Combinatorial network optimization appears to fit well as a model of brain structure: connections in the brain are a critically constrained resource, hence their deployment in a wide range of cases is finely optimized to “‘save wire". This review focuses on minimization of large-scale costs, such as total volume for mammal dendrite and axon arbors and total wirelength for positioning of connected neural components such as roundworm ganglia (and also mammal cortex areas). Phenomena of good optimization raise questions about mechanisms (...) for their achievement: the examples of optimized neuroanatomy here turn out to include candidates for some of the most complex biological structures known to be derivable purely from simple physical energy minimization processes. Part of the functional role of such fine-tuned wiring optimization may be as a compact strategy for generating self-organizing complex neuroanatomical.. (shrink)
Neuroanatomy and neurophysiology are insufficient to specify function. Modeling is essential to elucidate function, but psychophysics is also required. An example is the cognitive and sensorimotor branches of the visual system: anatomy shows direct cross talk between the branches. Psychophysics in normal humans shows links from cognitive to sensorimotor, but the reverse link is excluded by visual illusions affecting the cognitive system but not the sensorimotor system.
The present review of literature surveys two main issues related to self-referential processes: (1) Where in the brain are these processes located, and do they correlate with brain areas uniquely specialized in self-processing? (2) What are the empirical and theoretical links between inner speech and self-awareness? Although initial neuroimaging attempts tended to favor a right hemispheric view of selfawareness, more recent work shows that the brain areas which support self-related processes are located in both hemispheres and are not uniquely activated (...) during self-reflective tasks. Furthermore, self-awareness at least partially relies on internal speech. An activation of Broca's area (which is known to sustain inner speech) is observed in a significant number of brain-imaging studies of self-reflection. Loss of inner speech following brain damage produces self-awareness deficits. Inner speech most likely can internally reproduce social mechanisms leading to self-awareness. Also, the process of self-reflection can be seen as being a problem-solving task, and self-talk as being a cognitive tool the individual uses to effectively work on the task. It is noted that although a large body of knowledge already exists on self-awareness, little is known about individual differences in dispositional self-focus and types of self-attention (e.g., rumination vs. self-reflection). (shrink)
Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the ‘dynamic core’). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized (...) properties of consciousness, both physiological (for example, consciousness is associated with widespread, relatively fast, low amplitude interactions in the thalamocortical system), and phenomenal (for example, consciousness involves the existence of a private flow of events available only to the experiencing subject). While no theory accounts fully for all of these properties at present, we find that ND and its recent extensions fare well. (shrink)
A unifying theory of general anesthetic-induced unconsciousness must explain the common mechanism through which various anesthetic agents produce unconsciousness. Functional-brain-imaging data obtained from 11 volunteers during general anesthesia showed specific suppression of regional thalamic and midbrain reticular formation activity across two different commonly used volatile agents. These findings are discussed in relation to findings from sleep neurophysiology and the implications of this work for consciousness research. It is hypothesized that the essential common neurophysiologic mechanism underlying anesthetic-induced unconsciousness is, as with (...) sleep-induced unconsciousness, a hyperpolarization block of thalamocortical neurons. A model of anesthetic-induced unconsciousness is introduced to explain how the plethora of effects anesthetics have on cellular functioning ultimately all converge on a single neuroanatomic/neurophysiologic system, thus providing for a unitary physiologic theory of narcosis related to consciousness. (shrink)
Possible systemic effects of general anesthetic agents on neural information processing are discussed in the context of the thalamocortical suppression hypothesis presented by Drs. Alkire, Haier, and Fallon (this issue) in their PET study of the anesthetized state. Accounts of the neural requisites of consciousness fall into two broad categories. Neuronal-specificity theories postulate that activity in particular neural populations is sufficient for conscious awareness, while process-coherence theories postulate that particular organizations of neural activity are sufficient. Accounts of anesthetic narcosis, on (...) the other hand, explain losses of consciousness in terms of neural signal-suppressions, transmission blocks, and the disruptions of signal interpretation. While signal-suppression may account for the actions of some anesthetic agents, the existence of anesthetics, such as choralose, that cause both loss of consciousness and elevated discharge rates, is problematic for a general theory of narcosis that is based purely on signal suppression and transmission-block. However, anesthetic agents also alter relative firing rates and temporal discharge patterns that may disrupt the coherence of neural signals and the functioning of the neural networks that interpret them. It is difficult at present, solely on the basis of regional brain metabolic rates, to test process-coherence hypotheses regarding organizational requisites for conscious awareness. While these pioneering PET studies have great merit as panoramic windows of mind-brain correlates, wider ranges of theory and empirical evidence need to be brought into the formulation of truly comprehensive theories of consciousness and anesthesia. (shrink)
