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Biomedical subjects

D L Wright

Publications and source records attributed to D L Wright.

At least 19 recordsLinked to original sources
PubMed1998

Contextual dependencies during perceptual-motor skill performance: influence of task difficulty.

The present experiment was designed to address the role of task difficulty for the development of contextual-dependent behaviour during perceptual-motor task acquisition. Task difficulty in the present study was manipulated by restricting the time that the subject; (a) viewed task-relevant information, and (b) was afforded to execute a sequence of key presses. Assuming these manipulations made the acquisition of the key press tasks more difficult, it was hypothesised that reducing the time for either of these processes would result in a greater dependence on reinstating the training context at the time of test. This was based on previous findings reported by Wright and Shea (1991) which indicated that task difficulty can contribute to the development of context-dependent behaviour. The results of the study revealed that viewing time was a potent difficulty manipulation. This is supported by the slower acquisition rates for subjects exposed to short as opposed to long viewing conditions during training. More importantly, the impact of changing the intentional-incidental stimuli relationship that was apparent during training, during the test was greatest for the individuals who experienced shorter viewing times during the training phase. Thus, the proposed influence of task difficulty on contextual-dependent performance was supported. This dependency was manifested as a slowing in both the initiation and execution of the correct key presses. It is proposed that individuals trained in the more difficult viewing condition during training, when faced with an incongruence in the acquisition and test stimuli, must engage additional data-driven verification processes to supplement their extant knowledge in order to execute an appropriate response.

Humans↗
PubMed1998

Fiber grouping in the feline vestibular nerve before and after labyrinthectomy.

The vestibular nerve is composed of fibers with a wide spectrum of diameters. The fibers of largest diameter are known to innervate the type I hair cells of the cristae, while the small-diameter fibers innervate the type II hair cells. Midsized fibers (dimorphic fibers) represent neurons that innervate both type I and type II hair cells. Reports by others have commented on the tendency for clustering of fibers with like diameters. Rigorous statistical proof for or against clustering has not yet been presented. The explanation for this is, in part, the mathematic complexity of analyzing clustering in a system composed of three elements. We report a new method for analysis of fiber clustering and apply this method to large-, medium-, and small-diameter fibers in the feline vestibular nerve. The fiber grouping in the caudal and rostral ends of the vestibular nerves of six normal animals is compared to that in similar areas of the nerves of five animals 12 to 17 months after unilateral labyrinthectomy. No statistically significant clustering of fiber types was found in the rostral portion of either the control or the labyrinthectomized animals. In the caudal portion of the control nerves, clustering of the large fibers was demonstrated (p < .005, chi2 test). This clustering was not demonstrated after labyrinthectomy. An explanation of these findings is discussed. The method used in this study to analyze fiber clustering may be applicable to other nerve systems of greater complexity.

Animals↗
PubMed1997

Towards a novel augmented-reality tool to visualize dynamic 3-D anatomy.

Using augmented reality (AR) to teach dynamic 3-D anatomy may impart better understanding of bone dynamics during body movement. We are currently developing an AR tool that will allow superimposition and registration of bone structures on real anatomical counterparts of a human subject. This article describes the application, the problems to be solved, and reports on preliminary developmental studies of a first prototype of the tool. Specifically, studies test approaches to simulating real-time dynamic anatomy, and the feasibility in achieving registration of 3-D anatomical bones on their real counterparts. Such a tool will offer several unique advantages over traditional teaching methods and overcome many of their current limitations.

Anatomy↗
PubMed1996

Contextual dependencies during perceptual-motor skill acquisition: gone but not forgotten!

The development and resiliency of contextual dependencies developed during perceptual-motor skill acquisition was assessed. Incidental aspects of the stimulus used to instigate the production of previously practised typing sequences were manipulated during either an immediate or delayed retention test. The findings from the immediate test offered further support for the existence of contextual-dependent performance for perceptual-motor responding. However, the dependency was attenuated by using a delayed retention test. Experiment 2 pursued two alternative explanations for the diminished dependency effect revealed in Experiment 1. In Experiment 2 some subjects were explicitly encouraged to reinstate aspects of the incidental contextual information that was present during training prior to administration of a delayed test. The dependency present only in the immediate test in Experiment 1 reemerged after contextual reinstatement. The present data are discussed with respect to the inclusion of incidental contextual stimuli as part of the long-term sensorimotor memory representation.

