It has been shown recently that a significant portion of brain electrical field potentials consists of scale-free dynamics. These scale-free brain dynamics contain complex spatiotemporal structures and are modulated by task performance. Here we show that the fMRI signal recorded from the human brain is also scale free; its power-law exponent differentiates between brain networks and correlates with fMRI signal variance and brain glucose metabolism. Importantly, in parallel to brain electrical field potentials, the variance and power-law exponent of the fMRI signal decrease during task activation, suggesting that the signal contains more long-range memory during rest and conversely is more efficient at online information processing during task. Remarkably, similar changes also occurred in task-deactivated brain regions, revealing the presence of an optimal dynamic range in the fMRI signal. The scale-free properties of the fMRI signal and brain electrical field potentials bespeak their respective stationarit...

It is highly desirable to measure neuronal activity by mapping the changes in local cerebral blood volume (CBV) even though this is an indirect method. We wanted to further explore the effects of physiological properties that might influence the results obtained in functional magnetic resonance (fMRI) studies. Male Sprague Dawley rats b.wt. 200 to 230 g were used. The MRI recordings were performed on a Biospec Avance 47T spectrometer with a 12 cm gradient system, 200 mT/m in combination with a 35 mm RF resonator. The conditions studied were; (n=3 rats per group), (1) Isoflurane 1.5% in Air, (2) Isoflurane 2.0% in Air,(3) Isoflurane 1.5% in 60% oxygen (O2 and 40% nitrous oxide (N2O), (4) Isoflurane 2.0% in 60% O2 and 40% N2O, (5) Isoflurane 1.5% in 40% O2 and 60% nitrogen (N2, (6) Isoflurane 2.0% in 40% O2 and 60% N2. Arterial PO2, PCO2, pH and Blood pressure, before and after bicuculline stimulation were measured. Under the studied conditions the best reaction of bicuculline stimulation, indeed, was 1.5% i...

Although the non-invasive measurement of visually evoked responses has been extensively studied, the structural basis of variabilities in latency in healthy humans is not well understood. We investigated how tissue properties of optic radiation could predict interindividual variability in the latency of the initial visually evoked component (C1), which may originate from the primary visual cortex (V1). We collected C1 peak latency data using magnetoencephalography (MEG) and checkerboard stimuli, and multiple structural magnetic resonance imaging (MRI) data from 20 healthy subjects. While we varied the contrast and position of the stimuli, the C1 measurement was most reliable when high-contrast stimuli were presented to the lower visual field (LVF). We then attempted to predict interindividual variability in C1 peak latency in this stimulus condition with a multiple regression model using MRI parameters along the optic radiation. We found that this model could predict >20% of variance in C1 latency, when th...

Human structural neuroimaging studies have supported the preferential effects of healthy aging on frontal cortex, but reductions in other brain regions have also been observed. We investigated the regional network pattern of gray matter using magnetic resonance imaging (MRI) in young adult and old rhesus macaques (RMs) to evaluate age effects throughout the brain in a nonhuman primate model of healthy aging in which the full complement of Alzheimer's disease (AD) pathology does not occur. Volumetric T1 MRI scans were spatially normalized and segmented for gray matter using statistical parametric mapping (SPM2) voxel-based morphometry. Multivariate network analysis using the scaled subprofile model identified a linear combination of two gray matter patterns that distinguished the young from old RMs. The combined pattern included reductions in bilateral dorsolateral and ventrolateral prefrontal and orbitofrontal and superior temporal sulcal regions with areas of relative preservation in vicinities of the cer...

Successful learning is often contingent on feedback. In instrumental conditioning, an animal or human learns to perform specific responses to obtain reward. Instrumental conditioning is often used by behavioral psychologists to train an animal (or human) to produce a desired behavior. Shaping involves reinforcing those behaviors, which in a stepwise manner are successively closer to the desired behavior until the desired behavior is reached. Here, we aimed to extend this traditional approach to directly shape neural activity instead of overt behavior. To achieve this, we scanned 22 human subjects with functional magnetic resonance imaging and performed image processing in parallel with acquisition. We delineated regions of interest (ROIs) in finger and toe motor/somatosensory regions and used an instrumental shaping procedure to induce a regionally specific increase in activity by providing an explicit monetary reward to reinforce neural activity in the target areas. After training, we found a significant ...

