Neural correlates of saccadic suppression in humans

When you look into a mirror and move your eyes left to right, you will see that you cannot observe your own eye movements. This demonstrates the phenomenon of saccadic suppression: during saccadic eye movements, visual sensitivity is much reduced. Given that humans make more than 100,000 eye movements each day, it is clear why suppression is needed: without it, the motion on the retina would prevent us from seeing anything at all. Psychophysical data show that suppression is stimulus selective: it is strongest for the kind of stimuli that preferentially activate magnocellular thalamic neurons. This has led to the hypothesis that saccadic suppression selectively targets the magnocellular stream. We used fMRI to find brain areas with a stimulus-selective suppression of the BOLD signal that matches the psychophysical data. We found such a neural correlate of saccadic suppression in the dorsal stream (hMT+, V7) and in ventral area V4. These areas receive magnocellular input; hence our findings are consistent with the magnocellular hypothesis. The range of effects in our data and in single cell data, however, argues against a single thalamic mechanism that suppresses all cortical input. Instead, we speculate that saccadic suppression relies on multiple mechanisms operating in different cortical areas.     

The logic of failure

Unlike other living creatures, humans can adapt to uncertainty. They can form hypotheses about situations marked by uncertainty and can anticipate their actions by planning. They can expect the unexpected and take precautions against it. In numerous experiments, we have investigated the manner in which humans deal with these demands. In these experiments, we used computer simulated scenarios representing, for example, a small town, ecological or economic systems or political systems such as a Third World country. Within these computer-simulated scenarios, the subjects had to look for information, plan actions, form hypotheses, etc.     

The Discourse of the Birds

Modern humans spend much of their time deploying a very rarefied form of intelligence, manipulating abstract symbols while their muscled body is mostly inert. Other animals, in a constant and largely unmediated relation with their earthly surroundings, think with the whole of their bodies. This kind of distributed sentience, this intelligence in the limbs, is especially keen in the case of birds of flight. Unlike most creatures of the ground, who must traverse an opaque surface of only two-plus dimensions as we make our way through the world, a soaring bird continually adjusts minute muscles in its wings to navigate an omnidimensional plenum of currents and interference patterns that alter from moment to moment. Flight itself may usefully be considered as a kind of thinking—as a sort of gliding within the mind. Moreover, since birds are commonly the most mobile inhabitants of any woodland, able to fly over and scan numerous events occurring on the ground, their varied utterances provide a crucial source of information for many other animals. This paper, written as a philosophic essay, explores avian cognition from a phenomenological standpoint. It then reflects upon the vocalizations of birds—noting the major role that such avian calls, cries, and songs have played in the development of human culture.     

Scanning Strategies Do Not Modulate Face Identification: Eye-Tracking and Near-Infrared Spectroscopy Study

Background

During face identification in humans, facial information is sampled (seeing) and handled (processing) in ways that are influenced by the kind of facial image type, such as a self-image or an image of another face. However, the relationship between seeing and information processing is seldom considered. In this study, we aimed to reveal this relationship using simultaneous eye-tracking measurements and near-infrared spectroscopy (NIRS) in face identification tasks.

Methodology/Principal Findings

22 healthy adult subjects (8 males and 14 females) were shown facial morphing movies in which an initial facial image gradually changed into another facial image (that is, the subject''s own face was changed to a familiar face). The fixation patterns on facial features were recorded, along with changes in oxyhemoglobin (oxyHb) levels in the frontal lobe, while the subjects identified several faces. In the self-face condition (self-face as the initial image), hemodynamic activity around the right inferior frontal gyrus (IFG) was significantly greater than in the familiar-face condition. On the other hand, the scanning strategy was similar in almost all conditions with more fixations on the eyes and nose than on other areas. Fixation time on the eye area did not correlate with changes in oxyHb levels, and none of the scanning strategy indices could estimate the hemodynamic changes.

Conclusions/Significance

We conclude that hemodynamic activity, i.e., the means of processing facial information, is not always modulated by the face-scanning strategy, i.e., the way of seeing, and that the right IFG plays important roles in both self-other facial discrimination and self-evaluation.     

