Postmortem studies indicate a temporal sequence of primary allocortical and secondary neocortical degeneration during Alzheimer disease (AD) progression. Hippocampus (HC) atrophy correlates with allocortical neuronal degeneration and atrophy of the corpus callosum (CC) reflects loss of intracortical projecting pyramidal neurons in neocortex. First, we wanted to determine the temporal sequence and rate of degeneration of HC and CC in AD. Second, to answer the question, whether rates of atrophy were correlated with rates of cognitive decline and third, whether both markers could be proposed as potential morphological parameters for mapping drug effects on brain structure in longitudinally studied AD patients and healthy control subjects. MRI-derived measures of CC and HC were compared between 27 clinically diagnosed AD patients and 28 age- and gender-matched healthy control subjects. Rates of CC and HC atrophy were determined in 21 AD patients and 10 control subjects studied longitudinally. We found mean rel...

Task-based functional magnetic resonance imaging (tfMRI) has been widely used to induce functional brain activities corresponding to various cognitive tasks. A relatively under-explored question is whether there exist fundamental differences in fMRI signal composition patterns that can effectively classify the task states of tfMRI data, furthermore, whether there exist key functional components in characterizing the diverse tfMRI signals. Recently, fMRI signal composition patterns of multiple tasks have been investigated via deep learning models, where relatively large populations of fMRI datasets are indispensable and the neurological meaning of their results is elusive. Thus, the major challenges arise from the high dimensionality, low signal-to-noise ratio, inter-individual variability, a small sample size of fMRI data, and the explainability of classification results. To address the above challenges, we proposed a computational framework based on group-wise hybrid temporal and spatial sparse representa...

The use of brain slices is an important tool to perform mechanistic studies in neuroscience. It enables the researcher to isolate aspects of physiological function and to explore the impact of specific signaling pathways, gene promoters, and inhibitors ...

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 ...

Primary visual cortex in ferrets is a model system for studying the plasticity and development of neuronal feature maps, such as maps of retinotopy, orientation and spatial frequency. Previous studies examining the nature of these maps and their relatio...

It has been shown that the blood oxygenation level dependent (BOLD) functional MRI signal at magnetic field strengths of ≤ 1.5T arises predominantly from large vessels, which can be quite distant from the sites of neuronal activity. To improve the spatial localization to the active tissues/capillaries, the use of high field magnets has been proposed. To test this hypothesis, we evaluated the microvascular versus the macrovascular contribution to the BOLD response at high fields (4 and 7T) following visual stimulation in humans. Diffusion-weighted BOLD fMRI was used to selectively attenuate the fast-moving (large-vessel) fMRI signals. Two acquisition schemes were used: a gradient-echo scheme which is sensitive to both large- and small-vessel BOLD effects and a spin-echo scheme which should mitigate large-vessel BOLD effects. A comparison was made between the two sets of results. Diffusion-weighted BOLD fMRI was performed on 24 normal humans with graded flow-crushing gradients (4-7 b values). The visual stim...

The re-emergence of task-related activation patterns during awake rest has been reported to play a role in memory consolidation and perceptual learning. This study aimed to test whether such reactivation occurs in the primary sensorimotor cortex following a visuomotor task. During functional magnetic resonance imaging (fMRI) scanning, 42 healthy participants (13 women and 29 men) learned visuomotor tracking, while a rotational perturbation was introduced between the cursor position and joystick angle. This visuomotor task block was interleaved with a control block, during which participants passively viewed a replay of their previously performed cursor movements. Half of the participants used their right hand, whereas the other half used their left hand to control the joystick. Resting-state scans were acquired before and after the visuomotor task sessions. A multivariate pattern classifier was trained to classify task and control blocks and was then tested on resting-state scans collected before and after...

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 recent years diffusion MRI (dMRI) studies have advanced from relatively few number of gradient directions acquired with a single diffusion weighting to more complex multi-shell acquisition schemes and reconstruction methods (Tuch 2004; Tournier et al...

The subjective experience of one's environment is constructed by interactions among sensory, cognitive, and affective processes. For centuries, meditation has been thought to influence such processes by enabling a nonevaluative representation of sensory events. To better understand how meditation influences the sensory experience, we used arterial spin labeling functional magnetic resonance imaging to assess the neural mechanisms by which mindfulness meditation influences pain in healthy human participants. After 4 d of mindfulness meditation training, meditating in the presence of noxious stimulation significantly reduced pain unpleasantness by 57% and pain intensity ratings by 40% when compared to rest. A two-factor repeated-measures ANOVA was used to identify interactions between meditation and pain-related brain activation. Meditation reduced pain-related activation of the contralateral primary somatosensory cortex. Multiple regression analysis was used to identify brain regions associated with individ...