Patterns of muscular strain in the embryonic heart wall.

The hypothesis that inner layers of contracting muscular tubes undergo greater strain than concentric outer layers was tested by numerical modeling and by confocal microscopy of strain within the wall of the early chick heart. We modeled the looped heart as a thin muscular shell surrounding an inner layer of sponge-like trabeculae by two methods: calculation within a two-dimensional three-variable lumped model and simulated expansion of a three-dimensional, four-layer mesh of finite elements. Analysis of both models, and correlative microscopy of chamber dimensions, sarcomere spacing, and membrane leaks, indicate a gradient of strain decreasing across the wall from highest strain along inner layers.

At the heart of the ventral attention system: the right anterior insula.

The anterior insula has been hypothesized to provide a link between attention-related problem solving and salience systems during the coordination and evaluation of task performance. Here, we test the hypothesis that the anterior insula/medial frontal operculum (aI/fO) provides linkage across systems supporting task demands and attention systems by examining the patterns of functional connectivity during word recognition and spatial attention functional imaging tasks. A shared set of frontal regions (right aI/fO, right dorsolateral prefrontal cortex, bilateral anterior cingulate) were engaged, regardless of perceptual domain (auditory or visual) or mode of response (word production or button press).

Age-related effects on word recognition: reliance on cognitive control systems with structural declines in speech-responsive cortex.

Speech recognition can be difficult and effortful for older adults, even for those with normal hearing. Declining frontal lobe cognitive control has been hypothesized to cause age-related speech recognition problems. This study examined age-related changes in frontal lobe function for 15 clinically normal hearing adults (21-75 years) when they performed a word recognition task that was made challenging by decreasing word intelligibility.

An increased precision comparison of TMS-induced motor cortex BOLD fMRI response for image-guided versus function-guided coil placement.

Objective: To examine with high precision the differences between function-guided and image-guided transcranial magnetic stimulation (TMS).

Method: Using a calibrated TMS coil holder/positioner, interleaved TMS/functional magnetic resonance imaging (fMRI), and individualized anatomy-based regional normalization, we conducted a two-phase study of TMS coil positioning guided by either function (elicited thumb motion) or image-based targeting of the "hand knob," the anatomy associated with fMRI activation during thumb motion.

Results: In every case, image-guided TMS coil placement produced a thumb movement response at thresholds similar to those found under function guidance.

Cortical and subcortical brain effects of transcranial magnetic stimulation (TMS)-induced movement: an interleaved TMS/functional magnetic resonance imaging study.

Background: To date, interleaved transcranial magnetic stimulation and functional magnetic resonance imaging (TMS/fMRI) studies of motor activation have not recorded whole brain patterns. We hypothesized that TMS would activate known motor circuitry with some additional regions plus some areas dropping out.

Methods: We used interleaved TMS/fMRI (11 subjects, three scans each) to elucidate whole brain activation patterns from 1-Hz TMS over left primary motor cortex.

A high resolution assessment of the repeatability of relative location and intensity of transcranial magnetic stimulation-induced and volitionally induced blood oxygen level-dependent response in the motor cortex.

Objective: Using functional magnetic resonance imaging, we assessed variation in location and intensity of blood oxygen level-dependent contrast associated with movements induced by transcranial magnetic stimulation or volition.

Background: Anatomic location and within-subject repeatability of blood oxygen level-dependent responses induced by transcranial magnetic stimulation comprise critical information to the use of interleaved transcranial magnetic stimulation/functional magnetic resonance imaging as a neuroscience tool.

Methods: Eleven healthy adults were scanned 3 times each at 1.

Acute vagus nerve stimulation using different pulse widths produces varying brain effects.

Background: Vagus nerve stimulation (VNS) is an approved treatment for epilepsy and has been investigated in clinical trials of depression. Little is known about the relationship of VNS parameters to brain function. Using the interleaved VNS /functional magnetic resonance imaging (fMRI) technique, we tested whether variations of VNS pulse width (PW) would produce different immediate brain activation in a manner consistent with single neuron PW studies.

A review of functional neuroimaging studies of vagus nerve stimulation (VNS).

Vagus nerve stimulation (VNS) is a new method for preventing and treating seizures, and shows promise as a potential new antidepressant. The mechanisms of action of VNS are still unknown, although the afferent direct and secondary connections of the vagus nerve are well established and are the most likely route of VNS brain effects. Over the past several years, many groups have used functional brain imaging to better understand VNS effects on the brain.

Prefrontal cortex transcranial magnetic stimulation does not change local diffusion: a magnetic resonance imaging study in patients with depression.

Objective: To determine whether transcranial magnetic stimulation over the left dorsolateral prefrontal cortex produces pathologic changes or leakage of the blood-brain barrier in patients with depression by using apparent diffusion coefficient magnetic resonance imaging.

Background: Transcranial magnetic stimulation is a new technology for noninvasively stimulating the brain. It appears to be a relatively safe technique, with some important exceptions.

Mechanisms and state of the art of transcranial magnetic stimulation.

In 1985, Barker et al. built a transcranial magnetic stimulation (TMS) device with enough power to stimulate dorsal roots in the spine. They quickly realized that this machine could likely also noninvasively stimulate the superficial cortex in humans.

Vagus nerve stimulation (VNS) synchronized BOLD fMRI suggests that VNS in depressed adults has frequency/dose dependent effects.

Stimulation of the vagus nerve in the neck can reduce seizures in epilepsy patients, and may be helpful in treating depression. PET studies have shown that vagus nerve stimulation (VNS) in epilepsy patients causes acute dose (intensity) dependent changes in regional cerebral blood flow. We sought to use the newly developed VNS synchronized fMRI technique to examine whether VNS BOLD signal changes depend on the frequency of stimulation.

Cellular changes in experimental left heart hypoplasia.

Hypoplastic left heart syndrome (HLHS) is a rare but deadly congenital malformation, which can be created experimentally in the chick embryo by left atrial ligation (LAL). The goal of this study was to examine the cellular changes leading to the profound remodeling of ventricular myocardial architecture that occurs in this model. Hypoplasia of left heart structures was produced after 3H-thymidine prelabeling by partial LAL at stage 24, thereby reducing its volume, and redistributing blood preferentially to the developing right ventricle (RV).