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Biomedical subjects

William H Warren

Publications and source records attributed to William H Warren.

15 recordsLinked to original sources
PubMed2005

Do humans integrate routes into a cognitive map? Map- versus landmark-based navigation of novel shortcuts.

Do humans integrate experience on specific routes into metric survey knowledge of the environment, or do they depend on a simpler strategy of landmark navigation? The authors tested this question using a novel shortcut paradigm during walking in a virtual environment. The authors find that participants could not take successful shortcuts in a desert world but could do so with dispersed landmarks in a forest. On catch trials, participants were drawn toward the displaced landmarks whether the landmarks were clustered near the target location or along the shortcut route. However, when landmarks appeared unreliable, participants fell back on coarse survey knowledge. Like honeybees (F. C. Dyer, 1991), humans do not appear to derive accurate cognitive maps from path integration to guide navigation but, instead, depend on landmarks when they are available.

Adolescent↗
PubMed2004

Path perception during rotation: influence of instructions, depth range, and dot density.

How do observers perceive their direction of self-motion when traveling on a straight path while their eyes are rotating? Our previous findings suggest that information from retinal flow and extra-retinal information about eye movements are each sufficient to solve this problem for both perception and active control of self-motion [Vision Res. 40 (2000) 3873; Psych. Sci. 13 (2002) 485]. In this paper, using displays depicting translation with simulated eye rotation, we investigated how task variables such as instructions, depth range, and dot density influenced the visual system's reliance on retinal vs. extra-retinal information for path perception during rotation. We found that path errors were small when observers expected to travel on a straight path or with neutral instructions, but errors increased markedly when observers expected to travel on a curved path. Increasing depth range or dot density did not improve path judgments. We conclude that the expectation of the shape of an upcoming path can influence the interpretation of the ambiguous retinal flow. A large depth range and dense motion parallax are not essential for accurate path perception during rotation, but reference objects and a large field of view appear to improve path judgments.

Awareness↗
PubMed2004

Visual guidance of intercepting a moving target on foot.

How do people walk to a moving target, and what visual information do they use to do so? Under a pursuit strategy, one would head toward the target's current position, whereas under an interception strategy, one would lead the target, ideally by maintaining a constant target-heading angle (or constant bearing angle). Either strategy may be guided by the egocentric direction of the target, local optic flow from the target, or global optic flow from the background. In four experiments, participants walked through a virtual environment to reach a target moving at a constant velocity. Regardless of the initial conditions, they walked ahead of the target for most of a trial at a fairly constant speed, consistent with an interception strategy (experiment 1). This behavior can be explained by trying to maintain a constant target-heading angle while trying to walk a straight path, with transient steering dynamics. In contrast to previous results for stationary targets, manipulation of the local optic flow from the target (experiment 2) and the global optic flow of the background (experiments 3 and 4) failed to influence interception behavior. Relative motion between the target and the background did affect the path slightly, presumably owing to its effect on perceived target motion. We conclude that humans use an interception strategy based on the egocentric direction of a moving target.

Adult↗
PubMed2003

Behavioral dynamics of steering, obstacle avoidance, and route selection.

The authors investigated the dynamics of steering and obstacle avoidance, with the aim of predicting routes through complex scenes. Participants walked in a virtual environment toward a goal (Experiment 1) and around an obstacle (Experiment 2) whose initial angle and distance varied. Goals and obstacles behave as attractors and repellers of heading, respectively, whose strengths depend on distance. The observed behavior was modeled as a dynamical system in which angular acceleration is a function of goal and obstacle angle and distance. By linearly combining terms for goals and obstacles, one could predict whether participants adopt a route to the left or right of an obstacle to reach a go (Experiment 3). Route selection may emerge from on-line steering dynamics, making explicit path planning unnecessary.

Adolescent↗
PubMed2002

Demonstration of Epstein-Barr virus in carcinomas of various sites.

EBV is an etiological agent in infectious mononucleosis, is implicated in some malignant lymphomas and lymphoepithelioma-like carcinomas, and has been sporadically reported in carcinomas of the breast, lung, and other sites. We studied immunohistochemically benign and malignant tumors of the breast, lung, colon, and prostate and found EBV in some carcinomas of those sites. Also, EBV reactions were noted in hyperplasias and dysplasias, e.g., breast carcinomas in situ and prostatic intraepithelial neoplasia. Benign tumor counterparts were negative. PCR analysis of selected cases confirmed the presence of EBV. Our results suggest that EBV is not restricted to lymphoepithelioma-like carcinomas but may play an oncogenic role in frequent epithelial cancers and possibly also in hyperplasias and certain dysplasias preceding carcinomas.

