Functional MRI based on the blood oxygenation level-dependent (BOLD) contrast in gradient echo images has been used to monitor cerebral activation in response to peripheral stimuli in rat. No previous report on functional MRI during peripheral stimulation is available for mice. Functional MRI experiments were performed in rats and in mice using a 4.7-Tesla MRI scanner. Periodical electric stimulation (10-15 sec. stimulation, 40-60 sec. rest) was delivered at 3 Hz via bipolar subcutaneous electrodes during α-Chloralose anesthesia, artificial ventilation and complete muscle relaxation as reported earlier (Spenger et al., Exp Neurol 2000, 166:1102). Data were obtained in single and multislice experiments using spiral gradient echo MR imaging. We could thus improve the time resolution to 300 ms per image, which is approximately 13 times faster than conventional gradient echo imaging. In rats, the rise time for the BOLD response was found to be in the range of 4 sec. The BOLD signal was usually followed by an u...

Influential functional magnetic resonance imaging (fMRI)-based models have involved a dorsal frontoparietal network in the orienting of both endogenous and exogenous attention, and a ventral system in attentional reorienting to task-relevant events. Nonetheless, given the low temporal resolution and susceptibility to epiphenomenal activations of fMRI, such depictions remain highly debated. We hereby benefited from the high temporal resolution and causal power of event-related transcranial magnetic stimulation to explore the implications of key dorsal and ventral parietal regions in those two types of attention. We provide for the first time causal evidence of right intraparietal sulcus involvement in both types of attentional orienting, while we link the temporoparietal junction with the orienting of exogenous but not endogenous spatial attention.

Grey matter thickness derived from high-resolution magnetic resonance images is a useful non-invasive method of characterizing a macroscopic property of the cerebral cortex. When combined with an atlas of the species in question, these measurements can ...

Human episodic memory is supported by networks of white matter tracts that connect frontal, temporal, and parietal regions. Degradation of white matter microstructure is increasingly recognized as a general mechanism of cognitive deterioration with aging. However, atrophy of gray matter regions also occurs and, to date, the potential role of specific white matter connections has been largely ignored. Changes to frontotemporal tracts may be important for the decline of episodic memory; while frontotemporal cooperation is known to be critical, the precise pathways of interaction are unknown. Diffusion-weighted MRI tractography was used to reconstruct three candidate fasciculi known to link components of memory networks: the fornix, the parahippocampal cingulum, and the uncinate fasciculus. Age-related changes in the microstructure of these tracts were investigated in 40 healthy older adults between the ages of 53 and 93 years. The relationships between aging, microstructure, and episodic memory were assessed...

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 common marmoset (Callithrix jacchus) is increasingly being used as a model organism for primate neuroscience research. Establishing the mesoscopic structural mapping of the marmoset brain is essential for future mapping of the neural circuitry, stru...

The endocannabinoid anandamide [ N -arachidonoylethanolamine (AEA)] is thought to function as an endogenous protective factor of the brain against acute neuronal damage. However, this has never been tested in an in vivo model of acute brain injury. Here, we show in a longitudinal pharmacological magnetic resonance imaging study that exogenously administered AEA dose-dependently reduced neuronal damage in neonatal rats injected intracerebrally with the Na+/K+-ATPase inhibitor ouabain. At 15 min after injury, AEA (10 mg/kg) administered 30 min before ouabain injection reduced the volume of cytotoxic edema by 43 ± 15% in a manner insensitive to the cannabinoid CB1receptor antagonist SR141716A. At 7 d after ouabain treatment, 64 ± 24% less neuronal damage was observed in AEA-treated (10 mg/kg) rats compared with control animals. Coadministration of SR141716A prevented the neuroprotective actions of AEA at this end point. In addition, (1) no increase in AEA and 2-arachidonoylglycerol levels was detected at 2, 8...

Alzheimer's disease (AD) and antecedent factors associated with AD were explored using amyloid imaging and unbiased measures of longitudinal atrophy in combination with reanalysis of previous metabolic and functional studies. In total, data from 764 participants were compared across five in vivo imaging methods. Convergence of effects was seen in posterior cortical regions, including posterior cingulate, retrosplenial, and lateral parietal cortex. These regions were active in default states in young adults and also showed amyloid deposition in older adults with AD. At early stages of AD progression, prominent atrophy and metabolic abnormalities emerged in these posterior cortical regions; atrophy in medial temporal regions was also observed. Event-related functional magnetic resonance imaging studies further revealed that these cortical regions are active during successful memory retrieval in young adults. One possibility is that lifetime cerebral metabolism associated with regionally specific default acti...

MRI has a potential for early diagnosis of individuals at risk for developing Alzheimer’s disease (AD). Cognitive performance in elderly patients with AD has been associated with measures of cortical gyrification (Cai et al. 2017) and thickness (CT) (Le...

Magnetic resonance elastography (MRE) is a noninvasive medical imaging technique that can quantitatively assess brain viscoelastic mechanical properties to provide sensitive measurements of neural tissue health. Previous work has shown that global brain...