What is the connection between mirror processes and mindreading? The paper begins with definitions of mindreading and of mirroring processes. It then advances four theses: (T1) mirroring processes in themselves do not constitute mindreading; (T2) some types of mindreading (“low-level” mindreading) are based on mirroring processes; (T3) not all types of mindreading are based on mirroring (“high-level” mindreading); and (T4) simulation-based mindreading includes but is broader than mirroring-based mindreading. Evidence for the causal role of mirroring in mindreading is drawn from (...) intention attribution, emotion attribution, and pain attribution. Arguments for the limits of mirroring-based mindreading are drawn from neuroanatomy, from the lesser liability to error of mirror-based mindreading, from the role of imagination in some types of mindreading, and from the restricted range of mental states involved in mirroring. “High-level” simulational mindreading is based on enactment imagination, perspective shifts, or self-projection, which are found in activities like prospection and memory as well as theory of mind. The role of cortical midline structures in executing these activities is examined. (shrink)
It is suggested that the anatomical structures whichmediate consciousness evolved as decisiveembellishments to a (non-conscious) design strategypresent even in the simplest monocellular organisms.Consciousness is thus not the pinnacle of ahierarchy whose base is the primitive reflex, becausereflexes require a nervous system, which the monocelldoes not possess. By postulating that consciousness isintimately connected to self-paced probing of theenvironment, also prominent in prokaryotic behavior,one can make mammalian neuroanatomy amenable todramatically simple rationalization.
Depending on how one looks at it, we have been enjoying or suffering a significant empirical turn in moral psychology during this first decade of the 21st century. While philosophers have, from time to time, considered empirical matters with respect to morality, those who took an interest in actual (rather than ideal) moral agents were primarily concerned with whether particular moral theories were ‘too demanding’ for creatures like us (Flanagan, 1991; Williams, 1976; Wolf, 1982). Faithful adherence to Utilitarianism or Kantianism (...) would appear to be inconsistent with other things we value, like personal integrity and flourishing, which depend upon pursuing individually determined projects and ways of life in rather single-minded ways. Maximizing the good is a full-time job, and the impartiality recommended by Kantian theory can get in the way of showing special care for those we know and love. All this is standard philosophical fare. However, more recently, philosophers and psychologists have begun to treat moral psychology as a legitimate branch of cognitive science. They inquire into the evolution of morality (e.g., Joyce, 2007; Nichols 2004), debate the human uniqueness of moral capacities (e.g., deWaal, 2006; Hauser, 2006), investigate the causal etiology of moral judgments (e.g., Haidt & Greene, 2002; Hauser et al., 2006; Prinz, 2006), attempt to map the neuroanatomy of moral reasoning (e.g., Greene et al., 2001; Greene et al., 2004; Moll, et al., 2005), and consider what other affective and cognitive capacities are required by a creature who sees the world in moral terms. (See also Sinnott-Armstrong, 2007, 2008a, 2008b). 1 In this essay, I discuss two issues whose interdependence and central importance for empirically informed moral psychology have not been fully grasped, or so I believe. First is what I call the Explananda Challenge. Let us assume that the primary question for moral psychology is this: How is it possible for human beings to be moral creatures? Deceptively simple, this question obscures a number of rather more difficult ones.. (shrink)
Delusions are currently characterised as false beliefs produced by incorrect inference about external reality (DSM IV). This inferential conception has proved hard to link to explanations pitched at the level of neurobiology and neuroanatomy. This paper provides that link via a neurocomputational theory, based on evolutionary considerations, of the role of the prefrontal cortex in regulating offline cognition. When pathologically neuromodulated the prefrontal cortex produces hypersalient experiences which monopolise offline cognition. The result is characteristic psychotic experiences and patterns of thought. (...) This bottom-up account uses neural network theory to integrate recent theories of the role of dopamine in delusion with the insights of inferential accounts. It also provides a general model for evolutionary psychiatry which avoids theoretical problems imported from evolutionary psychology. (shrink)
The excellent and highly interesting commentaries address the following concerns: (1) neuroanatomy and neurophysiology of catatonia; (2) cognitive-motor deficits in catatonia; (3) conceptual issues; (4) general methodology in neuropsychiatric research; and (5) neurophilosophical implications. The specific problems, issues, and aspects raised by the different commentators are grouped under these categories in Table R1 presented below. These five areas of concern are then discussed in the order listed in the five sections of the Response.
