With no statutory definition of death, the accepted medical definition relies on brain stem death criteria as a definitive measure of diagnosing death. However, the use of brain stem death criteria in this way is precarious and causes widespread confusion amongst both medical and lay communities. Through critical analysis, this paper considers the insufficiencies of brain stem death. It concludes that brain stem death cannot be successfully equated with either biological death or (...) the loss of integrated bodily function. The overemphasis of the brain-stem and its consequences leaves the criteria open to significant philosophical critique. Further, in some circumstances, the use of brain stem death criteria causes substantial emotional conflict for families and relatives. Accordingly, a more holistic and comprehensive definition of death is required. (shrink)

Adult stem cell populations must coordinate their own maintenance with the generation of differentiated cell types to sustain organ physiology, in a spatially controlled manner and over long periods. Quantitative analyses of clonal dynamics have revealed that, in epithelia, homeostasis is achieved at the population rather than at the single stem cell level, suggesting that feedback mechanisms coordinate stem cell maintenance and progeny generation. In the central nervous system, however, little is known of the possible community processes (...) underlying neural stem cell maintenance. Recent work, in part based on intravital imaging made possible in the adult zebrafish, conclusively highlights that homeostasis in neural stem cell pools may rely on population asymmetry and long‐term spatiotemporal coordination of neural stem cell states and fates. These results suggest that neural stem cell assemblies in the vertebrate brain behave as self‐organized systems, such that the stem cells themselves generate their own intrinsic niche. (shrink)

Recent developments in 3D cultures exploiting the self‐organization ability of pluripotent stem cells have enabled the generation of powerful in vitro systems termed brain organoids. These 3D tissues recapitulate many aspects of human brain development and disorders occurring in vivo. When combined with improved differentiation methods, these in vitro systems allow the generation of more complex “assembloids,” which are able to reveal cell diversities, microcircuits, and cell–cell interactions within their 3D organization. Here, the ways in which human (...) brain organoids have contributed to demystifying the complexities of brain development and modeling of developmental disorders is reviewed and discussed. Furthermore, challenging questions that are yet to be addressed by emerging brain organoid research are discussed. (shrink)

Stem cells isolated from adult mammalian tissues may provide new approaches for the autologous treatment of disease and tissue repair. Although the potential of adult stem cells has received much attention, it has also recently been brought into question. This article reviews the recent work describing the ability of non‐hematopoietic stem cells derived from adult bone marrow to form neural derivatives and their potential for brain repair. Earlier transplantation experiments imply that grafted adult stem cells (...) can differentiate into neural derivatives. Recent reports suggest, however, that such findings may be misleading and grafted cells acquiring different identities may merely be explained by their fusion with host cells and not the result of radical changes to their program of cellular differentiation. Nonetheless, in vitro studies have shown that neural development by bone‐marrow‐derived stem cells also appears possible. Understanding the molecular mechanisms that specify the neural lineage will lead to the development of tools for the targeted production of neural cell types in vitro that may ultimately provide a source of material to treat specific neurological deficits. BioEssays 24:708–713, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

This paper discusses the evidence for the role of CREB in neural stem/progenitor cell (NSPC) function and oncogenesis and how these functions may be important for the development and growth of brain tumours. The cyclic‐AMP response element binding (CREB) protein has many roles in neurons, ranging from neuronal survival to higher order brain functions such as memory and drug addiction behaviours. Recent studies have revealed that CREB also has a role in NSPC survival, differentiation and proliferation. Recent (...) work has shown that over‐expression of CREB in transgenic animals can impart oncogenic properties on cells in various tissues and that aberrant CREB expression is associated with tumours in patients. It is the central position of CREB, downstream of key developmental and growth signalling pathways, which give CREB the ability to influence a spectrum of cell activities, such as cell survival, growth and differentiation in both normal and cancer cells. (shrink)

