The central question facing sleep and dream science today seems to be: What is the physiological basis of the subset of NREM dreams that are qualitatively indistinguishable from REM dreams (“apex dreams”)? Two competing answers have emerged: (1) all apex dreams are generated by REM sleep control mechanisms, albeit sometimes covertly; and (2) all such dreams are generated by forebrain mechanisms, independently of classical pontine sleep-cycle control mechanisms. The principal objection to the first answer is that it lacks evidential (...) support. The principal objection to the second answer (which is articulated in my target article) is that it takes inadequate account of interactions that surely exist between the putative forebrain mechanisms and the well established brainstem mechanisms of conscious state control. My main response to this objection (elaborated below) is that it conflates nonspecific brainstem modulation – which supports consciousness in general – with a specific pontine mechanism that is supposed to generate apex dreaming in particular. The latter mechanism is in fact neither necessary nor sufficient for apex dreaming. The putative forebrain mechanisms, by contrast, are necessary for apex dreaming (although they are nor sufficient, in the limited sense that all conscious states of the forebrain are modulated by the brainstem). (shrink)

Excitation at widely dispersed loci in the cerebral cortex may represent a neural correlate of consciousness. Accordingly, each unique combination of excited neurons would determine the content of a conscious moment. This conceptualization would be strengthened if we could identify what orchestrates the various combinations of excited neurons. In the present paper, cholinergic afferents to the cerebral cortex are hypothesized to enhance activity at specific cortical circuits and determine the content of a conscious moment by activating certain combinations of postsynaptic (...) sites in select cortical modules. It is proposed that these selections are enabled by learning-related restructuring that simultaneously adjusts the cytoskeletal matrix at specific constellations of postsynaptic sites giving all a similar geometry. The underlying mechanism of conscious awareness hypothetically involves cholinergic mediation of linkages between microtubules and microtubule-associated protein-2 . The first reason for proposing this mechanism is that previous studies indicate cognitive-related changes in MAP-2 occur in cholinoceptive cells within discrete cortical modules. These cortical modules are found throughout the cerebral cortex, measure 1–2 mm2, and contain approximately 103–104cholinoceptive cells that are enriched with MAP-2. The subsectors of the hippocampus may function similarly to cortical modules. The second reason for proposing the current mechanism is that the MAP-2 rich cells throughout the cerebral cortex correspond almost exactly with the cortical cells containing muscarinic receptors. Many of these cholinoceptive, MAP-2 rich cells are large pyramidal cell types, but some are also small pyramidal cells and nonpyramidal types. The third reason for proposing the current mechanism is that cholinergic afferents are module-specific; cholinergic axons terminate wholly within individual cortical modules. The cholinergic afferents may be unique in this regard. Finally, the tapering apical dendrites of pyramidal cells are proposed as primary sites for cholinergic mediation of linkages between MAP-2 and microtubules because especially high amounts of MAP-2 are found here. Also, the possibility is raised that muscarinic actions on MAP-2 could modulate microtubular coherence and self-collapse, phenomena that have been suggested to underlie consciousness. (shrink)

We hypothesize that threat of dehydration provided selection pressure for the evolutionary emergence and persistence of the anterior communicating artery (ACoA – the inter‐arterial connection that completes the Circle of Willis) in early amniotes.The ACoA is a hemodynamically insignificant artery, but, as we argue in this paper, its privileged position outside the blood‐brain barrier gives it a crucial sensing function for the osmolarity of the blood against the background of the rest of the brain, which efficiently protects itself from dehydration. (...) Till now, the questions of why the ACoA evolved, and what its physiological function is, have remained unsatisfactorily answered. The traditional view—that the ACoA serves as a collateral source of vascularization in case of arterial stenosis—is anthropocentric, and not in accordance with principles of natural selection that apply more generally. Diseases underlying arterial stenosis are associated with aging and the human lifestyle, so this cannot explain why the ACoA formed hundreds of millions of years ago and persisted in amniotes to this day.The peculiar hemodynamic properties of the ACoA could be selected traits that allowed for more efficient forebrain detection of dehydration and complex behavioral responses to water loss, a major advantage in the survival of early amniotes. This hypothesis also explains insufficient hydration often seen in elderly humans. (shrink)

