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Biomedical subjects

E Brenner

Publications and source records attributed to E Brenner.

At least 55 records · Page 3Linked to original sources
PubMed1999

Perceived distance, shape and size.

If distance, shape and size are judged independently from the retinal and extra-retinal information at hand, different kinds of information can be expected to dominate each judgement, so that errors in one judgement need not be consistent with errors in other judgements. In order to evaluate how independent these three judgments are, we examined how adding information that improves one judgement influences the others. Subjects adjusted the size and the global shape of a computer-simulated ellipsoid to match a tennis ball. They then indicated manually where they judged the simulated ball to be. Adding information about distance improved the three judgements in a consistent manner, demonstrating that a considerable part of the errors in all three judgements were due to misestimating the distance. Adding information about shape that is independent of distance improved subjects' judgements of shape, but did not influence the set size or the manually indicated distance. Thus, subjects ignored conflicts between the cues when judging the shape, rather than using the conflicts to improve their estimate of the ellipsoid's distance. We conclude that the judgements are quite independent, in the sense that no attempt is made to attain consistency, but that they do rely on some common measures, such as that of distance.

Cues↗
PubMed1999

Interaction between the perceived shape of two objects.

The difference between the way in which binocular disparity scales with viewing distance and the way in which motion parallax scales with viewing distance introduces a potential indirect cue for viewing distance: the viewing distance is the only distance at which disparity and motion specify the same depth. The present study examines whether this information is used. Two simulated ellipsoids were presented on a computer screen in complete darkness. The two ellipsoids were 6 degrees to the left and right of straight ahead. Subjects set the width and depth of each ellipsoid to match a tennis ball, and set the distance of the one on the right to half that of the one on the left. The distance of the left ellipsoid varied between trials. On half of the trials it was static. On the other half it was rotating up and down around its frontal horizontal axis. Rotating the left ellipsoid influenced its set depth: rotating ellipsoids were set to be much more spherical. There was no influence on the set depth of the other ellipsoid, or on the set width of either. The set distance of the right ellipsoid was also unaffected. We conclude that subjects do not combine binocular disparity and motion parallax to obtain more veridical information about viewing distance.

Distance Perception↗
PubMed1999

A new view on grasping.

Reaching out for object is often described as consisting of two components that are based on different visual information. Information about the object's position and orientation guides the hand to the object, while information about the object's shape and size determines how the fingers move relative to the thumb to grasp it. We propose an alternative description, which consists of determining suitable positions on the object - on the basis of its shape, surface roughness, and so on - and then moving one's thumb and fingers more or less independently to these positions. We modeled this description using a minimum-jerk approach, whereby the finger and thumb approach their respective target positions approximately orthogonally to the surface. Our model predicts how experimental variable such as object size, movement speed, fragility, and required accuracy will influence the timing and size of the maximum aperture of the hand. An extensive review of experimental studies on grasping showed that the predicted influences correspond to human behavior.

Arm↗
PubMed1999

Grip formation as an emergent property. Response To commentaries on "A new view on grasping"

We begin our response by discussing the commentators' arguments concerning our proposal to abandon the classical distinction between transport and grip. In the second section, we argue that the minimum-jerk model is not fundamental to our approach, but very convenient. In the third section, we discuss how the experimental results that the commentators mention fit into our new approach. We conclude that the predictive capacity of our model, combined with its simplicity, makes it very useful for understanding grasping.

Journal Article↗
PubMed1998

Masseteric nerve: a possible donor for facial nerve anastomosis?

In the medical treatment of facial nerve paralysis a large number of different techniques have been developed to restore the function of the facial nerve. These include (a) the ipsilateral nerve grafting (e.g., partial hypoglossal-facial, spinal accessory-facial, partial glossopharyngeal-facial), (b) crossfacial nerve grafting and (c) temporal muscle flaps or even free muscle transfers. None of these techniques uses the masseteric nerve as a graft for reconstruction of the facial nerve. This preliminary report deals with the anatomical basis, which could lead to a new technique. The masseteric nerve leaves the infratemporal fossa through the mandibular notch, accompanied by the masseteric artery. At this level the nerve consists in nine of 36 cases studied of only one branch (25.0%), in 17 cases of two branches (47.0%), in nine cases of three (25.0%), and in the remaining case of four branches (2.8%). There are three main reasons for considering the masseteric nerve as a possible donor for at least the orbicular branch of the facial nerve: (1) The approach to the mandibular notch is quite simple; (2) since the nerve consists of two or more branches in 75.0% of the cases, severe dysfunction of the masseter muscle should not occur; (3) if there is complete denervation of the masseter muscle, its function may be taken over by the temporalis muscle.