Analysis of Variance↗
PubMed1995

Contextual dependencies: influence on response latency.

The present experiments were designed to examine the influence of contextual stimuli on perceptual-motor performance. Experiment 1 revealed that contextual dependencies can develop for simple perceptual-motor tasks. Furthermore, the extent of the dependency is mediated in part by whether the contextual information is removed or replaced with alternative contextual information at the time of test. Data from Experiment 2 and 3 showed that manipulating the potency of incidental contextual stimuli results in a systematic decrement or increment in subsequent performance, depending on whether the contextual stimuli during the test were changed or reinstated. To date, such an orderly influence of contextual stimuli is more commonly demonstrated in the animal learning literature than with human experimentation.

Adolescent↗
PubMed1994

A rapid and selective endothelin-converting enzyme assay: characterization of a phosphoramidon-sensitive enzyme from guinea pig lung membrane.

Endothelin-1 (ET-1) is the most potent vasoconstrictor hormone known to date. Biosynthesis of ET-1 from its precursor big endothelin-1 (BET-1) is mediated by endothelin-converting enzyme (ECE), a phosphoramidon-sensitive metalloprotease. We have established a simple, rapid, and selective assay for the evaluation of ECE activity. This assay is based on the quantitative determination of [125I]ET-1 released from (3-[125I]idotyrosyl13)BET-1 by binding to the membrane-bound endothelin (ET) receptor. Using this assay we have discovered that guinea pig lung membrane (GPLGM) contains a phosphoramidon-sensitive ECE. Treatment of GPLGM with 0.06% lubrol increased ECE activity and ET binding of the membrane preparation. Lubrol-treated GPLGM (L-GPLGM) contains a high density of ET binding sites (Bmax = 2000 fmol/mg protein) and shows no proteolytic activity for degredation of ET-1. At protein concentrations suitable for measurement of ECE activity (0.2 mg/ml), L-GPLGM contains a high concentration of ET receptors and shows a rapid rate of ET-1 binding to the membrane preparation (binding equilibrium in < 5 min). Thus, we have utilized L-GPLGM preparation for both ECE activity and measurement of ET-1 binding in a single-step assay for the determination of enzyme activity. ECE activity of L-GPLGM was fully inhibited by phosphoramidon, 1,10-phenanthroline, and EDTA. Class-specific inhibitors of serine, cysteine, and aspartic proteases showed no significant effect on ECE activity in L-GPLGM. These results show that GPLGM contains exclusively a phosphoramidon-sensitive ECE.

Animals↗
PubMed1992

The contribution of elaborative processing to the contextual interference effect.

This study examined the influence of supplemental intertask and intratask processing on the retention of three motor sequences practiced in conditions of high and low contextual interference. Subjects practiced in either a blocked or random practice format and experienced additional intratask processing, intertask processing, or no additional processing. Each of three movement sequences were practiced for 18 trials. The subjects were required to perform the sequences as fast and as accurately as possible. Retention performance and recall of the movement sequences were assessed after a 21-day retention interval. The results replicated those of Wright (1991), indicating a benefit for individuals engaging intertask processing during a low contextual interference practice condition. Furthermore, supplementing random practice with additional intertask processing not only slowed the rate of task acquisition, but also resulted in retention performance that was significantly poorer than that exhibited by individuals exposed to random practice with no additional processing. This suggests there may be a limit to the extent of interference that can be established during practice that will lead to a facilitation in retention performance.

Humans↗
PubMed1992

The dual-task methodology and assessing the attentional demands of ambulation with walking devices.

