Filter
-
(43)
-
(35)
-
(14)
-
(2)
-
(1)
-
(22)
-
(2)
-
(91)
-
(1)
-
(1)
-
(115)
-
(2)
-
(2)
-
(6061)
-
(72)
-
(71)
-
(96)
1691 - 1700
of 33803 results
-
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for medically refractory Parkinson's disease. Although DBS has recognized clinical utility, its biologic mechanisms are not fully understood, and whether dopamine release is a potential factor in those mechanisms is in dispute. We tested the hypothesis that STN DBS-evoked dopamine release depends on the precise location of the stimulation site in the STN and the site of recording in the caudate and putamen. We conducted DBS with miniature, scaled-to-animal size, multicontact electrodes and used functional magnetic resonance imaging to identify the best dopamine recording site in the brains of nonhuman primates (rhesus macaques), which are highly representative of human brain anatomy and circuitry. Real-time stimulation-evoked dopamine release was monitored using in vivo fast-scan cyclic voltammetry. This study demonstrates that STN DBS-evoked dopamine release can be reduced or increased by redirecting STN stimulation to...Jun 1, 2016
-
AbstractPrevious lesion research with non-human primates has demonstrated the hippocampal involvement in delayed match and non-match to sample (DMS/DNMS) tasks. Earlier functional imaging work in our laboratory with humans has found that BOLD activity in the medial temporal lobe (MTL), in particular the right hippocampus, is increased during performance of the memory task. The present study extends this line of work by investigating development of the neural correlates underlying memory on the DMS/DNMS task. The hippocampal activity of 7-12 year old children was investigated using high resolution (4 Tesla) event-related functional magnetic resonance imaging (fMRI). Results indicate that children recruit similar brain regions as adults, suggesting that at least by this age, children’s reliance on MTL structures is at or very close to adult levels.Nov 13, 2001
-
AbstractNavigation is arguably one of the most important behaviors associated with survival. Although a common, optimized strategy among individuals within a species could be advantageous, in reality, navigation has an incredible degree of variability, both bet...Oct 21, 2019
-
AbstractThe claustrum has reciprocal connectivity with multiple cortical networks and potentially has an important role in orchestrating activity across these functional networks. However, the claustrum’s sheet-like shape and close apposition to medially lying ...Nov 16, 2016
-
Long-term aluminum (Al) exposure increases the risk of mild cognitive impairment (MCI). The aim of the present study was to investigate the neural mechanisms of Al-induced MCI. In our study, a total of 52 individuals with occupational Al exposure >10 years were enrolled and divided into two groups: MCI (Al-MCI) and healthy controls (Al-HC). Plasma Al concentrations and Montreal Cognitive Assessment (MoCA) score were collected for all participants. And diffusion tensor imaging and resting-state functional magnetic resonance imaging were used to examine changes of white matter (WM) and functional connectivity (FC). There was a negative correlation between MoCA score and plasma Al concentration. Compared with the Al-HC, fractional anisotropy value for the right fornix (cres)/stria terminalis (FX/ST) was higher in the Al-MCI. Furthermore, there was a difference in FC between participants with and without MCI under Al exposure. We defined the regions with differing FC as a “pathway,” specifically the connectivi...Aug 1, 2024
-
Gray matter atrophy, glucose hypometabolism, and β-amyloid Aβ deposition are well-described hallmarks of Alzheimer's disease, but their relationships are poorly understood. The present study aims to compare the local levels of these three alterations in humans with Alzheimer's disease. Structural magnetic resonance imaging, 18F-fluorodeoxyglucose positron emission tomography (PET), and 18F-florbetapir PET data from 34 amyloid-negative healthy controls and 20 demented patients with a high probability of Alzheimer's disease etiology (attested using neuroimaging biomarkers as recently recommended) were analyzed. For each patient and imaging modality, age-adjusted Z -score maps were computed, and direct between-modality voxelwise comparison and correlation analyses were performed. Significant differences in the levels of atrophy, hypometabolism, and Aβ deposition were found in most brain areas, but the hierarchy differed across regions. A cluster analysis revealed distinct subsets of regions: (1) in the hippoc...Nov 14, 2012
-
AbstractTransactive response DNA binding protein 43 (TDP-43) is the major pathological protein in motor neuron disease. In some models of TDP-43 overexpression, mice do not survive when the transgene is on throughout normal development. We utilized an inducible...Nov 11, 2021
-
AbstractOur previous studies have established the utility of Mn-enhanced MRI (MEMRI) for detecting aggregate sound-evoked activity within the inferior colliculus (IC) of hearing and deaf mice. The present goal was to determine the spatial resolution of MEMRI by examining sound frequency-dependent patterns of activity in the mouse IC. Electrophysiological recordings have established the tonotopic map in mouse IC using threshold stimulation. However, there is little information on the spatial pattern of activity for suprathreshold stimulation. Following Mn injections, mice were exposed to one of the following acoustic stimuli in the free field at 65-89 dB SPL: wideband (1-59 kHz), high frequency band pass (20-50 kHz), or pure tones (16 or 40 kHz). Wideband stimulation elicited a diffuse pattern of IC enhancement covering most of the central nucleus, and this spatial pattern became more confined to the ventral-caudal IC with high frequency band pass stimulation. The spatial pattern resolved into a clear ventral-cauda...Nov 16, 2005
-
AbstractBlood brain barrier (BBB) integrity is lost several neurological conditions in which astrocytes are damaged. We have studied the focal lesions induced by systemic injection of 3-choloropropanediol, a toxicant that induces early astrocytic (but not neuronal) death followed by BBB leakage. Anatomical images of coronal brain sections illustrate the regional selectivity of the lesions, with affected areas including symmetrical brain stem and midbrain nuclei: primarily the inferior colliculi and red nuclei. The MRI intensity in the lesioned areas peaked at 2 days post-injection, correlating with the later BBB breakdown, and diminished thereafter; returning to close to pre-injection levels by 30 days in parallel with the return of astrocytes. T2 measurements of the lesioned areas increased at 2 days indicating increased water content in the lesioned areas, consistent with cellular damage and BBB leakage. T2 was not increased at 6 hours, a time when astrocyte swelling is marked but the vasculature is intact. Inje...Oct 25, 2004
-
Comprehensive analysis of brain function depends on understanding the dynamics of diverse neural signaling processes over large tissue volumes in intact animals and humans. Most existing approaches to measuring brain signaling suffer from limited tissue penetration, poor resolution, or lack of specificity for well-defined neural events. Here we discuss a new brain activity mapping method that overcomes some of these problems by combining MRI with contrast agents sensitive to neural signaling. The goal of this “molecular fMRI” approach is to permit noninvasive whole-brain neuroimaging with specificity and resolution approaching current optical neuroimaging methods. In this article, we describe the context and need for molecular fMRI as well as the state of the technology today. We explain how major types of MRI probes work and how they can be sensitized to neurobiological processes, such as neurotransmitter release, calcium signaling, and gene expression changes. We comment both on past work in the field an...Apr 13, 2016