Browsing by Subject "Consciousness"
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Item Open Access A Philosophical Examination of Working Memory(2019) Beninger, Max HansonWorking memory—the mental capacity to “hold on to” information after it ceases to be perceptually available—is one of the most discussed topics in psychology and neuroscience. Despite the importance of working memory in the sciences, however, there is only a small amount of philosophical research on the topic. The aim of my dissertation is to provide a philosophically-informed account of working memory, and to assess its relationship to other mental phenomena, including attention and consciousness.
In chapter one, I provide a broad historical overview of working memory. I begin by outlining William James’ original distinction between “primary” and “secondary” memory, and work my way up to present-day neuroscientific investigations of working memory. One of the main conclusions of this chapter is that there is no single working memory “module” in the brain. Instead, working memory is best conceptualized as a functionally-defined process that is potentially realized by multiple neural mechanisms.
In chapter two, I explore the link between working memory and attention. Recent evidence from psychology and neuroscience indicates that attention is (to some extent) involved in the process of working memory maintenance. However, it remains unclear whether the contents of working memory are always attended, or if working memory representations can be dynamically shifted in and out of the focus of attention. Drawing on empirical and phenomenological data, I argue that the second view is correct. Although attention plays an important role in working memory maintenance, working memory representations can persist—at least temporarily—outside the focus of attention.
Chapter three addresses a related question: namely, how working memory relates to consciousness. I distinguish three possible positions on this score: (i) working memory representations are always conscious; (ii) working memory representations can be either conscious or unconscious, but they are all accessible to consciousness; and (iii) working memory representations can be either conscious or unconscious, and some are inaccessible to consciousness. Based on the available empirical data, I argue in favor of position (ii). Evidence suggests that working memory representations can be unconscious, but such unconscious representations still appear to be consciously accessible, in the sense that they can be brought to consciousness at will.
Finally, in chapter four, I provide a critique of Peter Carruthers’ recent sensory-based account of working memory. According to Carruthers, attention only targets “mid-level” sensory areas, and thus the representations held in working memory will necessarily be sensory based in nature. I disagree. I point out that there is some evidence for attentional modulation outside of modality-specific sensory areas. I also highlight several empirical studies which provide preliminary support for the existence of non-sensory (i.e., amodal) working memory representations.
Item Open Access An evaluation of remifentanil-sevoflurane response surface models in patients emerging from anesthesia: model improvement using effect-site sevoflurane concentrations.(Anesth Analg, 2010-08) Johnson, Ken B; Syroid, Noah D; Gupta, Dhanesh K; Manyam, Sandeep C; Pace, Nathan L; LaPierre, Cris D; Egan, Talmage D; White, Julia L; Tyler, Diane; Westenskow, Dwayne RINTRODUCTION: We previously reported models that characterized the synergistic interaction between remifentanil and sevoflurane in blunting responses to verbal and painful stimuli. This preliminary study evaluated the ability of these models to predict a return of responsiveness during emergence from anesthesia and a response to tibial pressure when patients required analgesics in the recovery room. We hypothesized that model predictions would be consistent with observed responses. We also hypothesized that under non-steady-state conditions, accounting for the lag time between sevoflurane effect-site concentration (Ce) and end-tidal (ET) concentration would improve predictions. METHODS: Twenty patients received a sevoflurane, remifentanil, and fentanyl anesthetic. Two model predictions of responsiveness were recorded at emergence: an ET-based and a Ce-based prediction. Similarly, 2 predictions of a response to noxious stimuli were recorded when patients first required analgesics in the recovery room. Model predictions were compared with observations with graphical and temporal analyses. RESULTS: While patients were anesthetized, model predictions indicated a high likelihood that patients would be unresponsive (> or = 99%). However, after termination of the anesthetic, models exhibited a wide range of predictions at emergence (1%-97%). Although wide, the Ce-based predictions of responsiveness were better distributed over a percentage ranking of observations than the ET-based predictions. For the ET-based model, 45% of the patients awoke within 2 min of the 50% model predicted probability of unresponsiveness and 65% awoke within 4 min. For the Ce-based model, 45% of the patients awoke within 1 min of the 50% model predicted probability of unresponsiveness and 85% awoke within 3.2 min. Predictions of a response to a painful stimulus in the recovery room were similar