Ductus arteriosus: more than just the patent ductus arteriosus.

The ductus arteriosus is important to fetal circulation. Failure to close at birth is a common event. In this educational pictorial essay, we illustrate the association of the ductus arteriosus with a variety of congenital cardiac, vascular and pulmonary lesions. These lesions can impact the systemic circulation, the pulmonary circulation or the airway and include coarctation of the aorta, ductal origin of the pulmonary artery and vascular rings.

First antenatally confirmed case of arterial tortuosity syndrome.

Arterial tortuosity syndrome (ATS) is a rare, autosomal recessive, connective tissue disorder. It predominantly involves the arterial tree with clinical features reflecting the systems involved. There have been few cases of ATS suspected during antenatal screening ultrasound in high-risk families, but none confirmed. We present the first case of ATS confirmed antenatally in the fetus with cascade testing, detecting the disease in the mother as well.

Direct comparisons of hand and mouth kinematics during grasping, feeding and fork-feeding actions.

While a plethora of studies have examined the kinematics of human reach-to-grasp actions, few have investigated feeding, another ethologically important real-world action. Two seminal studies concluded that the kinematics of the mouth during feeding are comparable to those of the hand during grasping (Castiello, 1997; Churchill et al., 1999); however, feeding was done with a fork or spoon, not with the hand itself. Here, we directly compared grasping and feeding kinematics under equivalent conditions. Participants were presented with differently sized cubes of cheese (10-, 20- or 30-mm on each side) and asked to use the hand to grasp them or to use a fork to spear them and then bring them to the mouth to bite. We measured the apertures of the hand during grasping and the teeth during feeding, as well as reaching kinematics of the arm in both tasks. As in many past studies, we found that the hand oversized considerably larger (~11-27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size. Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4-11 mm) than the food item during biting and the oversizing did not increase with food size. Total movement times were longer when using the fork compared to the hand, particularly when using the fork to bring food to the mouth. While reach velocity always peaked approximately halfway through the movement, relative to the reach the mouth opened more slowly than the hand, perhaps because less time was required for the smaller oversizing. Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

Acute respiratory distress secondary to severe compression of the left main bronchus by the ductus arteriosus.

Two newborn infants presented with acute respiratory distress. In both cases, the left lung was opaque, hyperinflated, and associated with a rightward shift of the mediastinum. A diagnosis of retained fetal fluid secondary to vascular compression of the left bronchus by the ductus arteriosus was made by combining various imaging methods including chest radiograph, computed tomography (CT), and echocardiography. Although the initial chest radiographs were similar, the mechanisms of obstruction were different. The imaging emphasizes the importance of CT angiography to understanding the three-dimensional relationships resulting in bronchial compression.

A case of horseshoe lung and complex congenital heart disease in a term newborn.

We describe and illustrate a rare association of hypoplastic left heart syndrome, absent hilar left pulmonary artery, and an unusual bronchopulmonary malformation. This case highlights the utility of combination imaging of echocardiography and CT angiography in diagnosing a cyanotic newborn with a chest radiograph that is suspicious for lung hypoplasia.

The human dorsal stream adapts to real actions and 3D shape processing: a functional magnetic resonance imaging study.

We tested whether the control of real actions in an ever-changing environment would show any dependence on prior actions elicited by instructional cues a few seconds before. To this end, adaptation of the functional magnetic resonance imaging signal was measured while human participants sequentially grasped three-dimensional objects in an event-related design, using grasps oriented along the same or a different axis of either the same or a different object shape. We found that the bilateral anterior intraparietal sulcus, an area previously linked to the control of visually guided grasping, along with other areas of the intraparietal sulcus, the left supramarginal gyrus, and the right mid superior parietal lobe showed clear adaptation following both repeated grasps and repeated objects. In contrast, the left ventral premotor cortex and the bilateral dorsal premotor cortex, the two premotor areas often linked to response selection, action planning, and execution, showed only grasp-selective adaptation. These results suggest that, even in real action guidance, parietofrontal areas demonstrate differential involvement in visuomotor processing dependent on whether the action or the object has been previously experienced.

fMRI reveals a preference for near viewing in the human parieto-occipital cortex.

