Neural activity that occurs during the creation of a new memory trace can be observed using functional magnetic resonance imaging (fMRI). Event-related designs have been used to demonstrate that activity in prefrontal and medial temporal lobe areas is associated with successful memory storage. Here we contrasted activity associated with encoding success and encoding effort. Participants viewed a series of 150 words but attempted to remember only half of them. Encoding effort was manipulated using a cue in the form of a letter (R or F) presented after each word to instruct participants either to remember or to forget that word. Increased activity in left inferior prefrontal cortex was observed when words were followed by the cue to remember. In contrast, increased left medial temporal lobe activity was observed for words that were successfully recalled later. These results show that fMRI correlates of the intention to encode a word are different from fMRI correlates of whether that encoding is successful. P...

The Syrian hamster is a research model most widely used in studies focusing on sleep, aggression, and hormone regulation. Most recently, the Syrian hamster has been developed as a model of Ebola and Marburg hemorrhagic fever due to its superiority over ...

Although Congenital Central Hypoventilation Syndrome (CCHS) patients show impaired ventilatory responses to CO2 and reduced drive to breathe during sleep, affected patients increase ventilation to passive limb motion, indicating a degree of preserved integration of cyclic locomotor systems with respiration. Functional magnetic resonance imaging (fMRI) procedures can examine the neural processes mediating limb movement integration with respiratory patterns in CCHS. We examined brain fMRI signal changes in 16 CCHS patients and 32 age- and gender-matched control subjects to passive right foot movement. Each fMRI series consisted of 175 volumes over 350 s, with an initial 70 s baseline, three 40 s challenges separated by 40 s rest periods, and ending with 80 s baseline. Images were motion corrected, spatially normalized, and smoothed. Brain regions with altered fMRI responses between groups were determined using SPM2 (boxcar model, random effects, analysis of covariance, age as covariate, threshold P < 0.01), ...

The linear transform model of functional magnetic resonance imaging (fMRI) hypothesizes that fMRI responses are proportional to local average neural activity averaged over a period of time. This work reports results from three empirical tests that support this hypothesis. First, fMRI responses in human primary visual cortex (V1) depend separably on stimulus timing and stimulus contrast. Second, responses to long-duration stimuli can be predicted from responses to shorter duration stimuli. Third, the noise in the fMRI data is independent of stimulus contrast and temporal period. Although these tests can not prove the correctness of the linear transform model, they might have been used to reject the model. Because the linear transform model is consistent with our data, we proceeded to estimate the temporal fMRI impulse–response function and the underlying (presumably neural) contrast–response function of human V1.

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...

Application of fMRI techniques to the study of developmental plasticity first requires characterization of the heamodynamic response in young rats. To this end we are examining the developmental changes in the temporal and spatial patterns of activation caused by a characterized somatosensory stimulus, the forepaw shock, in neonatal and juvenile rats. Immobilization is provided by low-level isoflurane anesthesia. Functional imaging is performed at 4.7T using blood oxygenation level dependent (BOLD) contrast, as well as changes in cerebral blood volume (CBV) monitored by injection of blood pool contrast agents. In response to a 10 second epoch of paw shock, pups examined 20 or 30 days after birth show adult-like BOLD signal that is strongest in the contralateral primary somatosensory cortex. Further experiments will show the youngest age at which robust BOLD or CBV changes can be observed, and if there is evidence for refinement of the functional connectivity underlying somatosensory processing at these ages.

In an era where magnetic resonance imaging (MRI) is common place around the world, more and more cases of extreme alterations in brain morphology appear in the literature (Lancet 2007: 370:262) and popular press. Usually caused by early hydrocephalus, l...

The Society for Neuroscience (SfN) will honor several highly accomplished researchers who have made significant contributions to the advancement of women in neuroscience. The awards will be presented during Neuroscience 2021, SfN's annual meeting and the world's largest source of emerging news about brain science and health.

Although fMRI of the whole brain is routinely performed in humans, there are few reports of whole brain fMRI in rodents, due in part to the need for high spatial and temporal resolution. Instead, most rodent studies have focused on the primary sensory cortex. We have developed an 11.7 T MR imager for animals that can provide the high spatial and temporal resolution necessary for whole brain fMRI in rodents. We performed whole brain imaging in the rat during electrical stimulation of the forepaw. Functional MR images with BOLD contrast were obtained in 11 rats during forepaw stimulation (90 s rest, 45 s stimulation, 90 s rest). An echo planar imaging sequence with interleaved slices was used to image the entire brain every 1.5 seconds, from olfactory bulb to cerebellum, with an in-plane resolution of 300 microns. Excellent image quality with single shot echo planar imaging was achieved even at this high magnetic field by optimizing the MR imaging sequence and hardware. Activation was observed in the primary...

Lipopolysaccharide (LPS), a potent endotoxin, derived from the cell wall of gram-negative bacteria causes severe inflammation in the brain. Neuroinflammation is associated with several neurodegenerative diseases, including stroke, Parkinson’s disease, Alzheimer’s disease, multiple sclerosis and amyotrophic lateral sclerosis. The hallmark of brain inflammation is the activation of microglial cells that produce proinflammatory and neurotoxic factors, including cytokines and free radicals. In the present study we correlate magnetic resonance imaging (MRI) and immunohistochemistry applying different neuronal and glial markers to analyse neurodegenerative processes in a LPS-mediated model of neuroinflammation. As demonstrated by MRI, unilateral injection of LPS into the striatum of rats led to structural changes at different time points following endotoxin application. In parallel, immunfluorescence with Fluoro-Jade B showed an increased number of degenerating neurons in the striatum 24 hours, 3 and 7 days afte...