for the Ce- and ET-based models. DISCUSSION: Results confirmed, in part, our study hypothesis; accounting for the lag time between Ce and ET sevoflurane concentrations improved model predictions of responsiveness but had no effect on predicting a response to a noxious stimulus in the recovery room. These models may be useful in predicting events of clinical interest but large-scale evaluations with numerous patients are needed to better characterize model performance.Item Open Access Contributions of Dorsal/Ventral Hippocampus and Dorsolateral/Dorsomedial Striatum to Interval Timing(2016) Yin, Bin YinHumans and animals have remarkable capabilities in keeping time and using time as a guide to orient their learning and decision making. Psychophysical models of timing and time perception have been proposed for decades and have received behavioral, anatomical and pharmacological data support. However, despite numerous studies that aimed at delineating the neural underpinnings of interval timing, a complete picture of the neurobiological network of timing in the seconds-to-minutes range remains elusive. Based on classical interval timing protocols and proposing a Timing, Immersive Memory and Emotional Regulation (TIMER) test battery, the author investigates the contributions of the dorsal and ventral hippocampus as well as the dorsolateral and the dorsomedial striatum to interval timing by comparing timing performances in mice after they received cytotoxic lesions in the corresponding brain regions. On the other hand, a timing-based theoretical framework for the emergence of conscious experience that is closely related to the function of the claustrum is proposed so as to serve both biological guidance and the research and evolution of “strong” artificial intelligence. Finally, a new “Double Saturation Model of Interval Timing” that integrates the direct- and indirect- pathways of striatum is proposed to explain the set of empirical findings.
Item Open Access Investigations into the Neural Basis of Consciousness(2019) Giattino, CharlesThe overarching goal of this dissertation was to improve our understanding of the neural basis of consciousness by approaching the problem along two separate, complementary facets: examining the levels of consciousness and the contents of consciousness.
Chapter 2 examines how the level of consciousness changes under general anesthesia for surgery, and how neural (EEG) markers of this change relate to postoperative cognitive impairments afflicting many older adults. Older adult patients underwent neurocognitive testing before and after surgery, and their 32-channel EEG was recorded both before and during general anesthesia for surgery. Results showed that one of the most profound changes from the awake to the anesthetized brain—the anteriorization of alpha-band (8-12 Hz) activity—correlated with preoperative cognitive scores, which are themselves predictors for postoperative cognitive impairments. These results have added to our understanding of how manipulations of the level of consciousness under general anesthesia ramify into potentially long-lasting impairments to cognition, and how these impairments might be monitored and avoided.
Chapters 3 and 4 examined how the contents of consciousness relate to the selection mechanism of attention. Chapter 3 investigated the dissociability of these two phenomena by examining the neural mechanisms underlying the orienting of spatial attention without awareness. High-density (64-channel) EEG was recorded while subjects performed a novel task that combined classic spatial cueing with object-substitution masking to manipulate subjects’ awareness of the cues on ~half of the trials, allowing a direct comparison of orienting with and without awareness, controlled for having identical sensory stimulation. Results confirmed that attention could be oriented without awareness, leading to improved behavior (faster reaction times and better accuracy) and enhanced sensory processing (indexed by the P1 event-related potential, ERP) for validly (compared to invalidly) cued targets. Interestingly, the hallmark ERP for the orienting of attention in response to a cue, the N2pc, was only observed for conscious orienting, pointing to an alternate mechanism for unconscious orienting, such as via the subcortical retinotectal pathway.
Chapter 4 investigated the mechanisms and temporal dynamics of the attentional selection of conscious internal representations in working memory. EEG was recorded while subjects performed a modified delayed match-to-sample task where one of two sample objects, a face or a house, was retroactively cued on each trial. A multivariate classifier was trained on the pattern of alpha-band activity to determine if and when information about the selected object could be decoded from the alpha signal following the retrocue. Results showed that alpha could be used to decode the selected object, pointing to its general role as a top-down attentional control signal. This decoding was relatively transient, rather than sustained, which accords with recent proposals of “activity-silent” working memory and argues against accounts of working memory that posit sustained internal attention as the underlying mechanism. Together the results of Chapters 3 and 4 help inform our understanding of how attention operates both externally and internally to select the contents of consciousness.
