Level Of Arousal And Content Of Consciousness
There are two common but distinct dimensions of the term consciousness, one involving arousal and states of consciousness and the other involving content of consciousness and conscious states. To be conscious of anything the brain must be in a relatively high state of arousal , whether in wakefulness or REM sleep, vividly experienced in dreams although usually not remembered. Brain arousal level fluctuates in a circadian rhythm but may be influenced by lack of sleep, drugs and alcohol, physical exertion, etc. Arousal can be measured behaviorally by the signal amplitude that triggers some criterion reaction . Clinicians use scoring systems such as the Glasgow Coma Scale to assess the level of arousal in patients.
High arousal states are associated with conscious states that have specific content, seeing, hearing, remembering, planning or fantasizing about something. Different levels or states of consciousness are associated with different kinds of conscious experiences. The “awake” state is quite different from the “dreaming” state and from the state of deep sleep. In all three cases the basic physiology of the brain is affected, as it also is in altered states of consciousness, for instance after taking drugs or during meditation when conscious perception and insight may be enhanced compared to the normal waking state.
Consciousness Without A Cerebral Cortex
The thalamocortical complex does not seem to be critically essential for consciousness experience. Brainstem mechanisms by its own can create adequate consciousness state. This means that Consciousness without a cerebral cortex is possible . Penfield and Jasper note that a cortical removal even as radical as hemispherectomy deprived their patients certainly from of information and discriminative capacities but not consciousness . An explicit reference to the midbrain reticular formation was always included in Penfield and Jasper definition of their proposed centrencephalic system. Sprague in 1966 contribute significantly to consciousness research after performing complete removal of the posterior visual areas of one hemisphere in the cat. Agrees well with the Penfield and Jasper perspective that without cognizance of potential subcortical contributions to cortical damage deficit, the cortical functions will be counterfactually inflated . Striking scientific agreement arguing strongly against the necessity of cerebral cortex for consciousness experience is seen in children born without cortex, namely Hydranenecephalic children. It is a congenital anomaly of the brain where for genetic or acquired reasons the cerebral cortex is drastically under developed and replaced by cerebrospinal fluid .
Mayan And Incan Theories Of Consciousness
First appearing in the historical records of the ancient Mayan and Incan civilizations, various theories of multiple levels of consciousness have pervaded spiritual, psychological, medical, and moral speculations in both Eastern and Western cultures. Consciousness can be defined as human awareness to both internal and external stimuli. Because of occasional and sometimes substantial overlap between hypotheses, there have recently been attempts to combine perspectives to form new models that integrate components of separate viewpoints.
The Ancient Mayans were among the first to propose an organized sense of each level of consciousness, its purpose, and its temporal connection to humankind. Because consciousness incorporates stimuli from the environment as well as internal stimuli, the Mayans believed it to be the most basic form of existence, capable of evolution. The Incas, however, considered consciousness a progression not only of awareness but of concern for others as well.
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Which Region Of The Brain Is Necessary For Consciousness
For thousands of years, everyone from great thinkers, priests and philosophers to psychologists and neuroscientists have battled to understand human consciousness.
As far back as the ancient Maya and Inca four millennia ago, whole civilizations have struggled to define consciousness. Countless philosophers since then as well as many leading minds in many different fields today continue to do so.
There are many questions relating to what consciousness is from a philosophical standpoint
But, up until recently, there were just as many questions on the physical side too:
Specifically, which region of the brain is necessary for consciousness?
In the past few years, scientists think they might have found at least part of the answer to this latter question
To understand the answer though, we need to know a little about how the human brain works:
Harvard Scientists Think They’ve Pinpointed The Physical Source Of Consciousness
Scientists have struggled for millennia to understand human consciousness – the awareness of one’s existence. Despite advances in neuroscience, we still don’t really know where it comes from, and how it arises.
But researchers think they might be closer to identifying its physical origins, after a study pinpointing a network of three specific regions in the brain that appear to be crucial to consciousness.
“For the first time, we have found a connection between the brainstem region involved in arousal and regions involved in awareness, two prerequisites for consciousness,” said lead researcher Michael Fox from the Beth Israel Deaconess Medical Centre at Harvard Medical School back in 2016.
“A lot of pieces of evidence all came together to point to this network playing a role in human consciousness.”
Consciousness is generally thought of as being comprised of two critical components – arousal and awareness.
Researchers had already shown that arousal is likely regulated by the brainstem – the portion of the brain that links up with the spinal cord – seeing as it regulates when we sleep and wake, and our heart rate and breathing.
Awareness has been more elusive. Researchers have long thought that it resides somewhere in the cortex – the outer layer of the brain – but no one has been able to pinpoint where.
To figure this out, the team analysed 36 patients in hospital with brainstem lesions – 12 of them were in a coma and 24 were defined as being conscious.
