Consciousness, the brain and what matters

Grant Gillett argues that it is consciousness which makes a human or other being the 'locus of ethical value'. Since cortical functioning is, in Gillett's view, necessary for conscious activity, an individual whose neocortex is permanently non-functional is no longer a locus of ethical value and cannot be benefited or harmed in a morally relevant sense. This means that there is no obligation to continue treating those who have suffered neocortical death.     

Neural processes underlying conscious perception: Experimental findings and a global neuronal workspace framework

One striking property of perception is that it can be achieved in two seemingly different ways: either consciously or non-consciously. What distinguishes these two types of processing at the neural level? So far, empirical findings suggest that conscious perception is associated with an increase in activity at the sensory level, the specific involvement of a fronto-parietal network and an increase in long-distance functional connectivity and synchrony within a broad network of areas. We interpret these data in the framework of the global neuronal workspace model which proposes that the neural basis of conscious access is a sudden self-amplifying process leading to a global brain-scale pattern of activity. In contradiction with several theories which assume that there is a continuum of perception, associated with a gradual change in the intensity of brain activation, the model predicts a sharp non-linear transition between non-conscious and conscious processing.     

The deprivation argument against abortion

The most plausible pro-life argument claims that abortion is seriously wrong because it deprives the foetus of something valuable. This paper examines two recent versions of this argument. Don Marquis's version takes the valuable thing to be a 'future like ours', a future containing valuable experiences and activities. Jim Stone's version takes the valuable thing to be a future containing conscious goods, which it is the foetus's biological nature to make itself have. I give three grounds for rejecting these arguments. First, they lead to unacceptable inequalities in the wrongness of killing. Second, they lead to counterintuitive results in a range of imaginary cases. Third, they ignore the role of psychological connectedness in determining the magnitude or seriousness of deprivation-based harms: because the foetus is only weakly psychologically connected to its own future, it cannot be seriously harmed by being deprived of that future.     

Contributions of magno- and parvocellular channels to conscious and non-conscious vision

The dorsal and ventral cortical pathways, driven predominantly by magnocellular (M) and parvocellular (P) inputs, respectively, assume leading roles in models of visual information processing. Although in prior proposals, the dorsal and ventral pathways support non-conscious and conscious vision, respectively, recent modelling and empirical developments indicate that each pathway plays important roles in both non-conscious and conscious vision. In these models, the ventral P-pathway consists of one subpathway processing an object''s contour features, e.g. curvature, the other processing its surface attributes, e.g. colour. Masked priming studies have shown that feed-forward activity in the ventral P-pathway on its own supports non-conscious processing of contour and surface features. The dorsal M-pathway activity contributes directly to conscious vision of motion and indirectly to object vision by projecting to prefrontal cortex, which in turn injects top-down neural activity into the ventral P-pathway and there ‘ignites’ feed-forward–re-entrant loops deemed necessary for conscious vision. Moreover, an object''s shape or contour remains invisible without the prior conscious registration of its surface properties, which for that reason are taken to comprise fundamental visual qualia. Besides suggesting avenues for future research, these developments bear on several recent and past philosophical issues.     

A new neural framework for visuospatial processing

The division of cortical visual processing into distinct dorsal and ventral streams is a key framework that has guided visual neuroscience. The characterization of the ventral stream as a 'What' pathway is relatively uncontroversial, but the nature of dorsal stream processing is less clear. Originally proposed as mediating spatial perception ('Where'), more recent accounts suggest it primarily serves non-conscious visually guided action ('How'). Here, we identify three pathways emerging from the dorsal stream that consist of projections to the prefrontal and premotor cortices, and a major projection to the medial temporal lobe that courses both directly and indirectly through the posterior cingulate and retrosplenial cortices. These three pathways support both conscious and non-conscious visuospatial processing, including spatial working memory, visually guided action and navigation, respectively.     