Breast Neoplasms↗
PubMed2002

Neuroendocrine tumors of the bronchopulmonary tract: a reappraisal of their classification after 20 years.

This article is an overview of the classification of pulmonary neuroendocrine neoplasms, their presentation, their pathologic appearance, and their clinical management. In addition, the original classification, based on histologic features, is reassessed in the light of newer areas in study, including neurosecretory products, neuroendocrine markers, ultrastructural studies, ploidy analysis, cell adhesion markers, apoptosis, oncogene mutation analysis, and genetic alterations. The histologic classification proposed in 1983 remains the single most valuable factor in establishing the diagnosis and, together with the TNM status, the prognosis of this group of interesting neoplasms.

Bronchial Neoplasms↗
PubMed2002

Modulation of tumor-infiltrating lymphocyte cytolytic activity against human non-small cell lung cancer.

The cytokines expressed in tumor microenvironments are thought to be important mediators of both the host immune response and tumor survival. The source of these cytokines includes tumor cells, infiltrating leukocytes, fibroblasts, and other stromal elements. We previously reported that tumor-infiltrating lymphocytes (TIL) from human non-small cell lung cancer (NSCLC) express predominantly type 1 cytokines, which are known to enhance cell-mediated immunity. The purpose of this study is to assess the cytokine mRNA expression of human NSCLC primary cell lines and the capacity of the tumor-associated cytokines to modulate the development of TIL cytolytic activity against the autologous tumor. Cytokine mRNA expression was determined by RT-PCR and the capacity of TIL to kill autologous lung tumor cells was measured by the chromium-51 (51Cr) release assay. All NSCLC primary cell lines expressed mRNA for IL-4, IL-6, and transforming growth factor-beta1 (TGFbeta1), whereas IL-10 was expressed in only 1/7 cell lines. When added to TIL cultures stimulated with anti-CD3+IL-2, IL-4 and IL-10 enhanced and TGF-beta1 suppressed the development of TIL cytolytic activity against autologous tumor cells. The effects of IL-6 were inconsistent and for the group, were not statistically significant. These results demonstrate that human NSCLC cells express cytokines with the capacity to regulate the in situ anti-tumor immune response. However, the effects of tumor-derived cytokines varied qualitatively and quantitatively suggesting the balance between specific type 2 cytokines or TGF-beta1 within tumor microenvironments may influence prognosis or response to immunotherapy.

CD3 Complex↗
PubMed2002

Virtual reality in behavioral neuroscience and beyond.

Virtual reality (VR) has finally come of age for serious applications in the behavioral neurosciences. After capturing the public imagination a decade ago, enthusiasm for VR flagged due to hardware limitations, an absent commercial market and manufacturers who dropped the mass-market products that normally drive technological development. Recently, however, improvements in computer speed, quality of head-mounted displays and wide-area tracking systems have made VR attractive for both research and real-world applications in neuroscience, cognitive science and psychology. New and exciting applications for VR have emerged in research, training, rehabilitation, teleoperation, virtual archeology and tele-immersion.

Behavioral Sciences↗
PubMed2002

Path integration from optic flow and body senses in a homing task.

We examined the roles of information from optic flow and body senses (eg vestibular and proprioceptive information) for path integration, using a triangle completion task in a virtual environment. In two experiments, the contribution of optic flow was isolated by using a joystick control. Five circular arenas were used for testing: (B) both floor and wall texture; (F) floor texture only, reducing information for rotation; (W) wall texture only, reducing information for translation; (N) a no texture control condition, and (P) an array of posts. The results indicate that humans can use optic flow for path integration and are differentially influenced by rotational and translational flow. In a third experiment, participants actively walked in arenas B, F, and N, so body senses were also available. Performance shifted from a pattern of underturning to overturning and exhibited decreased variability, similar responses with and without optic flow, and no attrition. The results indicate that path integration can be performed by integrating optic flow, but when information from body senses is available it appears to dominate.

Adult↗
PubMed2002

Heading perception in patients with advanced retinitis pigmentosa.

