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PubMed2006

Unconscious processing embedded in conscious processing: evidence from gaze time on Chinese sentence reading.

The current study aims to separate conscious and unconscious behaviors by employing both online and offline measures while the participants were consciously performing a task. Using an eye-movement tracking paradigm, we observed participants' response patterns for distinguishing within-word-boundary and across-word-boundary reverse errors while reading Chinese sentences (also known as the "word inferiority effect"). The results showed that when the participants consciously detected errors, their gaze time for target words associated with across-word-boundary reverse errors was significantly longer than that for targets words associated with within-word-boundary reverse errors. Surprisingly, the same gaze time pattern was found even when the readers were not consciously aware of the reverse errors. The results were statistically robust, providing converging evidence for the feasibility of our experimental paradigm in decoupling offline behaviors and the online, automatic, and unconscious aspects of cognitive processing in reading.

Analysis of Variance↗
PubMed2006

Conscious contributions to subliminal priming.

Choice reaction times to visual stimuli (targets) may be influenced by preceding subliminal stimuli (primes). Some authors reported a straight priming effect i.e., responses were faster when primes and targets called for the same response than when they called for different responses. Others found the reversed pattern of results. Eimer and Schlaghecken [Eimer, M. & Schlaghecken, F. (2002). Links between conscious awareness and response inhibition: evidence from masked priming. Psychonomic Bulletin &Review, 9, 514-520.] showed recently that straight priming occurs whenever a prime is not efficiently masked thereby the information provided by the prime is accessible for consciousness. In the present study, a hypothesis is tested that straight priming is due to mediation of consciousness. To test this hypothesis, prime validity was manipulated. We showed that even when no mask was used so that participants could fully and consciously perceive the prime and participants were informed that primes were mostly invalid, for the short prime-target ISI interval (100 ms) straight priming occurred. The priming was inverse when the ISI was 800 ms. This indicates that participants were able to use the information provided by the prime to prepare the response opposite to that cued by the prime but only if the time between the prime and the target was long enough.

Adult↗
PubMed2005

Predicting the stream of consciousness from activity in human visual cortex.

Can the rapid stream of conscious experience be predicted from brain activity alone? Recently, spatial patterns of activity in visual cortex have been successfully used to predict feature-specific stimulus representations for both visible and invisible stimuli. However, because these studies examined only the prediction of static and unchanging perceptual states during extended periods of stimulation, it remains unclear whether activity in early visual cortex can also predict the rapidly and spontaneously changing stream of consciousness. Here, we used binocular rivalry to induce frequent spontaneous and stochastic changes in conscious experience without any corresponding changes in sensory stimulation, while measuring brain activity with fMRI. Using information that was present in the multivariate pattern of responses to stimulus features, we could accurately predict, and therefore track, participants' conscious experience from the fMRI signal alone while it underwent many spontaneous changes. Prediction in primary visual cortex primarily reflected eye-based signals, whereas prediction in higher areas reflected the color of the percept. Furthermore, accurate prediction during binocular rivalry could be established with signals recorded during stable monocular viewing, showing that prediction generalized across viewing conditions and did not require or rely on motor responses. It is therefore possible to predict the dynamically changing time course of subjective experience with only brain activity.

Adult↗
PubMed2004

Spin-mediated consciousness theory: possible roles of neural membrane nuclear spin ensembles and paramagnetic oxygen.

A novel theory of consciousness is proposed in this paper. We postulate that consciousness is intrinsically connected to quantum spin since the latter is the origin of quantum effects in both Bohm and Hestenes quantum formulism and a fundamental quantum process associated with the structure of space-time. That is, spin is the "mind-pixel". The unity of mind is achieved by entanglement of the mind-pixels. Applying these ideas to the particular structures and dynamics of the brain, we theorize that human brain works as follows: through action potential modulated nuclear spin interactions and paramagnetic O2/NO driven activations, the nuclear spins inside neural membranes and proteins form various entangled quantum states some of which survive decoherence through quantum Zeno effects or in decoherence-free subspaces and then collapse contextually via irreversible and non-computable means producing consciousness and, in turn, the collective spin dynamics associated with said collapses have effects through spin chemistry on classical neural activities thus influencing the neural networks of the brain. Our proposal calls for extension of associative encoding of neural memories to the dynamical structures of neural membranes and proteins. Thus, according our theory, the nuclear spin ensembles are the "mind-screen" with nuclear spins as its pixels, the neural membranes and proteins are the mind-screen and memory matrices, and the biologically available paramagnetic species such as O2 and NO are pixel-activating agents. Together, they form the neural substrates of consciousness. We also present supporting evidence and make important predictions. We stress that our theory is experimentally verifiable with present technologies. Further, experimental realizations of intra-/inter-molecular nuclear spin coherence and entanglement, macroscopic entanglement of spin ensembles and NMR quantum computation, all in room temperatures, strongly suggest the possibility of a spin-mediated mind.

