The influence of visual landscape on the free flight behavior of the fruit fly Drosophila melanogaster

To study the visual cues that control steering behavior in the fruit fly Drosophila melanogaster, we reconstructed three-dimensional trajectories from images taken by stereo infrared video cameras during free flight within structured visual landscapes. Flies move through their environment using a series of straight flight segments separated by rapid turns, termed saccades, during which the fly alters course by approximately 90° in less than 100 ms. Altering the amount of background visual contrast caused significant changes in the fly’s translational velocity and saccade frequency. Between saccades, asymmetries in the estimates of optic flow induce gradual turns away from the side experiencing a greater motion stimulus, a behavior opposite to that predicted by a flight control model based upon optomotor equilibrium. To determine which features of visual motion trigger saccades, we reconstructed the visual environment from the fly’s perspective for each position in the flight trajectory. From these reconstructions, we modeled the fly’s estimation of optic flow on the basis of a two-dimensional array of Hassenstein–Reichardt elementary motion detectors and, through spatial summation, the large-field motion stimuli experienced by the fly during the course of its flight. Event-triggered averages of the large-field motion preceding each saccade suggest that image expansion is the signal that triggers each saccade. The asymmetry in output of the local motion detector array prior to each saccade influences the direction (left versus right) but not the magnitude of the rapid turn. Once initiated, visual feedback does not appear to influence saccade kinematics further. The total expansion experienced before a saccade was similar for flight within both uniform and visually textured backgrounds. In summary, our data suggest that complex behavioral patterns seen during free flight emerge from interactions between the flight control system and the visual environment

Collision-avoidance and landing responses are mediated by separate pathways in the fruit fly, Drosophila melanogaster

Flies rely heavily on visual feedback for several aspects of flight control. As a fly approaches an object, the image projected across its retina expands, providing the fly with visual feedback that can be used either to trigger a collision-avoidance maneuver or a landing response. To determine how a fly makes the decision to land on or avoid a looming object, we measured the behaviors generated in response to an expanding image during tethered flight in a visual closed-loop flight arena. During these experiments, each fly varied its wing-stroke kinematics to actively control the azimuth position of a 15°×15° square within its visual field. Periodically, the square symmetrically expanded in both the horizontal and vertical directions. We measured changes in the fly's wing-stroke amplitude and frequency in response to the expanding square while optically tracking the position of its legs to monitor stereotyped landing responses. Although this stimulus could elicit both the landing responses and collision-avoidance reactions, separate pathways appear to mediate the two behaviors. For example, if the square is in the lateral portion of the fly's field of view at the onset of expansion, the fly increases stroke amplitude in one wing while decreasing amplitude in the other, indicative of a collision-avoidance maneuver. In contrast, frontal expansion elicits an increase in wing-beat frequency and leg extension, indicative of a landing response. To further characterize the sensitivity of these responses to expansion rate, we tested a range of expansion velocities from 100 to 10000° s^(-1). Differences in the latency of both the collision-avoidance reactions and the landing responses with expansion rate supported the hypothesis that the two behaviors are mediated by separate pathways. To examine the effects of visual feedback on the magnitude and time course of the two behaviors, we presented the stimulus under open-loop conditions, such that the fly's response did not alter the position of the expanding square. From our results we suggest a model that takes into account the spatial sensitivities and temporal latencies of the collision-avoidance and landing responses, and is sufficient to schematically represent how the fly uses integration of motion information in deciding whether to turn or land when confronted with an expanding object

JMASM 53: MicceriRD

Fortran 77 and 90 modules (REALPOPS.lib) exist for invoking the 8 distributions estimated by Micceri (1989). These respective modules were created by Sawilowsky et al. (1990) and Sawilowsky and Fahoome (2003). The MicceriRD (Micceri’s Real Distributions) Python package was created because Python is increasingly used for data analysis and, in some cases, Monte Carlo simulations

Identity Maintenance Through Emotional Release and Rejuvenation: A Link Between Hardcore Dancing and the Straightedge Collective Identity

For many, the hardcore punk rock show experience can act as a way to ritualize participation (and reinforce meanings) in the identities one associates with the experience. Blumer\u27s expressive crowd offers insight into how such ritualized, yet seemingly chaotic behavior provides to many a cathartic release in a socially-stimulated, approved, and maintained atmosphere. In the process, such a release has consequences for the Straightedge identity tied to the experience, since Straightedge and hardcore punk coexist in the social construction of a larger sub-culture. In this study, participation as such in the Straightedge (a lifestyle-based, diffuse social movement in which one resists drugs) collective identity is examined. Those in the Straightedge subculture who do not attend shows, dance at shows, and attend shows without dancing were interviewed via asynchronous e-mailing (and a few phone interviews) to qualitatively compare the three groups based on how they experience being Straightedge at hardcore shows and in general. The dancing process was observed via participant observation of Straightedge and non-Straightedge dancers. Finally, an interview with some of the observed dancers was conducted using asynchronous emailing. As the findings allow, the overall Straightedge collective identity is often tied to other lower-level identities, in this case as one who dances at hardcore shows. Here, identity maintenance is explained with an alternative form of Burke\u27s Identity Control model, which in this study explains processes of group or social identity instead of role identity, as Burke et al. use it. The cathartic release of the expressive crowd (a la Blumer) is posited as the social situational aspect of (the adapted) Burke\u27s Identity Control model to provide a subjective, yet structural Symbolic Interactionist account for this often-observed yet seldom-explained social phenomenon