Posterior parietal cortex in primates contains several functional areas associated with visual control of body effectors (e.g., arm, hand and head) which contain neurons tuned to specific depth ranges appropriate for the effector. For example, the macaque ventral intraparietal area (VIP) is involved in head movements and is selective for motion in near-space around the head. We used functional magnetic resonance imaging to examine activation in the putative human VIP homologue (pVIP), as well as parietal and occipital cortex, as a function of viewing distance when multiple cues to target depth were available (Expt 1) and when only oculomotor cues were available (Expt 2). In Experiment 1, subjects viewed stationary or moving disks presented at three distances (with equal retinal sizes). Although activation in pVIP showed no preference for any particular spatial range, the dorsal parieto-occipital sulcus (dPOS) demonstrated a near-space preference, with activation highest for near viewing, moderate for arm's length viewing, and lowest for far viewing. In Experiment 2, we investigated whether the near response alone (convergence of the eyes, accommodation of the lens and pupillary constriction) was sufficient to elicit this same activation pattern. Subjects fixated lights presented at three distances which were illuminated singly (with luminance and visual angle equated across distances). dPOS displayed the same gradient of activation (Near>Medium>Far) as that seen in Experiment 1, even with reduced cues to depth. dPOS seems to reflect the status of the near response (perhaps driven largely by vergence angle) and may provide areas in the dorsal visual stream with spatial information useful for guiding actions toward targets in depth.

What does the brain do when you fake it? An FMRI study of pantomimed and real grasping.

Given that studying neural bases of actions is very challenging with fMRI, numerous experiments have used pantomimed actions as a proxy to studying neural circuits of real actions. However, the underlying assumption that the same neural mechanisms mediate real and pantomimed actions has never been directly tested. Moreover, the assumption is called into question by neuropsychological evidence suggesting that real actions depend on the dorsal stream of visual processing whereas pretend actions also recruit the ventral stream. Here, we directly tested these ideas in neurologically intact subjects. Ten right-handed participants performed four tasks: 1) grasping real three-dimensional objects, 2) reaching toward the objects and touching them with the knuckle without hand preshaping, 3) pantomimed grasping in an adjacent location where no object was present, and 4) pantomimed reaching toward an adjacent location. As expected, in the anterior intraparietal area, there was significantly higher activation during real grasping than that during real reaching. However, the activation difference between pantomimed grasping and pantomimed reaching did not reach statistical significance. There was also no effect of pantomimed grasping within the ventral stream, including an object-selective area in the lateral occipital cortex. Instead, we found that pantomimed grasping was mediated by right-hemisphere activation, particularly the right parietal cortex. These results suggest that areas typically invoked by real actions may not necessarily be driven by "fake" actions. Moreover, pantomimed grasping may not tap object-related areas within the ventral stream, but rather may rely on mechanisms within the right hemisphere that are recruited by artificial and less practiced actions.

Clipped tube fenestration after extracardiac Fontan allows for simple transcatheter coil occlusion.

BACKGROUND: Expensive devices are increasingly used to close a patent fenestration after a modified Fontan operation. We report our 5-year institutional experience of clipped tube fenestration after extracardiac Fontan operation, which allows for simple transcatheter coil occlusion. METHODS: We retrospectively reviewed 30 children, median age of 4.0 years (range, 2.4 to 8.8 years) who underwent extracardiac Fontan operation between May 1996 and May 2001, and were fenestrated using a 4- to 8-mm diameter clipped tube graft. RESULTS: Ten children had a patent fenestration occluded by transcatheter placement of 15 detachable coils (5- to 8-mm diameter). Aortic oxygen saturations increased on average by 5.5% (2% to 14%) and mean pressures in the Fontan circuit by 2.5 mm Hg (0 to 3 mm Hg). Four had immediate complete occlusion angiographically and 6 had trivial residual shunt, but complete occlusion by echocardiography at follow-up. There have been no immediate complications, late coil embolizations, thromboembolic events, or documented hemolysis within a follow-up after coil implantation of 1.7 years (0.4 to 4.5 years). Spontaneous fenestration closure was documented in 8 patients at cardiac catheterization and 9 patients by echocardiography with consistent improvement in resting transcutaneous oxygen saturation. Two children with a patent fenestration have been considered inappropriate for closure, and there was one early surgical death. There have been no complications related to the tube fenestration modification within a follow-up postoperation of 2.6 years (0.1 to 5.5 years). CONCLUSIONS: Clipped tube fenestration after extracardiac Fontan operation is a useful surgical modification that allows for simple transcatheter coil occlusion.