Item Open Access L'Épilepsie comme "crise" de la conscience: Perspectives narratives, philosophiques, et neuroscientifiques(2019-04-16) Uchitel, Julie“Each seizure is like a sort of hemorrhage of innervation. The center of image formation in my brain suffers a seminal leak, a hundred thousand images erupt at once, in visual fireworks. There is an atrocious clenching of body and soul (several times I have been sure I had died). But what constitutes personality, rational being, always held fast; otherwise, suffering would have been nullified, because I would have been purely passive, whereas I always retained consciousness, even when I could no longer speak.” Flaubert, Gustave, 1821-1880. Correspondance, 1853 (Paris, L. Conard) 270-271 The most intimate correspondence of Gustave Flaubert reveals that the renowned French author, prized for his mastery of free indirect discourse and other “realist” effects in works such as Madame Bovary and L’Éducation Sentimentale, suffered from epilepsy. Careful examination of his correspondence reveals that these works are imbued with references to his seizures, presented in highly metaphorical, imaginative and literary language not typically associated with epilepsy. In his description of the experience of having a seizure, Flaubert notes that “I always retained consciousness” despite a “rational ebbing”; he was mentally present during his seizures, although not in control of the contents or modalities of his consciousness. This assertation is distinctly different from popular understandings of epileptic seizures, which often assume that someone having a seizure is completely unaware of their surroundings, or unconscious, as their body is racked by convulsions. Flaubert’s description demonstrates that not only was he present, he also suffered an interruption, a dismantling, of his normal conscious state: “a hundred thousand images erupt at once” and there is a “terrible clenching of body and soul”. This raises the question, do seizures somehow unleash the floodgates of sensorial memory (images, sounds, tastes), even as the body loses control? It is evident that Flaubert was not fully conscious during his seizures, as we would describe that characterizes our everyday experience of consciousness, yet it is also evident that he was not fully unconscious. The medical field has long recognized this characteristic of seizures, that the state of consciousness during a seizure is not exactly the same as the conscious state of an individual not having a seizure. To distinguish between the two, the term ictal state refers to the period during which an individual is having a seizure and may demonstrate abnormal mental states, while the interictal state refers to any time that the individual with epilepsy is not having a seizure. Yet these distinctions fail to signal that the qualia of consciousness may be different between these two states, and different for different individuals. In the French literary sphere, a number of individuals with epilepsy have written on the subjective experience of having a seizure, delving into the most minute details of the conscious state during a seizure. These narratives, ranging from patient memoirs to graphic novels, demonstrate that each individual with epilepsy experiences a seizure differently, and different types of seizures can differentially affect the conscious state. For example, for those with focal seizures with preserved awareness (seizures that involve abnormal electrical activity in only one part of the brain) authors note a loss of sensation of the body, but not of the mind: “There was a tearing of my soul from my body,” attested Flaubert. Alternatively, for those with generalized tonic-clonic seizures (seizures that involve abnormal electrical activity throughout the entire brain), there is often a complete loss of perception of the body and within the mind: “For each seizure, time stops, like a little death” (Durand, Une Cicatrice dans la tête). If the subjective experience of having a seizure differs from one individual to another, is it also true that epilepsy can differentially affect human consciousness? Or is it more appropriate to say that the ictal consciousness is not bound by the same rules that we have assigned to the interictal consciousness of the individual with epilepsy? On a more fundamental level, what does human consciousness consist of? What is the connection between the physical human brain and the intangible mind? Science, unfortunately, has yet to answer these questions, despite the many advancements of neuroscience in recent decades. Philosophy, on the other hand, has put forth many theories of the relationship between the physical body (and brain) and the intangible mind, including those of René Descartes, Immanuel Kant, Sigmund Freud, Henri Bergson, and Maurice Merleau-Ponty. In recent years, philosophy has become increasingly integrated with neuroscience, as seen in the works of Stanislas Dehaene, Catherine Malabou, Antonio Damasio, and Andrea Cavanna. Still, very little consideration has been given to epilepsy’s effects on the conscious state and what these effects reveal about human consciousness itself. This is where literature must intervene. The works of individuals with epilepsy, such as Flaubert, Valérie Pineau-Valencienne, and Élodie Durand, give us a glimpse into an ictal consciousness that is at the same time neurological, ontological, cultural, and subjective in its nature. Literature holds a key to understanding how epilepsy influences the conscious mind, through individuals’ representations of the conventions, patterns, and characteristic features of ictal and interictal consciousness. Joint consideration of neuroscience and literature is thus necessary for a fuller understanding of the relationship between epilepsy and consciousness. The present thesis aims to explore these very questions and considerations. This thesis takes an interdisciplinary approach to examining epilepsy from the perspectives of literature and neuroscience, framed by philosophical theory, to explore what the modifications of human consciousness during a seizure—a “crisis” of consciousness—can reveal about consciousness itself. French literature was selected as the core of this thesis