It is the central hypothesis of this paper that the mental states commonly referred to as altered states of consciousness are principally due to transient prefrontal cortex deregulation. Supportive evidence from psychological and neuroscientific studies of dreaming, endurance running, meditation, daydreaming, hypnosis, and various drug-induced states is presented and integrated. It is proposed that transient hypofrontality is the unifying feature of all altered states and that the phenomenological uniqueness of each state is the result of the differential viability of various (...) frontal circuits. Using an evolutionary approach, consciousness is conceptualized as hierarchically ordered cognitive function. Higher-order structures perform increasingly integrative functions and thus contribute more sophisticated content. Although this implies a holistic approach to consciousness, such a functional hierarchy localizes the most sophisticated layers of consciousness in the zenithal higher-order structure: the prefrontal cortex. The hallmark of altered states of consciousness is the subtle modification of behavioral and cognitive functions that are typically ascribed to the prefrontal cortex. The theoretical framework presented yields a number of testable hypotheses. (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.

This review considers a number of recent theories on the neural basis of consciousness, with particular attention to the theories of Bogen, Crick, Llinás, Newman, and Changeux. These theories allot different roles to various key brain areas, in particular the reticular and intralaminar nuclei of the thalamus and the cortex. Crick's hypothesis is that awareness is a function of reverberating corticothalamic loops and that the spotlight ofintramodalattention is controlled by the reticular nucleus of the thalamus. He also proposed different mechanisms (...) for attention and intention . The current review presents a new hypothesis, based on elements from these hypotheses, includingintermodalattention and olfaction and pain, which may pose problems for Crick's original theory. This work reviews the possible role in awareness and intermodal attention and intention of the cholinergic system in the basal forebrain and the tegmentum; the reticular, the intralaminar, and the dorsomedial thalamic nuclei; the raphe and locus coeruleus; the reticular formation; the ventral striatum and extended amygdala; insula cortex, and other selected cortical areas. Both clinical and basic research data are covered. The conclusion is reached that the brain may work by largely nonlinear parallel processing and much intramodal shifts of attention may be effected by intracortical, or multiple corticothalamic mechanisms . But this is constrained by the functional anatomy of the circuits concerned and waking “awareness” is modulated by the many “nonspecific” systems . But the principal agents for intermodal attention shifts, the “searchlight,” may be two key nuclei of the cholinergic system in the mesencephalon. Clinical loss of consciousness results from damage to these nuclei but not from damage to the cholinergic nucleus basalis of the basal forebrain. (shrink)

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)

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)

Two paradigms have guided emotion research over the past decades. The dual-system view embraces the long-held Western belief, espoused most prominently by decision-making and social cognition researchers, that emotion and reason are often at odds. The integrative view, which asserts that emotion and cognition work synergistically, has been less explored experimentally. However, the integrative view (a) may help explain several findings that are not easily accounted for by the dual-system approach, and (b) is better supported by a growing body of (...) evidence from human neuroanatomy that has often been overlooked by experimental neuroscience. (shrink)

Although emotion is closely associated with motivation, and interacts with perception, cognition, and action, many conceptualizations still treat emotion as separate from these domains. Here, a comparative/evolutionary anatomy framework is presented to motivate the idea that long-range, distributed circuits involving the midbrain, thalamus, and forebrain are central to emotional processing. It is proposed that emotion can be understood in terms of large-scale network interactions spanning the neuroaxis that form “functionally integrated systems.” At the broadest level, the argument is made that (...) we need to move beyond a Newtonian view of causation to one involving complex systems where bidirectional influences and nonlinearities abound. Therefore, understanding interactions between subsystems and signal integration becomes central to unraveling the organization of the emotional brain. (shrink)

At the end of the nineteenth century, Ludwig Edinger completed the first comparative survey of the microscopic anatomy of vertebrate brains. He is regarded as the founder of the field of comparative neuroanatomy. Modern commentators have misunderstood him to have espoused an anti-Darwinian linear view of brain evolution, harkening to the metaphysics of the scala naturae. This understanding arises, in part, from an increasingly contested view of nineteenth-century morphology in Germany. Edinger did espouse a progressionist, though not strictly linear, (...) view of forebrain evolution, but his work also provided carefully documented evidence that brain stem structures vary in complexity independently from one another and across species in a manner that is not compatible with linear progress. This led Edinger to reject progressionism for all brain structures other than the forebrain roof, based on reasoning not too dissimilar from those his successors used to dismiss it for the forebrain roof. (shrink)