This paper discusses recent neuroscientific research that indicates a solution for what we label the ''causal problem'' of pain qualia, the problem of how the brain generates pain qualia. In particular, the data suggest that pain qualia naturally supervene on activity in a specific brain region: the anterior cingulate cortex (ACC). The first section of this paper discusses several philosophical concerns regarding the nature of pain qualia. The second section overviews the current state of knowledge regarding the neuroanatomy and physiology (...) of pain processing. The third section highlights the recent research by Rainville et al. [(1997) Pain affect encoded in human anterior cingulate but not somatosensory cortex, Science, 277, 968-971], which suggests that pain affect is encoded in the ACC. The final section of the paper spells out exactly how these data affect the causal problem of pain qualia. (shrink)
To date, a wide range of interdisciplinary scholarship has done little to clarify either the why or the how of empathy. Preston & de Waal (P&deW) attempt to remedy this, although it remains unclear whether empathy consists of two discrete processes, or whether a perceptual and motor component are joined in some sort of behavioral inevitability. Although it is appealing to offer a neuroanatomy of empathy, the present level of neuropsychology may not support such reductionism.
A new view of the functional role of the left anterior cortex in language use is proposed. The experimental record indicates that most human linguistic abilities are not localized in this region. In particular, most of syntax (long thought to be there) is not located in Broca's area and its vicinity (operculum, insula, and subjacent white matter). This cerebral region, implicated in Broca's aphasia, does have a role in syntactic processing, but a highly specific one: It is the neural home (...) to receptive mechanisms involved in the computation of the relation between transformationally moved phrasal constituents and their extraction sites (in line with the Trace-Deletion Hypothesis). It is also involved in the construction of higher parts of the syntactic tree in speech production. By contrast, basic combinatorial capacities necessary for language processing – for example, structure-building operations, lexical insertion – are not supported by the neural tissue of this cerebral region, nor is lexical or combinatorial semantics. The dense body of empirical evidence supporting this restrictive view comes mainly from several angles on lesion studies of syntax in agrammatic Broca's aphasia. Five empirical arguments are presented: experiments in sentence comprehension, cross-linguistic considerations (where aphasia findings from several language types are pooled and scrutinized comparatively), grammaticality and plausibility judgments, real-time processing of complex sentences, and rehabilitation. Also discussed are recent results from functional neuroimaging and from structured observations on speech production of Broca's aphasics. Syntactic abilities are nonetheless distinct from other cognitive skills and are represented entirely and exclusively in the left cerebral hemisphere. Although more widespread in the left hemisphere than previously thought, they are clearly distinct from other human combinatorial and intellectual abilities. The neurological record (based on functional imaging, split-brain and right-hemisphere-damaged patients, as well as patients suffering from a breakdown of mathematical skills) indicates that language is a distinct, modularly organized neurological entity. Combinatorial aspects of the language faculty reside in the human left cerebral hemisphere, but only the transformational component (or algorithms that implement it in use) is located in and around Broca's area. Key Words: agrammatism; aphasia; Broca's area; cerebral localization; dyscalculia; functional neuroanatomy; grammatical transformation; modularity; neuroimaging; syntax; trace deletion. (shrink)
Evolutionary thinking has expanded in the last decades, spreading from its traditional stronghold - the explanation of speciation and adaptation in Biology - to new domains including the human sciences. The essays in this collection attest to the illuminating power of evolutionary thinking when applied to the understanding of the human mind. The contributors to Cognition, Evolution and Rationality use an evolutionary standpoint to approach the nature of the human mind, including both cognitive and behavioral functions. Cognitive science is by (...) its nature an interdisciplinary subject and the essays use a variety of disciplines including the Philosophy of Science, the Philosophy of Mind, Game Theory, Robotics and Computational Neuroanatomy to investigate the workings of the mind. The topics covered by the essays range from general methodological issues to long-standing philosophical problems such as how rational human beings actually are. This book will be of interest across a number of fields, including philosophy, evolutionary theory and cognitive science. (shrink)