For nearly two centuries, developmental biologists have known that body organs are derived from distinct germ layers. They have argued that adult stem cells formed in one of these, mesoderm for example, cannot give rise to cells that originate in another. We disagree. An exception to this “rule” has been described in crayfish recently. In this species, hemocytes appear to replenish neurogenic cells. This may happen in humans as well. In women who were given male bone marrow‐derived cells, Y (...) chromosome positive cheek cells and brain neurons were detected. While repopulation of these tissues by bone marrow derived cells may not occur normally, and while it does not appear to be terribly efficient, the phenomenon should be studied in more detail. Perhaps cells in the marrow could be used to regenerate tissues elsewhere. (shrink)

Are there persuasive approaches to embryonic stem cell (ESC) research that appeal, not just to those fellow-citizens in one’s own ideological camp, nor just to those undecided citizens in the middle, but to those citizens on the other side of the issue? I believe that there are such arguments and in this short paper I try to develop one of them. In particular, I argue that certain beliefs shared by some proponents and some opponents of ESC research—beliefs about the (...) personal identity and moral status of those who are victims of terrible brain diseases—are beliefs that should lead us to adopt a qualified endorsement of ESC research. (shrink)

Balancing self‐renewal and differentiation of stem cells is an important issue in stem cell and cancer biology. Recently, the Drosophila neuroblast (NB), neural stem cell has emerged as an excellent model for stem cell self‐renewal and tumorigenesis. It is of great interest to understand how defects in the asymmetric division of neural stem cells lead to tumor formation. Here, we review recent advances in asymmetric division and the self‐renewal control of Drosophila NBs. We summarize molecular (...) mechanisms of asymmetric cell division and discuss how the defects in asymmetric division lead to tumor formation. Gain‐of‐function or loss‐of‐function of various proteins in the asymmetric machinery can drive NB overgrowth and tumor formation. These proteins control either the asymmetric protein localization or mitotic spindle orientation of NBs. We also discuss other mechanisms of brain tumor suppression that are beyond the control of asymmetric division. (shrink)

In 1968, the Harvard criteria equated irreversible coma and apnea with human death and later, the Uniform Determination of Death Act was enacted permitting organ procurement from heart-beating donors. Since then, clinical studies have defined a spectrum of states of impaired consciousness in human beings: coma, akinetic mutism, minimally conscious state, vegetative state and brain death. In this article, we argue against the validity of the Harvard criteria for equating brain death with human death. Brain death does (...) not disrupt somatic integrative unity and coordinated biological functioning of a living organism. Neurological criteria of human death fail to determine the precise moment of an organism’s death when death is established by circulatory criterion in other states of impaired consciousness for organ procurement with non-heart-beating donation protocols. The criterion of circulatory arrest 75 s to 5 min is too short for irreversible cessation of whole brain functions and respiration controlled by the brain stem. Brain -based criteria for determining death with a beating heart exclude relevant anthropologic, psychosocial, cultural, and religious aspects of death and dying in society. Clinical guidelines for determining brain death are not consistently validated by the presence of irreversible brain stem ischemic injury or necrosis on autopsy; therefore, they do not completely exclude reversible loss of integrated neurological functions in donors. The questionable reliability and varying compliance with these guidelines among institutions amplify the risk of determining reversible states of impaired consciousness as irreversible brain death. The scientific uncertainty of defining and determining states of impaired consciousness including brain death have been neither disclosed to the general public nor broadly debated by the medical community or by legal and religious scholars. Heart-beating or non-heart-beating organ procurement from patients with impaired consciousness is de facto a concealed practice of physician-assisted death, and therefore, violates both criminal law and the central tenet of medicine not to do harm to patients. Society must decide if physician-assisted death is permissible and desirable to resolve the conflict about procuring organs from patients with impaired consciousness within the context of the perceived need to enhance the supply of transplantable organs. (shrink)

Progress in the neurosciences is profoundly changing our conception of ourselves. Contrary to time-honored intuition, the mind turns out to be a complex of brain functions. And contrary to the wishful thinking of some philosophers, there is no stemming the revolutionary impact that brain research will have on our understanding of how the mind works. Brain-Wise is the sequel to Patricia Smith Churchland's Neurophilosophy, the book that launched a subfield. In a clear, conversational manner, this book examines (...) old questions about the nature of the mind within the new framework of the brain sciences. What, it asks, is the neurobiological basis of consciousness, the self, and free choice? How does the brain learn about the external world and about its own introspective world? What can neurophilosophy tell us about the basis and significance of religious and moral experiences? Drawing on results from research at the neuronal, neurochemical, system, and whole-brain levels, the book gives an up-to-date perspective on the state of neurophilosophy—what we know, what we do not know, and where things may go from here. (shrink)