Major changes took place during the last quarter of the nineteenth century in the ways that the brain tissue was maintained, manipulated and studied, and, consequently, in the ways that its structure, functions and pathologies were seen and represented in neurological literature. The paper exemplifies these changes by comparing German neuroanatomy in the 1860s and early 1870s with the turn-of-the-century view of the brain . It argues for the crucial importance of a method—serial sectioning—to the emergence of the new (...) view of the brain. Serial sectioning in turn owes its existence to the new techniques in staining and sectioning that were introduced in the 1870s and 1880s. In particular, the paper highlights the role of a cutting device, the microtome, in enabling serial sectioning and in thereby contributing to the emergence of a new view of the brain. (shrink)

The evolutionary neurological foundations of religious experience are detailed. Human beings have been burying and preparing their dead for the Hereafter for more than 100,000 years. These behaviors and beliefs are related to activation of the amygdala, hippocampus, and temporal lobe, which are responsible for religious, spiritual, and mystical trancelike states, dreaming, astral projection, near‐death and out‐of‐body experiences, and the hallucination of ghosts, demons, angels, and gods. Abraham, Moses, Muhammad, and Jesus Christ, and others who have communed with angels or (...) gods display limbic system hyperactivity, whereas patients report religious hallucinations or out‐of‐body experiences when limbic structures are stimulated or excessively activated. It is postulated that limbic and temporal lobe structures account for the sexual and violent aspects of religious behavior and also serve as a “transmitter to God,” and that the evolution of these structures made spiritual experience possible. (shrink)

in a nervous system of a given species. This chapter provides a critical perspective on the role of connectomes in neuroscientific practice and asks how the connectomic approach fits into a larger context in which network thinking permeates technology, infrastructure, social life, and the economy. In the first part of this chapter, we argue that, seen from the perspective of ongoing research, the notion of connectomes as “complete descriptions” is misguided. Our argument combines Rachel Ankeny’s analysis of neuroanatomical wiring diagrams (...) as “descriptive models” with Hans-Joerg Rheinberger’s notion of “epistemic objects,” i.e., targets of research that are still partially unknown. Combining these aspects we conclude that connectomes are constitutively epistemic objects: there just is no way to turn them into permanent and complete technical standards because the possibilities to map connection properties under different modeling assumptions are potentially inexhaustible. In the second part of the chapter, we use this understanding of connectomes as constitutively epistemic objects in order to critically assess the historical and political dimensions of current neuroscientific research. We argue that connectomics shows how the notion of the “brain as a network” has become the dominant metaphor of contemporary brain research. We further point out that this metaphor shares (potentially problematic) affinities to the form of contemporary “network societies.” We close by pointing out how the relation between connectomes and networks in society could be used in a more fruitful manner. (shrink)

In recent years new findings in vertebrate neuroanatomy have challenged received views on the evolution of the brain. Established theories suggesting that new structures are added to older structures or that old structures are modified into new ones are being re-evaluated. Modification processes, such as invasion and parcellation, have proved to be less valid than originally assumed. Discoveries of neuroanatomical homologies add to the cladistic interpretation problems.

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)

Any attempt to elucidate the nature and mechanism of passivity phenomena, i.e., experiences that one’s conscious actions or thoughts have not been ‘willed’ by oneself, requires an integrative philosophical–neurobiological approach. The model proposed here adopts some fundamental positions that have long been advocated by philosophers and theoretical psychologists and have now found support from functional neuroanatomy. First, we experience our actions not from the standpoint of the executive but through the perception of its effects. Second, the ‘self’ is not (...) an agent of behaviour. Third, behaviour is energised and integrated by basic drives . Fourth, the view that the experience of an acting self is related to drive reduction associated with voluntary actions is perhaps less well developed. The model thus proposes that passivity phenomena are actions that are induced by the perception of salient events but that are not integrated with or conducive to the overall motivational state of the organism. It has been suggested that, following the perception of salient events, competition arises between automatic response tendencies seeking expression. The prefrontal cortex appears to play an important role not only in determining which events are to be perceived but also which of the corresponding response dispositions is to be selected and actualised in overt behaviour. Thus, action selection is the outcome of competition between response tendencies in the context of prefrontal biasing signals that represent drives and strivings for goals. Action selection may be uncoupled from drives and strivings as a result of a lowering of the threshold for action selection—as is suggested to be the case in schizophrenic passivity phenomena—or due to disconnection from prefrontal regions—as may be the case in the alien limb syndrome. (shrink)