A developmental theory of erotic/romantic attraction is presented that provides the same basic account for opposite-sex and same-sex desire in both men and women. It proposes that biological variables, such as genes, prenatal hormones, and brain neuroanatomy, do not code for sexual orientation per se but for childhood temperaments that influence a child's preferences for sex-typical or sex-atypical activities and peers. These preferences lead children to feel different from opposite-or same-sex peers ââ¬â to perceive them as dissimilar, unfamiliar, and exotic. (...) This, in turn, produces heightened nonspecific autonomic arousal that subsequently gets eroticized to that same class of dissimilar peers: Exotic becomes erotic. Specific mechanisms for effecting this transformation are proposed. The theory claims to accommodate both the empirical evidence of the biological essen-. (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)
What were the circumstances that led to the development of our cognitive abilities from a primitive hominid to an essentially modern human? The answer to this question is of profound importance to understanding our present nature. Since the steep path of our cognitive development is the attribute that most distinguishes humans from other mammals, this is also a quest to determine human origins. This collection of outstanding scientific problems and the revelation of the many ways they can be addressed indicates (...) the scope of the field to be explored and reveals some avenues along which research is advancing. Distinguished scientists and researchers who have advanced the discussion of the mind and brain contribute state-of-the-art presentations of their field of expertise. Chapters offer speculative and provocative views on topics such as body, culture, evolution, feelings, genetics, history, humor, knowledge, language, machines, neuroanatomy, pathology, and perception. This book will appeal to researchers and students in cognitive neuroscience, experimental psychology, cognitive science, and philosophy. * Includes a contribution by Noam Chomsky, one of the most cited authors of our time. (shrink)
Arbib et al. describe mathematical and computational models in neuroscience as well as neuroanatomy and neurophysiology of several important brain structures. This is a useful guide to mathematical and computational modelling of the structure and function of nervous system. The book highlights the need to develop a theory of brain functioning, and it offers some useful approaches and concepts.
Philosophers who discuss the emotions have usually treated amusement as a non-emotional mental state. Two prominent philosophers making this claim are Henri Bergson and John Morreall, who maintain that amusement is too abstract and intellectual to qualify as an emotion. Here, the merit of this claim is assessed. Through recent work in neuroanatomy there is reason to doubt the legitimacy of dichotomies that separate emotion and the intellect. Findings suggest that the neuroanatomical structure of amusement is similar to other commonly (...) recognized emotion states. On the basis of these it is argued that amusement should be considered an emotion. Les philosophes qui adressent la question des émotions traitent généralement l’état d’amusement comme un êtat mental excluant l’émotion. Parmi les philosophes importants à défendre cette thèse, Henri Bergson et John Morreall soutiennent que l’amusement est trop abstrait et intellectuel pour être tenu pour une émotion. Nous réévaluons cette thèse. De récents travaux en neuroanatomie fournissent des raisons de douter de la légitimité de la dichotomie entre émotion et intellect. Certaines autres découvertes suggèrent que la structure neuroanatomique de l’amusement est très similaire à d’autres états émotifs. Sur la base de ces travaux, nous argumentons que l’amusement doit être considéré comme une émotion. (shrink)
Striedter's book offers precious insight into the comparative neuroanatomy of vertebrate brains, but it stops short of addressing what their evolution is all about: how effectively neural networks process information important for survival. To understand the principles of brain evolution, neuroanatomy needs to be combined not only with genetics, neurophysiology, and ethology, but also with quantitative network analyses.