The concept of brain death was recently described as being “at once well settled and persistently unresolved.” Every day, in the United States and around the world, physicians diagnose patients as brain dead, and then proceed to transplant organs from these patients into others in need. Yet as well settled as this practice has become, brain death continues to be the focus of controversy, with two journals in bioethics dedicating major sections to the topic within the last (...) two years.By way of background, the Uniform Determination of Death Act states that “[a]n individual who has sustained either: irreversible cessation of circulatory and respiratory functions, or irreversible cessation of all functions of the entire brain, including the brain stem, is dead. A determination of death must be made in accordance with accepted medical standards.” In other words, death can be defined by either cardiorespiratory or neurological criteria, with “brain death” representing the loss of all brain function. This standard, or closely related variants, has become the accepted approach throughout the United States and in many parts of the world. (shrink)

Since the 1980s, Islamic scholars and medical experts have used the tools of Islamic law to formulate ethico-legal opinions on brain death. These assessments have varied in their determinations and remain controversial. Some juridical councils such as the Organization of Islamic Conferences' Islamic Fiqh Academy (OIC-IFA) equate brain death with cardiopulmonary death, while others such as the Islamic Organization of Medical Sciences (IOMS) analogize brain death to an intermediate state between life and death. Still other councils have (...) repudiated the notion entirely. Similarly, the ethico-legal assessments are not uniform in their acceptance of brain-stem or whole-brain criteria for death, and consequently their conceptualizations of, brain death. Within the medical literature, and in the statements of Muslim medical professional societies, brain death has been viewed as sanctioned by Islamic law with experts citing the aforementioned rulings. Furthermore, health policies around organ transplantation and end-of-life care within the Muslim world have been crafted with consideration of these representative religious determinations made by transnational, legally-inclusive, and multidisciplinary councils. The determinations of these councils also have bearing upon Muslim clinicians and patients who encounter the challenges of brain death at the bedside. For those searching for ‘Islamically-sanctioned’ responses that can inform their practice, both the OIC-IFA and IOMS verdicts have palpable gaps in their assessments and remain clinically ambiguous. In this paper we analyze these verdicts from the perspective of applied Islamic bioethics and raise several questions that, if answered by future juridical councils, will better meet the needs of clinicians and bioethicists. (shrink)

This article proposes a methodological schema for engaging in a productive discussion of ethical issues regarding human brain organoids, which are three-dimensional cortical neural tissues created using human pluripotent stem cells. Although moral consideration of HBOs significantly involves the possibility that they have consciousness, there is no widely accepted procedure to determine whether HBOs are conscious. Given that this is the case, it has been argued that we should adopt a precautionary principle about consciousness according to which, if (...) we are not certain whether HBOs have consciousness—and where treating HBOs as not having consciousness may cause harm to them—we should proceed as if they do have consciousness. This article emphasizes a methodological advantage of adopting the precautionary principle: it enables us to sidestep the question of whether HBOs have consciousness and, instead, directly address the question of what kinds of conscious experiences HBOs can have, where the what-kind-question is more tractable than the whether-question. By addressing the what-kind-question, we will be able to examine how much moral consideration HBOs deserve. With this in mind, this article confronts the what-kind-question with the assistance of experimental studies of consciousness and suggests an ethical framework which supports restricting the creation and use of HBOs in bioscience. (shrink)

It is a commonplace of contemporary thought that the mind is located in the brain. Although there have been some challenges to this view, it has remained mainstream outside of a few specialized discussions, and plays a prominent role in a wide variety of philosophical arguments. It is further assumed that the source of this view is empirical. I argue it is not. Empirical discoveries show conclusively that the brain is the central organ of mental life, but do (...) not show that it is the mind's location . The data are just as compatible with a view where mentality is a human capacity on the model of circulation or respiration, with the brain playing the same kind of role as the heart or lungs. The standard conception of the brain as the locus of mind stems, I claim, from the imposition of a Cartesian conception of the self on a materialist ontology. Recognizing that the empirical data do not justify such a move casts doubt on the foundations of a number of philosophical discussions and raises new questions about the nature of the psychological subject. (shrink)