Systematic eye movements do not account for the perception of motion during attentive tracking.

It has been suggested that attention can disambiguate stimuli that have equal motion energy in opposite directions (e.g. a counterphasing grating), such that a clear motion direction is perceived. The direction of this movement is determined by the observer and can be changed at will. Assuming that the responses of front-end motion detectors are equal for the two opponent directions, it has been proposed that the unambiguous motion perceived with attentive tracking arises from an independent mechanism that monitors the shifts of attention directed to the moving feature of interest. However, while perceiving motion under attentive tracking conditions, observers often report a strong impression that they are making eye movements. In this study, we investigated whether systematic eye movements are present during attentive tracking and, as a result, could be responsible for the subjective experience of movement. We had observers track an object in smooth motion, apparent motion and ambiguous motion, either with eye movements or with attention. The results show that there are negligible eye movements during attentive tracking, which are neither systematic nor correlated with the stimulus. Given that neither eye movements nor retinal image motion can account for subjectively perceived motion, as well as the absence of any other plausible explanation, we find it tempting evidence for an earlier suggestion that the percept of movement must arise from a specialized mechanism.

Attention response functions: characterizing brain areas using fMRI activation during parametric variations of attentional load.

We derived attention response functions for different cortical areas by plotting neural activity (measured by fMRI) as a function of attentional load in a visual tracking task. In many parietal and frontal cortical areas, activation increased with load over the entire range of loads tested, suggesting that these areas are directly involved in attentional processes. However, in other areas (FEF and parietal area 7), strong activation was observed even at the lowest attentional load (compared to a passive baseline using identical stimuli), but little or no additional activation was seen with increasing load. These latter areas appear to play a different role, perhaps supporting task-relevant functions that do not vary with load, such as the suppression of eye movements.

Aging effects on vernier hyperacuity: a function of oscillation rate but not target contrast.

PURPOSE: Most previous studies have shown static vernier acuity for high-contrast targets to be largely unaffected by aging; those examining adult age differences on oscillatory displacement thresholds have consistently reported marked age deficits. The goals of this study were to (1) measure the age deficit on oscillatory discrimination beyond that attributable to any change in spatial discrimination by using the same target configuration for both task types and (2) determine whether an age-related change in the contrast response of the visual system contributes to age differences on static or oscillatory discrimination. METHODS: The displacement thresholds of young and old observers for a vernier task configuration were determined at two target contrast levels (0.08 and 0.64) for static and oscillating targets (2 and 6 Hz) RESULTS: No age differences were seen on static displacement thresholds at either high or low contrast. A marked age deficit that emerged when oscillation was increased was unrelated to target contrast or observer contrast sensitivity. CONCLUSIONS: Age-related declines in oscillatory discrimination beyond those attributable to spatial discrimination do not appear to be attributable to optical factors nor to a decline in the contrast response of the senescent visual system. These findings are discussed in terms of a functional decline in the magnocellular pathway, or "neural entropy," possibly due to random cell loss.

Distinguishing subregions of the human MT+ complex using visual fields and pursuit eye movements.

In humans, functional imaging studies have demonstrated a homologue of the macaque motion complex, MT+ [suggested to contain both middle temporal (MT) and medial superior temporal (MST)], in the ascending limb of the inferior temporal sulcus. In the macaque monkey, motion-sensitive areas MT and MST are adjacent in the superior temporal sulcus. Electrophysiological research has demonstrated that while MT receptive fields primarily encode the contralateral visual field, MST dorsal (MSTd) receptive fields extend well into the ipsilateral visual field. Additionally, macaque MST has been shown to receive extraretinal smooth-pursuit eye-movement signals, whereas MT does not. We used functional magnetic resonance imaging (fMRI) and the neural properties that had been observed in monkeys to distinguish putative human areas MT from MST. Optic flow stimuli placed in the full field, or contralateral field only, produced a large cluster of functional activation in our subjects consistent with previous reports of human area MT+. Ipsilateral optic flow stimuli limited to the peripheral retina produced activation only in an anterior subsection of the MT+ complex, likely corresponding to putative MSTd. During visual pursuit of a single target, a large portion of the MT+ complex was activated. However, during nonvisual pursuit, only the anterolateral portion of the MT+ complex was activated. This subsection of the MT+ cluster could correspond to putative MSTl (lateral). In summary, we observed three distinct subregions of the human MT+ complex that were arranged in a manner similar to that seen in the monkey.

