This article explains the problems with Alan Shewmon’s critique of brain death as a valid sign of human death, beginning with a critical examination of his analogy between brain death and severe spinal cord injury. The article then goes on to assess his broader argument against the necessity of the brain for adult human organismal integration, arguing that he fails to translate correctly from biological to metaphysical claims. Finally, on the basis of a deeper metaphysical analysis, I offer a revised (...) rationale for the validity of the neurological criterion of human death. (shrink)

A broad range of evidence regarding the functional organization of the vertebrate brain – spanning from comparative neurology to experimental psychology and neurophysiology to clinical data – is reviewed for its bearing on conceptions of the neural organization of consciousness. A novel principle relating target selection, action selection, and motivation to one another, as a means to optimize integration for action in real time, is introduced. With its help, the principal macrosystems of the vertebrate brain can be seen to form (...) a centralized functional design in which an upper brain stem system organized for conscious function performs a penultimate step in action control. This upper brain stem system retained a key role throughout the evolutionary process by which an expanding forebrain – culminating in the cerebral cortex of mammals – came to serve as a medium for the elaboration of conscious contents. This highly conserved upper brainstem system, which extends from the roof of the midbrain to the basal diencephalon, integrates the massively parallel and distributed information capacity of the cerebral hemispheres into the limited-capacity, sequential mode of operation required for coherent behavior. It maintains special connective relations with cortical territories implicated in attentional and conscious functions, but is not rendered nonfunctional in the absence of cortical input. This helps explain the purposive, goal-directed behavior exhibited by mammals after experimental decortication, as well as the evidence that children born without a cortex are conscious. Taken together these circumstances suggest that brainstem mechanisms are integral to the constitution of the conscious state, and that an adequate account of neural mechanisms of conscious function cannot be confined to the thalamocortical complex alone. (Published Online May 1 2007) Key Words: action selection; anencephaly; central decision making; consciousness; control architectures; hydranencephaly; macrosystems; motivation; target selection; zona incerta. (shrink)

D. Alan Shewmon has advanced a well-documented challenge to the widely accepted total brain death criterion for death of the human being. We show that Shewmon's argument against this criterion is unsound, though he does refute the standard argument for that criterion. We advance a distinct argument for the total brain death criterion and answer likely objections. Since human beings are rational animals – sentient organisms of a specific type – the loss of the radical capacity for sentience involves a (...) substantial change, the passing away of the human organism. In human beings total brain death involves the complete loss of the radical capacity for sentience, and so in human beings total brain death is death. (shrink)

I investigate Thomas Aquinas's metaphysical account of human death, which is defined in terms of a rational soul separating from its material body. The question at hand concerns what criterion best determines when this separation occurs. Aquinas argues that a body has a rational soul only insofar as it is properly organised to support the soul's vegetative, sensitive, and rational capacities. According to the ‘higher‐brain’ concept of death, when a body can no longer provide the biological foundation necessary for the (...) operation of conscious rational thought and volition, a substantial change occurs in which the rational soul departs and the body left behind is a ‘humanoid animal’ or a mere ‘vegetable.’I argue that the separation of soul and body does not occur until the body ceases to function as a unified, integrated organism. A rational soul is not only the seat of a human being's rational capacities; it is also the principle of the body's sensitive and vegetative capacities. Since Aquinas defines a human being as a composite of soul and body, and not with merely the exercise of rational capacities, the determination of death requires incontrovertible evidence that the body has ceased all the operations that correspond to the soul's proper capacities. The evidence of this is the body's loss of its integrative organic unity and the criterion for determining when this loss occurs is the irreversible cessation of whole‐brain functioning. (shrink)

Human life is operationally defined by the onset and cessation of organismal function. At postnatal stages of life, organismal integration critically and uniquely requires a functioning brain. In this article, a distinction is drawn between integrated and coordinated biologic activities. While communication between cells can provide a coordinated biologic response to specific signals, it does not support the integrated function that is characteristic of a living human being. Determining the loss of integrated function can be complicated by medical interventions that (...) uncouple elements of the natural biologic hierarchy underlying our intuitive understanding of death. Such medical interventions can allow living human beings who are no longer able to function in an integrated manner to be maintained in a living state. In contrast, medical intervention can also allow the cells and tissues of an individual who has died to be maintained in a living state. To distinguish between a living human being and living human cells, two criteria are proposed: either the persistence of any form of brain function or the persistence of autonomous integration of vital functions. Either of these criteria is sufficient to determine a human being is alive. (shrink)

The main idea in this series of essays is that subjective awareness depends upon the intralaminar nuclei of each thalmus. This implies that the internal structure and external relations of ILN make subjective awareness possible. An array of material relevant to this proposal was briefly reviewed in Part I. This Part II considers in more detail some semantic aspects and a bit of philosophic background as these pertain to propositions 0, 1, and 2 of Part I. Part II should be (...) read in conjunction with Part I. (shrink)

How certain neural mechanisms momentarily endow with the subjective awareness percepts and affects represented elsewhere is more likely to be clarified when structures essential to Mc are identified. The loss of C with bilateral thalmic lesions involving the intralaminar nuclei contrasts with retention of C after large cortical ablations depriving C of specific contents. A role of ILN in the perception of primitive sensations is suggested by their afference of directly ascending pathways. A role for ILN in awareness of cortical (...) activity is suggested by their widespread afference from cortex, a property shared with striatum. A role for ILN in volition is suggested by their heavy projection to striatum. Unlike striatum, ILN also project widely to almost all neocortex, enabling an effect on ideation; this last property is in common with other structures but none of them has the same direct cortical afference. And passage through the reticular nucleus of ILN efferents to cortex could impact the attention-selective action of nRt. It is suggested that the quickest route to a better understanding of C involves more intensive study of ILN. No other structure seems, in the light of our current knowledge, a more likely site for Mc. (shrink)

Patrick Lee and Germain Grisez have argued that the total brain dead patient is still dead because the integrated entity that remains is not even an animal, not only because he is not sentient but also, and more importantly, because he has lost the radical capacity for sentience. In this essay, written from within and as a contribution to the Catholic philosophical tradition, I respond to Lee and Grisez’s argument by proposing that the brain dead patient is still sentient because (...) an animal with an intact but severed spinal cord can still perceive and respond to external stimuli. The brain dead patient is an unconscious sentient organism. (shrink)