Objective: The stem of the superior longitudinal fascicle (SLF) was characterized volumetrically and biophysically (in terms of fractional (FI) and lattice anisotropy (LI) indices) in vivo in four patients with left perisylvian ischemic stroke lesions, and in four healthy adult human subjects using DT-MRI. Quantitative analysis was performed anterior to the site of the lesion to assess the integrity and size of SLF, allowing for the identification of potential secondary degeneration changes of this association fiber pathway. Methods: A Siemens Sonata 1.5 Tesla scanner was used. Scans included MP-RAGE T1 scans and echo-planar diffusion tensor-MRI (DT-MRI). The echo-planar based protocol included diffusion tensor imaging to sample the diffusion tensor, D, using a seven-shot EPI technique with TR=200ms, TE=89ms, 36 averages, image matrix=128x128, voxel size=2x2x2mm3, b=1000s/mm2, 60 contiguous coronal slices for a total acquisition time of approx. 13 min, and a SNR of approx. 40. Custom made software and semi...

We correlated tissue pathology to various types of post-mortem MRI from 5 secondary progressive multiple sclerosis (MS) patients. Prior to rapid autopsy protocol, the donor underwent a post-mortem in situ MRI which included T2-weighted, T1-weighted and magnetization transfer ratio (MTR) images. Lesions were segmented and classified automatically in the post-mortem MRI. Following imaging, one hemisphere was fixed whole. A post-fixation MRI was performed in a custom-designed slicing box to aid in co-registration of MRI and tissue location. The fixed brain was cut into 1 cm thick coronal slices. 66 areas of interest were selected for immunohistochemical analysis using the following MRI categories: regions that were normal-appearing on all images (N=15); regions of T2 hyperintensity that were normal-appearing on T1 and MTR (T2 only,N=22); and regions of T2 hyperintensity which were hypointense on T1 and MTR (T2T1MTR,N=29). Normal-appearing regions on MRI corresponded to myelinated white matter. 73% of T2 only ...

Amyloid deposition in Alzheimer’s disease (AD) occurs many years before cognitive impairment. Brain imaging techniques targeting plaques will have an important diagnostic value and may help in identifying individuals in preclinical stages of AD. Magnetic resonance imaging (MRI) has a much higher resolution than positron enhanced tomography (PET) imaging and, therefore, is a more sensitive method to detect amyloid plaques. In our initial proof-of-concept studies (Magnetic Resonance in Medicine, in press), we utilized Aβ1-40 peptide, labeled with gadolinium or monocrystalline iron oxide nanoparticles (MION). When either of these ligands is injected in vivo systemically with mannitol to transiently open the blood-brain-barrier, we are able to image ex vivo the majority of Aβ plaques in Tg mice. Using Gd labeled Aβ1-40 and in vivo μMRI, we can also detect a substantial percentage of amyloid lesions. There is a high correlation between the numerical density of Aβ plaques detected by μMRI and by immunohistochemi...

Functional Magnetic Resonance Imaging (fMRI) is a powerful tool for studying brain function in living intact specimen. Thus far it has only been used in mammals and in the case of laboratory animals its use was even restricted to simple stimulation paradigms due to the required anaesthesia. However fMRI has far more potentials such as repeated observations on neuronal information processing during the performance of simple and cognitive tasks. This study explores fMRI to study auditory processing in the thalamic and telencephalic auditory regions in the brain of songbirds. They represent a well documented animal model for vocal learning and related functional changes in the involved brain regions, even under anaesthetised conditions. We exposed anaesthetised male European starlings to various acoustic stimuli with increasing degree of complexity, ranging from white noise to conspecific song. We localised and monitored the auditory brain responses as a function of stimulus exposure time. Field L showed acti...

Preliminary studies suggest that MRI may be useful for distinguishing between vasogenic edema (open BBB edema) and cytotoxic or cellular edema (closed BBB edema). Cold injury-induced brain trauma (CIBT) is the classic small-animal model of vasogenic cerebral edema. Rats were anesthetized and maintained at 37oC. The skull was exposed, and a cooled brass probe was placed in direct contact with the skull, over the right hemisphere, for 2 minutes. Twenty-four hours later MRI was performed. Images were collected on a 7T horizontal bore MR system with 220mT/m actively shielded gradients (TR/TE = 8/0.05 s, pixel resolution = 115x230x1000µm. The T2 weighted image and T2 map clearly delineated the borders of the infarct. The contrast in both images was maximal at the base of the infarct. BBB integrity was also assessed 24-hours after CIBT from gadolinium (Gd)-enhanced, T1-weighted images obtained 30 minutes after a tail-vein injection of Gd-DTPA. It was noteworthy that BBB breakdown was most extensive along the top...