due to the breadth of literary works that discuss epilepsy, philosophical works that present theories of human consciousness, and the organic inspiration provided by Flaubert’s correspondence. The dialogue between these fields offers great possibilities for progress in our understanding of interictal consciousness, ictal consciousness, and more generally, human consciousness itself. The thesis first addresses neuroscience’s understanding of epilepsy, the underlying biology of epilepsy, and how consciousness is defined and conceptualized within the clinical context. Then, it presents a formal literary analysis of a variety of literary texts by authors depicting epilepsy, be it their own epilepsy, that of a relative, or of a fictional character. Although a seizure is a unique event for each individual, common representational patterns exist among narrative accounts of the experience of having a seizure. These include i) a loss of the corporeal self, with preservation of the conscious self, ii) a loss of the conscious self, with a plunge into the unconscious, iii) hallucinations and their frequent confusion with reality, iv) modifications, most frequently uncontrollable outpourings, of memory, and 5) violent and hallucinogenic transitions between the ictal and interictal states. The above-mentioned literary texts of individuals with epilepsy inspired the second component of this thesis: an analysis of the spoken narratives of patients with epilepsy at Duke University Hospital. In this research study, which required Duke Health Internal Review Board approval, patients with epilepsy in the Epilepsy Monitoring Unit were interviewed about their subjective experience of having a seizure. Patients were presented with a series of questions about this experience and the specific wording they used to describe seizures was documented. Conversational analyses were used to identify the presence of specific narrative expressions, figures of speech, and representational patterns that patients used to describe epilepsy. These representations are then aligned with various philosophers’ theories of consciousness to consider the intertwinement of literature, neuroscience, and philosophy, with the intention of unifying these domains. A new concept to describe human consciousness is presented; namely, consciousness in equilibrium. This term refers to the notion that consciousness may take on varying states which possess differing qualia, but that internal forces continually work to guide it back to a baseline state. In the same sense that many biological processes are regulated by homeostasis, consciousness, too, is regulated by homeostatic functions. This equilibrium lies along a spectrum, ranging from fully conscious states to fully unconscious states, such that the states of consciousness may at times blend together rather than take on discrete qualia. Significant perturbations away from equilibrium, provoke what many call an abnormal state of consciousness in the individual. This may be likened to how chemical imbalances in the body perturb it away from its resting state, homeostasis, and may provoke physical illness. Epilepsy, then, perturbs this equilibrium, taking the individual to a state of consciousness outside of homeostatic limits, but still within the capabilities of the human mind. An individual may feel divorced from the perception of the body, as Flaubert described during his focal seizures with preserved awareness: “there is an atrocious clenching of body and soul”. Alternatively, an individual may deviate so far from equilibrium that consciousness itself no longer seems to exist, as in the case of Durand, who suffered from generalized tonic-clonic seizures: “Here where I am, I no longer am” (Durand, 2010). Overall, this thesis, a product of interdisciplinary inquiry, presents a novel exploration of human consciousness considered from the perspective of epilepsy. It puts French literature, neuroscience, and philosophy in dialogue with one another to advance towards a new conception of ictal and interictal consciousness. A double critique is presented: a humanistic critique of neuroscience and a neuroscientific critique of works in the humanities. This bidimensional model considers subjective and objective perspectives, permitting enriched study of the different types of epilepsy and its effects on consciousness. These considerations are not only of intellectual interest, it also presents important humanistic and clinical benefits. Patients with epilepsy often report feeling deprived of autonomy and powerless with respect to their seizures. Improving dialogue will empower individuals to make use of narrative tools to explore the psychological tension caused by epilepsy. Epilepsy here is no longer merely a neurological condition; it is also the key to a pressing question shared by all: what do I know about my own consciousness? Epilepsy here is no longer merely a neurological condition; it is a phenomenological and philosophical prompt to explore the ictal crises of consciousness that highlight, by contrast, the limitations of normative consciousness of consciousness.Item Open Access They’re There, Now What?: The Identities, Behaviors, and Perceptions of Black Judges(2016) Means, Taneisha NicolePrior to the Civil Rights Movement, fewer than 50 Black judges had been elected or appointed to the judiciary. As of August 2015, there are over 1,000 Black state and federal judges. As the number of black judges has increased, one question arises: have American courts been altered purely by this substantial increase? One expectation—and, at times, a prediction—behind the increased descriptive representation of Black judges is that their mere presence would alter the judiciary. It was supposed that these judges would substantively represent Black interests in the decisions they made. In other words, it was suspected, and predicted, that Blacks in the judiciary would enhance equality and justice by being aware of, responsive to, and advocating for African Americans. This theory about the likely role of Black judges derives from theoretical work on political representation and racial group consciousness, and empirical studies of Black elite behavior in other political institutions.