The current debate regarding the suitability of anencephalics as organ donors is due primarily to misunderstandings. The anatomical and neurophysiological literature shows that the anencephalic lacks a cerebrum because of the failure of neuralplate fusion. However, even the incomplete function of an atrophic brain stem is currently accepted at law in most if not all countries as sufficient for brain life: which is to say, cessation of breathing is currently required in order to make the diagnosis of (...) brain death. Because of the extensive incompleteness of the anencephalic's brain, it is not possible to postpone death significantly by mechanical ventilation and intravenous feeding. It is acceptable to maintain life for a short period of time in order to allow organ transplantation subsequent to the declaration of death at the point of cessation of the capacity for spontaneous respiration. The most important issue is not transplantation, but the issue of brain life raised by the case of anencephalics. Since brain life in any significant sense begins only after the closure of the neural tube on the 30th day after conception, it is reasonable to take this as the point at which brain life begins. Laws should be amended in all countries to allow the abortion of anencephalics at any time, in that they do not at any time possess brain life. Keywords: anencephaly, organ transplantation, beginning of life, brain death, abortion CiteULike Connotea Del.icio.us What's this? (shrink)

The current debate regarding the suitability of anencephalics as organ donors is due primarily to misunderstandings. The anatomical and neurophysiological literature shows that the anencephalic lacks a cerebrum because of the failure of neuralplate fusion. However, even the incomplete function of an atrophic brain stem is currently accepted at law in most if not all countries as sufficient for brain life: which is to say, cessation of breathing is currently required in order to make the diagnosis of (...) brain death. Because of the extensive incompleteness of the anencephalic's brain, it is not possible to postpone death significantly by mechanical ventilation and intravenous feeding. It is acceptable to maintain life for a short period of time in order to allow organ transplantation subsequent to the declaration of death at the point of cessation of the capacity for spontaneous respiration. The most important issue is not transplantation, but the issue of brain life raised by the case of anencephalics. Since brain life in any significant sense begins only after the closure of the neural tube on the 30th day after conception, it is reasonable to take this as the point at which brain life begins. Laws should be amended in all countries to allow the abortion of anencephalics at any time, in that they do not at any time possess brain life. (shrink)

The complexity of the human brain creates a spectrum of sophisticated behavioral repertoires, such as language, tool use, self-awareness, symbolic thought, cultural learning, and consciousness. Understanding how the human brain achieves that has been a longstanding challenge for neuroscientists and may bring insights into the evolution of human cognition and disease states. Human pluripotent stem cells could differentiate into specialized cell types and tissues in vitro. From this pluripotent state, it is possible to generate models of the (...) human brain, such as brain organoids. The recent observation that brain organoids can spontaneously develop complex neural network activity in a dish can help one understand how neural network oscillations evolve and vary between normal and disease states. Moreover, this finding can be leveraged to other applications outside medicine, including engineering and artificial intelligence. However, as the brain model technology becomes more complex, it raises a series of ethical and moral dilemmas. This article discusses the status of this technology, some of its current limitations, and a vision of the future. (shrink)

The current model of adult neurogenesis in mammals suggests that adult‐born neurons are generated by stem cells that undergo long‐term self‐renewal, and that a lifetime supply of stem cells resides in the brain. In contrast, it has recently been demonstrated that adult‐born neurons in crayfish are generated by precursors originating in the immune system. This is particularly interesting because studies done many years ago suggest that a similar mechanism might exist in rodents and humans, with bone marrow (...) providing stem cells that can generate neurons. However, the relevance of these findings for natural mechanisms underlying adult neurogenesis in mammals is not clear, because of uncertainties at many levels. We argue here that the recent findings in crayfish send a strong signal to re‐examine existing data from rodents and humans, and to design new experiments that will directly test the contributions of the immune system to adult neurogenesis in mammals. (shrink)