Levels of processing during non-conscious perception: a critical review of visual masking

Understanding the extent and limits of non-conscious processing is an important step on the road to a thorough understanding of the cognitive and cerebral correlates of conscious perception. In this article, we present a critical review of research on subliminal perception during masking and other related experimental conditions. Although initially controversial, the possibility that a broad variety of processes can be activated by a non-reportable stimulus is now well established. Behavioural findings of subliminal priming indicate that a masked word or digit can have an influence on perceptual, lexical and semantic levels, while neuroimaging directly visualizes the brain activation that it evokes in several cortical areas. This activation is often attenuated under subliminal presentation conditions compared to consciously reportable conditions, but there are sufficiently many exceptions, in paradigms such as the attentional blink, to indicate that high activation, per se, is not a sufficient condition for conscious access to occur. We conclude by arguing that for a stimulus to reach consciousness, two factors are jointly needed: (i) the input stimulus must have enough strength (which can be prevented by masking) and (ii) it must receive top-down attention (which can be prevented by drawing attention to another stimulus or task). This view leads to a distinction between two types of non-conscious processes, which we call subliminal and preconscious. According to us, maintaining this distinction is essential in order to make sense of the growing neuroimaging data on the neural correlates of consciousness.     

Bioethics, vulnerability, and protection

What makes individuals, groups, or even entire countries vulnerable? And why is vulnerability a concern in bioethics? A simple answer to both questions is that vulnerable individuals and groups are subject to exploitation, and exploitation is morally wrong. This analysis is limited to two areas. First is the context of multinational research, in which vulnerable people can be exploited even if they are not harmed, and harmed even if they are not exploited. The type of multinational research likely to raise the most ethical concerns is that in which the investigators or sponsors are from a powerful industrialised country or a giant pharmaceutical company and the research is conducted in a developing country. Second is the situation of women, who are made vulnerable in cultural settings or in entire countries in which they are oppressed and powerless. In the face of cultural values and practices, or governmental policies, these women suffer serious consequences for their health and even lives. Examples are provided, and it is suggested that in some cases vulnerable individuals can be harmed but not exploited. On the positive side, recent developments reveal a new awareness of exploitation and efforts to enhance the ability of developing countries to protect themselves and their citizens from exploitation at the hands of powerful sponsors of research. In addition, human rights principles are increasingly being used to monitor the actions (or inaction) of governments regarding women's reproductive rights and vulnerability with respect to HIV/AIDS, and to take remedial actions.     

Do Embryos Have Interests? Why Embryos Are Identical to Future Persons but Not Harmed by Death

Are embryos deserving of moral consideration in our actions? A standard view suggests that embryos are considerable only if they have interests. One argument for embryonic interests contends that embryos are harmed by death because they are deprived of valuable future lives as adult persons. Some have challenged this argument on the grounds that embryos aren’t identical to adults: either due to the potential for embryos to twin or because we do not exist until the fetus develops consciousness. These arguments fail to show that embryos do not have future adult lives. There is a better reason to think that embryos cannot have interests; namely, because they are not capable of having desires. Others have held this view but have not sufficiently justified it. The justification lies in the fact that the capacity for desires is necessary to make sense of the normativity of interests.     

Ectogenesis,abortion and a right to the death of the fetus

Many people believe that the abortion debate will end when at some point in the future it will be possible for fetuses to develop outside the womb. Ectogenesis, as this technology is called, would make possible to reconcile pro‐life and pro‐choice positions. That is because it is commonly believed that there is no right to the death of the fetus if it can be detached alive and gestated in an artificial womb. Recently Eric Mathison and Jeremy Davis defended this position, by arguing against three common arguments for a right to the death of the fetus. I claim that their arguments are mistaken. I argue that there is a right to the death of the fetus because gestating a fetus in an artificial womb when genetic parents refuse it violates their rights not to become a biological parent, their rights to genetic privacy and their property rights. The right to the death of the fetus, however, is not a woman's right but genetic parents’ collective right which only can be used together.     

Genetic therapy, person-regarding reasons and the determination of identity -- a reply to Robert Elliot

I have outlined two ways of defending the claim that there are so-called person-regarding reasons for practising gene therapy on human conceptuses. One is metaphysical and concerns our nature and identity. The upshot of it is that, in cases of most interest, this therapy does not affect our identity, by bringing into existence anyone of our kind who would not otherwise have existed. The other defence is value theoretical and claims that even if genetic therapy were to affect the identity of beings our kind, there could still be person-regarding reasons for performing it, since we can be benefited and harmed by being caused to exist or not to exist. Robert Elliot has attacked both of these lines, and my present objective is to show how his criticisms can be deflected.     

