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)
This paper examines the impact that recent advances in clinical neurology, introspectionist psychology and neuroscience have upon the philosophical psycho?neural Identity Theory. Topics covered include (i) the nature and properties of phenomenal consciousness based on a study of the ?basic? visual field, i.e. that obtained in the complete dark, the Ganzfeld, and during recovery from occipital lobe injuries; (ii) the nature of the ?body?image? of neurology and its relation to the physical body; (iii) Descartes? error in choosing extension in space (...) as the criterion for distinguishing the physical and the mental; (iv) the technical distinction between sensing and perceiving; (v) why phenomenal Direct Realism is incorrect whereas epistemic DR and the representative theory are correct; (vi) the ontological and topological status of phenomenal space and physical space. This leads to considerations of the current ?binding problems? in neuroscience; the role of the brain mechanisms that construct the sensory fields of phenomenal consciousness; the ?homunculus? fallacy; the key difference between epistemic and non?epistemic perception as revealed by brain injury studies; and how the brain codes information, contrasting topological and vectorial coding, with particular reference to the binding problem. My conclusion is that the Identity Theory is incompatible with the scientific evidence from an integrated approach to modern introspectionist psychology, clinical neurology, and neuroscience. However, Cartesian Dualism is even more incompatible with the evidence. This leaves only two viable theories. The first is Bohr's theory of brain?consciousness complementarity. The second is the Broad?Price?Smythies theory of extension, which is a topological theory of the relation between phenomenal space and physical space. (shrink)
There are currently two main philosophical theories of perception - Direct Realism and the Representative Theory. The former is supported by most contemporary philosophers, whereas the latter forms the groundwork for most scientific theories in this area. The paper describes a recent experiment involving retinal and cortical rivalry that provides strong empirical evidence that the Direct Realist theory is incorrect. There are of course a large number of related experiments on visual perception that would tend to lead us to the (...) same conclusion, but the experiment described in this paper does so in a singularly direct and straightforward manner. Often the most telling experiments are the simplest. (shrink)
This paper describes a new theory of consciousness based on previous work by C.D. Broad, H.H. Price, Andrei Linde and others. This hypothesis states that the Universe consists of three fundamental entities - space-time, matter and consciousness, each with their own degrees of freedom. The paper pays particular attention to three areas that impact on this theory: the demonstration by neuroscience and psychophysics that we do not perceive the world as it actually is but as the brain computes it most (...) probably to be; the need to delineate between phenomenal space-time and physical space-time. Recent theories in physics that suggest that the Universe has more than three spatial dimensions are relevant here; the role of consciousness in the block Universe described by Special Relativity. The integration of these topics suggests a new physical theory of the nature of consciousness. (shrink)
This paper concentrates on the basic properties of ''consciousness'' that temporal coding is postulated to relate to. A description of phenomenal consciousness based on what introspection tells us about its contents is offered. This includes a consideration of the effect of various brain lesions that result in cortical blindness, apperceptive and associative agnosia, and blindsight, together with an account of the manner in which sight is regained after cortical injuries. I then discuss two therories of perception-Direct Realism and the Representative (...) Theory. This includes a discussion of the concept of the body-image, phantom limbs, the alleged projection of sensations, the ontological status of phenomenal space, the homunculus argument, the validity of topographic coding, the difference between the stimulus field and the visual field, and two theories of brain-mind relationship-the Identity Theory and the Bohr-Heisenberg theory of brain-mind complementarity. Finally I suggest that the binocular rivalry obtained in the case of the stroboscopic patterns that result from intermittent photic stimulation of one eye, when used in animal expeiments with unit recording, offers a good experimental method of investigating the binding problem. (shrink)
This paper presents an enquiry into the essential nature of phenomenal consciousness and its relation to the neural correlates of consciousness in the brain . It first combines critical accounts of current ideas about the nature of NCCs themselves and about what constitutes phenomenal consciousness. This is followed by an examination of how these two may be related with a particular focus on pointing out the defects in the currently most popular hypothesis in this field, namely the identity theory. The (...) conclusion is that we need a better theory. A candidate for this theory is presented in some detail that involves higher-dimensional geometry. (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.
This paper focuses on perception and surveys the scientific evidence that the theory of direct realism adopted by most contemporary philosophers is incorrect. This evidence is provided by experiments on the spatial and temporal "filling-in" of percepts. It also examines the myth of the projection of sensations. The conclusion is that we do not perceive the world as it actually is, but as the brain computes it most probably to be.
We can in fact obtain scientific information about the contents of consciousness by the methods of introspectionist psychology. An example comes from the author's work on the stroboscopic patterns and from the way psychedelic drugs alter color perception.