Is there anything special about the ethical problems of intracerebral stem-cell transplantation and other forms of cell or tissue transplantation in the brain that provides neuroethics with a distinctive normative profile, setting it apart from other branches of medical ethics? This is examined with reference to some of the ethical problems associated with interventions in the brain such as potential changes in personal identity and potential changes in personality. It is argued that these problems are not sufficiently (...) specific to justify the autonomy of neuroethics as a separate discipline and can be handled by the established principles of medical ethics. The paper concludes with a constructive proposal how to deal with interventions in the brain for which the patient is unable to give valid ex-ante consent. (shrink)

Brain organoid research raises ethical challenges not seen in other forms of stem cell research. Given that brain organoids partially recapitulate the development of the human brain, it is plausible that brain organoids could one day attain consciousness and perhaps even higher cognitive abilities. Brain organoid research therefore raises difficult questions about these organoids' moral status – questions that currently fall outside the scope of existing regulations and guidelines. This paper shows how these gaps (...) can be addressed. We outline a moral framework for brain organoid research that can address the relevant ethical concerns without unduly impeding this important area of research. (shrink)

A hypothesis on the physiological conditions of consciousness is presented. It is assumed that the occurrence of states of consciousness causally depends on the formation of complex representational structures. Cortical neural networks that exhibit a high representational activity develop higher-order, self-referential representations as a result of self-organizing processes. The occurrence of such states is identical with the appearance of states of consciousness. The underlying physiological processes can be identified. It is assumed that neural assemblies instantiate mental representations; hence consciousness depends (...) on the rate at which large active assemblies are generated. The formation of assemblies involves the activation of the N-methyl-D-aspartate receptor channel complex which controls different forms of synaptic plasticity including rapid changes of the connection strengths. The various causes of unconsciousness (e.g., anaesthetics or brain stem lesions) have a common denominator: they directly or indirectly inhibit the formation of assemblies. (shrink)

There is a persisting tension that exists between the block universe conception of time in modern physics and philosophy and the conception of time that stems naturally from experience, and entropic asymmetries have been proposed to explain this tension. This article argues that as biochemical processes in the brain depend upon spontaneous entropy increases in the forward-time direction, this should provide an entropic basis for the unidirectionality of psychological processes. As this view does not depend on considerations of abstract (...) information processing or a past hypothesis, it provides advantages over previous entropy-based proposals attempting to explain asymmetries in temporal experience. (shrink)

The Uniform Determination of Death Act (UDDA) provides that “an individual who has sustained either (1) irreversible cessation of circulatory and respiratory functions or (2) irreversible cessation of all functions of the entire brain, including the brain stem, is dead.” We show that the UDDA contains two conflicting interpretations of the phrase “cessation of functions.” By one interpretation, what matters for the determination of death is the cessation of spontaneous functions only, regardless of their generation by artificial (...) means. By the other, what matters is the cessation of both spontaneous and artificially supported functions. Because each UDDA criterion uses a different interpretation, the law is conceptually inconsistent. A single consistent interpretation would lead to the conclusion that conscious individuals whose respiratory and circulatory functions are artificially supported are actually dead, or that individuals whose brain is entirely and irreversibly destroyed may be alive. We explore solutions to mitigate the inconsistency. (shrink)

If education is to make a difference it is widely acknowledged that we must aim to educate for understanding, but this means being clear about what we mean by understanding. This paper argues for a concept of personal understanding, recognising both the commonality and individuality of each pupil's understandings, and the relationship between understanding and interpretation, analysis and synopsis, and the quest for meaning. In supporting this view, the paper advocates an emergentist notion of person‐hood, and considers the neurophysiological reasons (...) for asserting the individuality of human minds, brains, and the creation of personal meanings. The notion of personal meanings would, however, seem to run counter to the post‐modern denial of the autonomous self, and the tradition in philosophy, most recently stemming from Wittgenstein, that insists that meanings and understandings are essentially social, and not personal—a view also advocated by John White in regard to education. In contrast, this paper argues that meanings and understandings are both social and personal. Once we reinstate the notion of personal minds and personal understandings, alongside the social, we may see more clearly what it means to educate for understanding, and why this might begin to make a difference. (shrink)

