Primary consciousness
Encyclopedia
Primary consciousness is a term the American biologist Gerald Edelman
coined to describe the ability, found in humans and some animals, to integrate observed events with memory to create an awareness of the present and immediate past of the world around them. This form of consciousness is also sometimes called "sensory consciousness". Put another way, primary consciousness is the presence of various subjective
sensory contents of consciousness such as sensations, perception
s, and mental images. For example, primary consciousness includes a person's experience of the blueness of the ocean, a bird's song, and the feeling of pain. Thus, primary consciousness refers to being mentally aware of things in the world in the present without any sense of past and future; it is composed of mental images bound to a time around the measurable present.
Conversely, higher order consciousness
can be described as being "conscious of being conscious"; it is accompanied by reflective thought and includes a past as well as speculation about the future.
Primary consciousness can be subdivided into two forms, focal awareness
and peripheral awareness. Focal awareness encompasses the center of attention
, whereas peripheral awareness consists of things outside the center of attention, which a person or animal is only dimly aware of.
for the neurophysiological
basis of primary consciousness was proposed by Gerald Edelman. This theory of consciousness is premised upon three major assumptions:
Edelman's theory focuses on two nervous system
organizations: the brainstem and limbic system
s on one side and the thalamus
and cerebral cortex
on the other side. The brain stem and limbic system take care of essential body functioning and survival, while the thalamocortical system receives signals from sensory receptors and sends out signals to voluntary muscles such as those of the arms and legs. The theory asserts that the connection of these two systems during evolution
helped animals learn adaptive behavior
s. This connection allows past signals related to values set by the limbic-brain stem system and categorized signals from the outside world to be correlated, resulting in memory in conceptual areas. This memory is then linked to the organism's current perception, which results in an awareness of the present, or primary consciousness. In other words, Edelman posits that primary consciousness arises from the correlation of conceptual memory to a set of ongoing perceptual categorizations—a "remembered present".
Other scientists have argued against Edelman's theory, instead suggesting that primary consciousness might have emerged with the basic vegetative systems of the brain. That is, the evolutionary origin might have come from sensations and primal emotions arising from sensors
and receptors, both internal and surface, signaling that the well-being of the creature was immediately threatened—for example, hunger for air, thirst, hunger, pain, and extreme temperature change. This is based on neurological data showing the thalamic
, hippocampal
, orbitofrontal
, insula
, and midbrain sites are the key to consciousness of thirst.
These scientists also point out that the cortex might not be as important to primary consciousness as some neuroscientists have believed. Evidence of this lies in the fact that studies show that systematically disabling parts of the cortex in animals does not remove consciousness. Another study found that children born without a cortex are conscious. Instead of cortical mechanisms, these scientists emphasize brainstem mechanisms as essential to consciousness. Still, these scientists concede that higher order consciousness does involve the cortex and complex communication between different areas of the brain.
and unconscious
states, but must also provide a guide by which the conscious level, or extent of consciousness, can be determined. Measures of consciousness are each associated with particular theories.
Certain defining theories are included below:
Worldly discrimination theory asserts that any mental state that is manifested in behavior
is conscious; thus, an organism is consciously aware of something in the world if it can discriminate it with choice behavior.
Signal detection theory quantifies discriminability of a stimulus among a set of different stimuli.
Integration theories focus on finding a divide between conscious and unconscious processes. According to integration theories, conscious contents are widely available to many cognitive and/or neural processes.
These theories are then accompanied with measures of the level of consciousness, which are subdivided into behavioral measures and physiological measures.
have been used to assess whether a stimulus
is consciously perceived or not. These EEG
measures either float free of theory, gaining credibility through reliable correlation, or assume a version of integration theory in which the appearance of a particular ERP indicates global availability or locally recurrent processing.
Abundant evidence indicates that consciously perceived inputs elicit widespread brain activation, as compared with inputs that do not reach consciousness.