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Does Consciousness Require Prefrontal Activity
However, the view that conscious states always require fronto-parietal activity locked together stands in the way of mind melding. It implies that what is going on in the parietal and temporal lobes of the second person is not itself a conscious state, but merely an incomplete part of one. If so, then the first person is not actually getting in touch with a conscious state of the second person. In order to meet this objection, evidence that conscious states can exist in full in the parietal and temporal lobes, without connections to the prefrontal lobes, is required.
I think De Sousa is fundamentally correct in stating that phenomenal consciousness is mainly associated with activity of sensory regions , whereas, access consciousness requires the additional involvement of frontal areas . De Sousa lists some of the best evidence in favour of the view that consciousness can exist in the posterior region of the cortex alone, which is also shared by Zeki and Lamme . Gennaro also contains an excellent catalogue of such evidence. The next section contains a list of such states.
Problem Of Other Minds
Many philosophers consider experience to be the essence of consciousness, and believe that experience can only fully be known from the inside, subjectively. But if consciousness is subjective and not visible from the outside, why do the vast majority of people believe that other people are conscious, but rocks and trees are not? This is called the problem of other minds. It is particularly acute for people who believe in the possibility of philosophical zombies, that is, people who think it is possible in principle to have an entity that is physically indistinguishable from a human being and behaves like a human being in every way but nevertheless lacks consciousness. Related issues have also been studied extensively by Greg Littmann of the University of Illinois, and by Colin Allen regarding the literature and research studying artificial intelligence in androids.
On July 7, 2012, eminent scientists from different branches of neuroscience gathered at the University of Cambridge to celebrate the Francis Crick Memorial Conference, which deals with consciousness in humans and pre-linguistic consciousness in nonhuman animals. After the conference, they signed in the presence of Stephen Hawking, the ‘Cambridge Declaration on Consciousness’, which summarizes the most important findings of the survey:
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Biological Function And Evolution
Opinions are divided as to where in biological evolution consciousness emerged and about whether or not consciousness has any survival value. Some argue that consciousness is a byproduct of evolution. It has been argued that consciousness emerged exclusively with the first humans, exclusively with the first mammals, independently in mammals and birds, or with the first reptiles. Other authors date the origins of consciousness to the first animals with nervous systems or early vertebrates in the Cambrian over 500 million years ago.Donald Griffin suggests in his book Animal Minds a gradual evolution of consciousness. Each of these scenarios raises the question of the possible survival value of consciousness.
Global Disorders Of Consciousness
Given the absence of any accepted criterion of the minimal neuronal correlates necessary for consciousness, the distinction between a persistently vegetative patient who shows regular sleep-wave transitions and may be able to move or smile, and a minimally conscious patient who can communicate in a meaningful manner and who shows some signs of consciousness, is often difficult. In global anesthesia the patient should not experience psychological trauma but the level of arousal should be compatible with clinical exigencies.
Blood-oxygen-level-dependent fMRI have demonstrated normal patterns of brain activity in a patient in a vegetative state following a severe traumatic brain injury when asked to imagine playing tennis or visiting rooms in his/her house. Differential brain imaging of patients with such global disturbances of consciousness reveal that dysfunction in a widespread cortical network including medial and lateral prefrontal and parietal associative areas is associated with a global loss of awareness. Impaired consciousness in epileptic seizures of the temporal lobe was likewise accompanied by a decrease in cerebral blood flow in frontal and parietal association cortex and an increase in midline structures such as the mediodorsal thalamus.
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Vegetative State And The Intentional Action Inference
The Intentional Action Inference is operative when subjective reportsare not available. For example, it is deployed in arguing that somepatients diagnosed as being in the vegetative state are conscious.
A patient in the vegetative state appears at times to be wakeful, withcycles of eye closure and eye opening resembling those of sleep andwaking. However, close observation reveals no sign of awareness or ofa functioning mind: specifically, there is no evidencethat the patient can perceive the environment or his/her own body,communicate with others, or form intentions. As a rule, the patientcan breathe spontaneously and has a stable circulation. The state maybe a transient stage in the recovery from coma or it may persist untildeath.
Vegetative state patients are not clinically comatose but fall shortof being in a minimally conscious state. Unlikevegetative state patients, minimally conscious state patientsseemingly perform intentional actions.
Owen et al. draw on a neural correlate of imagination, a mentalaction. Arguing that the neural correlate provides evidence of thepatients executing an intentional action, they invoke a versionof the Intentional Action Inference to argue that performance providesevidence for specific consciousness tied to the information carried inthe brain areas activated. Of note, experiments stimulating theparahippocampal place area induces seeming hallucinations of places.
Consciousness: New Concepts And Neural Networks
- 1Department of Neurosurgery, Huashan Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China
- 2Center for Neuroscience Research, Loma Linda University School of Medicine, Loma Linda, CA, United States
The definition of consciousness remains a difficult issue that requires urgent understanding and resolution. Currently, consciousness research is an intensely focused area of neuroscience. However, to establish a greater understanding of the concept of consciousness, more detailed, intrinsic neurobiological research is needed. Additionally, an accurate assessment of the level of consciousness may strengthen our awareness of this concept and provide new ideas for patients undergoing clinical treatment of consciousness disorders. In addition, research efforts that help elucidate the concept of consciousness have important scientific and clinical significance. This review presents the latest progress in consciousness research and proposes our assumptions with regard to the network of consciousness.