Automata, Living and Non-Living: Descartes' Mechanical Biology and His Criteria for Life

Despite holding to the essential distinction between mind and body, Descartes did not adopt a life-body dualism. Though humans are the only creatures which can reason, as they are the only creatures whose body is in an intimate union with a soul, they are not the only finite beings who are alive. In the present note, I attempt to determine Descartes' criteria for something to be 'living.' Though certain passages associate such a principle with the presence of a properly functioning heart, I show that there are important reasons for also understanding life in terms of a degree of complexity of design.     

When encoding yields remembering: insights from event-related neuroimaging.

To understand human memory, it is important to determine why some experiences are remembered whereas others are forgotten. Until recently, insights into the neural bases of human memory encoding, the processes by which information is transformed into an enduring memory trace, have primarily been derived from neuropsychological studies of humans with select brain lesions. The advent of functional neuroimaging methods, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), has provided a new opportunity to gain additional understanding of how the brain supports memory formation. Importantly, the recent development of event-related fMRI methods now allows for examination of trial-by-trial differences in neural activity during encoding and of the consequences of these differences for later remembering. In this review, we consider the contributions of PET and fMRI studies to the understanding of memory encoding, placing a particular emphasis on recent event-related fMRI studies of the Dm effect: that is, differences in neural activity during encoding that are related to differences in subsequent memory. We then turn our attention to the rich literature on the Dm effect that has emerged from studies using event-related potentials (ERPs). It is hoped that the integration of findings from ERP studies, which offer higher temporal resolution, with those from event-related fMRI studies, which offer higher spatial resolution, will shed new light on when and why encoding yields subsequent remembering.     

Risk sensitivity and theory of mind in human coordination

What humans do when exposed to uncertainty, incomplete information, and a dynamic environment influenced by other agents remains an open scientific challenge with important implications in both science and engineering applications. In these contexts, humans handle social situations by employing elaborate cognitive mechanisms such as theory of mind and risk sensitivity. Here we resort to a novel theoretical model, showing that both mechanisms leverage coordinated behaviors among self-regarding individuals. Particularly, we resort to cumulative prospect theory and level-k recursions to show how biases towards optimism and the capacity of planning ahead significantly increase coordinated, cooperative action. These results suggest that the reason why humans are good at coordination may stem from the fact that we are cognitively biased to do so.     

Ecology's dark matter: The elusive and enigmatic niche

Ecologists are often frustrated that their universe, populated by strange and wilful creatures, seems fuzzy and unpredictable. Physicists, in contrast, seem to have it much better. But that's because we usually focus on Newtonian physics. In fact, physicists seem happy to live with all kinds of strange beasts, including dark matter, something they have never seen, but which they nevertheless believe makes up most of the matter in the universe. Here I argue that niches are ecology's dark matter. We are embarrassed by them, because we do not quite know what they are, and yet their presence can be universally felt; otherwise, ecological communities, like galaxies without dark matter, would simply collapse. I describe how we could potentially better describe these dark shapes that haunt our science and why this is important. In particular, I present the outline of a method for demonstrating whether or not plant species have complementary resource-use niches; something that has been difficult to show unequivocally. The presence of such resource-use niches would put to rest once and for all the notion of species equivalence and the neutral world that this assumption entails. I conclude that ecologists should take a leaf out of the physicists’ book and accept that the continued search for the esoteric niche is a legitimate and central (if frustrating) part of ecology.     

The Body as Gift,Resource or Commodity? Heidegger and the Ethics of Organ Transplantation

Three metaphors appear to guide contemporary thinking about organ transplantation. Although the gift is the sanctioned metaphor for donating organs, the underlying perspective from the side of the state, authorities and the medical establishment often seems to be that the body shall rather be understood as a resource. The acute scarcity of organs, which generates a desperate demand in relation to a group of potential suppliers who are desperate to an equal extent, leads easily to the gift’s becoming, in reality, not only a resource, but also a commodity. In this paper, the claim is made that a successful explication of the gift metaphor in the case of organ transplantation and a complementary defence of the ethical primacy of the giving of organs need to be grounded in a philosophical anthropology which considers the implications of embodiment in a different and more substantial way than is generally the case in contemporary bioethics. I show that Heidegger’s phenomenology offers such an alternative, with the help of which we can understand why body parts could and, indeed, under certain circumstances, should be given to others in need, but yet are neither resources nor properties to be sold. The phenomenological exploration in question is tied to fundamental questions about what kind of relationship we have to our own bodies, as well as about what kind of relationship we have to each other as human beings sharing the same being-in-the-world as embodied creatures.     