Consideration of the amazing organized intricacy of human cortical anatomy entails a deeper appreciation of nature that is fully consistent with a mature religious spirit. A brain seems at first glance to be a mere lump of grayish claylike stuff, but facts of basic neuroanatomy compel us to consider that this particular kind of stuff may really contain all the richly tangible and richly ghostly inner essences of emotion, thought, and behavior. Humans are the “college graduates” of evolution. The (...) human cortex is 3,400 times the volume of, yet only slightly thicker (about 3 millimeters) than, that of the mouse. This remarkable sheet is as thin as a graduation‐day “mortarboard” cap, but its 2,600 square centimeter area is four times as large (about 20 × 20 inches if a square; both metric and English units used deliberately). Zooming in, there are about 50 billion cortical neurons; though named after “pyramids,” they are more like tiny “magic trees,” with branches and roots so long and fine that there are 1 or 2 miles of these electrically scintillating fibers within each cubic millimeter of cortex. Cortical neurons communicate intimately: viewed from above, beneath a single square millimeter 100,000 nerve cells intertwine; each such neuron makes 5,000 or more connections with others. These and many additional amazing facts about brain tissue, together with some conjectures about dense connectedness in the mathematics of graph theory, help to bear out the groundwork prepared by such pioneers as Ralph Wendell Burhoe that the spirit and knowledge of science might rejoin that of religion. If it takes enchanted matter to contain consciousness, this is a kind of enchantment that science may well be able to penetrate for eventual thoroughgoing understanding. Inevitable by‐products will be greater reverence for nature and greater awe at the mystery of nature's origin. (shrink)

This paper focuses on the make-up of different cultures in experimental neurology, neuroanatomy, and clinical psychiatry. These cultures served as important research bases for early regenerative concepts and projects in the area of neurology and psychiatry at the beginning of the 20th century. Nevertheless, the developments in brain research and clinical neurology cannot be regarded to be isolated from broader societal developments, as the discourses on social de- and regeneration, neurasthenia, nerve-weakness and experiences of the brain-injured after WWI show. (...) Societal and cultural developments directly influenced researchers’ conceptualisation, scientific ideas, and even their experimental and clinical orientation. They directly reflect which scientific problems the neuroscientists felt inclined to address and what areas they began to leave aside. Using the concept of socio-technical experiments, it is demonstrated that research methodologies in neuronal de- and regeneration studies were not simply a product of recent advances in the scientific differentiation of somatic neurology or brain-psychiatry. Moreover, they resulted in important interdisciplinary attempts which emerged from great collaborative work including neuroscientists from various areas of investigation in both basic and clinical contexts. (shrink)

Autism is a group of complex neurodevelopmental disorders characterized by impaired social interaction and restricted/repetitive behavior. We performed a large-scale retrospective analysis of 1,996 clinical neurological structural magnetic resonance imaging (MRI) examinations of 781 autistic and 988 control subjects (aged 0 to 32 years), and extracted regionally distributed cortical thickness measurements, including average measurements as well as standard deviations which supports the assessment of intra-regional cortical thickness variability. The youngest autistic participants (< 2.5 years) were diagnosed after imaging and were (...) identified retrospectively. The largest effect sizes and the most common findings not previously published in the scientific literature involve abnormal intra-regional variability in cortical thickness affecting many (but not all) regions of the autistic brain, suggesting irregular gray matter development in autism that can be detected with MRI. Atypical developmental patterns have been detected as early as 0 years old in individuals who would later be diagnosed with autism. (shrink)

A variety of scientific disciplines have set as their task explaining mental activities, recognizing that in some way these activities depend upon our brain. But, until recently, the opportunities to conduct experiments directly on our brains were limited. As a result, research efforts were split between disciplines such as cognitive psychology, linguistics, and artificial intelligence that investigated behavior, while disciplines such as neuroanatomy, neurophysiology, and genetics experimented on the brains of non-human animals. In recent decades these disciplines integrated, and (...) with the advent of techniques for imaging activity in human brains, the term cognitive neuroscience has been applied to the integrated investigations of mind and brain. This book is a philosophical examination of how these disciplines continue in the mission of explaining our mental capacities. (shrink)

The controversy of neuroanatomy on the principal structure of the nervous systems, which took place at the end of the nineteenth century, is described. Two groups of scientists are identified: one that favoured the idea of a discrete cellular organization of the nervous tissue, and one that favoured a syncytial organization. These two interpretations arose from different histological techniques that produced conflicting pictures of the organization of the nervous tissue. In an experimental reexamination of the techniques used at the (...) end of the nineteenth century, the present study concerns the impact of these different histological procedures on the controversy about the principle nature of the nervous tissue. This controversy could not be resolved by neuroanatomy itself until the 1950s when electron microscopy was introduced into neurobiology. Thus, in a critical period of the conceptual development of neurosciences, neuroanatomy failed to establish a proper base for an interpretation of the functional morphology of nervous tissues. (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)

