AIRSTREAM: A Neural Network Model of Auditory Scene Analysis and Source Segregation

Multiple sound sources often contain harmonics that overlap and may be degraded by environmental noise. The auditory system is capable of teasing apart these sources into distinct mental objects, or streams. Such an "auditory scene analysis" enables the brain to solve the cocktail party problem. A neural network model of auditory scene analysis, called the AIRSTREAM model, is presented to propose how the brain accomplishes this feat. The model clarifies how the frequency components that correspond to a give acoustic source may be coherently grouped together into distinct streams based on pitch and spatial cues. The model also clarifies how multiple streams may be distinguishes and seperated by the brain. Streams are formed as spectral-pitch resonances that emerge through feedback interactions between frequency-specific spectral representaion of a sound source and its pitch. First, the model transforms a sound into a spatial pattern of frequency-specific activation across a spectral stream layer. The sound has multiple parallel representations at this layer. A sound's spectral representation activates a bottom-up filter that is sensitive to harmonics of the sound's pitch. The filter activates a pitch category which, in turn, activate a top-down expectation that allows one voice or instrument to be tracked through a noisy multiple source environment. Spectral components are suppressed if they do not match harmonics of the top-down expectation that is read-out by the selected pitch, thereby allowing another stream to capture these components, as in the "old-plus-new-heuristic" of Bregman. Multiple simultaneously occuring spectral-pitch resonances can hereby emerge. These resonance and matching mechanisms are specialized versions of Adaptive Resonance Theory, or ART, which clarifies how pitch representations can self-organize durin learning of harmonic bottom-up filters and top-down expectations. The model also clarifies how spatial location cues can help to disambiguate two sources with similar spectral cures. Data are simulated from psychophysical grouping experiments, such as how a tone sweeping upwards in frequency creates a bounce percept by grouping with a downward sweeping tone due to proximity in frequency, even if noise replaces the tones at their interection point. Illusory auditory percepts are also simulated, such as the auditory continuity illusion of a tone continuing through a noise burst even if the tone is not present during the noise, and the scale illusion of Deutsch whereby downward and upward scales presented alternately to the two ears are regrouped based on frequency proximity, leading to a bounce percept. Since related sorts of resonances have been used to quantitatively simulate psychophysical data about speech perception, the model strengthens the hypothesis the ART-like mechanisms are used at multiple levels of the auditory system. Proposals for developing the model to explain more complex streaming data are also provided.

A Neural Network Architecture for Figure-ground Separation of Connected Scenic Figures

A neural network model, called an FBF network, is proposed for automatic parallel separation of multiple image figures from each other and their backgrounds in noisy grayscale or multi-colored images. The figures can then be processed in parallel by an array of self-organizing Adaptive Resonance Theory (ART) neural networks for automatic target recognition. An FBF network can automatically separate the disconnected but interleaved spirals that Minsky and Papert introduced in their book Perceptrons. The network's design also clarifies why humans cannot rapidly separate interleaved spirals, yet can rapidly detect conjunctions of disparity and color, or of disparity and motion, that distinguish target figures from surrounding distractors. Figure-ground separation is accomplished by iterating operations of a Feature Contour System (FCS) and a Boundary Contour System (BCS) in the order FCS-BCS-FCS, hence the term FBF, that have been derived from an analysis of biological vision. The FCS operations include the use of nonlinear shunting networks to compensate for variable illumination and nonlinear diffusion networks to control filling-in. A key new feature of an FBF network is the use of filling-in for figure-ground separation. The BCS operations include oriented filters joined to competitive and cooperative interactions designed to detect, regularize, and complete boundaries in up to 50 percent noise, while suppressing the noise. A modified CORT-X filter is described which uses both on-cells and off-cells to generate a boundary segmentation from a noisy image.

A Neural Network for Synthesizing the Pitch of an Acoustic Source

This article describes a neural network model capable of generating a spatial representation of the pitch of an acoustic source. Pitch is one of several auditory percepts used by humans to separate multiple sound sources in the environment from each other. The model provides a neural instantiation of a type of "harmonic sieve". It is capable of quantitatively simulating a large body of psychoacoustical data, including new data on octave shift perception.