Relaxation of canine airway smooth muscle

Relaxation of airway smooth muscle is an inadequately understood yet critical process that, if impaired, may have significant implications for asthma. Here we explore why relaxation is an important process to consider, how it may determine airway hyperresponsiveness, and some of the factors that influence relaxation of the airway smooth muscle. These include mechanical and biochemical factors such as deep inspirations or large amplitude oscillation of the muscle, plastic properties of the muscle, the load the muscle experiences, calcium, phosphorylation of the myosin light chain, cytoskeletal proteins, and sensitization.     

A potent effect of observational learning on chimpanzee tool construction

Although tool use occurs in diverse species, its complexity may mark an important distinction between humans and other animals. Chimpanzee tool use has many similarities to that seen in humans, yet evidence of the cumulatively complex and constructive technologies common in human populations remains absent in free-ranging chimpanzees. Here we provide the first evidence that chimpanzees have a latent capacity to socially learn to construct a composite tool. Fifty chimpanzees were assigned to one of five demonstration conditions that varied in the amount and type of information available in video footage of a conspecific. Chimpanzees exposed to complete footage of a chimpanzee combining the two components to retrieve a reward learned to combine the tools significantly more than those exposed to more restricted information. In a follow-up test, chimpanzees that constructed tools after watching the complete demonstration tended to do so even when the reward was within reach of the unmodified components, whereas those that spontaneously solved the task (without seeing the modification process) combined only when necessary. Social learning, therefore, had a powerful effect in instilling a marked persistence in the use of a complex technique at the cost of efficiency, inhibiting insightful tool use.     

IL-21/IL-21R信号在IBD病变形成机制中作用的研究进展

炎症性肠病(Inflammatory bowel disease,IBD)的发病机制至今尚不明确,普遍认为是由肠黏膜免疫调节异常、持续性肠道感染、肠黏膜屏障缺损、遗传和环境等多种因素相互作用导致的。近年来,研究发现IBD患者血清中IL-21水平异常升高,提示IL-21/IL-21R信号可能在IBD的病变形成中发挥重要作用。IL-21是一种重要的具有多重生物学功能的细胞因子,通过对CD4+T细胞、CD8+T细胞、Th17细胞、B细胞、巨噬细胞、树突状细胞等多种细胞产生影响,从而参与IBD的发生发展。本文就IL-21/IL-21R信号在炎症性肠病发病机制中的研究进展进行综述。     

Review. The multiple roles of cultural transmission experiments in understanding human cultural evolution

In this paper, we explore how experimental studies of cultural transmission in adult humans can address general questions regarding the 'who, what, when and how' of human cultural transmission, and consequently inform a theory of human cultural evolution. Three methods are discussed. The transmission chain method, in which information is passed along linear chains of participants, has been used to identify content biases in cultural transmission. These concern the kind of information that is transmitted. Several such candidate content biases have now emerged from the experimental literature. The replacement method, in which participants in groups are gradually replaced or moved across groups, has been used to study phenomena such as cumulative cultural evolution, cultural group selection and cultural innovation. The closed-group method, in which participants learn in groups with no replacement, has been used to explore issues such as who people choose to learn from and when they learn culturally as opposed to individually. A number of the studies reviewed here have received relatively little attention within their own disciplines, but we suggest that these, and future experimental studies of cultural transmission that build on them, can play an important role in a broader science of cultural evolution.     

Defining and detecting crossover-interference mutants in yeast

The analysis of crossover interference in many creatures is complicated by the presence of two kinds of crossovers, interfering and noninterfering. In such creatures, the values of the traditional indicators of interference are subject not only to the strength of interference but also to the relative frequencies of crossing over contributed by the two kinds. We formalize the relationship among these variables and illustrate the possibilities and limitations of classical interference analysis with meiotic tetrad data from wild-type Saccharomyces cerevisiae and from mlh1 and ndj1 mutants.     