The purposes of this article are (1) to provide a preliminary examination of the attentional demands of ambulating with two commonly prescribed walking aids (a standard walker and a rolling walker) and (2) to introduce the dual-task methodology to the physical therapy community. Five subjects familiar with the appropriate use of the walkers and five subjects uninformed as to the correct use of the walkers participated in the study. Each subject completed the three phases of the experiment: (1) performing the reaction time (RT) task only; (2) performing each of the walking tasks only; and (3) performing each of the walking tasks in conjunction with the RT task, which constituted the dual-task conditions. The findings indicated that walking aided by either the rolling walker or the standard walker was highly attention demanding. More importantly, it appears that greater attentional demand was required when ambulating with the standard walker. These results are discussed with respect to the gait modifications and accuracy demands required when using these walkers. The usefulness of the dual-task methodology as a research tool for addressing clinically oriented questions is emphasized, and some potential applications of this methodology for the therapist within the clinic are discussed.

Adult↗
PubMed1992

Frontal sinus fractures in the pediatric population.

Full development of the frontal sinus is not achieved until approximately 19 years of age. An evaluation of frontal sinus injuries isolated to the subset of patients less than 20 years old has yet to be reported. In order to determine whether age was a factor in the clinical course of patients with frontal sinus fractures, 209 patients who sustained frontal sinus fractures from January 1985 to April 1990 were identified using the trauma registry from all six major trauma centers, one of which is a pediatric trauma center, in a county of 2.5 million people. Forty patients (19%) were between the ages of 6 and 19 years at the time of their injury. Computed tomography imaging of these pediatric patients identified associated head and neck fractures in 37 (93%) as well as significant central nervous system injury in 22 (55%). Seventeen pediatric patients were treated nonoperatively and 1 died prior to the planned surgery. A detailed analysis of extent of injury and treatment together with a comparison of the 169 adult and the 40 pediatric patients is presented.

Abbreviated Injury Scale↗
PubMed1991

Summary knowledge of results.

Summary knowledge of results (KR) involves delaying the presentation of KR until a predetermined number of trials has been completed. Schmidt, Young, Swinnen, and Shapiro (1989) found an optimal summary length of 15 trials (compared to 1, 5, and 10) and Schmidt, Lange, and Young (1990) found an optimum length of 5 trials (compared to 1, 10, and 15) for 1 and 2 kinematic degree of freedom timing tasks, respectively. Experiment 1 was designed to determine the optimal summary length for learning a simple isometric force production task. The results indicated better retention for the 16-trial summary than for 8- or 1-trial summaries. Experiment 2 was an initial attempt to determine the locus of the 16-trial summary effect. Specifically, Experiment 2 focused on the role played by both the information provided in the summary presentations and the practice per se of the first 14 trials in the 16-trial block. The results suggest KR is important to ensure response stability. However, it also appears important to restrict the subject's immediate utilization of KR. This latter requirement may potentially aid the parameterization process, resulting in a reduction in response bias.

Humans↗
PubMed1991

When forgetting benefits motor retention.

Recent research (Lee & Weeks, 1987; Weeks, Lee, & Elliott, 1987) investigating the processes responsible for the contextual interference phenomenon has used a modified short-term motor retention paradigm to support the reconstruction explanation (Lee & Magill, 1985; Magill, 1989; Magill & Hall, 1990). The present experiment was an extension of these experiments in which forgetting of an acquisition task was induced through performance of either a similar or dissimilar distractor task during the intertrial interval. The effects of an extra practice trial with the acquisition task as well as no activity during the intertrial interval were also investigated. In addition, forgetting of the acquisition task was assessed prior to a reconstruction trial, which immediately preceded a 2-min filled retention interval. Both similar and dissimilar distractor tasks caused equivalent amounts of forgetting of the acquisition task prior to the reconstruction trial. However, retention of the acquisition task was significantly improved if its reconstruction occurred following forgetting due to interference from performance of a similar distractor task. These findings suggest forgetting and subsequent reconstruction alone are not sufficient for improved retention. These processes must occur in the context of a similar task for improved retention.

Analysis of Variance↗
PubMed1991

Contextual dependencies in motor skills.