We hypothesize that threat of dehydration provided selection pressure for the evolutionary emergence and persistence of the anterior communicating artery (ACoA – the inter‐arterial connection that completes the Circle of Willis) in early amniotes.The ACoA is a hemodynamically insignificant artery, but, as we argue in this paper, its privileged position outside the blood‐brain barrier gives it a crucial sensing function for the osmolarity of the blood against the background of the rest of the brain, which efficiently protects itself from dehydration. (...) Till now, the questions of why the ACoA evolved, and what its physiological function is, have remained unsatisfactorily answered. The traditional view—that the ACoA serves as a collateral source of vascularization in case of arterial stenosis—is anthropocentric, and not in accordance with principles of natural selection that apply more generally. Diseases underlying arterial stenosis are associated with aging and the human lifestyle, so this cannot explain why the ACoA formed hundreds of millions of years ago and persisted in amniotes to this day.The peculiar hemodynamic properties of the ACoA could be selected traits that allowed for more efficient forebrain detection of dehydration and complex behavioral responses to water loss, a major advantage in the survival of early amniotes. This hypothesis also explains insufficient hydration often seen in elderly humans. (shrink)

Most parts of the brain are conserved across reptiles and birds (sauropsids) and mammals. Two major qualitative differences occur in the upper part, or pallium, of the telencephalon, the most rostral part of the brain. Mammals have a six‐layered neocortex and also exhibit a different morphological organization in the lateral half, or sector, of their pallium than do sauropsids. These differences of lateral pallial construction may derive from small but crucial differences in migration patterns of neuronal precursors generated at or (...) above the corner of the lateral ventricle, the corticostriatal junction (CS). Sauropsids have a large structure, the dorsal ventricular ridge, that is proliferated from this region, and its anterior part (ADVR) receives ascending projections from the dorsal thalamus. Mammals have multiple structures in this same region—the lateral part of neocortex, amygdala, and claustrum‐endopiriform formation. We propose here that, as the degree of development of structures that form the deeper tier of the pallium varies across the stages of embryology and across phylogeny, mutations may have occurred during evolution at the origin of mammals that had profound consequences for the fate of neural populations generated in the region of the CS and its neighboring pallial germinal zone. BioEssays 24:530–541, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

The paradigmatic assumption that REM sleep is the physiological equivalent of dreaming is in need of fundamental revision. A mounting body of evidence suggests that dreaming and REM sleep are dissociable states, and that dreaming is controlled by forebrain mechanisms. Recent neuropsychological, radiological, and pharmacological findings suggest that the cholinergic brain stem mechanisms that control the REM state can only generate the psychological phenomena of dreaming through the mediation of a second, probably dopaminergic, forebrain mechanism. The latter mechanism (...) (and thus dreaming itself) can also be activated by a variety of nonREM triggers. Dreaming can be manipulated by dopamine agonists and antagonists with no concomitant change in REM frequency, duration, and density. Dreaming can also be induced by focal forebrain stimulation and by complex partial (forebrain) seizures during nonREM sleep, when the involvement of brainstem REM mechanisms is precluded. Likewise, dreaming is obliterated by focal lesions along a specific (probably dopaminergic) forebrain pathway, and these lesions do not have any appreciable effects on REM frequency, duration, and density. These findings suggest that the forebrain mechanism in question is the final common path to dreaming and that the brainstem oscillator that controls the REM state is just one of the many arousal triggers that can activate this forebrain mechanism. The “REM-on” mechanism (like its various NREM equivalents) therefore stands outside the dream process itself, which is mediated by an independent, forebrain “dream-on” mechanism. Key Words: acetylcholine; brainstem; dopamine; dreaming; forebrain; NREM; REM; sleep. (shrink)