Current research on the neural basis of consciousness is based mainly on neuroimaging, physiology and psychophysics. This target article reviews what is known about biochemical factors that may contribute to the development of consciousness, based on loss of consciousness (i.e., coma). There are two theories of the biochemical mode of action of general anaesthetics. One is that anaesthesia is a direct (i.e., not receptor-mediated) effect of the anaesthetic on cellular neurophysiological function; the other is that some alteration of receptor function (...) occurs. General anaesthetics are mainly GABA agonists but some (such as ketamine) are glutamate antagonists. They also affect other systems, particularly cholinergic ones. There are various comas of metabolic origin. For example, a combination of small doses of the iron chelators desferrioxamine and prochlorperazine induce a profound and long lasting coma in humans. The mechanisms that might mediate this include redox mechanisms at the glutamate synapse, post-synaptic endocytosis of dopamine and iron, and intracellular iron-dopamine complexes, which are powerful dismuters of the superoxide anion. New findings in cell biology relating to endocytosis and recycling of receptors are discussed in a wider context. These biochemical events may induce coma by two mechanisms: (i) Consciousness may depend on widespread cortical (or cortico-thalamic) activation. (ii) Whereas these biochemical changes are widespread, only the changes in a subset of consciousness' neurons may count. An experimental program to distinguish between these two alternatives is proposed. (shrink)
This paper reviews the present status of the material dualist theory of brain-consciousness relations. I cover first the history of its development by Priestly, Broad, Price, Carr, Jourdan, and myself. The theory is then described with its basis in higher-dimensional geometry, the phenomenology of consciousness, the neurological concept of the body image, and the application of Leibniz's Law to the current dominant identity theory of brain-consciousness relations. A model based on Flatland is developed to illustrate the theory followed by a (...) discussion of its application to recent findings in NDE cases together with the use by Jourdan and Brumblay of higherdimensional geometry to account for the remarkable phenomenology revealed. Finally I discuss possible ways to test the theory by experiment. (shrink)
Mood in humans is a complex phenomenon that integrates emotion , cognition, perception, ideation, and action in a coherent manner. In bipolar disorder extremes of mood occur outside the normal range, in which all the above functions are coherently affected. Mood is controlled by a series of separate but interactive brain circuits that involve much of the brain, but particularly the limbic system. The question addressed in this paper is whether the coordination of all these separate systems into one coherent (...) functional mood is mediated by non-linear dynamics acting between these systems as equal participants; or whether it is affected by a single master regulator controlling the others. The possible roles, as master regulators, of non-linear dynamically linked populations of neurons, and of the C1–C3 adrenergic nuclei in the medulla is discussed. (shrink)
This commentary reviews and extends the target article's treatment of the topic of the role of acetylcholine in hallucinatory experience in health and disease. Particular attention is paid to differentiating muscarinic and nicotinic effects in modulating the use of virtual reality mechanisms by the brain. Then, attention is drawn to the similarities between these aspects of brain function and certain aspects of television digital compression technology.
This paper reviews the evidence, from studies of acute denervation plasticity, that NCCs in the sensory cortex are composed of particular patterns of intracolumnar excitation in a certain type of neuron, and not of specific anatomically identified neurons. This leads to an enquiry as to what the microneurological basis of NCCs in general may be. Further evidence is examined as to the possible NCCs of the stroboscopic patterns. The hypotheses are presented that the geometrical bright phase patterns arise as dissipative (...) structures generated by interacting cortical rhythms; whereas the non-geometrical dark phase patterns have as their NCCs dendritic potentials in the GABAergic gap-junction linked network in layers II and III of the visual cortex. (shrink)
Mark Crooks effectively demolishes Dennett's theory by concentrating on its internal defects. In which case I would like to contribute to this discussion by examining some scientific evidence that may be relevant. Dennett claims that hallucinations do not involve any actual sensory element but only a change in our beliefs. A schizophrenic does not actually hear the voices he complains about--he develops the false belief that he is hearing something. This puts hallucinations on a par with the patient's delusions e.g. (...) his false belief that other people are persecuting him. The majority view, in contrast, is that hallucinations represent defective function in the sensory system. In this impasse, evidence from functional magnetic resonance imaging studies should help. These allow us to identify those areas of the brain that are activated under the conditions we are interested in. If the majority are right, then a subject having hallucinations should show increased activity in some part of his sensory brain. On the other hand, if Dennett is right, the subject should show no such increased activity but, instead, possibly abnormal activity in the part of the brain related to the formation of delusions. To answer this question I performed a Medline search of the literature on imaging studies in hallucinations occurring under various circumstances. The results were interesting. 2012 APA, all rights reserved). (shrink)
Presenting some modern views on the problem of the nature of mind and its relationship to the brain, this book, published in 1965, brings together contributors from various disciplines which are affected by this issue. Coming from different philosophical outlooks as well as subjects, these contributors also comment on each other’s’ chapters with a view of developing thought on the approaches to the problem. The theory of mind-brain relationship is vital to human interest and has been in debate throughout western (...) thought over centuries, split mainly into dualist and monistic theories. These discussions had and still have wide impact philosophy, psychology, religion and cosmology, among other areas. (shrink)