotaxic space—where and how variable? Neuroimage, 11(1):66–84]. However, other qualitative reports of V1 location [Smith, G. (1904). The morphology of the occipital region of the cerebral hemisphere in man and the apes. Anatomischer Anzeiger, 24:436–451; Stensaas, S.S., Eddington, D.K., and Dobelle, W.H. (1974). The topography and variability of the primary visual cortex in man. J Neurosurg, 40(6):747–755; Rademacher, J., Caviness, V.S., Steinmetz, H., and Galaburda, A.M. (1993). Topographical variation of the human primary cortices: implications for neuroimaging, brain mapping, and neurobiology. Cereb Cortex, 3(4):313–329] suggested a consistent relationship between V1 and the surrounding cortical folds. Here, the relationship between folds and the location of V1 is quantified using surface-based analysis to generate a probabilistic atlas of human V1. High-resolution (about 200 μm) magnetic resonance imaging (MRI) at 7 T of ex vivo human cerebral hemispheres allowed identification of the full area via the stria of Gennari: a myeloarchitectonic feature specific to V1. Separate, whole-brain scans were acquired using MRI at 1.5 T to allow segmentation and mesh reconstruction of the cortical gray matter. For each individual, V1 was manually identified in the high-resolution volume and projected onto the cortical surface. Surface-based intersubject registration [Fischl, B., Sereno, M.I., Tootell, R.B., and Dale, A.M. (1999b). High-resolution intersubject averaging and a coordinate system for the cortical surface. Hum Brain Mapp, 8(4):272–84] was performed to align the primary cortical folds of individual hemispheres to those of a reference template representing the average folding pattern. An atlas of V1 location was constructed by computing the probability of V1 inclusion for each cortical location in the template space. This probabilistic atlas of V1 exhibits low prediction error compared to previous V1 probabilistic atlases built in volumetric coordinates. The increased predictability observed under surface-based registration suggests that the location of V1 is more accurately predicted by the cortical folds than by the shape of the brain embedded in the volume of the skull. In addition, the high quality of this atlas provides direct evidence that surface-based intersubject registration methods are superior to volume-based methods at superimposing functional areas of cortex and therefore are better suited to support multisubject averaging for functional imaging experiments targeting the cerebral cortex.

The auditory cortex

Recognizing other people, animals or objects by the sound they make is something that most of us take for granted. In fact, this ability relies on a series of rich and complex processes that begin when sounds are transduced into electrical signals by the exquisitely sensitive hair cell receptors that lie inside the cochlea of the inner ear. These messages are then encoded as volleys of action potentials by the axons of the vestibulo-cochlear nerve and transmitted via a complex chain of nuclei in the brainstem, midbrain and thalamus towards the auditory cortex (Figure 1A), where the interpretation and recognition of sounds is thought to take place.

Imaging cortical anatomy by high-resolution MR at 3.0T: detection of the stripe of Gennari in visual area 17.

The brain can be parcellated into numerous anatomical and functional subunits. The classic work by Brodmann (Vergleichende Lokalisationslehre der Grosshirnrinde in ihren Prinzipien dargestellt auf Grund des Zellenbaues. Leipzig: Barth; 1909) identified areas of the cerebral cortex based on histological differences. An alternative to his cytoarchitectonic approach is the myeloarchitectonic approach. MRI has excellent white/gray matter contrast in the brain due to the presence of myelin, and thus seems uniquely suited for in vivo studies of cortical myeloarchitecture. Here it is demonstrated that the stripe or stria of Gennari can be consistently detected in human occipital cortex. T(1)-weighted images obtained at 3T from six of 10 normal volunteers, with resolutions of 350 x 350 x 600 mu clearly demonstrate this myelin-rich intracortical layer. It is concluded that the striate cortex (area 17 of Brodmann) of the human brain can be delineated in vivo on T(1)-weighted images, potentially enabling detection of specific cortical boundaries within individual brains.

Improvements of plasma spraying processes for hybrid microelectronics : M. Braguier, J. Bejat, R. Tueta, M. Verna, G. Aubin and C. Naturel. IERE Conf. Hybrid Microelectron. Canterbury. 15 (25–27 Sept. 1973)

Previous studies demonstrated substantial variability of the location of primary visual cortex (V1) in stereotaxic coordinates when linear volume-based registration is used to match volumetric image intensities [Amunts, K., Malikovic, A., Mohlberg, H., Schormann, T., and Zilles, K. (2000). Brodmann’s areas 17 and 18 brought into stereotaxic space—where and how variable? Neuroimage, 11(1):66–84]. However, other qualitative reports of V1 location [Smith, G. (1904). The morphology of the occipital region of the cerebral hemisphere in man and the apes. Anatomischer Anzeiger, 24:436–451; Stensaas, S.S., Eddington, D.K., and Dobelle, W.H. (1974). The topography and variability of the primary visual cortex in man. J Neurosurg, 40(6):747–755; Rademacher, J., Caviness, V.S., Steinmetz, H., and Galaburda, A.M. (1993). Topographical variation of the human primary cortices: implications for neuroimaging, brain mapping, and neurobiology. Cereb Cortex, 3(4):313–329] suggested a consistent relationship between V1 and the surrounding cortical folds. Here, the relationship between folds and the location of V1 is quantified using surface-based analysis to generate a probabilistic atlas of human V1. High-resolution (about 200 μm) magnetic resonance imaging (MRI) at 7 T of ex vivo human cerebral hemispheres allowed identification of the full area via the stria of Gennari: a myeloarchitectonic feature specific to V1. Separate, whole-brain scans were acquired using MRI at 1.5 T to allow segmentation and mesh reconstruction of the cortical gray matter. For each individual, V1 was manually identified in the high-resolution volume and projected onto the cortical surface. Surface-based intersubject registration [Fischl, B., Sereno, M.I., Tootell, R.B., and Dale, A.M. (1999b). High-resolution intersubject averaging and a coordinate system for the cortical surface. Hum Brain Mapp, 8(4):272–84] was performed to align the primary cortical folds of individual hemispheres to those of a reference template representing the average folding pattern. An atlas of V1 location was constructed by computing the probability of V1 inclusion for each cortical location in the template space. This probabilistic atlas of V1 exhibits low prediction error compared to previous V1 probabilistic atlases built in volumetric coordinates. The increased predictability observed under surface-based registration suggests that the location of V1 is more accurately predicted by the cortical folds than by the shape of the brain embedded in the volume of the skull. In addition, the high quality of this atlas provides direct evidence that surface-based intersubject registration methods are superior to volume-based methods at superimposing functional areas of cortex and therefore are better suited to support multisubject averaging for functional imaging experiments targeting the cerebral cortex.