Previous studies suggest that nocebo effects, sometimes termed “negative placebo effects,” can contribute appreciably to a variety of medical symptoms and adverse events in clinical trials and medical care. In this study, using a within-subject design, we combined functional magnetic resonance imaging (fMRI) and an expectation/conditioning manipulation model to investigate the neural substrates of nocebo hyperalgesia using heat pain on the right forearm. Thirteen subjects completed the study. Results showed that, after administering inert treatment, subjective pain intensity ratings increased significantly more on nocebo regions compared with the control regions in which no expectancy/conditioning manipulation was performed. fMRI analysis of hyperalgesic nocebo responses to identical calibrated noxious stimuli showed signal increases in brain regions including bilateral dorsal anterior cingulate cortex (ACC), insula, superior temporal gyrus; left frontal and parietal operculum, medial frontal gyrus, orbita...

Objectives - Recent studies suggest a positive role for stem cells in the regeneration of tissue following an ischemic insult. We hypothesize that spleen derived mononuclear cells (MNC’s) are actively recruited from the blood stream by signals released from ischemic brain tissue. In order to monitor migration of intravenously injected progenitor cells by high field MRI, we magnetically labeled primary culture spleen derived MNC’s with Very-Small-Superparamagnetic-Iron-Oxide-Particles (VSOP). Materials and Methods – MNCs were isolated from transgenic GFP expressing mice and magnetically labelled with VSOP. 30 mice were treated with both 30 min and 60 min middle cerebral artery occlusion (MCAO) for stroke induction. 1 × 106 magnetically labelled cells were injected into the tail vein at various time points after MCAO. T2 and T2* weighted images were taken of mouse brains at 7T. For MR-histological correlation, Prussian Blue staining was performed for the magnetic label, and confocal microscopy for GFP fluore...

The ability to generate appropriate responses in social situations often requires the integration of emotional information conveyed through facial expressions with ongoing cognitive processes. Neuroimaging studies have begun to address how cognitive and emotional neural systems interact, but most of these studies have used emotional oddball stimuli as distractors in order to dissociate emotional from cognitive neural systems. Therefore, the manner in which these systems interact when behavioral responses must be directly guided by the emotional content of stimuli remains largely unknown. Here, we used functional magnetic resonance imaging (fMRI) to investigate the neural systems involved in response inhibition for faces conveying particular emotions. Participants (6 male, 7 female; ages 17-27) performed go/no-go tasks involving either letters or happy and sad faces. The fMRI results indicated that inhibiting responses to emotional faces activated inferior frontal/insular cortex, whereas response inhibition...

Currently, no in vivo method is available for analyzing the integrity and functionality of the spinal cord in animal models of spinal cord injury (SCI). Damage and recovery are usually assessed by locomotor tests in the living animal or by histology post mortem. The fact that manganese ions mimic calcium and shorten the T1 relaxation time of water protons in magnetic resonance imaging (MRI) has brought them to the in vivo application. Manganese is taken up into cells resulting in a strong contrast enhancement in MRI that indicates neuronal function and activity. We show that intracerebroventricular injection of manganese chloride solution leads to uptake within the complete central nervous system. Following SCI manganese uptake in the spinal cord is reduced. Furthermore, the amount of manganese uptake correlates with the extent of damage as assessed histologically and by clinical locomotor tests. We have previously shown that inhibition of apoptosis by administration of neutralizing antibodies directed aga...

Previous studies using the serial prediction task (SPT) have shown that attending to the locations of objects activates the dorsal part of premotor cortex more than attending to the sizes of objects. The opposite holds for the ventral part of the premotor cortex. The present study used functional magnetic resonance imaging to investigate whether the learning of arbitrary stimulus-response mappings influences this functional dissociation. One experimental group learned to assign stimuli to response buttons based on stimulus size; another group did so based on stimulus location. More specifically, one-half of the participants in both experimental groups learned to assign stimuli to finger movements of their right hand, whereas the other half assigned stimuli to finger movements of their left hand. During scanning, all participants performed both size SPT and location SPT. Thus, we investigated the effects of the attended stimulus property (size or location), the motor effector assigned to it (fingers of left...