A model of subjective report and objective discrimination as categorical decisions in a vast representational space

Subliminal perception studies have shown that one can objectively discriminate a stimulus without subjectively perceiving it. We show how a minimalist framework based on Signal Detection Theory and Bayesian inference can account for this dissociation, by describing subjective and objective tasks with similar decision-theoretic mechanisms. Each of these tasks relies on distinct response classes, and therefore distinct priors and decision boundaries. As a result, they may reach different conclusions. By formalizing, within the same framework, forced-choice discrimination responses, subjective visibility reports and confidence ratings, we show that this decision model suffices to account for several classical characteristics of conscious and unconscious perception. Furthermore, the model provides a set of original predictions on the nonlinear profiles of discrimination performance obtained at various levels of visibility. We successfully test one such prediction in a novel experiment: when varying continuously the degree of perceptual ambiguity between two visual symbols presented at perceptual threshold, identification performance varies quasi-linearly when the stimulus is unseen and in an ‘all-or-none’ manner when it is seen. The present model highlights how conscious and non-conscious decisions may correspond to distinct categorizations of the same stimulus encoded by a high-dimensional neuronal population vector.     

The effect of stimulus duration and motor response in hemispatial neglect during a visual search task

Patients with hemispatial neglect exhibit a myriad of profound deficits. A hallmark of this syndrome is the patients' absence of awareness of items located in their contralesional space. Many studies, however, have demonstrated that neglect patients exhibit some level of processing of these neglected items. It has been suggested that unconscious processing of neglected information may manifest as a fast denial. This theory of fast denial proposes that neglected stimuli are detected in the same way as non-neglected stimuli, but without overt awareness. We evaluated the fast denial theory by conducting two separate visual search task experiments, each differing by the duration of stimulus presentation. Specifically, in Experiment 1 each stimulus remained in the participants' visual field until a response was made. In Experiment 2 each stimulus was presented for only a brief duration. We further evaluated the fast denial theory by comparing verbal to motor task responses in each experiment. Overall, our results from both experiments and tasks showed no evidence for the presence of implicit knowledge of neglected stimuli. Instead, patients with neglect responded the same when they neglected stimuli as when they correctly reported stimulus absence. These findings thus cast doubt on the concept of the fast denial theory and its consequent implications for non-conscious processing. Importantly, our study demonstrated that the only behavior affected was during conscious detection of ipsilesional stimuli. Specifically, patients were slower to detect stimuli in Experiment 1 compared to Experiment 2, suggesting a duration effect occurred during conscious processing of information. Additionally, reaction time and accuracy were similar when reporting verbally versus motorically. These results provide new insights into the perceptual deficits associated with neglect and further support other work that falsifies the fast denial account of non-conscious processing in hemispatial visual neglect.     

Consciousness: here,there and everywhere?

The science of consciousness has made great strides by focusing on the behavioural and neuronal correlates of experience. However, while such correlates are important for progress to occur, they are not enough if we are to understand even basic facts, for example, why the cerebral cortex gives rise to consciousness but the cerebellum does not, though it has even more neurons and appears to be just as complicated. Moreover, correlates are of little help in many instances where we would like to know if consciousness is present: patients with a few remaining islands of functioning cortex, preterm infants, non-mammalian species and machines that are rapidly outperforming people at driving, recognizing faces and objects, and answering difficult questions. To address these issues, we need not only more data but also a theory of consciousness—one that says what experience is and what type of physical systems can have it. Integrated information theory (IIT) does so by starting from experience itself via five phenomenological axioms: intrinsic existence, composition, information, integration and exclusion. From these it derives five postulates about the properties required of physical mechanisms to support consciousness. The theory provides a principled account of both the quantity and the quality of an individual experience (a quale), and a calculus to evaluate whether or not a particular physical system is conscious and of what. Moreover, IIT can explain a range of clinical and laboratory findings, makes a number of testable predictions and extrapolates to a number of problematic conditions. The theory holds that consciousness is a fundamental property possessed by physical systems having specific causal properties. It predicts that consciousness is graded, is common among biological organisms and can occur in some very simple systems. Conversely, it predicts that feed-forward networks, even complex ones, are not conscious, nor are aggregates such as groups of individuals or heaps of sand. Also, in sharp contrast to widespread functionalist beliefs, IIT implies that digital computers, even if their behaviour were to be functionally equivalent to ours, and even if they were to run faithful simulations of the human brain, would experience next to nothing.     