Action Potentials↗
PubMed2004

Rewards and punishments, goal-directed behavior and consciousness.

A parsimonious account of consciousness is given in which it emerges as a direct consequence of basic neural processes without the necessity of any higher order system. In this model, pleasant or unpleasant conscious feelings of various stimuli in the environment stem from their higher order associations to innate rewards or punishments. When a conditioned stimulus (CS) is associated with a reward, it acquires pleasant feelings due to the temporal correlation of the activations representing its sensory features with those representing innate visceral reward acquisition processes. When the CS is associated with the punishment, it acquires unpleasant feelings due to the correlation of its sensory features with the innate visceral inhibition of punishment acquisition processes. The correlations involve coherent activity between the sensory cortex, the limbic system, the orbital and medial prefrontal cortex, and more lateral prefrontal areas where stimuli can be incorporated into working memory. A conscious act involves responses (or attempts to improve the environment) made on the basis of the feelings of such stimuli. Covert memory scans, in which comparisons are made of the reward and punishment associations of the outcomes of previous responses, are related to the motivations and attention behind the conscious selection of a current response. This model appears to fit together various empirical observations. Its relations to some higher or more abstract mental processes, and some evolutionary implications are discussed.

Animals↗
PubMed2007

The involvement of the central cholinergic system in the pressor and bradycardic effects of centrally administrated melittin in normotensive conscious rats.

Recently we demonstrated that centrally administrated melittin, a phospholipase A(2) (PLA(2)) activator, caused pressor and bradycardic effect in the normotensive conscious rats. In the current study we aimed to determine the mediation of central cholinergic system in the pressor and bradycardic effect of centrally administrated melittin. Studies were performed in normotensive male Sprague-Dawley rats. 1.5, 3.0 or 6.0microg/5.0microl doses of melittin were injected intracerebroventricularly (i.c.v.). Melittin caused dose- and time-dependent increases in mean arterial pressure (MAP) and decrease in heart rate (HR). In order to test the mediation of central cholinergic system on the pressor and bradycardic effect of melittin, the rats were pretreated with mecamylamine (50microg; i.c.v.), cholinergic nonselective nicotinic receptor antagonist, atropine sulfate (10microg; i.c.v.), a cholinergic nonselective muscarinic receptor antagonist, hemicholinium-3 (20microg; i.c.v.), a high affinity neuronal choline uptake inhibitor, methyllycaconitine (10 and 25microg; i.c.v.) or alpha-bungarotoxin (10 and 25microg; i.c.v.), selective antagonists of alpha-7 subtype nicotinic acetylcholine receptors (alpha7nAChRs), 15min prior to melittin (3.0microg) injection. Pretreatment with mecamylamine, hemicholinium-3, methyllycaconitine or alpha-bungarotoxin partially attenuated the pressor and bradicardia effect of elicited by melittin in the normotensive conscious rats whereas pretreatment with atropine had no effect. In conclusion, i.c.v. administration of melittin increases MAP and decreases HR in conscious rats. The activation of central nicotinic cholinergic receptors, predominantly alpha7nAChRs, partially acts as a mediator in the pressor responses to i.c.v. injection of melittin in the normotensive conscious rats. Moreover, decreased uptake of choline to the cholinergic terminals may consider that melittin activates central choline and acetylcholine release, as well.

Aconitine↗
PubMed2005

Conscious intention and motor cognition.

The subjective experience of conscious intention is a key component of our mental life. Philosophers studying 'conscious free will' have discussed whether conscious intentions could cause actions, but modern neuroscience rejects this idea of mind-body causation. Instead, recent findings suggest that the conscious experience of intending to act arises from preparation for action in frontal and parietal brain areas. Intentional actions also involve a strong sense of agency, a sense of controlling events in the external world. Both intention and agency result from the brain processes for predictive motor control, not merely from retrospective inference.

Brain↗
PubMed2003

Brain, conscious experience and the observing self.

