Posterior cingulate, parietal, temporal, and prefrontal cortices have been implicated as brain regions affected in the early stages of Alzheimer's disease (AD). To evaluate whether atrophy in these brain regions occurs prior to the onset of cognitive symptoms in individuals at risk for AD, we compared 11 cognitively normal ε4 homozygotes with a reported family history of AD (mean ±SD age = 55±4 yr; 3M, 8F) to 22 gender-, age-, and educationally-matched ε4 non-carriers (mean±SD age = 56±5 yr; 6M, 16F) using voxel-based MRI morphometry. T1-weighted, volumetric MRI's were acquired using a 1.5 T scanner. SPM99 was used to transform them into the coordinates of a standard brain atlas, correct them for inhomogeneities, segment them for gray matter, smooth them, and create a statistical brain map of significant group differences in gray matter density. Significance was taken at p ≤ 0.005 (uncorrected for multiple comparisons) for hypothesized regional effects. In comparison with the ε4 noncarriers, the ε4 homozyg...

Neuroimaging studies have often failed to observe activity in the hippocampal region during memory retrieval. Recently, two functional magnetic resonance imaging studies reported activity in the hippocampal region associated with recollective success. In both, participants studied pictures of objects and were given a recognition memory test with words that either did or did not name the studied objects. The recognition test was therefore cross-modal or associative in nature. These findings raise the question of what circumstances are required to observe activity in the hippocampal region during memory retrieval. Here, we report that robust hippocampal activity for targets relative to foils occurred during retrieval in a recognition memory task when single words were used at both study and test, as well as when pictures of single nameable objects were used at both study and test. The hippocampal region is involved not just in overtly associative tasks but more broadly in the recollection of recently occurri...

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...

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...

The present study examined the effects of a selective inducible nitric oxide synthase (iNOS) inhibitor on neuronal cell survival and post-traumatic recovery in rats following a lateral fluid percussion injury. Aminoguanidine at the dosage of 100 mg/kg or normal saline was injected intraperitoneally into rats 2 hours before or 30 minutes after the head injury. Animals were sacrificed at 4h, 1, 3 and 7 days post-injury. Treatment with iNOS inhibitor aminoguanidine significantly reduced lesion volumes in rats after fluid percussion, as evaluated by high-resolution magnetic resonance imaging (MRI). Immunohistochemical analysis showed a marked induction of iNOS expression in macrophages in the subarachnoid space and cerebral ventricles ipsilateral to the injury in rats killed at 1-day. In parallel with the appearance of iNOS positive macrophages, apoptotic neurons were observed in the ipsilateral cerebral cortex by in situ terminal transferase d-UTP nick-end labelling (TUNEL). In rats receiving prophylactic or ...