Biomedical subjects

M E McCarty

Publications and source records attributed to M E McCarty.

6 recordsLinked to original sources

PubMed1999

Visual control of reaching and grasping in infants.

The role of visual input during reaching and grasping was evaluated. Groups of infants (5, 7, and 9 months old) and adults reached for an illuminated object that sometimes darkened during the reach. Behavioral and kinematic measures were assessed during transport and grasp. Both infants and adults could complete a reach and grasp to a darkened object. However, vision was used during the reach when the object remained visible. Infants contacted the object more often when it remained visible, though they had longer durations and more movement units. In contrast, adults reached faster and more precisely during transport and grasp when the object remained visible. Thus, continuous sight of the object was not necessary, but when it was available, infants used it for contacting the object whereas adults used it to reach and grasp more efficiently.

Adult↗

PubMed1999

Problem solving in infancy: the emergence of an action plan.

Young children's strategies were evaluated as they grasped and used objects. Spoons containing food and toys mounted on handles were presented to 9-, 14-, and 19-month-old children with the handle alternately oriented to the left and right. The alternating orientations revealed strategies that the children used for grasping items. Younger children usually reached with their preferred hand, disregarding the item's orientation. In the case of the spoon, this strategy produced awkward grasps that had to be corrected later. Older children anticipated the problem, alternated the hand used, and achieved an efficient radial grip (i.e., handle grasped with base of thumb toward food or toy end) for both orientations. A model of the development of action-selection strategies is proposed to illustrate planning in children younger than 2 years.

Female↗

PubMed1995

Sympathetic blockade of isolated rat hindlimbs by intra-arterial guanethidine: the effect on blood flow and arterial-venous shunting.

In order to improve the understanding of the role of sympathetic nerve degeneration in reimplantation failure, the hindlimbs of eight rats (Group I) underwent near-complete amputation. The soft tissues of the hindlimb were transected at the proximal thigh with the femoral artery, vein and femur left intact. The femoral vessels were clamped and guanethidine was infused into a branch of the femoral artery of the right leg of each animal, while saline was injected into the left leg. The clamps were removed after 15 minutes. A baseline preoperative injection of radiolabeled microspheres was made, and subsequent injections at 6, 12, 18, and 24 hours postoperation. Twelve rats (Group II) were then used to assess the amount of arterial-venous shunting preoperatively (n = 6) and at 18 hours postoperation (n = 6), by venous sampling. Blood flow to both limbs increased postoperation, but there was significantly more flow in the guanethidine treated limb at 18 and 24 hours postoperation. The amount of shunting was approximately 50% in both limbs at 18 hours, as compared to 10% preoperation. These results highlight the potential benefit of guanethidine and other sympathetic blocking agents in reimplantation to increase blood flow, decrease tissue ischemia and increase anastomotic patency rates. They also suggest that sympathetic nerve degeneration did not affect the volume of arterial-venous shunting in this model, but the difference in blood flow was likely due to arteriolar vasospasm. Further study is needed to elucidate the clinical significance of sympathetic nerve degeneration in reimplantation failure.

Animals↗

PubMed1993

Visual guidance in infants' reaching toward suddenly displaced targets.

This experiment evaluated the role of visual input about the location of a target object and the location of the hand in reaching by infants and adults. 5- and 9-month-old infants were presented with illuminated toys to reach for in a dark room. On no-switch trials, the toy remained illuminated throughout the infant's reach, whereas on switch trials the first-lit toy was replaced during the reach by a second-lit toy at a different position. On approximately half of the trials of each type a luminescent marker was attached to the reaching hand. Adult subjects (tested without the hand marker) fully compensated to the second-lit toy on switch trials, during a second reaching segment. On switch trials, 9-month-olds partially adjusted to the second-lit toy when wearing the hand marker and did not adjust without it. On no-switch trials, 9-month-olds reached just as accurately with or without the hand marker. 5-month-olds were generally inaccurate in their reaching and were unaffected by the presence or absence of the hand marker. The findings suggest that during the development of reaching there is an increase in visual guidance during the approach phase of reaches.

Adult↗

PubMed1991

Postural sway of human infants while standing in light and dark.

Postural sway was measured in 12-14-month-old human infants and in adults while they were standing in the light and dark. Spectral density analyses conducted on all frequencies, at specific frequencies, and for individual subjects showed that infants generally did not sway significantly more in the dark than in the light, whereas adults did. For example, infants' dark/light sway proportions were 1.12 and 1.21 for the anterior-posterior and lateral dimensions, respectively, compared to adult values of 2.23 and 3.43 for one-footed stance, and 1.43 and 2.13 for two-footed stance. A statistical power analysis indicated that if the dark/light proportions for infants had been comparable to those for adults, significant differences could have been detected. These findings indicate that the early regulation of standing posture does not depend on the continuous availability of visual information.

Dark Adaptation↗

PubMedDate not supplied

How infants use vision for grasping objects.

The role of vision was examined as infants prepared to grasp horizontally and vertically oriented rods. Hand orientation was measured prior to contact to determine if infants differentially oriented their hands relative to the object's orientation. Infants reached for rods under different lighting conditions. Three experiments are reported in which (1) sight of the hand was removed (N = 12), (2) sight of the object was removed near the end of the reach (N = 40, including 10 adults), and (3) sight of the object was removed prior to reach onset (N = 9). Infants differentially oriented their hand to a similar extent regardless of lighting condition and similar to control conditions in which they could see the rod and hand throughout the reach. In preparation for reaching, infants may use the current sight of the object's orientation, or the memory of it, to orient the hand for grasping; sight of the hand had no effect on hand orientation.

Attention↗