Conscious perception, like the sight of a coffee cup, seems to involve the brain identifying a stimulus. But conscious input activates more brain regions than are needed to identify coffee cups and faces. It spreads beyond sensory cortex to frontoparietal association areas, which do not serve stimulus identification as such. What is the role of those regions? Parietal cortex support the 'first person perspective' on the visual world, unconsciously framing the visual object stream. Some prefrontal areas select and interpret conscious events for executive control. Such functions can be viewed as properties of the subject, rather than the object, of experience - the 'observing self' that appears to be needed to maintain the conscious state.

Brain↗
PubMed2006

Immediate oxygen therapy prevents brain cell injury in carbon monoxide poisoned rats without loss of consciousness.

In CO-poisoned patients without loss of consciousness no significant long-term functional differences in outcome have been shown in any hyperbaric versus normobaric oxygen studies. Since brain histology changes cannot be studied in CO-poisoned patients we evaluated the efficacy of normobaric and hyperbaric oxygen therapy in preventing brain cell injury in CO-poisoned animals without loss of consciousness. Wistar rats without loss of consciousness after exposure to 3000ppm of CO for 60min were exposed to ambient air (group 1), 100% oxygen at a pressure of 1bar (group 2) and 100% oxygen at a pressure of 3bar (group 3). The rats were sacrificed after two weeks, brain samples were stained with hematoxylin-eosin and a percentage of pyknotic cells in hippocampus was reported. Analyses of differences in percentage of pyknotic cells between different kinds of therapy showed that the percentage of pyknotic cells of the second group (2.3+/-1.2%) treated with normobaric oxygen and the third group (4.5+/-4.0%) treated with hyperbaric oxygen were similar, and both of them were significantly different, with a much lower percentage of pyknotic cells, from the first group left on ambient air (47.7+/-10.0%). In conclusion, immediate normobaric and hyperbaric oxygen therapy equally prevents hippocampal cell injury in CO-poisoned rats without loss of consciousness.

Animals↗
PubMed2005

Global workspace theory of consciousness: toward a cognitive neuroscience of human experience.

Global workspace (GW) theory emerged from the cognitive architecture tradition in cognitive science. Newell and co-workers were the first to show the utility of a GW or "blackboard" architecture in a distributed set of knowledge sources, which could cooperatively solve problems that no single constituent could solve alone. The empirical connection with conscious cognition was made by Baars (1988, 2002). GW theory generates explicit predictions for conscious aspects of perception, emotion, motivation, learning, working memory, voluntary control, and self systems in the brain. It has similarities to biological theories such as Neural Darwinism and dynamical theories of brain functioning. Functional brain imaging now shows that conscious cognition is distinctively associated with wide spread of cortical activity, notably toward frontoparietal and medial temporal regions. Unconscious comparison conditions tend to activate only local regions, such as visual projection areas. Frontoparietal hypometabolism is also implicated in unconscious states, including deep sleep, coma, vegetative states, epileptic loss of consciousness, and general anesthesia. These findings are consistent with the GW hypothesis, which is now favored by a number of scientists and philosophers.

Cognition↗
PubMed2005

Event-related potential measures of consciousness: two equations with three unknowns.

This is a brief review of event-related brain potentials (ERPs) as indices of cortical information processing in conditions in which conscious perception of stimuli is supposed to be absent: sleep, coma, vegetative state, general anesthesia, neglect as well as presentation of subliminal or masked stimuli. Exogenous ERP components such as N1 and P2 are much more likely to remain in all these conditions than endogenous components. Further, all varieties of the late posterior positive ERP waves (e.g., P3b, P600, late positive complex) are most difficult to be elicited in such conditions, indicating that the cortical activity underlying the late posterior positivity may have a particularly close relationship to brain mechanisms of conscious perception. Contrary to what might be expected, reliable ERP effects indicating complex analysis of semantic stimulus features (i.e., meaning) can be recorded without conscious awareness, generally, as easy as (in some conditions, even easier than) ERP components related to rather simple physical stimulus features. It should be emphasized, however, that we never should overestimate our confidence about the degree of subjects' unawareness. Particularly in the conditions in which no behavioral response can be obtained (e.g., sleep, coma, anesthesia), residual conscious processing, at least in some subjects and on some trials, cannot be ruled out.

Anesthesia↗
PubMed2005

Clinical pragmatism and the care of brain damaged patients: toward a palliative neuroethics for disorders of consciousness.