Anastomosis, Surgical↗
PubMed1998

Hitting moving targets. Continuous control of the acceleration of the hand on the basis of the target's velocity.

Previous studies on how we hit moving targets have revealed that the direction in which we move our hand is continuously adjusted on the basis of the target's perceived position, with a delay of about 110 ms. In the present study we show that the acceleration of the hand is also under such continuous control. Subjects were instructed to hit moving targets (running spiders) as quickly as possible with a rod. We found that changing the velocity of the target influenced the speed with which the rod was moved. The influence was noticeable about 200 ms after the target's velocity changed. The extent of the influence was consistent with a direct dependence of the acceleration of the hand on the target's velocity. We conclude that the acceleration of the hand is continuously adjusted on the basis of the speed of the target, with a delay of about 200 ms.

Animals↗
PubMed1998

Judging distance from ocular convergence.

Subjects misjudge distances considerably when forced to rely on extra-retinal information. Nevertheless, they can reproducibly set a target to the same distance as a reference, or to double or half that distance, even when they have to look back and forth between them because they are prevented from seeing one when looking at the other. Our explanation for this apparent discrepancy is that people have access to reasonably accurate extra-retinal information on changes in ocular convergence, but can only use this information to judge distances if they had reliable information about the orientation of the eyes before the convergence changed.

Convergence, Ocular↗
PubMed1998

When is a background equivalent? Sparse chromatic context revisited.

Jenness and Shevell (Vision Res 1995;35:797-805) reported that a red background with white dots scattered on it has a different influence on a target's apparent colour than an equivalent uniform background. We show that this finding depends on what one considers an equivalent background. Jenness and Shevell averaged the chromaticity and luminance of the background with the dots, and 'superimposed' the target onto this new background. This changed the luminance and chromaticity of both the target and the surround. We show that if only the surround is changed, it is irrelevant whether the latter is red with white dots scattered over it, or a uniform field with the same space averaged chromaticity and luminance. Our findings are consistent with a local contrast mechanism that has a limited spatial resolution.

Adaptation, Ocular↗
PubMed1998

[Use of the internal mammary artery in reconstructive microsurgery in the thoracic region: anatomical-radiologic study].

In this study, the topographic anatomy and the diameter of the internal mammary (thoracic) vessels was investigated in regard to their potential as a recipient vessel in reconstructive microsurgery in the ventral thoracic region. Particularly for reconstruction of large thoracic wall defects as well as for female breast reconstruction with free tissue transplantation, these vessels seem to be suitable due to their location. We performed an anatomical study on 86 cadavers and a radiological investigation on 50 female patients and volunteers. We found a mean diameter on 50 female patients and volunteers. We found a mean diameter of 1.8 mm of the artery and 2.1 mm of the commitant vein at the level of the fourth rib, one to two centimeters parasternally. We conclude that the internal mammary vessels can serve as recipient vessels in reconstructive microsurgery in the ventral thoracic region at the level of the fourth rib or cranially. Hypothetically, free muscle flaps for the treatment of sternal osteitis, free fasciocutaneous flaps to replace presternal burn scars or appropriate flaps to fill up a funnel chest cavity subcutaneously may be anastomosed to the internal mammary vessels.

Adult↗
PubMed1997

[The conservative and surgical therapy of traumatic humeral shaft fractures].

Sixty-three patients with humeral shaft fractures were evaluated clinically and radiographically 18 months after injury; 27 patients were treated surgically (group A) and 36 patients conservatively (group B). Analysis of the results according to a score by Kwasny revealed 6.2 points in group A and 2.2 points in group B (P < 0.0001; F = 46.9). The results of these two comparable groups suggest that conservative treatment of humeral shaft fractures is superior regarding mobility of the shoulder and elbow, strength, the incidence of neurological complications, pain, subjective rating and cosmesis. There were no differences on roentgenograms between the two groups (P = 0.48).

Adolescent↗
PubMed1997

The distance used for scaling disparities is the same as the one used for scaling retinal size.

To determine the physical size and global three-dimensional (3-D) shape of an object, retinal size and retinal disparity have to be scaled in accordance with the object's distance. We examined whether the distance used for scaling retinal disparity is the same as the distance used for scaling retinal size. Subjects adjusted the 3-D shape (size and depth) of a computer-simulated ellipsoid to match a tennis ball. Analysis of the errors when only the ellipsoid was visible in an otherwise completely dark room suggests that the distance used for scaling retinal disparity is indeed the same as that used for scaling retinal size. This was confirmed by showing that the correspondence between the distance used for scaling retinal disparity and that used for scaling retinal size does not improve when more information about distance is available (room lights on), although both distances are then much closer to the simulated distance. Finally, we show that this correspondence is not due to the use of distance-invariant higher order binocular information.