The dynamic core hypothesis (DCH) proposes that consciousness arises from neural dynamics in the thalamocortical system, as measured by the quantity neural complexity (CN). CN is an information-theoretic measure; the CN value is high if each subset of a neural system can take on many different states, and if these states make a difference to the rest of the system.
The information integration theory of consciousness (IITC) shares with the DCH the idea that conscious experiences provide informative discriminations among a vast repertoire of possible experiences. In the IITC, the quantity phi is defined as the information that is integrated across the informational "weakest link" of a system. Importantly, phi is a measure of the capacity of a neural system to integrate information, whereas CN is a measure of the actual dynamics of the system. A third measure, causal density (CD), measures the fraction of causal interactions among elements of a system that are statistically significant.
conscious content assumes primary consciousness but not vice versa, subjective measures risk missing or rejecting the presence of sensory consciousness simply because metacognition isn't observed.
Furthermore, there is the problem of post-decision wagering, which has been criticized because there is a possibility that advantageous wagering could be learned unconsciously; as a result, post-decision wagering would not in fact be considered a conscious behavior. For example, individual differences in risk aversion
may lead to variations in wagering performance even with the same underlying conscious phenomenology.
Thus, although behavioral measures are mostly used for assessing which contents are conscious, some brain-based measures seem better suited for measuring conscious level. Objective measures also have their challenges, however. First, objective measures still require a response criterion, for example the decision of whether or not to push a button. Second, they may not even measure consciousness at all because many behavioral proxies, such as forced-choice decision accuracy, are capable of being learned unconsciously.
means that the human brain can simultaneously occupy two states: waking and dreaming. The dreaming portion has experiences and therefore has primary consciousness, while the waking self recognizes the dreaming and can be seen as having a sort of secondary consciousness
in the sense that there is an awareness of mental state. Studies have been able to show that lucid dreaming is associated with EEG power and coherence profiles that are significantly different from both non-lucid dreaming and waking. Lucid dreaming situates itself between those two states. Lucid dreaming is characterized by more 40 Hz power than non-lucid dreaming, especially in frontal regions. Since it is 40 Hz power that has been correlated with waking consciousness in previous studies, it can be suggested that enough 40 Hz power has been added to the non-lucid dreaming brain to support the increase in subjective awareness
that permits lucidity but not enough to cause full awakening.
Dreaming is thus a virtual reality
experience with a remarkably predictive simulation of external reality. Lucid dreamers may experience primary consciousness (the dream) and secondary consciousness (the waking) separately but simultaneously. Moreover, primary consciousness has recently been proposed by us to be characteristic of dreaming. It remains to be seen whether the enactment of dream behaviors uses the same brain processes as those that mediate those very behaviors in waking, and whether conscious within a dream is governed by the same processes.
during complex partial epileptic seizures
. One study analyzed 40 patients with complex partial seizures to determine their level of consciousness during seizures. The data acquired was based on patients' subjective descriptions of their experience and descriptions from family members who witnessed the seizures. This study found there was a complete absence of consciousness in only 65% of people during the core period of the seizures. Meanwhile, 35% of seizures included some form of primary consciousness. Five seizure descriptions even reported some form of secondary consciousness, albeit short and intermittent. The level and contents of consciousness during epileptic seizures show considerable variability.
scans in three different scenarios:
The data suggest that the anterior and posterior cingulate cortex
as well as the anterior wall of the third ventricle
, are major elements of a circuit including thalamic
, hippocampal
, orbitofrontal
, insula
, and midbrain sites that are needed for the generation of consciousness of thirst.
This study shows that consciousness of some key sensations like thirst is governed by the oldest regions of the brain, which raises the question of whether it is really then possible to say when primary consciousness developed.