Unraveling the mysteries of consciousness, lost and regained, and perhaps even intervening so as to prompt recovery are advances for which neither the clinical nor the lay community are prepared. These advances will shake existing expectations about severe brain damage and will find an unprepared clinical context, perhaps even one inhospitable to what should clearly be viewed as important advances. This could be the outcome of this line of inquiry, if this exceptionally imaginative research can continue at all. This work faces a restrictive research environment that has the potential to imperil it. Added to the complexity of the scientific challenges that must be overcome is the societal context in which these investigations must occur. Research on human consciousness goes to the heart of our humanity and asks us to grapple with fundamental questions about the self. Added to this is the regulatory complexity of research on subjects who may be unable to provide their own consent because of impaired decision-making capacity, itself a function of altered or impaired consciousness. These factors can lead to a restrictive view of research that can favor risk aversion over discovery. In this paper, I attempt to explain systematically some of these challenges. I suggest that some of the resistance might be tempered if we view the needs of patients with severe brain injury through the prism of palliative care and adopt that field's ethos and methods when caring for and conducting research on individuals with severe brain damage and disorders of consciousness. To make this argument I draw upon the American pragmatic tradition and utilize clinical pragmatism, a method of moral problem-solving that my colleagues and I have developed to address ethical challenges in clinical care and research.

Brain Damage, Chronic↗
PubMed1999

Changes in micturition after spinal cord injury in conscious rats.

OBJECTIVES: To determine the feasibility of urodynamic monitoring of voiding function in conscious, female spinal cord-injured (SCI) rats and to compare the voiding function in SCI rats and those with normal spinal cord (NSC). METHODS: Cystometrograms were performed on conscious, female Sprague-Dawley rats. Parameters measured included voided volume, residual volume, volume threshold for inducing micturition, voiding efficiency, micturition pressure, pressure threshold for inducing micturition, and bladder contraction duration. SCI animals were studied 2 to 3 weeks after T8-T10 spinal cord transection. RESULTS: Approximately one half of SCI rats exhibited uninhibited bladder contractions before voiding. These contractions were not observed in NSC rats. Compared with NSC rats, SCI rats had larger volume thresholds (1.43 versus 0.34 mL, P <0.001) and voided volumes (0.72 versus 0.31 mL, P <0.01). Although SCI rats had larger micturition pressures (65 versus 35 cm H2O, P <0.001), residual volumes were increased (0.71 versus 0.03 mL, P <0.001) and voiding efficiency was decreased (50% versus 92%, P <0.001) compared with the measurements in NSC rats. The micturition pressure threshold was slightly lower (23%, P <0.05) and the bladder contraction duration was longer (33%, P <0.05) in SCI rats than in NSC rats. CONCLUSIONS: Cystometric studies in conscious female SCI and NSC rats revealed significant changes in the activity of the lower urinary tract after spinal cord transection. Fifty-five percent of SCI rats exhibited detrusor hyperreflexia during bladder filling and decreased voiding efficiency compared with NSC animals. This method of cystometric evaluation in the conscious animal is likely to be useful for evaluating new pharmacologic treatments for neurogenic bladder dysfunction.

Animals↗
PubMed2001

Cooperation of the basal ganglia, cerebellum, sensory cerebrum and hippocampus: possible implications for cognition, consciousness, intelligence and creativity.

It is suggested that the anatomical structures which mediate consciousness evolved as decisive embellishments to a (non-conscious) design strategy present even in the simplest unicellular organisms. Consciousness is thus not the pinnacle of a hierarchy whose base is the primitive reflex, because reflexes require a nervous system, which the single-celled creature does not possess. By postulating that consciousness is intimately connected to self-paced probing of the environment, also prominent in prokaryotic behavior, one can make mammalian neuroanatomy amenable to dramatically straightforward rationalization. Muscular contraction is the nervous system's only externally directed product, and the signaling routes which pass through the various brain components must ultimately converge on the motor areas. The function of several components is still debatable, so it might seem premature to analyze the global operation of the circuit these routes constitute. But such analysis produces a remarkably simple picture, and it sheds new light on the roles of the individual components. The underlying principle is conditionally permitted movement, some components being able to veto muscular contraction by denying the motor areas sufficient activation. This is true of the basal ganglia (BG) and the cerebellum (Cb), which act in tandem with the sensory cerebrum, and which can prevent the latter's signals to the motor areas from exceeding the threshold for overt movement. It is also true of the anterior cingulate, which appears to play a major role in directing attention. In mammals, the result can be mere thought, provided that a second lower threshold is exceeded. The veto functions of the BG and the Cb stem from inhibition, but the countermanding disinhibition develops at markedly different rates in those two key components. It develops rapidly in the BG, control being exercised by the amygdala, which itself is governed by various other brain regions. It develops over time in the Cb, thereby permitting previously executed movements that have proved advantageous. If cognition is linked to overt or covert movement, intelligence becomes the ability to consolidate individual motor elements into more complex patterns, and creativity is the outcome of a race-to-threshold process which centers on the motor areas. Amongst the ramifications of these ideas are aspects of cortical oscillations, phantom limb sensations, amyotrophic lateral sclerosis (ALS) the difficulty of self-tickling and mirror neurons.