A model of the neuropsychology of anxiety is proposed. The model is based in the first instance upon an analysis of the behavioural effects of the antianxiety drugs in animals. From such psychopharmacologi-cal experiments the concept of a “behavioural inhibition system” has been developed. This system responds to novel stimuli or to those associated with punishment or nonreward by inhibiting ongoing behaviour and increasing arousal and attention to the environment. It is activity in the BIS that constitutes anxiety and that (...) is reduced by antianxiety drugs. The effects of the antianxiety drugs in the brain also suggest hypotheses concerning the neural substrate of anxiety. Although the benzodiazepines and barbiturates facilitate the effects of γ-aminobutyrate, this is insufficient to explain their highly specific behavioural effects. Because of similarities between the behavioural effects of certain lesions and those of the antianxiety drugs, it is proposed that these drugs reduce anxiety by impairing the functioning of a widespread neural system including the septo-hippocampal system, the Papez circuit, the prefrontal cortex, and ascending monoaminergic and cholinergic pathways which innervate these forebrain structures. Analysis of the functions of this system suggests that it acts as a comparator: it compares predicted to actual sensory events and activates the outputs of the BIS when there is a mismatch or when the predicted event is aversive. Suggestions are made as to the functions of particular pathways within this overall brain system. The resulting theory is applied to the symptoms and treatment of anxiety in man, its relations to depression, and the personality of individuals who are susceptible to anxiety or depression. (shrink)

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

The thesis advanced in this book is that feeling and cognition actualize through a process that originates in older brain formations and develops outward through limbic and cortical fields through the self-concept and private space into (as) the world. An iteration of this transition deposits acts, objects, feelings and utterances. Value is a mode of conceptual feeling that depends on the dominant phase in this transition: from desire through interest to object worth. Among the topics covered are subjective time and (...) change, the epochal nature of objects and their temporal extensibility and the evolution of value from inorganic matter into organic form. The theory of microgenesis informs this work. According to this theory, acts and objects evolve in milliseconds through phases that replicate patterns in forebrain evolution. The progression in the actualization of the mind/brain state is from archaic to recent in brain formation, from unity to diversity, from past to present and from mind to world. An account is given of the diversity of felt experience avoiding the reductionist moves characteristic of biological materialism and the inherent dualism of psychoanalytic and related theories. This book is intended for any reader interested in the psychology of the inner life and philosophy of mind, including philosophers, psychologists, psychiatrists and others with an interest in problems of value and moral feeling. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 10.4 (2003) 353-355 [Access article in PDF] Emotions and Narrative Selves Valerie Gray Hardcastle In their commentaries, both Phillips (2003) and Woody (2003) agree that the affective side of personhood needs to be better addressed in narrative views of self. In their arguments, they focus mainly on how a patient or a subject is here and now. In contrast, Kennett and Matthews (2003) take a (...) longer view and argue for the importance of a diachronic unity for selfhood. This commentary seeks to integrate these views by discussing how emotions are central to building our personal sense of unified agency. 1Phillips and Woody are right: most philosophical discussions of the narrative view of self are overly cognitive and focus too much attention on our linguistic story-telling abilities and not enough on what it is like to be a person experiencing the world. This is too bad, for it is our affective reactions that drive our personal life narratives. Consider: of all the experiences in the world, we only chose a small subset to become or represent who we are. I regularly eat cold cereal for breakfast before heading off to work, but if you ask me to describe myself, I describe my work or my children, not my breakfast-eating habits. Why is this? I identify with my work, my family life, or my play, but not with my sleeping patterns, the trajectories I chose when I drive, or how I brush my teeth. How is it that I have selected the former activities to highlight in my self-stories, but not the latter?I maintain that I choose the former because I have strong affective ties to them, ties that I do not have to driving routes or personal hygiene. And these ties are what determine what gets into our narratives of self. Actually, my claim is stronger than that. I believe that our emotions not only color what we do but they also allow us to act in the first place (this discussion is greatly expanded in my forthcoming book).Humans delight in pretending that our most prized and most humanly attribute is our forebrain, which houses, we also pretend, our capacity for rational thought. Since Plato at least we have held that subduing our passions to the iron rule of reason is our supreme aspiration; it is the ideal for human cognition. Ironically, we think that the more we are like Star Trek's alien Mr. Spock, the more human we really are.But what would life really be like with an overdeveloped forebrain and without emotion? Let us consider more carefully what it is we really prize about being human. We can rationalize well, it is true, but we do so in the service of personal goals. As Aristotle reminds us, we have practical rationality; we have means-ends reasoning with a point. This is just another way of saying that it is imperative that we identify what is important to us prior to cognizing.Obviously, one might scoff, we need an end to engage in means-ends reasoning. But often, I think, what having an end entails is not well appreciated. These days it is fashionable to believe that our fundamental ends—survival and reproduction—are set by our biology and that all [End Page 353] other ends (or most other ends) derive from them in some fashion. Maybe this story is true, but it obscures how ends—whether they be hardwired in or they come later—function in the human psyche.At a bare minimum, that we have particular ends tells us that we have to tag our abstractions, interpretations, and matched patterns with valances—some things are good, some things are bad, and some are indifferent. Tagging our experiences thus is just what it means to have emotions; we are reacting affectively to our world around us. And it is these reactions that determine which inputs we respond to and which we ignore. We literally cannot move about in our world without emotion. I think, perhaps, that this fact is what Phillips and Woody are... (shrink)