In this chapter, we aimed at further characterizing the functional neuroanatomy of the human rapid eye movement (REM) sleep at the population level. We carried out a meta-analysis of a large dataset of positron emission tomography (PET) scans acquired during wakefulness, slow wave sleep and REM sleep, and focused especially on the brain areas in which the activity diminishes during REM sleep. Results show that quiescent regions are confined to the inferior and middle frontal cortex and to the inferior parietal (...) lobule. Providing a plausible explanation for some of the features of dream reports, these findings may help in refining the concepts, which try to account for human cognition during REM sleep. In particular, we discuss the significance of these results to explain the alteration in executive processes, episodic memory retrieval and self representation during REM sleep dreaming as well as the incorporation of external stimuli into the dream narrative. (shrink)
So, here you are, reading about conscious will. How could this have happened? One way to explain it would be to examine the causes of your behavior. A team of scientists could study your reported thoughts, emotions, and motives, your genetics and your history of learning, experience, and development, your social situation and culture, your memories and reaction times, your physiology and neuroanatomy, and lots of other things as well. If they somehow had access to all the information they could (...) ever want, the assumption of psychology is that they could uncover the mechanisms that give rise to all your behavior, and so could certainly explain why you are reading these words at this moment. However, another way to explain the fact of your reading these lines is just to say that you decided to begin reading. You consciously willed what you are doing. The ideas of conscious will and psychological mechanism have an oil and water relationship, having never been properly reconciled. One way to put them together is to say that the mechanistic approach is the explanation preferred for scientific purposes, but that the person’s experience of conscious will is utterly convincing and important to the person – and so must be understood scientifically as well. The mechanisms underlying the experience of will are themselves a fundamental topic of scientific study. (shrink)
Although great progress in neuroanatomy and physiology has occurred lately, we still cannot go directly to those levels to discover the neural mechanisms of higher cognition and consciousness. But we can use neurocomputational methods based on these details to push this project forward. Here we describe vector subtraction as an operation that computes sequential paths through high-dimensional vector spaces. Vector-space interpretations of network activity patterns are a fruitful resource in recent computational neuroscience. Vector subtraction also appears to be implemented neurally (...) in primate frontal eye field activity, which computes dimensions of saccadic eye movements. We use this apparent neural implementation as a model and construct from it a general neurocomputational account of an important type of sequential cognitive and conscious process. We defend the biological plausibility of all components of the general model and show that it yields testable anatomical and physiological predictions. We close by suggesting some interesting consequences for consciousness if our model characterizes correctly the neural mechanisms producing a common type of episode in our conscious streams. (shrink)
The proposal that the hippocampus is important for the encoding of episodic information, but not familiarity-based recognition, is incompatible with the available data. An alternative way to think about functional specialization within the medial temporal lobe memory system is suggested, based on neuroanatomy.
The important Hebbian architecture for language may not be the phonological networks of perisylvian cortex, but rather the semantic networks of limbic cortex. Although the high-frequency EEG findings are intriguing, the results may not yet warrant a confident theory of neural assemblies. Nonetheless, Pulvermüller succeeds in framing a comprehensive theory of language function in the literal terms of neuroanatomy and neurophysiology.
In general, we endorse Aggleton & Brown's thesis that the neuroanatomy of amnesia comprises two functionally distinct systems, but we are disappointed in the lack of detail regarding the critical functional contribution of the hippocampus. We also take issue with the characterization of the cortical areas surrounding the hippocampus, particularly the decreased emphasis on the cortical input to the hippocampus.