Phenomenal consciousness or the subjective experience of feeling sensory stimuli is fundamental to human existence. Because of the ubiquity of their subjective experiences, humans seem to readily accept the anthropomorphic extension of these mental states to other animals. Humans will typically extrapolate feelings of pain to animals if they respond physiologically and behaviourally to noxious stimuli. The alternative view that fish instead respond to noxious stimuli reflexly and with a limited behavioural repertoire is defended within the context of our current (...) understanding of the neuroanatomy and neurophysiology of mental states. Consequently, a set of fundamental properties of neural tissue necessary for feeling pain or experiencing affective states in vertebrates is proposed. While mammals and birds possess the prerequisite neural architecture for phenomenal consciousness, it is concluded that fish lack these essential characteristics and hence do not feel pain. (shrink)

In arguing against the likelihood of consciousness in non-human animals, Descartes advances a slippery slope argument that if thought were attributed to any one animal, it would have to be attributed to all, which is absurd. This paper examines the foundations of Thomas Willis’ comparative neuroanatomy against the background of Descartes’ slippery slope argument against animal consciousness. Inspired by Gassendi’s ideas about the corporeal soul, Thomas Willis distinguished between neural circuitry responsible for reflex behaviour and that responsible for cognitively (...) or consciously mediated behaviour. This afforded Willis a non-arbitrary basis for distinguishing between animals with thought and consciousness and those without, a methodology which retains currency for neuroscience today. (shrink)

This target article presents a plausible evolutionary scenario for the emergence of the neural preconditions for language in the hominid lineage. In pleistocene primate lineages there was a paired evolutionary expansion of frontal and parietal neocortex (through certain well-documented adaptive changes associated with manipulative behaviors) resulting, in ancestral hominids, in an incipient Broca's region and in a configurationally unique junction of the parietal, occipital, and temporal lobes of the brain (the POT). On our view, the development of the POT in (...) our ancestors resulted in the neuroanatomical substrate consistent with the ability for representations in modality-neutral association cortex and, as a result of structure-imposing interaction with Broca's area, the hierarchically structured Evidence from paleoneurology and comparative primate neuroanatomy is used to argue that Homo habilis (2.5–2 million years ago) was the first hominid to have the appropriate gross neuroanatomical configuration to support conceptual structure. We thus suggest that the neural preconditions for language are met in H. habilis. Finally, we advocate a theory of language acquisition that uses conceptual structure as input to the learning procedures, thus bridging the gap between it and language. (shrink)

I sketch and defend an imperativist treatment of the phenomenology associated with disgusting smells. This treatment, I argue, allows us to make better sense than other intentionalist alter-natives both of the neuroanatomy of olfaction, and of a natural pre-theoretical stance regarding the sense of smell.

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)

Although deductive reasoning is a closed system, one's beliefs about the world can influence validity judgements. To understand the associated functional neuroanatomy of this belief-bias we studied 14 volunteers using event-related fMRI, as they performed reasoning tasks under neutral, facilitatory and inhibitory belief conditions. We found evidence for the engagement of a left temporal lobe system during belief-based reasoning and a bilateral parietal lobe system during belief-neutral reasoning. Activation of right lateral prefrontal cortex was evident when subjects inhibited a (...) prepotent response associated with belief-bias and correctly completed a logical task, a finding consistent with its putative role in cognitive monitoring. By contrast, when logical reasoning was overcome by belief-bias, there was engagement of ventral medial prefrontal cortex, a region implicated in affective processing. This latter involvement suggests that belief-bias effects in reasoning may be mediated through an influence of emotional processes on reasoning. (shrink)

The Oxford Handbook of Philosophy and Neuroscience is a state-of-the-art collection of interdisciplinary research spanning philosophy (of science, mind, and ethics) and current neuroscience. Containing chapters written by some of the most prominent philosophers working in this area, and in some cases co-authored with neuroscientists, this volume reflects both the breadth and depth of current work in this exciting field. Topics include the nature of explanation in neuroscience; whether and how current neuroscience is reductionistic; consequences of current research on the (...) neurobiology of learning and memory, perception and sensation, neurocomputational modeling, and neuroanatomy; the burgeoning field of neuroethics and the neurobiology of motivation that increasingly informs it; implications from neurology and clinical neuropsychology, especially in light of some bizarre symptoms involving misrepresentations of self; the extent and consequences of multiple realization in actual neuroscience; the new field of neuroeudamonia; and the neurophilosophy of subjectivity. This volume will interest philosophers working in numerous fields who wish to see how current neuroscience is being brought to bear directly on philosophical issues. It will also be of interest to neuroscientists who wish to learn how the research programs of some of their colleagues are being enriched by interaction with philosophers, and finally to those working in any interdisciplinary field who wish to see how two seemingly disparate disciplines--one traditional and humanistic, the other new and scientific--are being brought together to both disciplines' mutual benefit. (shrink)