Abstract:   Evolution leads to more and more complex structures, e.g., molecules, cells and organisms. By means of such structures elementary dynamic bio-electrical fields originate in single cells. They further develop into neurons with neuronal fields, and these combine and integrate in brains into global neuro-electrical fields (NEF) as a medium for the fast representation of outer stimuli. The present hypothesis proposes a specific state of the global NEF in brains as the signature of consciousness. This NEF changes periodically between two states, a de- and a hyperpolarized brain state, and these in turn are paralleled intimately by transitions between consciousness and unconsciousness. In the hyperpolarized state the elementary neuronal fields are enslaved and synchronized by strong oscillations, and under these conditions the NEF is of low information capacity. In the depolarized state, however, the elementary fields are freed to self-organize and superimpose into an integrated NEF rich in information. In this condition the NEF acquires a qualitatively new state variable: consciousness. This new variable is no longer physically measurable; it can only be perceived by introspection

Abstract: The neuroanatomical substrates controlling and regulating sleeping and waking, and thus consciousness, are located in the brain stem. Most crucial for bringing the brain into a state conducive for consciousness and information processing is the mesencephalic part of the brain stem. This part controls the state of waking, which is generally associated with a high degree of consciousness. Wakefulness is accompanied by a low-amplitude, high-frequency electroencephalogram, due to the fact that thalamocortical neurons fire in a state of tonic depolarization. Information can easily pass the low-level threshold of these neurons, leading to a high transfer ratio. The complexity of the electroencephalogram during conscious waking is high, as expressed in a high correlation dimension. Accordingly, the level of information processing is high. Spindles, and alpha waves in humans, mark the transition from wakefulness to sleep. These phenomena are related to drowsiness, associated with a reduction in consciousness. Drowsiness occurs when cells undergo moderate hyperpolarizations. Increased inhibitions result in a reduction of afferent information, with a lowered transfer ratio. Information processing subsides, which is also expressed in a diminished correlation dimension. Consciousness is further decreased at the onset of slow wave sleep. This sleep is controlled by the medullar reticular formation and is characterized by a high-voltage, low-frequency electroencephalogram. Slow wave sleep becomes manifest when neurons undergo a further hyperpolarization. Inhibitory activities are so strong that the transfer ratio further drops, as does the correlation dimension. Thus, sensory information is largely blocked and information processing is on a low level. Finally, rapid eye movement sleep is regulated by the pontine reticular formation and is associated with a ''wake-like'' electroencephalographic pattern. Just as during wakefulness, this is the expression of a depolarization of thalamocortical neurons. The transfer ratio of rapid eye movement sleep has not yet been determined, but seems to vary. Evidence exists that this type of sleep, associated with dreaming, with some kind of perception and consciousness, is involved in processing of ''internal'' information. In line with this, rapid eye movement sleep has higher correlation dimensions than slow-wave sleep and sometimes even higher than wakefulness. It is assumed that the ''near-the-threshold'' depolarized state of neurons in the thalamus and cerebral cortex is a necessary condition for perceptual processes and consciousness, such as occurs during waking and in an altered form during rapid eye movement sleep

Abstract: 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)

Abstract: “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)

Abstract: Participants were required to switch among randomly ordered tasks, and instructional cues were used to indicate which task to execute. In Experiments 1 and 2, the participants indicated their readiness for the task switch before they received the target stimulus; thus, each trial was associated with two primary dependent measures: (1) readiness time and (2) target reaction time. Slow readiness responses and instructions emphasizing high readiness were paradoxically accompanied by slow target reaction time. Moreover, the effect of task switching on readiness time was an order of magnitude smaller then the (objectively estimated) duration required for task preparation (Experiment 3). The results strongly suggest that participants have little conscious awareness of their preparedness and challenge commonly accepted assumptions concerning the role of consciousness in cognitive control

Abstract: 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)

Abstract: conscious content like ``the self in the act of In 1989 the philosopher Colin McGinn asked the knowing'' (see, e.g., chapters 7 and 20 in this following question: ``How can technicolor phe- volume) or high-level phenomenal properties like nomenology arise from soggy gray matter?'' ``coherence'' or ``holism'' (e.g., chapters 8 and 9 (1989: 349). Since then many authors in the ®eld in this volume). But what, precisely, does it mean of consciousness research have quoted this ques- that conscious experience has a ``content''? Is tion over and over, like a slogan that in a nut- this an entity open to empirical research pro- shell conveys a deep and important theoretical grams and interdisciplinary cooperation? And problem. It seems that almost none of them dis- what would it mean to map this content onto covered the subtle trap inherent in this question. physical states ``under a certain description''? In The brain is not gray. The brain is colorless. other words: What kinds of relations a

Abstract: Based on theoretical considerations of Aurell (1979) and Block (1995), we argue that object recognition awareness is distinct from purely sensory awareness and that the former is mediated by neuronal activities in areas that are separate and distinct from cortical sensory areas. We propose that two of the principal functions of neuronal activities in sensory cortex, which are to provide sensory awareness and to effect the computations that are necessary for object recognition, are dissociated. We provide examples of how this dissociation might be achieved and argue that the components of the neuronal activities which carry the computations do not directly enter the awareness of the subject. The results of these computations are sparse representations (i.e., vector or distributed codes) which are activated by the presentation of particular sensory objects and are essentially engrams for the recognition of objects. These final representations occur in the highest order areas of sensory cortex; in the visual analyzer, the areas include the anterior part of the inferior temporal cortex and the perirhinal cortex. We propose, based on lesion and connectional data, that the two areas in which activities provide recognition awareness are the temporopolar cortex and the medial orbitofrontal cortex. Activities in the temporopolar cortex provide the recognition awareness of objects learned in the remote past (consolidated object recognition), and those in the medial orbitofrontal cortex provide the recognition awareness of objects learned in the recent past. The activation of the sparse representation for a particular sensory object in turn activates neurons in one or both of these regions of cortex, and it is the activities of these neurons that provide the awareness of recognition of the object in question. The neural circuitry involved in the activation of these representations is discussed

Abstract: The neural and endocrine bases of the generation of thirst are reviewed. Based on this review, a hierarchical system of neural structures that regulate water conservation and acquisition is proposed. The system includes primary sensory-receptive areas; secondary sensory structures (circumventricular organs), which detect levels of hormones, including angiotensin II and vasopressin, which are involved in generating thirst; preoptic and hypothalamic structures; and an area within the ventrolateral quadrant of the periaqueductal gray matter. Hodological and other data are used to determine the hierarchical organization of the system. Based on studies of the effects of lesions to various structures within the hierarchy of the system, it is proposed that the awareness of thirst in rodents is either entirely or predominantly due to neuronal activities in a subsection of the ventrolateral periaqueductal gray matter. It is also hypothesized that the awareness of thirst in primates is due to neuronal activities in both the ventrolateral periaqueductal gray and in a region within the medial prefrontal and anterior cingulate cortex

Abstract: A lesion of striate cortex, area V1, produces blindness in the retinotopically corresponding part of the visual field, although in some cases visual abilities in the blind field remain that are paradoxically devoid of conscious visual percepts ("blindsight"). Here we demonstrate that the blindsight subject GY can experience visual sensations of phosphenes in his blind field induced by transcranial magnetic stimulation (TMS). Such blind field percepts could only be induced when stimulation was applied bilaterally, i.e. over GY's area V5/MT in both hemispheres.