Although most aspects of world and self-consciousness are inherently subjective, neuroscience studies in humans and non-human animals provide correlational and causative indices of specific links between brain activity and representation of the self and the world. In this article we review neuroanatomic, neurophysiological and neuropsychological data supporting the hypothesis that different levels of self and world representation in vertebrates rely upon i) a 'basal' subcortical system that includes brainstem, hypothalamus and central thalamic nuclei and that may underpin the primary (or (...) anoetic) consciousness likely present in all vertebrates; and ii) a forebrain system that include the medial and lateral structures of the cerebral hemispheres and may sustain the most sophisticated forms of consciousness (e.g. noetic (knowledge based) and autonoetic, reflective knowledge). We posit a mutual, bidirectional functional influence between these two major brain circuits. We conclude that basic aspects of consciousness like primary self and core self (based on anoetic and noetic consciousness) are present in many species of vertebrates and that, even self-consciousness (autonoetic consciousness) does not seem to be a prerogative of humans and of some non-human primates but may, to a certain extent, be present in some other mammals and birds. (shrink)

Insight is a cognitive feature that is usually regarded as being generated by the neocortex and being present only in humans and possibly some closely related primates. In this essay we show that especially corvids display behavioral skills within the domains of object permanence, episodic memory, theory of mind, and tool use/causal reasoning that are insightful. These similarities between humans and corvids at the behavioral level are probably the result of a convergent evolution. Similarly, the telencephalic structures involved in higher (...) cognitive functions in both species show a high degree of similarity, although the forebrain of birds has no cortex-like lamination. The neural substrate for insight-related cognitive functions in mammals and birds is thus not necessarily based on a laminated cortical structure but can be generated by differently organized forebrains. Hence, neither is insight restricted to mammals, as predicted from a “scala naturae”, nor is the laminated cortex a prerequisite for the highest cognitive functions. (shrink)

I have argued in other work that emotion, attentional functions, and executive functions are three interpenetrant global state variables, essentially differential slices of the consciousness pie. This paper will outline the columnar architecture and connectivities of the PAG (periaqueductal gray), its role in organizing prototype states of emotion, and the re-entry of PAG with the extended reticular thalamic activating system (“ERTAS”). At the end we will outline some potential implications of these connectivities for possible functional correlates of PAG networks that (...) are just starting to be mapped. Overall, we will look at many lines of evidence that PAG should be conceptualized as a peri-reticular structure that has a foundational role in emotion, in generating the meaningful organization of behavior by the brain through prototype emotional states, and in allowing the various emotional systems to globally influence and tune both the forebrain and brainstem. Finally, we address implications of these concepts for what is currently understood about consciousness, underlining the need for somewhat more humility within consciousness studies about our current level of understanding of consciousness in the brain, combined with a deeper appreciation of the intrinsic connections between emotion and consciousness. One hopes that more concerted empirical interest in structures underneath the thalamus, combined with a deeper appreciation for the fundamental role that organismic and social value must have in bootstrapping awareness in the developing brain, would begin more widely to influence the fundamental lines of neuroscientific research in both emotion studies and consciousness studies. (shrink)