Neuropsychological studies of humans and monkeys have provided evidence that the damage to the prefrontal cortex impairs the ability to discriminate the order of events sequentially presented during recency judgment paradigms. Previous neuroimaging studies investigated the temporal-order memory by contrasting it with item memory, and revealed that frontal activation was stronger during the temporal-order memory than during the item memory. The present functional magnetic resonance imaging (fMRI) study explored the precise neural correlates of the temporal-order retrieval per se using an intra-paradigm comparison within a recency judgment paradigm. In this paradigm, after subjects studied a list of words sequentially, they were presented with two of the studied words simultaneously and were asked which of the two words were studied more recently. Two types of such retrieval trials with varied amount of demands for the recency judgment were intermixed and compared using event-related fMRI. The comparison of ...

The utilization of stem cells as therapeutic agents is an active area of current research. Although cell-based therapy has been successfully implemented in animal models of stroke or Parkinson’s disease, clinical trials have demonstrated only modest therapeutic effects. Further research is needed to better understand the mechanisms governing cellular migration and differentiation. Magnetic resonance (MR) tracking of stem cells is a new emerging application that aims to obtain a better understanding of the dynamics of cell-tissue interactions, as well as to aid in guiding the development of effective cell therapies. In this study we report on the applicability of MR tracking of magnetically labeled (magnetofected) neural stem cells following transplantation into the dysmyelinated mouse brain. LacZ-transfected C17.2 neural stem cells were Feridex/poly-L-lysine labeled and transplanted into the lateral ventricle of neonatal shiverer mice. In vivo MR imaging was performed at 1, 4, 7 and 14 days after cell tran...

Autism is a neurodevelopmental disorder whose core features include abnormalities in social interaction, and which has been associated with both global and regionally focused overgrowth during the first years of life. Since the amygdala modulates a wide array of social behaviors, it is logical to look for structural amygdala abnormality in the young autistic brain. It has been previously shown that the amygdala is bilaterally enlarged in young (4 years) (Sparks et al, 2002) and older (7.5-12.5 years) (Schumann et al, 2004) children with autism. However, amygdala size in children younger than 4 years has not been examined, and there has been difficulty in replicating structural amygdala findings between studies using adult autistic subjects. We therefore performed a hand tracing of the amygdala in autistic and control subjects from a larger magnetic resonance imaging (MRI) study of brain development in autistic infants and toddlers. Autistic male subjects (n=15, age range 22.4-42.2 mos., mean 33.0 ± 6.1 mos...

Microelectrode recording and stimulation techniques as well as microinjections of pharmacologic agents to record or manipulate the activity of neuronal cell groups play an outstanding role in neurophysiology. Commonly, such experiments depend on accurate determination of the anatomic structure investigated. This has traditionally been done histologically by placing small dye marks or electrolytic lesions which are visualised on brain sections after sacrificing the experimental animal. MRI is now widely used as an aid in the planning of neurophysiological experiments to improve stereotaxic localisation of target structures. To further the benefit from MRI we developed a technique similar to traditional histological procedures, to directly visualise recording sites in deep brain structures of the monkey, consisting in local injections of small volumes of gadolinium (GDA), a clinically used MRI contrast agent. These GDA-microinjections were visualized by MRI sequences [TIR (TR=3500 ms, TE=66 ms, TI=350 ms) an...

Introduction The prefrontal cortex (PFC) is thought to play an important role especially for our ability to orchestrate thoughts and actions in accordance with internal goals. In experimental psychology, cognitive control has been investigated using the so-called task-switching paradigm. In this paradigm, participants have to selectively adapt their behavior to different situations and tasks. Most importantly, participants are always unequivocally told what to do and cannot deliberately decide which task to perform. This leads to the question whether the task-switching paradigm is suited to investigate active control processes. Methods The present fMRI study aimed at investigating processes which are relevant when participants themselves can decide which task to perform. Four simple discrimination tasks were used. The number of tasks to choose from was varied between a non-choice (1 degree of freedom; DF) and two choice conditions (2 DF or 3 DF). Results The behavioral results revealed a difference for the...