Magnetic Resonance Imaging (MRI)

BACKGROUND: Hemoglobin tetramers are the major oxygen-carrying molecules within the blood. We hypothesized that a lower hemoglobin level and its reduced oxygen-carrying capacity would associate with larger infarction in acute ischemic stroke patients.

OBJECTIVE: To determine whether there are non-motor regions of cerebellum in which sizeable infarcts have little or no impact on motor control.

Deformable image registration is used increasingly in image-guided interventions and other applications. However, validation and characterization of registration performance remain areas that require further study. We propose an analysis methodology for deriving tolerance limits on the initial conditions for deformable registration that reliably lead to a successful registration. This approach results in a concise summary of the probability of registration failure, while accounting for the variability in the test data.

BACKGROUND: In acupuncture, deqi is the sensory experience related to clinical efficacy. As the first study taking into account cultural differences on deqi sensation, this pilot survey aims to corroborate the acupuncturists' general experience in clinical practice with functional magnetic resonance imaging (fMRI) findings.

Spinocerebellar ataxia type 7 is a neurodegenerative polyglutamine disease characterized by ataxia and retinal degeneration. The longitudinal course is unknown, and relationships between repeat expansion, clinical manifestations, and neuropathology remain uncertain. We followed 16 affected individuals of a 61-member kindred over 27 years with electroretinograms, neurological examinations including the Brief Ataxia Rating Scale, neuroimaging in five, and autopsy in four cases.

Electrical microstimulation of FEF (FEF-EM) modulates neuronal activity in area V4 (Moore and Armstrong, 2003) and elicits functional magnetic resonance imaging (fMRI) activations in visual cortex in a bottom-up dependent manner (Ekstrom et al., 2008). Here we test the hypothesis that FEF-EM-induced modulations of fMRI activity are also function of task demands, which would suggest top-down dependent gating of FEF signals in early visual cortex.

Although the role of the middle temporal (MT/V5) area and its medial superior temporal (MST) satellites in motion processing has been well explored, relatively little is known about motion regions located more rostrally in the superior temporal sulcus (STS), such as the fundus of the superior temporal (FST) area, the superior temporal polysensory (STP) region, or beyond. To fill this void, we used contrast-enhanced functional magnetic resonance imaging in awake macaques and a five-step testing procedure that allowed us to identify six motion-sensitive regions within the STS.

Practicing simple visual detection and discrimination tasks improves performance, a signature of adult brain plasticity. The neural mechanisms that underlie these changes in performance are still unclear. Previously, we reported that practice in discriminating the orientation of noisy gratings (coarse orientation discrimination) increased the ability of single neurons in the early visual area V4 to discriminate the trained stimuli.

Observation of actions performed by others activates monkey ventral premotor cortex, where action meaning, but not object identity, is coded. In a functional MRI (fMRI) study, we investigated whether other monkey frontal areas respond to actions performed by others. Observation of a hand grasping objects activated four frontal areas: rostral F5 and areas 45B, 45A, and 46. Observation of an individual grasping an object also activated caudal F5, which indicates different degrees of action abstraction in F5. Observation of shapes activated area 45, but not premotor F5.