To evaluate the neural substrates of cross-modal binding during audio-visual speech integration, and those of the cross-modal divided attention, we performed 3 Tesla functional MRI in 17 normal volunteers. During the scan, the subjects were exposed to the phonemically congruent or incongruent auditory and visual speech. In each trial, 2 visual speeches were presented side-by-side simultaneously. Two auditory speeches were given sequentially, the first of which was synchronized to the visual speeches. Three different matching tasks were performed with event-related design: auditory-auditory (AA), visual-visual (VV), and auditory-visual (AV). Subjects were asked to discriminate if the prompted pair was congruent or not. During AV conditions, congruent trials evoked more prominent activation than incongruent ones in the left anterior superior temporal sulcus (STS) and posterior intraparietal sulcus (IPS). AV tasks compared with AA or VV revealed more prominent activation in the bilateral dorsal premotor corte...

Reinnervation of muscle typically does not take place if a main motor nerve is severed. Regrowing nerve is thought to depend on travel within an existing conduit such as a nerve graft or one provided by suture to the denervated distal portion of the nerve. A teenage patient who suffered a complete laceration of the sciatic nerve demonstrated partial recovery from paralysis five months after the injury although there had been no effort to repair or graft the nerve. High resolution magnetic resonance neurography demonstrated that new distal nerve had sprouted from the truncated terminus of the cut sciatic nerve and reached an adjacent portion of the hamstring muscle mass, traveling a distance of more than six centimeters to reach its target. Demonstration of this class of nerve regrowth and muscle reinnervation suggests that denervated role can play a significant role in directing the regrowth of severed nerves in human subjects.

We have recently demonstrated activation within the dorsal amygdala/sublenticular substantia innominata (SI) region to fearful facial expressions when contrasted with angry facial expressions (Whalen et al., 2001). This subtraction suggests that negative valence per se is not driving these signal changes. If so, we hypothesized that the facial expression of surprise, which is not necessarily negatively valenced, should also activate this region of the amygdala. Human subjects viewed blocked surprised, fearful and neutral facial expressions during functional magnetic resonance imaging (fMRI; GE 3T; 3mm coronal slices). Results demonstrate dorsal amygdaloid/SI activation to the facial expression of surprise when contrasted with neutral faces. In these same subjects, fearful facial expressions activated the ventral amygdala when contrasted with neutral facial expressions. Our working hypothesis is that activation of the ventral amygdala is consistent with the detection of valence differences, based upon what ...

Cerebral sulci are often used as landmarks in identifying brain anatomical structures, therefore correct detection and identification of cortical sulci are important in brain anatomical research. Here we present a fuzzy logic method to identify medial surfaces of the longitudinal fissure. The main sulcal medial surfaces were extracted by a sequence of image analysis steps: (1) A white matter (WM) segmentation was performed to make sulcal indentations more prominent. (2) A morphological closing was performed to obtain an ideally smoothed surface. (3) Sulcal separations were accomplished by subtracting the WM from the morphologically closed image. (4) Sulcal medial surfaces were obtained by applying a 3-D thinning on the sulcal separations. Knowledge of anatomical characteristics of the longitudinal cerebral fissure medial surfaces, i.e., shape, position, length, was encoded into fuzzy membership functions. The fuzzy degrees of the functions were calculated separately. A threshold was applied to the sum of t...

Periodic breathing is associated with substantial alterations in autonomic outflow and extreme heart rate variation that accompany the cessation and resumption of respiratory efforts. The breathing pattern provides an opportunity to determine neural structures recruited to initiate and terminate breathing efforts, and to assess sites involved in mediating sympathetic and parasympathetic outflow. We examined signal changes in neural sites during periodic breathing in quiet sleep in two patients with obstructive sleep apnea. Twenty-five volumes of 20 image slices through the brain (Echo Planar technique) were collected using a GE 1.5T Signa scanner during a 2.5 min period of quiet sleep as determined by MR-compatible EEG techniques. The images were corrected for slice timing and motion, and were spatially and intensity normalized. Correlations between breathing rate and signal intensity were calculated, and significant voxels overlaid onto T1 anatomical images. During apneic periods, both patients showed sig...