Definitions of dreaming are not required to map formal features of mental activity onto brain measures. While dreaming occurs during all stages of sleep, intense dreaming is largely confined to REM. Forebrain structures and many neurotransmitters can contribute to sleep and dreaming without negating brainstem and aminergic-cholinergic control mechanisms. Reductionism is essential to science and AIM has considerable heuristic value. Recent findings support sleep's role in learning and memory. Emerging technologies may address long-standing issues in sleep and dream research.

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)

The lesion and transplantation data cited by Sinden et al., when considered in tandem, seem to harbor an internal inconsistency, raising questions of false localization of function. The extrapolation of such data to cognitive impairment and potential treatment strategies in Alzheimer's disease is problematic. Patients with focal basal forebrain lesions (e.g., anterior communicating artery aneurysm rupture) might be a more appropriate target population.

(1) Substituting (as Solms does) forebrain for brainstem in the search for a dream “controller” is counterproductive, since a distributed system need have no single controller. (2) Evidence against episodic memory consolidation does not show that REM sleep has no role in other types of memory, contra Vertes & Eastman. (3) A generalization of Revonsuo's “threat simulation” model in reverse is more plausible and is empirically testable. [Hobson et al.; Solms; Revonsuo; Vertes & Eastman].

The neural transplantation research described by Sinden and colleagues provides part of the rationale for the clinical application of neural transplantation. The authors are asked to clarify their view of the role of the cholinergic system in cognition, to address extrahippocampal damage caused by transient forebrain ischemia, and to consider the effects of delayed neural degeneration in their structure-function analysis.

“Decortication” does not distinguish between removing all cerebral cortex, including three-layered allocortex or just six-layered neocortex. Functional decortication, by spreading depression, reversibly suppresses only neocortex, leaving minimal intentionality. Removal of all forebrain structures except a hypothalamic “island” blocks all intentional behaviors, leaving only tropisms. To what extent do Merker's examples retain allocortex, and how might such residues affect his interpretations? (Published Online May 1 2007).

Stein & Glasier suggest embryonic neural tissue grafts as a potential treatment strategy for Alzheimer's and Parkinson's disease. As an alternative, we suggest that the family of nerve growth factor-related neurotrophins and their trk (tyrosine kinase) receptors underlie cholinergic basal forebrain (CBF) and dopaminergic substantia nigra neuron degeneration in these diseases, respectively. Therefore, treatment approaches for these disorders could utilize neurotrophins.

On May 24, 1995, the American Medical Association Council on Ethical and Judicial Affairs issued a rather controversial opinion that it is ethically permissible to use anencephalic infants as living organ donors. Approximately 1,000 to 2,000 infants are born each year in the United States with anencephaly, a congenital birth defect whereby the infant has no forebrain and cerebrum. Without higher brain functions, the infants can never experience consciousness, thoughts, emotions, or pain. Fewer than half survive more than a (...) day, and more than 90 percent die within one week. However, by the time brain death occurs in anencephalic infants, their organs are no longer suitable for donor purposes because they have deteriorated beyond use.In 1988, the AMA Council declared that it is ethical to use the infants as organ donors only after they have died. Now the Council has revised that opinion, and it proposes to allow removal of organs before death, as long as the parents consent and two doctors concur in the diagnosis of anencephaly. (shrink)

Solms and the other authors in this series of BBS target articles accept the findings that the executive control of the REM/NREM cycle is still localized within a narrow region of the pontine brainstem. However, recent findings challenge this notion. We will review the recent data and suggest instead that the hypothalamus is the primary regulator of states of consciousness. If the hypothalamus indeed controls all the fun stuff, such as sex, eating, drinking, sleeping, and so on, then one can (...) more easily accept Solms's argument that dreams are also generated from the forebrain. [Solms]. (shrink)

