Magnetic Resonance Imaging (MRI)

Functional magnetic resonance imaging was used to map cerebral activation in 16 patients with obstructive sleep-disordered breathing (OSDB) and 16 healthy subjects, during the performance of a 2-back verbal working memory task. Six patients with OSDB were reimaged after a minimum period of 8 wk of treatment with positive airway pressure. Working memory speed in OSDB was significantly slower than in healthy subjects, and a group average map showed absence of dorsolateral prefrontal activation, regardless of nocturnal hypoxia.

BACKGROUND AND PURPOSE: To demonstrate dynamic changes in cerebral functional activation during a working memory task in a state of severe excessive daytime sleepiness.

INTRODUCTION: Studies of prefrontal cortical (PFC) function in schizophrenia have been inconsistent, with studies showing both increased and decreased PFC activation compared to healthy controls. Discrepant findings may be due to task performance effects or demographic differences between samples. We report functional magnetic resonance imaging (fMRI) data comparing subjects with schizophrenia and healthy controls performing a 2-back working memory (WM) task, addressing the effects of task performance.

The mechanisms of recognition involve reductions of activity in the medial temporal lobe. This preview discusses recent fMRI and MEG data from Gonsalves et al. (this issue of Neuron) that provide some of the strongest evidence to date demonstrating that reduced medial temporal activity is correlated with stronger recognition of items in humans. This result provides an important test of theories of recognition memory function based on previous neuroimaging and unit recording data.

BACKGROUND: Previous functional neuroimaging studies have demonstrated exaggerated amygdala responses and diminished medial prefrontal cortex responses during the symptomatic state in posttraumatic stress disorder (PTSD).

We describe a novel method for visualizing brain surface from anatomical magnetic resonance images (MRIs). The method utilizes standard 2D texture mapping capabilities of OpenGL graphics language. It combines the benefits of volume rendering and triangle-mesh rendering, allowing fast and realistic-looking brain surface visualizations. Consequently, relatively low-resolution triangle meshes can be used while the texture images provide the necessary details.

Recent reports of a high response to bodies in the fusiform face area (FFA) challenge the idea that the FFA is exclusively selective for face stimuli. We examined this claim by conducting a functional magnetic resonance imaging experiment at both standard (3.125 x 3.125 x 4.0 mm) and high resolution (1.4 x 1.4 x 2.0 mm). In both experiments, regions of interest (ROIs) were defined using data from blocked localizer runs. Within each ROI, we measured the mean peak response to a variety of stimulus types in independent data from a subsequent event-related experiment.

Recent computational modeling and slice physiology studies have suggested that long-term encoding may depend on sustained spiking during brief memory delays in parahippocampal neurons, and that this persistent spiking activity is modulated by effects of acetylcholine at muscarinic receptors.

The use of functional magnetic resonance imaging (fMRI) in cognitive neuroscience has expanded at an amazing rate in the past 10 years. Current research includes increasingly subtle and specific attempts to dissect the cognitive and emotional mechanisms called into play when humans make decisions. The present essay will briefly review some of the general considerations and domains of information needed when one designs fMRI-based experiments. However, the main theme will be the difficulties associated with designing, conducting, analyzing and interpreting such research.

Humans often create and appreciate visual symmetry in their environment, and the underlying brain mechanisms have been a topic of increasing interest. Here, symmetric versus random dot stimuli produced robust functional MRI (fMRI) activity in higher-order regions of human visual cortex (especially areas V3A, V4, V7, and LO) but little activity elsewhere in brain. This fMRI response was found both with and without attention controls. Moreover, it was highly correlated with the psychophysical perception of symmetry.