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The Free Veto Interpretation
Libet thought that an RP may not be a sufficient condition for an act to occur, since an intended act, preceded by an RP, can be aborted by a veto signal. According to the free veto hypothesis, the conscious mind can, in extreme situations, override the initial impulse that is reflected in the RP. A person, who feels an urge to hit someone, also has the capacity to veto the subconsciously generated impulse. The free veto saves at least part of our moral responsibility. It is, however, easy to imagine a situation where the ethically correct behavior requires a positive action, and not just to suppress primitive urges.
Brief Critical Review Of The Experimental Evidence
In the following, we sum up the present evidence for ICW, contrasting its traditional interpretation with rarely considered alternative explanations of the data. Figure 1 summarizes the main experiments referred to in the text below.
Schematic description of some of the experimental loci discussed in the text. SMA=Supplementary motor area, PFC=Prefrontal cortex, PMC=Premotor cortex, SSC=Somatosensory cortex. L-S1 and LS-2 corresponds to Libets stimulation of the hand, and of the somatosensory brain area, respectively. L-R1 is the recording of RP from SMA of Libet . S-R1 and S-R2 correspond roughly to the brain areas, where Soon et al. detected nerve signals 10 s before the awareness of a willful act. D-S1 and D-S2 correspond roughly to the areas stimulated by Desmurget et al. F-S is the stimulation to the SMA by Fried et al.
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The Coherence Of The Concept
Philosophers differ from non-philosophers in their intuitions about what consciousness is. While most people have a strong intuition for the existence of what they refer to as consciousness, skeptics argue that this intuition is false, either because the concept of consciousness is intrinsically incoherent, or because our intuitions about it are based in illusions. Gilbert Ryle, for example, argued that traditional understanding of consciousness depends on a Cartesian dualist outlook that improperly distinguishes between mind and body, or between mind and world. He proposed that we speak not of minds, bodies, and the world, but of individuals, or persons, acting in the world. Thus, by speaking of “consciousness” we end up misleading ourselves by thinking that there is any sort of thing as consciousness separated from behavioral and linguistic understandings.
Neurobiological Theories Of Consciousness
Recall that the Generic Consciousness question asks:
What conditions/states N of nervous systems are necessary and/orsufficient for a mental state, M, to be conscious as opposed tonot?
Victor Lamme notes:
Deciding whether there is phenomenality in a mental representationimplies putting a boundarydrawing a linebetweendifferent types of representationsWe have to start from theintuition that consciousness exists, and isa mental function in its own right. That intuition immediately impliesthat there is also unconscious information processing.
It is uncontroversial that there is unconscious informationprocessing, say processing occurring in a computer. What Lamme meansis that there are conscious and unconscious mental states. For example, there might be visual states of seeingX that are conscious or not .
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Why Is This Useful
For people in an unconscious state that are unable to wake up, there may be a possibility for some sort of therapy as scientists start understanding what parts of the brain control consciousness and thus, what parts to target. This would be similar to the way deep brain stimulation is currently being experimented with as a treatment for Parkinsons Disease.
It also might be possible to stimulate some parts of the brain to address depression as well as a variety of consciousness disorders.
Neurobiological Approach To Consciousness
A science of consciousness must explain the exact relationship between subjective mental states and brain states, the nature of the relationship between the conscious mind and the electro-chemical interactions in the body . Progress in neuropsychology and neurophilosophy has come from focusing on the body rather than the mind. In this context the neuronal correlates of consciousness may be viewed as its causes, and consciousness may be thought of as a state-dependent property of some undefined complex, adaptive, and highly interconnected biological system.
Discovering and characterizing neural correlates does not offer a theory of consciousness that can explain how particular systems experience anything at all, or how and why they are associated with consciousness, the so-called hard problem of consciousness, but understanding the NCC may be a step toward such a theory. Most neurobiologists assume that the variables giving rise to consciousness are to be found at the neuronal level, governed by classical physics, though a few scholars have proposed theories of quantum consciousness based on quantum mechanics.
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The Frontoparietal Circuits And Its Role In Consciousness
The contribution of frontoparietal activity to conscious perception was suggested by neuroimaging studies. In addition to visual perception due to activity in the ventral visual cortex, the parietal and prefrontal areas contribution seems to be essential for awareness . The network nodes for correlates of consciousness are thought to be divided to primary and secondary. Early activity in the occipital lobe correlates with the perceptual processes, which is detrimental for later process, namely, the activity in the frontoparietal areas. Access consciousness, in comparison to the phenomenal subjective consciousness due to mainly activation of sensory regions, refers to the direct control of experience through reasoning, reporting, or action. This type of higher functioning needs the involvement of the frontoparietal areas .