A Spectral Network Model of Pitch Perception

A model of pitch perception, called the Spatial Pitch Network or SPINET model, is developed and analyzed. The model neurally instantiates ideas front the spectral pitch modeling literature and joins them to basic neural network signal processing designs to simulate a broader range of perceptual pitch data than previous spectral models. The components of the model arc interpreted as peripheral mechanical and neural processing stages, which arc capable of being incorporated into a larger network architecture for separating multiple sound sources in the environment. The core of the new model transforms a spectral representation of an acoustic source into a spatial distribution of pitch strengths. The SPINET model uses a weighted "harmonic sieve" whereby the strength of activation of a given pitch depends upon a weighted sum of narrow regions around the harmonics of the nominal pitch value, and higher harmonics contribute less to a pitch than lower ones. Suitably chosen harmonic weighting functions enable computer simulations of pitch perception data involving mistuned components, shifted harmonics, and various types of continuous spectra including rippled noise. It is shown how the weighting functions produce the dominance region, how they lead to octave shifts of pitch in response to ambiguous stimuli, and how they lead to a pitch region in response to the octave-spaced Shepard tone complexes and Deutsch tritones without the use of attentional mechanisms to limit pitch choices. An on-center off-surround network in the model helps to produce noise suppression, partial masking and edge pitch. Finally, it is shown how peripheral filtering and short term energy measurements produce a model pitch estimate that is sensitive to certain component phase relationships.

A new world a new American foreign policy: the Carter administration, Nicaragua, and the legacy of the Vietnam War, 1977-1981

The impact of the Vietnam War conditioned the Carter administration’s response to the Nicaraguan revolution in ways that reduced US engagement with both sides of the conflict. It made the countries of Latin America counter the US approach and find their own solution to the crisis, and allowed Cuba to play a greater role in guiding the overthrow of Nicaraguan dictator Anastasio Somoza Debayle. This thesis re-evaluates Carter’s policy through the legacy of the Vietnam War, because US executive anxieties about military intervention, Congress’s increasing influence, and US public concerns about the nation’s global responsibilities, shaped the Carter approach to Nicaragua. Following a background chapter, the Carter administration’s policy towards Nicaragua is evaluated, before and after the fall of Somoza in July 1979. The extent of the Vietnam influence on US-Nicaraguan relations is developed by researching government documents on the formation of US policy, including material from the Jimmy Carter Library, the Library of Congress, the National Security Archive, the National Archives and Records Administration, and other government and media sources from the United Nations Archives, New York University, the New York Public Library, the Hoover Institution Archives, Tulane University and the Organization of American States. The thesis establishes that the Vietnam legacy played a key role in the Carter administration’s approach to Nicaragua. Before the overthrow of Somoza, the Carter administration limited their influence in Nicaragua because they felt there was no immediate threat from communism. The US feared that an active role in Nicaragua, without an established threat from Cuba or the Soviet Union, could jeopardise congressional support for other foreign policy goals deemed more important. The Carter administration, as a result, pursued a policy of non-intervention towards the Central American country. After the fall of Somoza, and the establishment of a new government with a left wing element represented by the Sandinistas, the Carter administration emphasised non-intervention in a military sense, but actively engaged with the new Nicaraguan leadership to contain the potential communist influence that could spread across Central America in the wake of the Nicaraguan revolution.

Diverse heritage: exploring literary identity in the American Southwest

Since the age of colonisation, the territory of New Mexico has been exposed to a diversity of cultural influence. Throughout recorded history various forces have battled for control of this territory, resulting in a continuous redefinition of its political, geographic and economic boundaries. Early representations of the Southwest have been defined as “strategies of negotiation” between Anglo, Hispanic and Native populations, strategies that are particularly evident in the territory of New Mexico. The contemporary identity of regions like northern New Mexico have destabilised the notion of what constitutes racial purity in regions which are defined by diversity. This thesis aims to evaluate the literary history of northern New Mexico in order to determine how exposure to a diversity of cultural influence has affected the region’s identity. An analysis of Anglo and Native writers from northern New Mexico will illustrate that these racial groups were influenced by the same geographic landscape. As such, their writing displays many characteristics unique to the region. In providing a comparative analysis of Native and Anglo authors from northern New Mexico, this thesis seeks to demonstrate commonalities of theme, structure and content. In doing so this research encourages a new perspective on New Mexico writing one which effectively de-centres contemporary notions of what the American canon should be.