What is the biological basis for human cognition? Our understanding why human brains make us smarter than other animals is still in its infancy. In recent years, astrocytes have been shown to be indispensable for neuronal survival, growth, synapse formation, and synapse function. Now, in a new study from Maiken Nedergaard and Steven Goldman's groups (Han et al., 2013), human glia progenitor cells have been transplanted into mouse forebrains. These progenitors survived, migrated widely, and gave rise to astrocytes that displayed (...) the characteristics of human astrocytes in the rodent host brains. Strikingly, the mice with transplanted human cells displayed improved long term potentiation (LTP) and learning, suggesting the potential importance of human astrocytes in the unique cognitive abilities of human brains. This landmark paper is an important first step toward future investigations of whether and how human astrocytes play a role in distinguishing the cognitive abilities of humans from those of other animals. (shrink)

We consider the evidence that RA†, the vitamin A metabolite, is involved in three fundamental aspects of the development of the CNS: (1) the stimulation of axon outgrowth in particular neuronal sub‐types; (2) the migration of the neural crest; and (3) the specification of rostrocaudal position in the developing CNS (forebrain, midbrain, hindbrain, spinal cord). The evidence we discuss involves RA‐induction of neurites in cell cultures and explants of neural tissue; the teratological effects of RA on the embryo's nervous (...) system; the observation that RA can be detected endogenously in the spinal cord; and the fact that the receptors and binding proteins for RA are expressed in precise domains and neuronal cell types within the nervous system. (shrink)

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)

The main objective of this essay is to validate some of the principal, currently competing, mammalian consciousness-brain theories by comparing these theories with data on both cognitive abilities and brain organization in birds. Our argument is that, given that multiple complex cognitive functions are correlated with presumed consciousness in mammals, this correlation holds for birds as well. Thus, the neuroanatomical features of the forebrain common to both birds and mammals may be those that are crucial to the generation of (...) both complex cognition and consciousness. The general conclusion is that most of the consciousness-brain theories appear to be valid for the avian brain. Even though some specific homologies are unresolved, most of the critical structures presumed necessary for consciousness in mammalian brains have clear homologues in avian brains. Furthermore, considering the fact that the reptile-bird brain transition shows more structural continuity than the stem amniote-mammalian transition, the line drawn at the origin of mammals for consciousness by several of the theorists seems questionable. An equally important point is that consciousness cannot be ruled out in the absence of complex cognition; it may in fact be the case that consciousness is a necessary prerequisite for complex cognition. (shrink)

Merker's core idea, that the experience of being conscious reflects the interactions of actions, targets, and motivations in the upper brainstem, with cortex providing the content of the conscious experience, merits serious consideration. However, we have two areas of concern: first, that his definition of consciousness is so broad that it is difficult to find any organisms with a brain that could be non-conscious; second, that the focus on one cortical–subcortical system neglects other systems (e.g., basal forebrain and brainstem (...) cholinergic systems and their cortical and thalamic target areas) which may be of at least equal significance. (Published Online May 1 2007). (shrink)

I dispute that consciousness is generated by core circuitry in the forebrain, with predominance of motor areas, as Cotterillproposes in Enchanted Looms and other theorists do also. Ipropose instead that conscious contents are the momentary modeof action of the integrated cortical field, expressed as a point vector ( dominant focus ), to which, in varying degree, allsectors of the network contribute. Consciousness is the brain''saccess to its own activity space, and is identical with the moment''sdominant mode of activity. The (...) dominant focus is generally weightedtoward enactively encoded percepts. Anticipation and preparation,perception and action, inextricably interdigitate. I also dispute the view of Cotterill and others that consciousnesshas unique agency, which bestowed adaptive advantage when the brain evolved. Being identical with the activity of the network,consciousness can have no additional agency, and it can offerno adaptive advantages beyond those that characterize the network. (shrink)

Dream content is more coherent, consistent over time, and continuous with waking emotional concerns than most brainstem-driven theories of dreaming allow, but dreaming probably has no adaptive function. A new neurocognitive perspective focusing on the forebrain system of dream generation should begin with the findings on dream content in adults and the developmental nature of dreaming in children. [Hobson et al.; Nielsen; Revonsuo; Solms; Vertes & Eastman].