PURPOSE: We investigated whether retinis pigmentosa (RP) patients with residual visual field of < 100 degrees could perceive heading from optic flow. METHODS: Four RP patients and four age-matched normally sighted control subjects viewed displays simulating an observer walking over a ground. In experiment 1, subjects viewed either the entire display with free fixation (full-field condition) or through an aperture with a fixation point at the center (aperture condition). In experiment 2, patients viewed displays of different durations. RESULTS: RP patients' performance was comparable to that of the age-matched control subjects: heading judgment was better in the full-field condition than in the aperture condition. Increasing display duration from 0.5 s to 1 s improved patients' heading performance, but giving them more time (3 s) to gather more visual information did not consistently further improve their performance. CONCLUSIONS: RP patients use active scanning eye movements to compensate for their visual field loss in heading perception; they might be able to gather sufficient optic flow information for heading perception in about 1 s.

Eye Movements↗
PubMed2002

A visual equalization strategy for locomotor control: of honeybees, robots, and humans.

Honeybees fly down the center of a corridor by equating the speed of optic flow in the lateral field of the two eyes. This flow-equalization strategy has been successfully implemented in mobile robots to guide behavior in cluttered environments. We investigated whether humans use a similar strategy to steer down a corridor and determined the relative contributions of equating the speed of flow (.27), the splay angles of base lines (.62), and the visual angles of texture on the left and right walls (.03) to steering behavior. A generalized equalization strategy based on the weighted linear combination of these variables closely models human behavior, providing robust visual control.

Animals↗
PubMed2002

Retinal flow is sufficient for steering during observer rotation.

How do people control locomotion while their eyes are simultaneously rotating? A previous study found that during simulated rotation, they can perceive a straight path of self-motion from the retinal flow pattern, despite conflicting extraretinal information, on the basis of dense motion parallax and reference objects. Here we report that the same information is sufficient for active control ofjoystick steering. Participants steered toward a target in displays that simulated a pursuit eye movement. Steering was highly inaccurate with a textured ground plane (motion parallax alone), but quite accurate when an array of posts was added (motion parallax plus reference objects). This result is consistent with the theory that instantaneous heading is determined from motion parallax, and the path of self-motion is determined by updating heading relative to environmental objects. Retinal flow is thus sufficient for both perceiving self-motion and controlling self-motion with a joystick; extraretinal and positional information can also contribute, but are not necessary.

Adult↗
PubMed2002

Delayed auditory feedback and rhythmic tapping: evidence for a critical interval shift.

Delayed auditory feedback (DAF) impairs performance in speech, music, and tapping, with maximal impairment in speech occurring at a delay of about 200 msec. This critical interval has played a central role in many explanations of the DAF effect, including both closed-loop feedback explanations and alternative proposals. We investigated the nature of the critical interval in rhythmic tapping--in particular, whether the critical interval has a constant value or is dependent on performance rate. Three experiments in which a synchronization-continuation paradigm was used consistently showed that the critical interval shifted with different tapping rates, with maximal impairment occurring when the delay approximately equaled the tapping rate. We address the implications of these results for theories of DAF.

Auditory Perception↗
PubMedDate not supplied

Comparing 2D vector field visualization methods: a user study.

We present results from a user study that compared six visualization methods for two-dimensional vector data. Users performed three simple but representative tasks using visualizations from each method: 1) locating all critical points in an image, 2) identifying critical point types, and 3) advecting a particle. Visualization methods included two that used different spatial distributions of short arrow icons, two that used different distributions of integral curves, one that used wedges located to suggest flow lines, and line-integral convolution (LIC). Results show different strengths and weaknesses for each method. We found that users performed these tasks better with methods that: 1) showed the sign of vectors within the vector field, 2) visually represented integral curves, and 3) visually represented the locations of critical points. Expert user performance was not statistically different from nonexpert user performance. We used several methods to analyze the data including omnibus analysis of variance, pairwise t-tests, and graphical analysis using inferential confidence intervals. We concluded that using the inferential confidence intervals for displaying the overall pattern of results for each task measure and for performing subsequent pairwise comparisons of the condition means was the best method for analyzing the data in this study. These results provide quantitative support for some of the anecdotal evidence concerning visualization methods. The tasks and testing framework also provide a basis for comparing other visualization methods, for creating more effective methods and for defining additional tasks to further understand the tradeoffs among the methods. In the future, we also envision extending this work to more ambitious comparisons, such as evaluating two-dimensional vectors on two-dimensional surfaces embedded in three-dimensional space and defining analogous tasks for three-dimensional visualization methods.

Algorithms↗