Gerald Edelman
Gerald Maurice Edelman is an American biologist who shared the 1972 Nobel Prize in Physiology or Medicine for work with Rodney Robert Porter on the immune system. Edelman's Nobel Prize-winning research concerned discovery of the structure of antibody molecules...
coined to describe the ability, found in humans and some animals, to integrate observed events with memory to create an awareness of the present and immediate past of the world around them. This form of consciousness is also sometimes called "sensory consciousness". Put another way, primary consciousness is the presence of various subjective
Subjectivity
Subjectivity refers to the subject and his or her perspective, feelings, beliefs, and desires. In philosophy, the term is usually contrasted with objectivity.-Qualia:...
sensory contents of consciousness such as sensations, perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...
s, and mental images. For example, primary consciousness includes a person's experience of the blueness of the ocean, a bird's song, and the feeling of pain. Thus, primary consciousness refers to being mentally aware of things in the world in the present without any sense of past and future; it is composed of mental images bound to a time around the measurable present.
Conversely, higher order consciousness
Secondary consciousness
Secondary consciousness, a term coined by Gerald Edelman, is an individual’s accessibility of their past history and future plans, as well as consciousness of their consciousness. The ability allows its possessors to go beyond the limits of the remembered present of primary consciousness. Primary...
can be described as being "conscious of being conscious"; it is accompanied by reflective thought and includes a past as well as speculation about the future.
Primary consciousness can be subdivided into two forms, focal awareness
Awareness
Awareness is the state or ability to perceive, to feel, or to be conscious of events, objects or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of...
and peripheral awareness. Focal awareness encompasses the center of attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
, whereas peripheral awareness consists of things outside the center of attention, which a person or animal is only dimly aware of.
Theories of Primary Consciousness
One prominent theoryTheory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
for the neurophysiological
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
basis of primary consciousness was proposed by Gerald Edelman. This theory of consciousness is premised upon three major assumptions:
- The laws of physicsPhysicsPhysics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
apply to consciousnessConsciousnessConsciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
, which rules out concepts such as spirits and a soul and allows for a purely physiologicalPhysiologyPhysiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
model of consciousness. - Consciousness is an evolved characteristic, which means it is a helpful characteristic from a DarwinianDarwinismDarwinism is a set of movements and concepts related to ideas of transmutation of species or of evolution, including some ideas with no connection to the work of Charles Darwin....
perspective. - There is no such thing as a "qualiaQualiaQualia , singular "quale" , from a Latin word meaning for "what sort" or "what kind," is a term used in philosophy to refer to subjective conscious experiences as 'raw feels'. Examples of qualia are the pain of a headache, the taste of wine, the experience of taking a recreational drug, or the...
-free" observer. Qualia are collections of personal or subjective experiences, feelings, and sensations that inevitably come with human awareness.
Edelman's theory focuses on two nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
organizations: the brainstem and limbic system
Limbic system
The limbic system is a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, septum, limbic cortex and fornix, which seemingly support a variety of functions including emotion, behavior, long term memory, and olfaction. The term "limbic" comes from the Latin...
s on one side and the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
and cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
on the other side. The brain stem and limbic system take care of essential body functioning and survival, while the thalamocortical system receives signals from sensory receptors and sends out signals to voluntary muscles such as those of the arms and legs. The theory asserts that the connection of these two systems during evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
helped animals learn adaptive behavior
Adaptive behavior
Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation. This is often characterized by a kind of behavior that allows an individual to change an unconstructive or disruptive behavior to something more constructive. These behaviors are most often...
s. This connection allows past signals related to values set by the limbic-brain stem system and categorized signals from the outside world to be correlated, resulting in memory in conceptual areas. This memory is then linked to the organism's current perception, which results in an awareness of the present, or primary consciousness. In other words, Edelman posits that primary consciousness arises from the correlation of conceptual memory to a set of ongoing perceptual categorizations—a "remembered present".