Cholinergic-rich grafts have been shown to be effective in restoring maze-learning deficits in rats with lesions of the forebrain cholinergic projection system. However, the relevance of those studies to developing novel therapies for Alzheimer's disease is questioned.

Everything we experience and do as individuals is assumed to be a function of the nervous system. It is as though we were born with a total supply of algorithms for all given forms of psychic states and solutions for immediate or eventual actions. There is evidence that the forebrain is, so to speak, the central processor for psychic experience and psychologically directed behavior. Since information itself is immaterial, all forms of psychic experience represent immaterial emanations of the (...) class='Hi'>forebrain, including sensations, perceptions, drives, affects, thoughts, and the precisely measured, cold hard facts of science. But it is to be emphasized that there can be no manufacture or communication of information without the intermediary of behaving entities. Because of the immateriality of information and the Gödel-like problem of self-reference, a central question arises as to whether or not we can ever rely on the brain with its viscoelastic properties to achieve a reliable yardstick for measuring time and space and the general nature of things. Most needed at the present time is a refined picture of the anatomy and chemistry of the brain’s circuitry accounting for its particular species of algorithms. Emphasis is given to the basic role of various proteins in generating subjective experience. Because of the role of resonance in contributing to the dynamical excitability of neural circuits, examples are given here of how it might play an algorithmic role at macroscopic, microscopic, molecular, and atomic levels. To describe this idea attention is focused on three evolutionary types of cortex that have developed in the triune evolution of the mammalian forebrain from the mammal-like reptiles to human beings. (shrink)

The dorsal and medial pallial formations of mammals, birds, and reptiles show overall functional striking similarities. Most of these similarities have been frequently considered examples of convergent evolution. However, a considerable amount of neurobiological comparative evidence suggests the presence of a common basic pattern of vertebrate forebrain organization. This common pattern can support functional conservation.

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)

This paper summarizes the main features of the microgenetic account of consciousness, of the transition from self to image, act and object, the epochal nature of this transition, and its relation to introspection, imagination, and agency. The affinities of microgenetic theory to many aspects of process thought should be evident to readers of this journal, but the theory, which was developed in pathological case study, rests on a wealth of clinical detail that is beyond the scope of this article. In (...) brief, the micro-temporal transition from archaic to recent formations (distributed systems) in the phyletic history of forebrain constitutes the absolute mental state, with consciousness the relation of self to image and/or object. The discussion touches on the overlap of states, the continuity of the core over successive states, and subjective time experience. (shrink)

There are strong resemblances between the neurobiological characteristics of hallucinations occurring in the particular case of schizophrenia and the hallucinatory activity observed during the rapid-eye-movement (dreaming) sleep stage: the same prefrontal dorsolateral deactivation; forebrain disconnectivity and disinhibition; sensory deprivation; and acetylcholine, monoamine, and glutamate modifications.

During development of the Xenopus embryo, the formation of the nervous system depends on an inductive interaction between mesoderm and ectoderm. The result is a neural tube that is regionally differentiated along the anterior–posterior axis from forebrain to spinal cord (Fig. 1). The discovery of genes whose transcripts can be used as molecular markers for different regions of the nervous system has permitted reassessment of the existing theories of neural tissue formation. Although the neural inducing molecules remain elusive, the (...) mechanism by which cells interact to form a regionally differentiated nervous system is becoming clearer. (shrink)