If education is to make a difference it is widely acknowledged that we must aim to educate for understanding, but this means being clear about what we mean by understanding. This paper argues for a concept of personal understanding, recognising both the commonality and individuality of each pupil's understandings, and the relationship between understanding and interpretation, analysis and synopsis, and the quest for meaning. In supporting this view, the paper advocates an emergentist notion of person‐hood, and considers the neurophysiological reasons (...) for asserting the individuality of human minds, brains, and the creation of personal meanings. The notion of personal meanings would, however, seem to run counter to the post‐modern denial of the autonomous self, and the tradition in philosophy, most recently stemming from Wittgenstein, that insists that meanings and understandings are essentially social, and not personal—a view also advocated by John White in regard to education. In contrast, this paper argues that meanings and understandings are both social (interpersonal) and personal. Once we reinstate the notion of personal minds and personal understandings, alongside the social, we may see more clearly what it means to educate for understanding, and why this might begin to make a difference. (shrink)

The convergence of human and artificial intelligence is currently receiving considerable scholarly attention. Much debate about the resulting _Hybrid Minds_ focuses on the integration of artificial intelligence into the human brain through intelligent brain-computer interfaces as they enter clinical use. In this contribution we discuss a complementary development: the integration of a functional in vitro network of human neurons into an _in silico_ computing environment. To do so, we draw on a recent experiment reporting the creation of silico-biological (...) intelligence as a case study (Kagan et al., 2022b ). In this experiment, multielectrode arrays were plated with stem cell-derived human neurons, creating a system which the authors call _DishBrain_. By embedding the system into a virtual game-world, neural clusters were able to receive electrical input signals from the game-world and to respond appropriately with output signals from pre-assigned motor regions. Using this design, the authors demonstrate how the _DishBrain_ self-organises and successfully learns to play the computer game ‘Pong’, exhibiting ‘sentient’ and intelligent behaviour in its virtual environment. The creation of such hybrid, silico-biological intelligence raises numerous ethical challenges. Following the neuroscientific framework embraced by the authors themselves, we discuss the arising ethical challenges in the context of Karl Friston’s Free Energy Principle, focusing on the risk of creating synthetic phenomenology. Following the _DishBrain’s_ creator’s neuroscientific assumptions, we highlight how DishBrain’s design may risk bringing about artificial suffering and argue for a congruently cautious approach to such synthetic biological intelligence. (shrink)

While philosophers have, for centuries, pondered upon the relation between mind and brain, neuroscientists have only recently been able to explore the connection analytically — to peer inside the black box. This ability stems from recent advances in technology and emerging neuroimaging modalities. It is now possible not only to produce remarkably detailed images of the brain’s structure (i.e. anatomical imaging) but also to capture images of the physiology associated with mental processes (i.e. functional imaging). We are able (...) to see how specific regions of the brain ‘light up’ when activities such as reading this book are performed, and how our neurons and their elaborate cast of supporting cells organize and coordinate their tasks. As demonstrated in the other chapters of this book, the mapping of the human mind (mostly by measuring regional changes in blood flow, initially by positron emission tomography (PET) and recently by functional magnetic resonance imaging or (fMRI)) has provided insight into the functional neuroanatomy of neuropsychiatric diseases. Amazingly, the idea that regional cerebral blood flow (rCBF) is related intimately to brain function goes back more than a century. As is often the case in science, this idea was initially the result of unexpected observations. The Italian physiologist Angelo Mosso first expressed the idea while studying pulsations of the living human brain that keep pace with the heartbeat (Mosso, 1881). These brain pulsations can be observed on the surface of the fontanelles in newborn children. Mosso believed that they reflected blood flow to the brain. He observed similar pulsations in an adult with a post-traumatic skull defect over the frontal lobes. While studying this subject, a peasant named Bertino, Mosso observed a sudden increase in the magnitude of the ‘brain’s heart-beats’ when the church bells signalled 12 o’clock, the time for a required prayer. The changes in brain pulsations occurred independently of any change in pulsations in the forearm.. (shrink)