In vivo assessment of stem cell transplantation by MRI will allow the evaluation of indirect markers of graft effects over time. Current clinical evaluation of fetal tissue transplants is achieved using a battery of behavioural and neuroimaging techniques. Application of neuroimaging techniques to stem cell grafts will be more problematical due to the diffuse nature of graft integration caused by cell migration into the host parenchyma. Therefore, more sensitive neuroimaging methods need to be developed to assess the effects of such cells in the clinical domain. Using serial T1, T2, T2* and proton density weighted MRI scans at 2 days pre-grafting and 2, 7, 14 and 56 days post-grafting we have measured the effects of unilateral grafting of conditionally immortalised MHP-36 stem cells (2 deposits of 50000 cells in 4μL NAC) on the systemic 3-NPA rat model of Huntington’s disease. Changes relative to pre-grafting in total brain volume, CSF volume and total tissue volume were measured. Temporal evolution of the...

In vivo visualization of the brain's functional architecture using fMRI is ubiquitous these days. However, in order to understand the how of the brain's information processing, it is of central importance to map the pattern of the neuronal connectivity in the same non-invasive manner. In this study, we have utilized MR techniques to visualize the functional activity and the pattern of axonal connectivity from the same cortical site. Cats were anesthetized using standard protocols. Subsequently, ultra-high field (9.4Tesla) fMRI signals were obtained during visual stimulation. Consecutively, high-resolution Diffusion Tensor Imaging (DTI) was used to assess the pattern of the axonal connectivity with respect to the layout of the functional activity. The MR parameters for functional scans were:64x64x64 matrix; FOV=5x5x4cm3, TE/image TR=12ms/1.5s. For DTI, a 3D Spin-EchoEPI sequence was used. The diffusion weighting parameters were: Diffusion time=16 msec, gradient duration=6 msec and gradient strength=17gauss/...

Injection of manganese, a calcium analogue and paramagnetic tract-tracing agent, into the high vocal center (HVc) of starlings labeled within a few hours the nucleus robustus archistriatalis (RA) and area X as observed by in vivo magnetic resonance imaging (MRI). Structures highlighted by manganese accumulation assumed the expected tri-dimensional shape of RA and area X as identified by classical histological or neurochemical methods. The volume of these nuclei could be accurately calculated by segmentation of the areas highlighted by manganese. Besides confirming previously established volumetric sex differences, manganese uptake into these nuclei revealed new functional sex differences affecting manganese transport. A faster transport was observed in males than in females and different relative amounts of Mn2+ were transported to RA and area X in males as compared to females. In males, similar amounts of Mn2+ were transported from HVc to these two nuclei despite their different size but in females, twice...

Accuracy of targeting is critical for the success of cell transplantation and recombinant viral vector mediated gene therapy. We compared the accuracy of conventional atlas guided stereotaxis to MRI guided stereotactic targeting into various basal ganglia nuclei in hemiparkinsonian (HP) monkeys. High resolution 3-D T1 weighted MR images of the brain were obtained in 27 HP monkeys fitted with a MRI compatible stereotactic frame. This was immediately followed by cranial surgery with the frame in situ. Thirteen additional HP monkeys underwent stereotactic atlas guided cranial surgery for placement of cell transplants. Following extensive behavioral testing, microelectrode recording (MER) and PET imaging all animals were euthanized and perfused with 4% paraformaldehyde. The brains were cut in coronal sections and stained to determine the accuracy of stereotactic placements. Preliminary data analysis indicate that MRI guided stereotaxis was accurate (2 caudate and 3 putamen targets) in 16 out of 16 animals anal...