Cues↗
PubMed1997

Four issues concerning colour constancy and relational colour constancy.

Four issues concerning colour constancy and relational colour constancy are briefly considered: (1) the equivalence of colour constancy and relational colour constancy; (2) the dependence of relational colour constancy on ratios of cone excitations due to light from different reflecting surfaces, and the association of such ratios with von Kries' coefficient rule; (3) the contribution of chromatic edges to colour constancy and relational colour constancy; and (4) the effects of instruction and observer training. It is suggested that cognitive factors affect colour constancy more than relational colour constancy, which may be an inherently more robust phenomenon.

Color Perception↗
PubMed1997

Internal mammary veins: classification and surgical use in free-tissue transfer.

The internal mammary artery has been well-investigated due to its frequent use in cardiac surgery. However, in reconstructive microsurgery in the thoracic region, the internal mammary vessels have been used rarely as recipient vessels, due to difficulties and lack of knowledge about the internal mammary veins. This study was designed to investigate the anatomy and topography of the veins. Its goal was to gain sufficient information about their availability in free-tissue transfer. Dissection of the vessels was performed in 86 cadavers bilaterally to the sternum. At the level of the fourth rib, which is the most desired access for microvascular anastomosis in reconstructive breast surgery with free flaps, the veins were found to be adequately large (range 0.64 to 4.45 mm). Results were in close agreement with 100 bilateral measurements obtained by color Doppler sonography in 16 patients preoperatively, and additionally in 34 healthy volunteers. Preoperative detection of vessels with the aid of sonography facilitated planning of surgical procedures. According to these findings, the internal mammary veins may be used as suitable recipient veins for free microvascular tissue transfer, especially for established autologous breast reconstruction with the free transverse rectus abdominis myocutaneous flap, or for reconstruction of complex thoracic-wall defects.

Adolescent↗
PubMed1997

Fast Responses of the Human Hand to Changes in Target Position.

If a target toward which an individual moves his hand suddenly moves, he adjusts the movement of his hand accordingly. Does he use visual information on the target's velocity to anticipate where he will reach the target? These questions were addressed in the present study. Subjects (N = 6 in each of 4 experiments) were instructed to hit a disk with a rod as soon as it appeared on a screen. Trajectories of the hand toward stationary disks were compared with those toward disks that jumped leftward or rightward as soon as the subject's hand started moving toward the screen, and with those in which either the disk or the background started moving leftward or rightward. About 110 ms after the disk was suddenly displaced, the moving hand was diverted in the direction of the perturbation. When the background moved, the disk's perceived position shifted in the direction in which the background was moving, but the disk appeared to be moving in the opposite direction. When hitting such disks, subjects adjusted their movement in accordance with the perceived position, rather than moving their hand in the direction of the perceived motion in anticipation of the disk's future displacement. Thus, subjects did not use the perceived velocity to anticipate where they would reach the target but responded only to the change in position.

arm movement↗
PubMed1997

Seroma as a common donor site morbidity after harvesting the latissimus dorsi flap: observations on cause and prevention.

This prospective study reveals that the incidence of seroma formation after harvesting the latissimus dorsi muscle by scalpel is reasonably moderate. This incidence is lower when the resulting skin flaps are tacked to the underlying structures with resorbable sutures. In contrast, electrocautery dissection shows a significantly much higher rate of seroma formation, probably because of thermal injury of the wide fascial wound layers or the subcutaneous fat tissue. Fifty-eight patients were distributed among three groups. Within each group a specific way of latissimus dorsi muscle harvesting and donor site treatment was accomplished. The group of scalpel dissection and skin flap fixation to the underlying layers with additional tacking sutures shows the lowest rate of seroma formation (9.1%, N = 2) due to the avoidance of shearing effects. A clearly higher incidence is present in the group of scalpel dissection without tacking sutures (38.1%, N = 8), whereas seromas most frequently result after electrocautery dissection without skin flap fixation (80.0%, N = 12).

Cysts↗
PubMed1997

[Spontaneous pregnancy after ligation of the uterine artery].

In this case report, the functional anastomoses of the uterine arteries are demonstrated. In our opinion, the selective ligation of one or both uterine arteries is the method of choice for treating severe gynaecological or obstetrical bleeding complications. Successful haemostasis and preservation of the uterus can be achieved permitting future spontaneous pregnancies.

Adult↗