High cardiovascular reactivity due to stress has been established as a risk factor for the development of cardiovascular disease. Animal and human studies indicate a role of forebrain regions, specifically the medial prefrontal cortex, the insular cortex and the amygdala, in mediating autonomic control of the cardiovascular system. However, the specific regions of the forebrain involved in the cardiovascular control during the stress response in humans are unknown. The purpose of this study is to investigate what proportion of a young healthy population demonstrates cardiovascular reactivity to a laboratory mental stress task, and to determine the forebrain regions involved in the stress response in high cardiovascular reactors (reactors) and low cardiovascular reactors (non reactors). Methods: In a prescreening trial, 50 volunteer subjects (mean age 24) performed 2 mental stress tasks: mental arithmetic (MA) and the Stroop Color Word Task (SCWT). Heart rate (HR) and Mean Arterial Pressure (MAP) were conti...

Introduction: Parcellation of the cerebellar cortex allows for detailed functional and structural imaging studies of the cerebellum. Volumetric changes during normal development and aging, or related to pathology, emphasize the relevance of morphometric analysis of cerebellar cortex. Previously, we described a parcellation system of the human cerebellar cortex based upon neuroanatomy [1]. In the present study morphometric analysis was performed on five normal humans, as well as intra- and inter-rater reliability measurements. Methods: The cerebellar cortex of five normal human subjects was parcellated using T1-weighted anatomic MR images. The method of parcellation applied here was based on our previous study, which delineated 20 parcellation units (PUs) in each cerebellar hemisphere and 12 PUs in each hemivermis [1]. Reliability measurements were performed on the resulting parcellations. Results and Discussion: Volumetric analysis and trials for intra- and inter-rater reliability were performed in a blind...

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...

Humans detect motions of images defined not only by luminance difference (first-order) but images segregated by the second-order characteristics such as texture, contrast, and so on. There have been few electrophysiological studies addressed on the mechanism underlying the second-order motion detection. First, we measured the magnetoencephalographic (MEG) response to the second-order motion defined by the sinusoidally modulated dots speeds but there was no obvious responses detected whereas the responses to the first-order sinusoidal grating at the same speed (2.6 deg/s) were found peaking at about 310 ms. Second, we measured the MEG responses to the apparent motions of the square areas. The areas were defined by the three characteristics: difference in the dots speeds (second-order apparent motion; SA), luminance of the dots (first-order; FA), and dots speeds and luminance (mixed; MA). For all the stimuli, MEG latencies decreased and the amplitudes increased as the motion distance increased. The latencies...

Despite neuropathological evidence for significant neuronal and glial cell reductions in specific cortical regions in bipolar disorder, MRI studies have not consistently demonstrated either global or regional cortical gray matter reductions. Several MRI studies have suggested that brain abnormalities may be more prominent in familial mood disorders. Therefore, this study examined DSE and MP-RAGE MRI images of 20 familial bipolar I subjects (age 38.9 ± 9.4 years) and 45 control subjects (age 34.6 ± 10.4 years) utilizing quantitative MRI tissue segmentation and Talairach-atlas based volumetric techniques. ANCOVA with age, sex, and intracranial volume as covariates was used for statistical analysis. The bipolar I disorder group demonstrated significantly increased sulcal (p=0.010) and ventricular CSF (p=0.015), as well as decreased white matter (p=0.043) and cortical gray matter(p=0.009). To further investigate the cortical gray matter reduction, Talairach atlas-based regional voluming revealed significantly ...

Smart molecular probes for both diagnostic and therapeutic purposes are expected to provide quantum advances in clinical medicine and biomedical research. We describe such a probe that targets β-amyloid plaques of Alzheimer’s disease and is detectable by magnetic resonance imaging (MRI) because of contrast imparted by gadolinium labeling. Three essential properties are shown to exist in this smart molecular probe, putrescine-gadolinium-amyloid-β peptide: 1) transport across the blood-brain-barrier following intravenous injection which is conferred by the polyamine moiety, 2) binding to plaques with high affinity by the putrescine-labeled amyloid-β peptide, and 3) MRI detectability conferred by the contrast agent, gadolinium. MRI was performed on ex vivo tissue specimens at a spatial resolution approximating plaque size (62.5 μm3), in order to prove the concept that the probe can selectively enhance plaques when administered intravenously. The plaque-to-background tissue contrast-to-noise ratio, that was pr...

Sensitivity changes, beginning at the first stages of visual transduction, permit neurons with modest dynamic range to respond to contrast variations across an enormous range of mean illumination. We have used functional magnetic resonance imaging (fMRI) to investigate how these sensitivity changes are controlled within the visual pathways. We measured responses in human visual area V1 to a constant-amplitude, contrast-reversing probe presented on a range of mean backgrounds. We found that signals from probes initiated in the L and M cones were affected by backgrounds that changed the mean absorption rates in the L and M cones, but not by background changes seen only by the S cones. Similarly, signals from S cone-initiated probes were altered by background changes in the S cones, but not by background changes in the L and M cones. Performance in psychophysical tests under similar conditions closely mirrored the changes in V1 fMRI signals. We compare our data with simulations of the visual pathway from phot...