Animals↗
PubMed2001

Early activation of the primary somatosensory cortex without conscious awareness of somatosensory stimuli in tumor patients.

The primary sensory cortex has usually been regarded as a necessary step in the information processing stream leading to conscious awareness. Recently, it has been proposed that that higher order associative areas rather than the primary sensory areas are the neural basis of conscious perception. In two patients with tumors near the central region we recorded magnetic somatosensory evoked fields. Magnetic source imaging revealed early (40 ms) neural activation in primary somatosensory cortex and absence of later (>60 ms) neural activation in the primary and associative areas in these patients. None of the patients showed conscious awareness of somatosensory stimuli applied to the corresponding body site although the first component of the evoked field was within normal limits. The time course of the magnetic responses and additional evidence on intensity ratings of somatosensory stimuli suggest that early activity in the primary somatosensory cortex is not sufficient for conscious experience to emerge.

Adult↗
PubMedDate not supplied

The Astrocentric Hypothesis: proposed role of astrocytes in consciousness and memory formation.

Consciousness is self-awareness. This process is closely associated with attention and working memory, a special form of short-term memory, which is vital when solving explicit task. Edelman has equated consciousness as the "remembered present" to highlight the importance of this form of memory (G.M. Edelman, Bright Air, Brilliant Fire, Basic Books, New York, 1992). The majority of other memories are recollections of past events that are encoded, stored, and brought back into consciousness if appropriate for solving new problems. Encoding prior experiences into memories is based on the salience of each event (A.R. Damasio, Descartes' Error, G.P. Putnam's Sons, New York, 1994; G.M. Edelman, Bright Air, Brilliant Fire, Basic Books, New York, 1992). It is proposed that protoplasmic astrocytes bind attended sensory information into consciousness and store encoded memories. This conclusion is supported by research conducted by gliobiologist over the past 15 years.

Animals↗
PubMedDate not supplied

A novel procedure for daily measurements of hemodynamical, hematological, and biochemical parameters in conscious unrestrained rats.

Accurate and chronic measurements of various parameters in conscious animals are fundamental for depicting pathological chronic conditions and their etiology in many experimental models, but they are often difficult to achieve. The aim of the present work was to develop and describe step-by-step a reproducible surgical procedure and daily manipulations for continuous, chronic use of conscious rats as models towards a better understanding of various cardiovascular and renal diseases and the testing of novel pharmacological drugs. The complete apparatus involved the use of a series of specialized devices (harness, rotating swivel, revolving arm) supporting a flexible, permanently implanted vascular catheter into the left femoral artery up to the abdominal aorta connected to a miniaturized individual peristaltic pump for delivering fluid at a constant rate. Such a set-up also enabled easy, quick, and reproducible daily blood sampling for the evaluation of more than 20 parameters, including the monitoring of heart rate (HR) and blood pressure in freely moving conscious rats. The overall success and survival rate reached 98% over 14 days and could be extended further. This model represents a much needed and valuable advance in surgical research techniques to evaluate the hemodynamic, hematological, biochemical, pharmacokinetic, and toxicological profile of any new drugs over time in conscious animal models such as rats. What makes this procedure satisfactory is the long-term reliable arterial access and reproducibility of the methodological approach for accurate and continuous measurements, minimizing the stress or invasiveness associated with the use of currently employed systems.

Animals↗
PubMed2004

Self-consciousness and trait anxiety as predictors of choking in sport.

The present study was designed to examine dispositional self-consciousness and trait anxiety as predictors of choking in sport. Sixty-six basketball players completed the Self-Consciousness Scale and the Sport Anxiety Scale prior to completing 20 free throws in low-pressure and high-pressure conditions. A manipulation check showed that participants experienced significantly higher levels of state anxiety in the high-pressure condition. A series of hierarchical multiple regression analyses supported the hypothesis that self-conscious athletes were more susceptible to choking under pressure. The best predictors of choking were private self-consciousness and somatic trait anxiety that together accounted for 35% of the explained variance. We discuss a number of possible explanations regarding the discrepancy between the present results and previous studies mainly relating to task characteristics, skill level of participants and manipulations of pressure.

Adult↗