The goal of this article is to review some aspects of brain anatomy and neurophysiology that are important for consciousness, and which hopefully may be of benefit to philosophers investigating the conscious mind. Taking as an initial point of reference the distinction between “the hard problem” and “the weak problems” of consciousness, we shall concentrate on questions pertaining to the second of these. A putative “consciousness system” in the brain will be presented, paying special attention to diffuse projection (...) systems. The “center of gravity” will be brain connectivity, since consciousness must, critically, be dependent on coherent activity and timing. “Detectors” of synchronicity and coincidence, like NMDA receptors, also necessarily play a role here. To be conscious, we do not need an entire brain. While even large hemispherectomies need not unequivocally affect consciousness, far smaller brain-stem lesions may be devastating in this regard. Even so, the recent discovery by Matthew F. Glasser et al. of 180 separate areas in the human brain cortex is intriguing from a teleological perspective, as it is quite unthinkable that any of them could be “redundant. (shrink)

The paradigmatic assumption that REM sleep is the physiological equivalent of dreaming is in need of fundamental revision. A mounting body of evidence suggests that dreaming and REM sleep are dissociable states, and that dreaming is controlled by forebrain mechanisms. Recent neuropsychological, radiological, and pharmacological findings suggest that the cholinergic brain stem mechanisms that control the REM state can only generate the psychological phenomena of dreaming through the mediation of a second, probably dopaminergic, forebrain mechanism. The latter mechanism (...) (and thus dreaming itself) can also be activated by a variety of nonREM triggers. Dreaming can be manipulated by dopamine agonists and antagonists with no concomitant change in REM frequency, duration, and density. Dreaming can also be induced by focal forebrain stimulation and by complex partial (forebrain) seizures during nonREM sleep, when the involvement of brainstem REM mechanisms is precluded. Likewise, dreaming is obliterated by focal lesions along a specific (probably dopaminergic) forebrain pathway, and these lesions do not have any appreciable effects on REM frequency, duration, and density. These findings suggest that the forebrain mechanism in question is the final common path to dreaming and that the brainstem oscillator that controls the REM state is just one of the many arousal triggers that can activate this forebrain mechanism. The “REM-on” mechanism (like its various NREM equivalents) therefore stands outside the dream process itself, which is mediated by an independent, forebrain “dream-on” mechanism. Key Words: acetylcholine; brainstem; dopamine; dreaming; forebrain; NREM; REM; sleep. (shrink)

The goal of this article is to review some aspects of brain anatomy and neurophysiology that are important for consciousness, and which hopefully may be of benefit to philosophers investigating the conscious mind. Taking as an initial point of reference the distinction between “the hard problem” and “the weak problems” of consciousness, we shall concentrate on questions pertaining to the second of these. A putative “consciousness system” in the brain will be presented, paying special attention to diffuse projection (...) systems. The “center of gravity” will be brain connectivity, since consciousness must, critically, be dependent on coherent activity and timing. “Detectors” of synchronicity and coincidence, like NMDA receptors, also necessarily play a role here. To be conscious, we do not need an entire brain. While even large hemispherectomies need not unequivocally affect consciousness, far smaller brain-stem lesions may be devastating in this regard. Even so, the recent discovery by Matthew F. Glasser et al. of 180 separate areas in the human brain cortex is intriguing from a teleological perspective, as it is quite unthinkable that any of them could be “redundant. (shrink)

This article presents a sobering view of the discipline of cognitive neuropsychology as practiced over the last three or four decades. Our judgment is that, although the study of abnormal cognition resulting from brain injury or disease in previously normal adults has produced a catalogue of fascinating and highly selective deficits, it has yielded relatively little advance in understanding how the brain accomplishes its cognitive business. We question the wisdom of the following three “choices” in mainstream cognitive neuropsychology: (...) (a) single‐case methodology, (b) dissociation between functions as the most important source of evidence, and (c) a central goal of diagramming the functional architecture of cognition rather than specifying how its components work. These choices may all stem from an excessive commitment to strict and fine‐grained modularity. Although different brain regions are undoubtedly specialized for different functions, we argue that parallel and interactive processing is a better assumption about cognitive processing. The essential goal of specifying representations and processes can, we claim, be significantly assisted by computational modeling which, by its very nature, requires such specification. (shrink)