Visual motion and the human brain: what has neuroimaging told us?

Recently, neuroimaging techniques have been applied to the study of human motion perception, complementing established techniques such as psychophysics, neurophysiology and neuropsychology. Because vision, particularly motion perception, has been studied relatively extensively, it provides an interesting case study to examine the contributions and limitations of neuroimaging to cognitive neuroscience. We suggest that in the domain of motion perception neuroimaging has: (1) revealed an extensive network of motion areas throughout the human brain, in addition to the well-studied motion complex (MT+); (2) verified and extended findings from other techniques; (3) suggested extensive top-down influences on motion perception; and (4) allowed experimenters to examine the neural correlates of awareness. We discuss these contributions, along with limitations and future directions for the neuroimaging of motion.

Balloon angioplasty of right ventricular outflow tract conduits.

Palliation of complex congenital heart disease, requiring reconstruction of the right ventricular outflow tract (RVOT), is standard practice. Survival of the homograft is a limiting factor. We examined the role of balloon angioplasty (BAP) in prolonging conduit life. Twelve patients underwent 15 BAP procedures between February 1989 and October 1997. The median age at conduit insertion was 28 months with detection of a significant echo gradient 42 months later. Calcification of homografts, with attendant obstruction and valve dysfunction, was present in all patients. BAP was performed within 1 month of echocardiography and reduced the gradient from a median of 57 to 38 mmHg (p < 0.0005). Echocardiographic follow-up showed persistent gradients (median 68 mmHg) and 11/12 patients went on to conduit replacement after BAP. Only one patient had replacement deferred as a result of BAP. Complications requiring intervention occurred in 20% of the procedures and included bleeding and an unusual balloon fracture. Although BAP can reduce the pressure gradient across the RVOT conduit, the effect is transient and the delay of surgery is not due to improved hemodynamic function. Approximately 10% of cases will benefit from BAP alone, but given the high rate of complications, we do not recommend this procedure as a means of prolonging conduit life.

Neuroimaging of cognitive functions in human parietal cortex.

Functional neuroimaging has proven highly valuable in mapping human sensory regions, particularly visual areas in occipital cortex. Recent evidence suggests that human parietal cortex may also consist of numerous specialized subregions similar to those reported in neurophysiological studies of non-human primates. However, parietal activation generalizes across a wide variety of cognitive tasks and the extension of human brain mapping into higher-order "association cortex" may prove to be a challenge.

The evolution of ductus arteriosus treatment.

The treatment of patent ductus arteriosus (PDA) has evolved over the years. We reviewed 231 non-premature children (group 1) undergoing surgical closure of a PDA between January 1985 and December 1997, and 30 children (group 2) undergoing transcatheter closure from May 1995 to December 1998. The median age and weight at operation in group 1 were 13 months (range, 0.5-174 months) and 9.5 kg (range, 1.9-49.7 kg), respectively. There was one intra-operative death (0.4%) secondary to hemorrhage. Immediate extubation was performed in 208 patients (90%). Intra-operative chest tube use decreased from 73.3% to 10% between the 1985-88 and 1996-97 periods (P < 0.001). Postoperative pneumothoraces occurred in 33/131 (25%) patients with only one patient (0.7%) requiring drainage. Eleven patients had complications including wound infection in four, vocal cord paralysis in three, and left pulmonary artery stenosis in one. The median length of stay (LOS) was 5 days (range, 2-43 days). Follow-up echocardiogram was performed in 146/230 patients (63%) and revealed a residual PDA in six (4%); two being re-ligated, two remaining clinically insignificant, and two spontaneously resolved at 7 and 28 months follow-up. The remaining 84 patients had no clinical signs of a residual PDA. In group 2, where a transcatheter coil occlusion technique was used, the median age and weight at procedure were 31 months (range, 9-320 months) and 14.9 kg (range, 9-69.7 kg), respectively. Vascular complications occurred in four patients (13.3%). One patient developed hemolysis and hemoglobinuria requiring hospital admission. Four patients required a second intervention. At the most recent echocardiographic assessment, four patients (13.3%) had a residual PDA.