Observing a Movement Correction during Walking Affects Evoked Responses but Not Unperturbed Walking

Seeing an action activates neurons in the premotor, motor, and somatosensory cortex. Since a significant fraction of these pyramidal neurons project to the spinal motor circuits, a central question is why we do not automatically perform the actions that we see. Indeed, seeing an action increases both cortical and spinal excitability of consistent motor patterns that correspond to the observed ones. Thus, it is believed that such imitative motor patterns are either suppressed or remain at a sub-threshold level. This would predict, however, that seeing someone make a corrective movement while one is actively involved in the same action should either suppress evoked responses or suppress or modulate the action itself. Here we tested this prediction, and found that seeing someone occasionally stepping over an obstacle while walking on a treadmill did not affect the normal walking pattern at all. However, cutaneously evoked reflexes in the anterior tibial and soleus muscles were modulated as if the subject was stepping over an obstacle. This result thus indicates that spinal activation was not suppressed and was neither at sub-threshold motor resonance. Rather, the spinal modulation from observed stepping reflects an adaptive mechanism for regulating predictive control mechanisms. We conclude that spinal excitability during action observation is not an adverse side-effect of action understanding but reflects adaptive and predictive motor control.     

Making the case for human life extension: personal arguments

In the close to medium future, the life sciences might permit a vast extension of the human life span. I will argue that this is a very desirable development for the individual person. The question whether death is a harm to the dying is irrelevant here. All it takes is that being alive is good for the living person and not being alive is not good for anyone. Thus, living persons who expect to live on happily are rationally required to want to stay alive. Eventual uncertainty whether it will be possible to be happy in the future provides no objection, but rather an incentive to try. This view, however, may be naive in assuming that persons are unchanging entities that exist separately from their psychological information. Objections have been derived from reductionistic views that value our future experiences in a way that declines with time, so that there will be a future point beyond which only negligible value accrues. If we adopt such a view, then we cannot now be concerned to have experiences beyond that point. I argue that these arguments fail to take into account all the reasons we might have to be concerned for the future and all kinds of such concern that come from them. The adoption of a plausible reductionistic account can arguably weaken our concern for the future and certainly change its quality in important ways. But this provides no objection to the desire to live forever, nor to live at all.     

Success and Its Price: The Institutionalization and Political Relevance of Industrial Ecology

As industrial ecology (IE) solidifies conceptually and methodologically, and as it gains visibility and legitimacy in academia, industry, and government, it is important that the IE community periodically evaluate the status of its emerging institutional arrangements. At the same time, industrial ecologists should assess the political relations developing between the field and the larger world. We analyze four institutional criteria: professional legitimacy, viable clientele, entrepreneurial acumen, and occupational opportunities, as well as a more controversial fifth measure-political relevance. Drawing a comparison with the field of ecology, we argue that efforts to foster IE institutionally can, ironically, conflict with the objective of seeing IE become "the science and engineering of sustainability". The article concludes by reflecting on the importance of this kind of critical appraisal and on why many observers of the field remain hopeful.     

Some Consequences of Animal Domestication for Humans

ABSTRACT

Throughout human evolution our species has had many kinds of interactions with others, including predatory, competitive, parasitic, mutualistic, and commensal. We still have such interactions in the modern world, with the most important resulting from our domestication of other species. Domestication created new kinds of interaction by which we controlled the freedom and reproduction of certain animals. Because domesticated populations became dependent on humans various adaptations by humans were necessary, and it is argued that these influenced the cultural, and possibly biological, evolution of our species.     

Beyond the senses: perception,the environment,and vision impairment

The ‘sensory turn’ in anthropology has generated a significant literature on sensory perception and experience. Whilst much of this literature is critical of the compartmentalization of particular ‘senses’, there has been limited exploration of how anthropologists might examine sensory perception beyond ‘the senses’. Based on ethnographic fieldwork with people who have impaired vision walking the South Downs landscape in England, this article develops such an approach. It suggests that the experiences of seeing in blindness challenge the conceptualization of ‘vision’ (and ‘non-vision’). In place of ‘vision’ (as a sense), the article explores ‘activities of seeing’ – an approach that contextualizes the visual to examine the biographically constituted and idiosyncratic nature of perception within an environment. Through an ethnography of seeing with anatomical eyes and ‘seeing in the mind's eye’, it articulates an approach that avoids associating perception with anatomy, or compartmentalizing experience into ‘senses’.