Redefining military memorials and commemoration and how they have changed since the 19th century with a focus on Anglo-American practice

This thesis is a study of military memorials and commemoration with a focus on Anglo-American practice. The main question is: How has history defined military memorials and commemoration and how have they changed since the 19th century. In an effort to resolve this, the work examines both historic and contemporary forms of memorials and commemoration and establishes that remembrance in sites of collective memory has been influenced by politics, conflicts and religion. Much has been written since the Great War about remembrance and memorialization; however, there is no common lexicon throughout the literature. In order to better explain and understand this complex subject, the work includes an up-to-date literature review and for the first time, terminologies are properly explained and defined. Particular attention is placed on recognizing important military legacies, being familiar with spiritual influences and identifying classic and new signs of remembrance. The thesis contends that commemoration is composed of three key principles – recognition, respect and reflection – that are intractably linked to the fabric of memorials. It also argues that it is time for the study of memorials to come of age and proposes Memorialogy as an interdisciplinary field of study of memorials and associated commemorative practices. Moreover, a more modern, adaptive, General Classification System is presented as a means of identifying and re-defining memorials according to certain groups, types and forms. Lastly, this thesis examines how peacekeeping and peace support operations are being memorialized and how the American tragic events of 11 September 2001 and the war in Afghanistan have forever changed the nature of memorials and commemoration within Canada and elsewhere. This work goes beyond what has been studied and written about over the last century and provides a deeper level of analysis and a fresh approach to understanding the field of Memorialogy.

“Something isn’t right here”: American exceptionalism and the creative nonfiction of the Vietnam War

In this thesis, I argue that few attempts were as effective in correcting the exceptionalist ethos of the United States than the creative nonfiction written by the veterans and journalists of the Vietnam War. Using critical works on creative nonfiction, I identify the characteristics of the genre that allowed Paul John Eakin to call it ‘a special kind of fiction.’ I summarise a brief history of creative nonfiction to demonstrate how it became a distinctly American form despite its Old World origins. I then claim that it was the genre most suited to the kind of ideological transformation that many hoped to instigate in U.S. society in the aftermath of Vietnam. Following this, the study explores how this “new” myth-making process occurred. I use Tim O’Brien’s If I Die in a Combat Zone and Philip Caputo’s A Rumor of War to illustrate how autobiography/memoir was able to demonstrate the detrimental effect that America’s exceptionalist ideology was having on its population. Utilising narrative and autobiographical theory, I contend that these accounts represented a collective voice which spoke for all Americans in the years after Vietnam. Using Neil Sheehan’s A Bright Shining Lie and C.D.B. Bryan’s Friendly Fire, I illustrate how literary journalism highlighted the hubris of the American government. I contend that while poiesis is an integral attribute of creative nonfiction, by the inclusion of extraneous bibliographic material, authors of the genre could also be seen as creating a literary context predisposing the reader towards an empirical interpretation of the events documented within. Finally, I claim that oral histories were in their essence a synthesis of “everyman” experiences very much in keeping with the American zeitgeist of the early Eighties. Focussing solely on Al Santoli’s Everything We Had, I demonstrate how such polyphonic narratives personalised the history of the Vietnam War.

LISA SERGIO: HOW MUSSOLINI'S "GOLDEN VOICE" OF PROPAGANDA CREATED AN AMERICAN MASS COMMUNICATION CAREER

In 1937 Lisa Sergio, "The Golden Voice" of fascist broadcasting from Rome, fled Italy for the United States. Though her mother was American, Sergio was classified as an enemy alien once the United States entered World War II. Yet Sergio became a U.S. citizen in 1944 and built a successful career in radio, working first at NBC and then WQXR in New York City in the days when women's voices were not thought to be appropriate for news or "serious" programming. When she was blacklisted as a communist in the early 1950s, Sergio compensated for the loss of radio employment by becoming principally an author and lecturer in Washington, D.C., until her death in 1989. This dissertation, based on her personal papers, is the first study of Sergio's American mass communication career. It points out the personal, political and social obstacles she faced as a woman in her 52-year career as a commentator on varied aspects of world affairs, religion and feminism. This study includes an examination of the FBI investigations of Sergio and the anti-communist campaigns conducted against her. It concludes that Sergio's success as a public communicator was predicated on both her unusual talents and her ability to transform her public image to reflect ideal American values of womanhood in shifting political climates.