The development of contextual dependencies during motor skill acquisition was examined. Environmental context was varied along intentional and incidental dimensions. Intentional stimuli were defined as essential for achieving skilled performance, whereas incidental stimuli were defined as those that have the potential to become associated with specific tasks due to their selective presence in the learning environment. Experiment 1 demonstrated the occurrence of contextual dependencies for the learning of four-key typing sequences. Contextual dependencies were diminished in Experiment 2 when the number of keys used in the sequences was reduced. In Experiment 3, a retention condition was incorporated, in which both the intentional and the incidental stimuli were not available; this confirmed that task difficulty mediated the development of contextual dependencies. These findings are discussed with respect to the incorporation of environmental contextual stimuli with memorial representations of movement information.

Adult↗
PubMed1991

How to plan today for tomorrow's potential disasters.

Hurricanes, earthquakes, and tornadoes are not the only disasters that can disrupt a patient accounts department's operations. Localized fires, power outages, vandalism, and hardware or software failure can pose even greater threats to operations. To minimize downtime and resume normal operations, disaster preparedness strategies should be part of a department's daily procedures.

Disaster Planning↗
PubMed1989

Effect of a microcomputer-based registry on adult immunizations.

A survey of patients attending the Cosmopolitan International Diabetes Center showed that one third of those born prior to 1935 did not know their immunization status, and only 56% of this group remembered ever receiving tetanus vaccine. In contrast, of those born after 1935, 98% gave a history of being vaccinated for tetanus, either as a child (76%) or as an adult (22%). Eight of the 35 patients who could not remember or denied receiving pneumococcal vaccine had in fact received it. Most patients could remember whether and when they had received influenza vaccine. A microcomputer-based registry was used to generate summaries of clinical information at each patient visit. These summaries included prevention-related items. There was a three- to five-fold increase in immunization rates when the dates of the most recent vaccinations were prominently displayed on the summary at the time of each visit.

Adult↗
PubMed1987

Lack of effect of warfarin on L-thyroxine metabolism.

The effect of a single 50 mg dose of warfarin sodium on thyroxine monodeiodination was examined in eight healthy human subjects. There was no evidence that warfarin inhibits 5'-monodeiodination, although such inhibition exists in rats.

Adult↗
PubMed1987

Neurokinin-induced salivation in the anesthetized rat: a three receptor hypothesis.

Substance P (3 micrograms/kg), neurokinin A (20 micrograms/kg), neurokinin B (6 micrograms/kg) and acetylcholine (875 micrograms/kg) all produced salivation upon i.v. infusion in the anesthetized rat. Against single equivalent agonist doses, atropine (135 micrograms/kg i.v.) blocked both acetylcholine- and neurokinin B-, but not substance P- or neurokinin A-induced salivation. [D-Pro2,D-Trp7,9]-substance P (1 mg/kg i.v.), a putative substance P antagonist, reduced responses to mammalian neurokinins but caused a 2-fold potentiation of acetylcholine-induced salivation. [D-Pro2,D-Trp6,8,Nle10]-Neurokinin B (1 mg/kg i.v.), a novel putative neurokinin B antagonist, significantly reduced substance P- and neurokinin B- but not acetylcholine- or neurokinin A-induced salivation. The three agonists (at doses that produced salivation) and [D-Pro2,D-Trp6,8,Nle10]-neurokinin B (1 mg/kg i.v.) lowered blood pressure in anesthetized rats by 35 to 40%. [D-Pro2,D-Trp7,9]-Substance P (1 mg/kg i.v.) had no significant effect on blood pressure. Hydralazine at 0.60 mg/kg (i.v.), a dose which lowered blood pressure by 47%, did not reduce substance P-induced salivation. Thus, blockade of neurokinin-induced salivation by [D-Pro2,D-Trp6,8,Nle10]-neurokinin B was probably not due to hypotension. Based on the differential effects of the three antagonists on neurokinin- and acetylcholine-induced salivation, we hypothesize the existence of three distinct neurokinin receptors in rat salivary gland, and suggest that neurokinin B receptors reside presynaptically.

Anesthesia↗