Magnetic Resonance Imaging (MRI)

A method to encode multiple two-dimensional Fourier transform (2D FT) images within a single echo train is presented. This new method, simultaneous echo refocusing (SER), is a departure from prior echo planar image (EPI) sequences which use repeated single-shot echo trains for multislice imaging. SER simultaneously acquires multiple slices in a single-shot echo train utilizing a shared refocusing process. The SER technique acquires data faster than conventional multislice EPI since it uses fewer gradient switchings and fewer preparation pulses such as diffusion gradients.

We present a method for diffusion tensor MRI in the beating heart that is insensitive to cardiac motion and strain. Using a stimulated echo pulse sequence with two electrocardiogram (ECG) triggers, diffusion-encoding bipolar gradient pulses are applied at identical phases in consecutive cardiac cycles. In this experiment, diffusion is encoded at a single phase in the cardiac cycle of less than 30 ms in duration. This encoding produces no phase shifts for periodic motion and is independent of intervening strains.

During recognition, one may sense items as familiar (item memory) and additionally recollect specific contextual details of the earlier encounters (source memory). Cognitive theory suggests that, unlike item memory, source memory requires controlled cue specification and monitoring processes. Functional imaging suggests that such processes may depend on left prefrontal cortex (PFC). However, the nature and possible anatomical segregation of these processes remains unknown.

BACKGROUND AND PURPOSE: Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) after stroke increases risk of hemorrhagic transformation, particularly in areas with blood-brain barrier leakage. Our aim was to characterize acute effects of rtPA administration on the integrity of microvascular barriers.

The integrity of the hippocampus and surrounding medial-temporal cortices is critical for episodic memory, with the hippocampus being posited to support relational or configural associative learning. The present event-related functional magnetic resonance imaging (fMRI) study investigated the role of specific medial-temporal lobe structures in learning during relational and item-based processing, as well as the extent to which these structures are engaged during item-based maintenance of stimuli in working memory.

Primate studies have demonstrated that motor cortex neurons show increased activity with increased force of movement. In humans, this relationship has received little study during a power grip such as squeezing, and has previously only been evaluated across a narrow range of forces. Functional MRI was performed in eight healthy subjects who alternated between rest and right hand squeezing at one of three force levels. During scanning, motor performances were recorded using a dynamometer.

Dorsal anterior cingulate cortex (dACC) is a brain region that subserves cognition and motor control, but the mechanisms of these functions remain unknown. Human neuroimaging and monkey electrophysiology studies have provided valuable insights, but it has been difficult to link the two literatures. Based on monkey single-unit recordings, we hypothesized that human dACC is comprised of a mixture of functionally distinct cells that variously anticipate and detect targets, indicate novelty, influence motor responses, encode reward values, and signal errors.

Artifacts generated by motion (e.g., ballistocardiac) of the head inside a high magnetic field corrupt recordings of EEG and EPs. This paper introduces a method for motion artifact cancellation. This method is based on adaptive filtering and takes advantage of piezoelectric motion sensor information to estimate the motion artifact noise. This filter estimates the mapping between motion sensor and EEG space, subtracting the motion-related noise from the raw EEG signal.

Although implantation of fetal dopamine (DA) neurons can reduce parkinsonism in patients, current methods are rudimentary, and a reliable donor cell source is lacking. We show that transplanting low doses of undifferentiated mouse embryonic stem (ES) cells into the rat striatum results in a proliferation of ES cells into fully differentiated DA neurons. ES cell-derived DA neurons caused gradual and sustained behavioral restoration of DA-mediated motor asymmetry.

Learning and memory in humans rely upon several memory systems, which appear to have dissociable brain substrates. A fundamental question concerns whether, and how, these memory systems interact. Here we show using functional magnetic resonance imaging (FMRI) that these memory systems may compete with each other during classification learning in humans.