Aging African American Women and the Impact of Positive Psychological Factors on Quality of Life

Aging African-American women are disproportionately affected by negative health outcomes and mortality. Life stress has strong associations with these health outcomes. The purpose of this research was to understand how aging African American women manage stress. Specifically, the effects of coping, optimism, resilience, and religiousness as it relates to quality of life were examined. This cross-sectional exploratory study used a self-administered questionnaire and examined quality of life in 182 African-American women who were 65 years of age or older living in senior residential centers in Baltimore using convenience sampling. The age range for these women was 65 to 94 years with a mean of 71.8 years (SD = 5.6). The majority (53.1%) of participants completed high school, with 23 percent (N = 42) obtaining college degrees and 19 percent (N = 35) holding advanced degrees. Nearly 58 percent of participants were widowed and 81 percent were retired. In addition to demographics, the questionnaire included the following reliable and valid survey instruments: The Brief Cope Scale (Carver, Scheier, & Weintraub, 1989), Optimism Questionnaire (Scheier, Carver, & Bridges, 1994), Resilience Survey (Wagnild & Young, 1987), Religiousness Assessment (Koenig, 1997), and Quality of Life Questionnaire (Cummins, 1996). Results revealed that the positive psychological factors examined were positively associated with and significant predictors of quality of life. The bivariate correlations indicated that of the six coping dimensions measured in this study, planning (r=.68) was the most positively associated with quality of life. Optimism (r=.33), resilience (=.48), and religiousness (r=.30) were also significantly correlated with quality of life. In the linear regression model, again the coping dimension of planning was the best predictor of quality of life (beta = .75, p <.001). Optimism (beta = .31, p <.001), resilience (beta = .34, p, .001) and religiousness (beta = .17, p <.01) were also significant predictors of quality of life. It appears as if positive psychology plays an important role in improving quality of life among aging African-American women.

Associations between Intake of Folate, Methionine, and Vitamins B-12, B-6 and Prostate Cancer Risk in American Veterans.

Prostate cancer (PC) is the second leading cause of cancer death in men. Recent reports suggest that excess of nutrients involved in the one-carbon metabolism pathway increases PC risk; however, empirical data are lacking. Veteran American men (272 controls and 144 PC cases) who attended the Durham Veteran American Medical Center between 2004-2009 were enrolled into a case-control study. Intake of folate, vitamin B12, B6, and methionine were measured using a food frequency questionnaire. Regression models were used to evaluate the association among one-carbon cycle nutrients, MTHFR genetic variants, and prostate cancer. Higher dietary methionine intake was associated with PC risk (OR = 2.1; 95%CI 1.1-3.9) The risk was most pronounced in men with Gleason sum <7 (OR = 2.75; 95%CI 1.32- 5.73). The association of higher methionine intake and PC risk was only apparent in men who carried at least one MTHFR A1298C allele (OR = 6.7; 95%CI = 1.6-27.8), compared to MTHFR A1298A noncarrier men (OR = 0.9; 95%CI = 0.24-3.92) (p-interaction = 0.045). There was no evidence for associations between B vitamins (folate, B12, and B6) and PC risk. Our results suggest that carrying the MTHFR A1298C variants modifies the association between high methionine intake and PC risk. Larger studies are required to validate these findings.

Design and Emergence in the Making of American Grand Strategy

The main research question of this thesis is how do grand strategies form. Grand strategy is defined as a state's coherent and consistent pattern of behavior over a long period of time in search of an overarching goal. The political science literature usually explains the formation of grand strategies by using a planning (or design) model. In this dissertation, I use primary sources, interviews with former government officials, and historical scholarship to show that the formation of grand strategy is better understood using a model of emergent learning imported from the business world. My two case studies examine the formation of American grand strategy during the Cold War and the post-Cold War eras. The dissertation concludes that in both these strategic eras the dominating grand strategies were formed primarily by emergent learning rather than flowing from advanced designs.

Selecting renal replacement therapies: what do African American and non-African American patients and their families think others should know? A mixed methods study.

BACKGROUND: Little is known regarding the types of information African American and non-African American patients with chronic kidney disease (CKD) and their families need to inform renal replacement therapy (RRT) decisions. METHODS: In 20 structured group interviews, we elicited views of African American and non-African American patients with CKD and their families about factors that should be addressed in educational materials informing patients' RRT selection decisions. We asked participants to select factors from a list and obtained their open-ended feedback. RESULTS: Ten groups of patients (5 African American, 5 non-African American; total 68 individuals) and ten groups of family members (5 African American, 5 non-African American; total 62 individuals) participated. Patients and families had a range (none to extensive) of experiences with various RRTs. Patients identified morbidity or mortality, autonomy, treatment delivery, and symptoms as important factors to address. Family members identified similar factors but also cited the effects of RRT decisions on patients' psychological well-being and finances. Views of African American and non-African American participants were largely similar. CONCLUSIONS: Educational resources addressing the influence of RRT selection on patients' morbidity and mortality, autonomy, treatment delivery, and symptoms could help patients and their families select RRT options closely aligned with their values. Including information about the influence of RRT selection on patients' personal relationships and finances could enhance resources' cultural relevance for African Americans.