Brain death or determination of death based on the neurological criterion has been an enduring source of controversy in academic and clinical circles. The controversy chiefly concerns how death is defined, and it also bears on the justification of the proposed criteria for death determination and their interpretation. Part of the controversy on brain death and death determination stems from disputed crucial medical facts, but in this paper I formulate another hypothesis about the nature of ongoing controversies. At (...) stake is a misunderstood relationship between, on the one hand, the nature of our lay views about death and, on the other hand, the nature of scientific insights into death and its determination. The misunderstanding of this relationship has partly anchored the controversy and continues to fuel it. Based on a perspective inspired by pragmatism, which stresses the positive contribution of science to ethical and policy debates but also challenges different forms of scientism in science and philosophy found in foundationalist interpretations, I scrutinize three different stances regarding the relationship between lay and scientific perspectives about the definition of death: foundational lay views, foundational expert views, and co-evolving views. I argue that only the latter is sustainable given recent challenges to foundationalist interpretations. (shrink)

: The transplantation of adult human neural stem cells into prenatal non-humans offers an avenue for studying human neural cell development without direct use of human embryos. However, such experiments raise significant ethical concerns about mixing human and nonhuman materials in ways that could result in the development of human-nonhuman chimeras. This paper examines four arguments against such research, the moral taboo, species integrity, "unnaturalness," and human dignity arguments, and finds the last plausible. It argues that the transfer of (...) human brain or retinal stem cells to nonhuman embryos would not result in the development of human-nonhuman chimeras that denigrate human dignity, provided such stem cells are dissociated. The article provides guidelines that set ethical boundaries for conducting such research that are consonant with the requirements of human dignity. (shrink)

The author of The Reality of Time and the Existence of God turns his critical conceptual acumen to finding an intellectually viable path between the current polarities of dualism and materialism. By considering human beings as language-using animals he can critically appraise “representational” views of concept formation, as well as show how current “research programs” which presuppose a “materialist” basis stem from an unwitting adoption of a dualist picture of mind and body. His alternative is rooted in classical thinkerslike (...) Aquinas and responsive to the critiques of Wittgenstein, yet constructive in ways in which those critiques failed to be. This essay aims to help readers undertake a taxing inquiry by guiding them through its main theses. (shrink)

The author of The Reality of Time and the Existence of God turns his critical conceptual acumen to finding an intellectually viable path between the current polarities of dualism and materialism. By considering human beings as language-using animals he can critically appraise “representational” views of concept formation, as well as show how current “research programs” which presuppose a “materialist” basis stem from an unwitting adoption of a dualist picture of mind and body. His alternative is rooted in classical thinkerslike (...) Aquinas and responsive to the critiques of Wittgenstein, yet constructive in ways in which those critiques failed to be. This essay aims to help readers undertake a taxing inquiry by guiding them through its main theses. (shrink)

Bioethics, Volume 36, Issue 1, Page 25-41, January 2022.

The potential use of stem cells in the treatment of a variety of human diseases has been a major driving force for embryonic stem cell research. Another productive area of research has been the use of human stem cells to reconstitute human organ systems in animals in an attempt to create new animal models for human diseases. However, the possibility of transplanting human embryonic brain cells or precursor brain cells into an animal fetus presents numerous (...) ethical challenges. This paper examines, from a Jewish perspective on human dignity, several bioethical concerns related to the reconstitution of animal brains with human neurons. (shrink)

While there is increasing pressure on scarce health care resources, advances in medical science have blurred the boundary between life and death. Individuals can survive for decades without consciousness and individuals whose whole brains are dead can be supported for extended periods. One suggested response is to redefine death, justifying a higher brain criterion for death. This argument fails because it conflates two distinct notions about the demise of human beings--the one, biological and the other, ontological. Death is a (...) biological phenomenon. This view entails the rejection of a higher brain criterion of death. Moreover, I claim that the justification of the whole brain (or brain stem) criterion of death is also cast into doubt by these advances in medical science. I proceed to argue that there is no need to redefine death in order to identify which treatments ought to be provided for the permanently and irreversibly unconscious. There are already clear treatment guidelines. (shrink)