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Biomedical subjects

William H Warren

Publications and source records attributed to William H Warren.

At least 19 recordsLinked to original sources
PubMed2006

Humans do not switch between path knowledge and landmarks when learning a new environment.

Using a metric shortcut paradigm, we have found that like honeybees (Dyer in Animal Behaviour 41:239-246, 1991), humans do not seem to build a metric "cognitive map" from path integration. Instead, observers take novel shortcuts based on visual landmarks whenever they are available and reliable (Foo, Warren, Duchon, & Tarr in Journal of Experimental Psychology-Learning Memory and Cognition 31(2):195-215, 2005). In the present experiment we examine whether humans, like ants (Wolf & Wehner in Journal of Experimental Biology 203:857-868, 2000), first use survey-type path knowledge, built up from path integration, and then subsequently shift to reliance on landmarks. In our study participants walked in an immersive virtual environment while head position and orientation were recorded. During training, participants learned two legs of a triangle with feedback: paths from Home to Red and Home to Blue. A configuration of colored posts surrounded the Red location. To test reliance on landmarks, these posts were covertly translated, rotated, or left unchanged during six probe trials. These probe trials were interspersed during the training procedure to measure changes over learning. Dependence on visual landmarks was immediate and sustained during training, and no significant learning effects were observed other than a decrease in hesitation time. Our results suggest that while humans have at least two distinct navigational strategies available to them, unlike ants, a computationally-simpler landmark strategy dominates during novel shortcut navigation.

Adult↗
PubMed2006

Kinematic adaptation to sudden changes in visual task constraints during reciprocal aiming.

In a series of three experiments the visual modulation of movement during a reciprocal aiming task was examined when participants were confronted with sudden changes in visually specified task constraints. Amplitude and precision constraints were manipulated independently in Experiments 1 and 2, respectively, while their simultaneous effects were analyzed in Experiment 3. Analysis of the evolution of kinematic characteristics following a sudden change in task constraints revealed two different times scales of adaptation: a rapid adjustment occurring during the deceleration phase of the first movement following change and a more gradual adaptation, affecting the kinematic pattern as a whole, occurring over the next few movements. Overall, the results indicate that visual information with respect to the adequacy of the unfolding movement is continuously monitored, even under the least constraining conditions, and serves to modulate the pattern of movement to (a) comply with the (new) task constraints and (b) optimally tailor the pattern of movement to the situation at hand. We interpret these findings in the framework of a dynamical perspective on movement organization, with information modulating the parameters of an otherwise invariant underlying dynamical structure.

Acclimatization↗
PubMed2006

The dynamics of perception and action.

How might one account for the organization in behavior without attributing it to an internal control structure? The present article develops a theoretical framework called behavioral dynamics that integrates an information-based approach to perception with a dynamical systems approach to action. For a given task, the agent and its environment are treated as a pair of dynamical systems that are coupled mechanically and informationally. Their interactions give rise to the behavioral dynamics, a vector field with attractors that correspond to stable task solutions, repellers that correspond to avoided states, and bifurcations that correspond to behavioral transitions. The framework is used to develop theories of several tasks in which a human agent interacts with the physical environment, including bouncing a ball on a racquet, balancing an object, braking a vehicle, and guiding locomotion. Stable, adaptive behavior emerges from the dynamics of the interaction between a structured environment and an agent with simple control laws, under physical and informational constraints.

Animals↗
PubMed2006

The dispersed neuroendocrine system, its bronchopulmonary elements, and neuroendocrine tumors presumed to be derived from them: myths, mistaken notions, and misunderstandings.

The increasing recognition of the dispersed neuroendocrine system and its importance in human physiology has impacted our understanding of physiology, pathophysiology, and histopathology. It has been the subject of a great deal of controversy and debate, giving rise to certain misunderstandings. This article attempts to put some of these issues in perspective, especially as they relate to the bronchopulmonary tree.

Bronchi↗
PubMed2006

Well-differentiated neuroendocrine carcinomas: the spectrum of histologic subtypes and various clinical behaviors.

The term "well-differentiated neuroendocrine carcinoma" was coined to describe a variety of demonstrably neuroendocrine tumors which were more aggressive (both with respect to their histologic appearance and their clinical course) than (typical) bronchial carcinoids but were also clearly distinguishable from small cell neuroendocrine carcinomas. This umbrella term encompasses a variety of tumors previously described by a variety of terms including "atypical" carcinoids, "malignant tumorlets," peripheral stage I small-cell carcinoma, as well as neoplasms described simply as "undifferentiated carcinoma" (prior to the recognition of their neuroendocrine properties). As such, this term is a broad term and is not simply synonymous with "atypical carcinoid." Over time, at least 3 subtypes have been identified based upon their histologic appearance and mitotic index, with correspondingly aggressive clinical courses.

Bronchial Neoplasms↗
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↗