The scope and limits of top-down attention in unconscious visual processing

Attentional selection plays a critical role in conscious perception. When attention is diverted, even salient stimuli fail to reach visual awareness. Attention can be voluntarily directed to a spatial location or a visual feature for facilitating the processing of information relevant to current goals. In everyday situations, attention and awareness are tightly coupled. This has led some to suggest that attention and awareness might be based on a common neural foundation, whereas others argue that they are mediated by distinct mechanisms. A body of evidence shows that visual stimuli can be processed at multiple stages of the visual-processing streams without evoking visual awareness. To illuminate the relationship between visual attention and conscious perception, we investigated whether top-down attention can target and modulate the neural representations of unconsciously processed visual stimuli. Our experiments show that spatial attention can target only consciously perceived stimuli, whereas feature-based attention can modulate the processing of invisible stimuli. The attentional modulation of unconscious signals implies that attention and awareness can be dissociated, challenging a simplistic view of the boundary between conscious and unconscious visual processing.     

Attitude of zoo visitors to the idea of feeding live prey to zoo animals

Two hundred UK zoo visitors were asked about their attitudes regarding the feeding of live prey to zoo animals. All visitors agreed with live insects being fed to lizards, providing it was done off-exhibit, and only 4% objected if done on-exhibit. Seventy-two percent of visitors agreed with live fish being fed to penguins on-exhibit and 84.5% agreed to feeding live fish off-exhibit. However, only 32% agreed to a live rabbit being fed to a cheetah on exhibit, whereas 62.5% agreed to this if done off-exhibit. In general we found female interviewees more likely to object to the feeding of live vertebrate prey. Comments volunteered by interviewees suggested that they agreed with feeding live vertebrate prey because ‘it is natural’. If they objected, it was because ‘it would upset them or their children’. Zoo Biol 16:343–347, 1997. © 1997 Wiley-Liss, Inc.     

WHEN DID YOU FIRST BEGIN TO FEEL IT? — LOCATING THE BEGINNING OF HUMAN CONSCIOUSNESS

In this paper we attempt to sharpen and to provide an answer to the question of when human beings first become conscious. Since it is relatively uncontentious that a capacity for raw sensation precedes and underpins all more sophisticated mental capacities, our question is tantamount to asking when human beings first have experiences with sensational content. Two interconnected features of our argument are crucial. First, we argue that experiences with sensational content are supervenient on facts about electrical activity in the cerebral cortex which can be ascertained through EEG readings. Second, we isolate from other notions of a'functioning brain'that which is required to underpin the view that a cortex is functioning in a way which could give rise to rudimentary conscious experiences. We investigate the development in the human fetus of the anatomical and chemical pathways which underpin (immature) cortical activity and the growth and maturation of the electrical circuitry specifically associated with sensational content in adult experience. We conclude (tentatively) that a fetus becomes conscious at about 30 to 35 weeks after conception; an answer based on a careful analysis of EEG readings at various stages of cortical development. Finally, we survey the possible ethical ramifications of our answer.     

Ethical issues in recommending and offering fetal therapy

Fetal therapy should be offered and recommended for a viable fetus when these criteria are met: invasive therapy is reliably judged to have a high probability of being life-saving or of preventing serious and irreversible disease, injury, or disability for the fetus and for the child it can become; such therapy is reliably judged to involve low mortality risk and low or manageable risk of serious disease, injury, or disability to the viable fetus and the child it can become; and the mortality risk and the risk of disease, injury, or disability to the pregnant women is reliably judged to be low or manageable. When one or more of these criteria are not satisfied, intervention is experimental and can only be offered, not recommended, on the basis of benefit to future patients and the autonomy of the pregnant woman.     

Commentary: ethics of clinical research without patients' consent.

What makes a research project ethical? A series of criteria need to be satisfied. Difficulties arise when only some of them can be satisfied or, as in the case of this trial, when two of them are mutually exclusive. The criteria are that the research is aimed at obtaining a desirable end, that the research subjects will not be harmed by being in the trial, and that the research subjects are consulted before going enrolled into the research.     

Human death--a view from the beginning of life

This paper presents a simple argument against definitions of the death of a human being in terms of death, or the cessation of functioning, of its brain: a human being is alive, and so is capable of dying, before it acquires a brain. Although a more accurate definition is sketched, it is stressed that it should not be taken for granted that it is ethically urgent to work out such a definition. What morally matters more than the death of a human being may be something for which its death is sufficient, but not necessary, namely the irreversible loss of its capacity for consciousness. It is when we lose this capacity that we lose our moral standing, as subjects who can be benefited and harmed, and who can have rights. But, as is also suggested, the loss of this capacity is ill suited to be what the death of a human being definitionally consists of.