Cognitive deficits were produced in rats by different methods of damaging the brain: chronic ingestion of alcohol, causing widespread damage to diffuse cholinergic and aminergic projection systems; lesions (by local injection of the excitotoxins, ibotenate, quisqualate, and AMPA) of the nuclei of origin of the forebrain cholinergic projection system (FCPS), which innervates the neocortex and hippocampal formation; transient cerebral ischaemia, producing focal damage especially in the CA1 pyramidal cells of the dorsal hippocampus; and lesions (by local injection of the (...) neurotoxin, colchicine) of the granule cells of the dentate gyrus. Following chronic alcohol or lesions of the FCPS, transplants of cholinergically rich fetal brain tissue into the terminal areas (neocortex and/or hippocampus) restored performance almost to control levels, with a time course consistent with growth of the transplants and integration with host tissue; transplants of cholinergically poor fetal tissue (hippocampus) were without effect, as were transplants of cholinergically rich tissue into the region containing the nuclei of origin of the FCPS. Grafts of primary cells enriched in glia and cultured neuroblastoma cells into the terminal areas of the FCPS were equally effective, suggesting that there are multiple mechanisms by which neural transplants can restore cognitive function following diffuse cholinergic damage. In contrast, after ischaemia- or neurotoxin-induced damage to CA1 or dentate granule cells respectively, cholinergically rich fetal transplants into the damaged hippocampal formation were ineffective in restoring performance. After ischaemic damage, however, performance was restored by suspension grafts of CA1 cells but not by transplants containing CA3 pyramidal cells or granule cells; and after colchicine damage it was restored by solid grafts containing granule but not CA1 pyramidal cells. Furthermore, electrophysiological evidence has demonstrated functional, graft type-specific host-graft functional neuronal connectivity. Thus, restoration of cognitive function by neural transplants is possible after damage to either diffuse (cholinergic) or point-to-point (intrahippocampal) forebrain systems, but the transplant must be appropriate to the damage to be repaired. Because the different types of brain damage studied provide analogues of human alcoholic dementia, Alzheimer's disease, and heart attack, these results are encouraging with regard to the eventual application of neural transplant surgery to the treatment of cognitive deficits in humans. (shrink)

Rolls's proposal that the amygdala is critical for the association of visual objects with reward is not consistent with recent ablation evidence. Stimulus-reward association learning is more likely to depend on basal forebrain efferents to the inferior temporal cortex, some of which pass through the amygdala. It is more likely that the amygdala is involved in rapid modulation of stimulus reward value.

My response addresses general commentary themes such as my neglect of the forebrain contribution to human consciousness, the bearing of blindsight on consciousness theory, the definition of wakefulness, the significance of emotion and pain perception for consciousness theory, and concerns regarding remnant cortex in children with hydranencephaly. Further specific topics, such as phenomenal and phylogenetic aspects of mesodiencephalic-thalamocortical relations, are also discussed. (Published Online May 1 2007).

In this series of articles, several new hypotheses on sleep and dreaming are presented. In each case, we feel the data do not adequately support the hypothesis. In their lengthy discourse, Hobson et al. represent to us the familiar reciprocal interaction model dressed in new clothes, but expanded beyond reasonable testability. Vertes & Eastman have proposed that REM sleep is not involved in memory consolidation. However, we do not find their arguments persuasive in that limited differences in activity in REM (...) and waking do not lend credence to the idea that memory consolidation occurs in one state and not the other. Solms makes an argument that dreams are generated from the dopaminergic forebrain based largely on pathological lesion studies in humans. We recognize that this argument has some intuitive appeal and agree with some of the tenets but we do not feel that the arguments are completely convincing due to the lack of anatomical controls, including symmetry and laterality. On the whole, there are interesting arguments put forward in these target articles but the evidence does not convince us that new vistas are opened. No Holy Grail of sleep here! [Hobson et al.; Solms; Vertes & Eastman]. (shrink)

This paper presents the results of some recent experiments in neuroscience and introspectionist psychology that reveal the role of virtual reality in normal visual perception, and the use of television information compression technology by the visual brain. This involves particularly the cholinergic system in the forebrain. This research throws new light on the nature of consciousness, in particular in connection with the debate between Naïve Realists and Physiological Realists.