Despite such predictions, there is no corresponding scholarly consensus regarding whether Black judges possess a racial group consciousness and have racially distinctive judicial behavior. Therefore, the theory undergirding the demand for increased diversification, as a means to transform the judiciary, remains unsubstantiated. This is precisely where this project, “They’re There, Now What?: The Identities, Behavior, and Perceptions of Black Judges,” seeks to intervene in and explore, if not settle, the matter of whether black judges possess a racial group consciousness and exhibit racially-distinctive judicial behavior. It addresses a set of interrelated questions relevant to understanding whether we can view Black judges as representatives in ways that are similar to how we view other Black political officials. I examine these questions using a multi-method approach. For my analyses, I draw on diverse materials: the published biographies of every Black judge appointed to the federal bench, a survey experiment with a nationally-representative adult sample, and semi-structured interviews with 30 Black judges.
This research, which engages with scholarship on representation, group consciousness, judicial behavior, and candidate perceptions, offers new insights into the lives, perceptions, and behavior of Black judges, as well as the manifestations of Black substantive representation in the judiciary. My dissertation argues that, despite the general reluctance to use the term “representation” when referring to judges, we can consider Black judges as representatives. Black judges behave as substantive representatives by (1) sharing and understanding the experience, history, and perspectives of Black Americans, (2) challenging language, persons, policies, and laws they feel negatively affect, or violate the rights and liberties of, African Americans, (3) respecting African American litigants, and (4) ensuring the rights of African Americans are protected and the needs of black Americans are being met.
Only through research that considers the perspectives, identities, perceptions, and behavior of Black judges will we arrive at a more comprehensive understanding of the importance of racial diversity in the courts. As this project finds, a link between descriptive representation and substantive representation can, and frequently does exist within the judicial context. Such a link is significant given that Blacks’ liberty and justice through the American legal system continues to be subject to those who exercise judicial power. This dissertation has implications for the discourse surrounding the need for increased descriptive and substantive representation of Blacks in the judiciary, and the factors that affect representation in the justice system.
Item Open Access Transformative Learning and Critical Consciousness: A Model for Preclerkship Medical School Substance Use Disorder Education.(Academic psychiatry : the journal of the American Association of Directors of Psychiatric Residency Training and the Association for Academic Psychiatry, 2023-04) Muzyk, Andrew; Mantri, Sneha; Mitchell, Phillip; Velkey, J Matthew; Reisinger, Deborah; Andolsek, KathrynObjective
Preparing medical students to provide compassionate person-centered care for people with substance use disorders (SUD) requires a re-envisioning of preclerkship SUD education to allow for discussions on stigma, social determinants of health, systemic racism, and healthcare inequities. The authors created a curricular thread that fosters the development of preclerkship medical students' critical consciousness through discussion, personal reflection, and inclusion of lived experiences.Methods
The authors used transformative learning theories to design and implement this thread in the 2021-2022 academic year in the Duke University School of Medicine preclerkship curriculum. Content included lectures, person-centered workshops, case-based learning, motivational interviewing of a standardized patient, and an opioid overdose simulation. Community advocates and people with SUD and an interdisciplinary faculty were involved in the thread design and delivery and modeled their lived experiences. Students wrote a 500-word critical reflection essay that examined their personal beliefs in the context of providing care for people with SUD.Results
One hundred and twenty-two students submitted essays and 30 (25%) essays were randomly selected for a qualitative analysis. Seven major themes emerged: race/racism, systemic barriers, bias and stigma, personal growth/transformation, language or word usage, future plans for advocacy, and existing poor outcomes. Students were able to link material with prior knowledge and experiences, and their attitudes towards advocacy and goals for future practice were positively influenced.Conclusion
By aligning the thread design with the principals of transformative learning, students developed their critical consciousness toward people with SUD and cultivated a holistic understanding of SUD.