Spatial organization of visuomotor reflexes in Drosophila

In most animals, the visual system plays a central role in locomotor guidance. Here, we examined the functional organization of visuomotor reflexes in the fruit fly, Drosophila, using an electronic flight simulator. Flies exhibit powerful avoidance responses to visual expansion centered laterally. The amplitude of these expansion responses is three times larger than those generated by image rotation. Avoidance of a laterally positioned focus of expansion emerges from an inversion of the optomotor response when motion is restricted to the rear visual hemisphere. Furthermore, motion restricted to rear quarter-fields elicits turning responses that are independent of the direction of image motion about the animal's yaw axis. The spatial heterogeneity of visuomotor responses explains a seemingly peculiar behavior in which flies robustly fixate the contracting pole of a translating flow field

Composition as a mode of being: Politics, ethics, and history in the writing classrooms of postmodernity

Henry Louis Gates, Jr. once commented that while he did not deny the importance, on the level of theory, of the (postmodern) project, such a project did not help him when he was trying to get a taxi on the corner of 125th and Lenox Avenue (Loose Canons 37-38). The postmodern project lacked what Gates calls practical performative force. The purpose of this dissertation is to establish postmodernity\u27s practical performative force for the composition classroom. It addresses four central questions: What is postmodernity? What is its relationship to composition? Why should composition teachers and students care about this relationship? How might composition use postmodernity to create new classroom practices and deal with reoccurring classroom problems? I believe that postmodern theory, if it can be refigured to match our current historical moment, offers composition two powerful discourses for creating practice and crossing disciplinary boundaries: an epistemological frame that allows for a plurality of diverse and even contradictory pedagogies in one classroom, and a theory of culture(s) that can help teachers negotiate the academic, political, and ethical challenges of today\u27s classrooms. Postmodernity is not, as Lester Faigley\u27s work implies, an abstract theory or research method that composition teachers apply to composition but, as Louise Wetherbee Phelps argues, a cultural condition in which we live

Sacred bundles of the Ioway Indians

It is with ambivalence that I present this study on the sacred bundles of the Ioway. Although I am an enrolled tribal member of the Kansas-Nebraska branch, and the bundle belief system among the Ioway is no longer active, several people expressed their belief that such a study, and especially the handling and the description of the sacred bundles was a spiritually unwise and even dangerous thing to do. I cannot disagree with this. And so one might ask why, then, did I do it? As the Native American Graves Protection and Repatriation Act has become a major issue to American Indians, the U.S. Government, and anthropologists, the repatriation of the dead to their homes as well as the return of sacred artifacts is something that has to be faced by every tribe. There are mixed feelings, as one who is brought up in their culture knows that it is not simply a matter of returning things. These things once had a proper cultural context, with songs and rites to be given, social forms to be observed, Keepers to be chosen, cautions to be undertaken. These returned things are not simply things. They are material manifestations of a vibrant, interconnected cultural system as well as a difficult, painful, and sometimes clouded past. Considered to have a kind of life, these things are, in the native view, like Old People returning to a home unrecognizable to them and sometimes to descendants who do not know them and their ways. I have thought about these manifestations of the past for over ten years now. Every step I have taken has led me to this place, even when I tried to go in a different direction. I always prayed that only if it was good should I continue in this manner. And so I find myself in this place. I still have much to learn. I have been given no authority to do what I have done. Sometimes, if no one else will do what needs to be done, it will go on to someone who will. I simply offer here what I have found out about these Old People, the sacred bundles of the Ioway. It is an ongoing process of knowledge and experience. In getting an academic degree, one must write down what has been learned and put it in a form called a thesis, a requirement to receive a diploma and go on in one\u27s quest to learn more. I offer here my experience and knowledge of what I have found so far. I offer it here to those descendants of the Ioway who seek to understand the past. The objective of this study is to begin to describe the sacred bundle system of the Ioway (also called Iowa) Indians, through historic context and examination of bundles in some museums. The work is primarily descriptive, ethnographic, and interpretive, as a basis for providing an emic perspective, which has been essentially lacking in earlier analyses. Ultimately, legitimate theoretical workers depend on descriptive work as the material for their arguments and as a data base for their explorations and proofs

Creating community through symbolic discourse: An analysis of Jesse Jackson\u27s rhetoric at the Democratic National Conventions, 1984--2000

The Reverend Jesse Louis Jackson has addressed the Democratic National Convention through five consecutive election cycles. Jackson\u27s political involvement works to challenge the majority value system. Each address aims to create a community consisting of minority voices in America by bringing them into the Democratic Party in hopes of changing national policy. Metaphorical strategy is used to symbolically create a community consisting of minority voices, the Democratic Party, and Jackson himself as the prophetic leader. Symbolically unifying the community against a common enemy strengthens Jackson\u27s community

Leadership Transitions: A Study of the Failure Rate of Career Progression Due to Individual Contributor versus People Leadership Mindsets in Post-Recessionary Southeast Tennessee and Northwest Georgia

Despite the efforts of many leadership development programs, more than 80 percent of new leaders transitioning into the first role as a leader fail to make a successful transition (Korn Ferry Leadership Principles, 2018). This paper studied a leader’s failure to shift his or her thinking and behaviors from an individual contributor mindset to a people leader mindset. This research is suggesting that organizations adopt two tools to improve leadership transition effectiveness: Leadership Transition Readiness Assessment, and Start, Stop, Change, and Transition questionnaire