What is the relationship between a visual percept and the underlying neuronal activity in parts of the brain? This manifesto reviews the theoretical framework of Crick and Kochfor answering these questions based on the neuroanatomy and physiology of mammalian cortex and associated subcortical structures. This evidence suggests that primates are not directly aware of neural activity in primary visual cortex, although they may be aware of such activity in extrastriate cortical areas. Psychophysical evidence in humans supporting this hypothesis is discussed.
The target article is an elegant synthesis of the developmental and functional data and views on the evolutionary origin of the mammalian isocortex, integrating results from cell and molecular biology, experimental neuroanatomy, and chemoarchitectonic studies. Complementarily, we give here an account of two modes of isocortical evolution (prosomere reshuffling and invention) in terms of costs of radiation and neural tissue.
Machine generated contents note: Part 1 - The Constituent Disciplines of Cognitive Science -- Philosophical Epistemology -- Glossary -- 1.0 What is Philosophical Epistemology? -- 1.1 The reduced history of Philosophy Part I - The Classical Age -- 1.2 Mind and World - The problem of objectivity -- 1.3 The reduced history of Philosophy Part II - The twentieth century -- 1.4 The philosophy of Cognitive Science -- 1.5 Mind in Philosophy: summary -- 1.6 The Nolanian Framework (so far) -- (...) Psychology -- 2.0 Why is Psychology so difficult? -- 2.1 A brief history of Experimental Psychology -- 2.2 Methodologies in Psychology -- 2.3 Perception -- 2.4 Memory -- 2.5 Mind in Psychology -- Linguistics -- 3.0 Introduction -- 3.1 Why Linguistics? -- 3.2 Computation and Linguistics -- 3.3 The main grammatical theories -- 3.4 Language development and linguistics -- 3.5 Toward a definition of context -- 3.6 The multifarious uses of Language -- 3.7 Linguistics and Computational Linguistics -- 3.8 Language and other symbol systems -- 3.9 On the notion of context -- 3.10 Mind in Linguistics: summary -- Neuroscience -- 4.0 The constituent disciplines of Neuroscience -- 4.1 The methodology of Neuroscience -- 4.2 Gross Neuroanatomy -- 4.3 Some relevant findings -- 4.4 Connectionism (PDP) -- 4.5 The victory of Neuroscience? -- 4.6 Mind in Neuroscience: summary -- Artificial Intelligence -- 5.0 Introduction -- 5.1 Al and Cognitive Science -- 5.2 Skeptics and their techniques -- 5.3 Al as Computer Science -- 5.4 Al as software -- 5.5 The current methodological debate -- 5.6 Context, syntax and semantics -- 5.7 Mind in Al -- 5.8 Texts on Al -- Etholoqy and Ethnoscience -- 6.1 Etology -- 6.2 Ethnoscience -- 6.3 Mind in Ethology arid Ethnoscience -- Part II - A New Foundation for Cognitive Science -- - Symbol Systems -- 7.1 Characteristics of symbol systems -- 7.2 Context and the layers of symbol systems -- 7.3 Mind and symbol systems -- Consciousness and Selfhood -- 8.0 Introduction -- 8.1 Cognitive views -- 8.2 What is at stake? -- 8.3 Consciousness as treated in Philosophy -- 8.4 The Development of Selfhood -- 8.5 The minimal requirements for this theory -- 8.6 Self as a filter -- 8.7 Self and motivation -- 8.8 Conclusions -- 8.9 Recent developments -- Cognitive Science and the Search for Mind -- 9.1 Introduction -- 9.2 Review -- 9.3 A Theory of Mind anyone? -- 9.4 Foundational considerations -- 9.5 Coda: the Nolanian Framework. (shrink)
The stratification in depth of chromatically homogeneous overlapping figures depends on a minimization rule which assigns the status of being “in front” to the figure that requires the formation of shorter modal contours. This rule has been proven valid also in birds, whose visual neuroanatomy is radically different from that of other mammals, thus suggesting an example of evolutionary convergence toward a perceptual universal. [Shepard].