Other scientists have argued against Edelman's theory, instead suggesting that primary consciousness might have emerged with the basic vegetative systems of the brain. That is, the evolutionary origin might have come from sensations and primal emotions arising from sensors
Sensory neuron
Sensory neurons are typically classified as the neurons responsible for converting external stimuli from the environment into internal stimuli. They are activated by sensory input , and send projections into the central nervous system that convey sensory information to the brain or spinal cord...
and receptors, both internal and surface, signaling that the well-being of the creature was immediately threatened—for example, hunger for air, thirst, hunger, pain, and extreme temperature change. This is based on neurological data showing the thalamic
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
, hippocampal
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, orbitofrontal
Orbitofrontal cortex
The orbitofrontal cortex is a prefrontal cortex region in the frontal lobes in the brain which is involved in the cognitive processing of decision-making...
, insula
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
, and midbrain sites are the key to consciousness of thirst.
These scientists also point out that the cortex might not be as important to primary consciousness as some neuroscientists have believed. Evidence of this lies in the fact that studies show that systematically disabling parts of the cortex in animals does not remove consciousness. Another study found that children born without a cortex are conscious. Instead of cortical mechanisms, these scientists emphasize brainstem mechanisms as essential to consciousness. Still, these scientists concede that higher order consciousness does involve the cortex and complex communication between different areas of the brain.
Neurophysiological Basis of Primary Consciousness
Physiologically, three fundamental facts stand out about primary consciousness:- Waking consciousness is associated with low amplitudeAmplitudeAmplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
, irregular EEGEEGEEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
activity in the 20–70Hz range.- Conversely, unconscious states like deep sleep, comaComaIn medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
, general anesthesia, and epileptic statesEpilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
of absence show a predominance of low frequencyFrequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, high-amplitudeAmplitudeAmplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
and more regular voltageVoltageVoltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s at less than 4Hz.
- Conversely, unconscious states like deep sleep, coma
- Consciousness seems to be instinctively associated with the thalamus and cortex, even if the extent to which this true is argued among scientists.
- Damage to the brainstem or thalamus can abolish consciousness, while damage to the sensory cortex appears to delete specific conscious features such as color visionColor visionColor vision is the capacity of an organism or machine to distinguish objects based on the wavelengths of the light they reflect, emit, or transmit...
, visual motion, conscious experiences of objects and faces, and the like.
- Damage to the brainstem or thalamus can abolish consciousness, while damage to the sensory cortex appears to delete specific conscious features such as color vision
- Consciousness is distinctively associated with widespread brain activation related to the conscious content.
- Perhaps two dozen experiments show that sensory input supporting consciousness spreads from the sensory cortexSensory cortexThe sensory cortex can refer informally to the primary somatosensory cortex, or it can be used as an umbrella term for the primary and secondary cortices of the different senses : the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the primary olfactory cortex on...
to parietalParietal lobeThe parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
, prefrontalPrefrontal cortexThe prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
, and medial-temporalTemporal lobeThe temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
cortex, while closely matched input that does not reach consciousness activates mainly local sensory regions. Further, the widespread activity appears to involve more globally coordinated activity.
- Perhaps two dozen experiments show that sensory input supporting consciousness spreads from the sensory cortex
Measuring Primary Consciousness
To be fully comprehensive, measures of consciousness must not only define and distinguish between consciousConsciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
and unconscious
Unconscious mind
The unconscious mind is a term coined by the 18th century German romantic philosopher Friedrich Schelling and later introduced into English by the poet and essayist Samuel Taylor Coleridge...
states, but must also provide a guide by which the conscious level, or extent of consciousness, can be determined. Measures of consciousness are each associated with particular theories.
Certain defining theories are included below:
Worldly discrimination theory asserts that any mental state that is manifested in behavior
Behavior
Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...
is conscious; thus, an organism is consciously aware of something in the world if it can discriminate it with choice behavior.
Signal detection theory quantifies discriminability of a stimulus among a set of different stimuli.
Integration theories focus on finding a divide between conscious and unconscious processes. According to integration theories, conscious contents are widely available to many cognitive and/or neural processes.
These theories are then accompanied with measures of the level of consciousness, which are subdivided into behavioral measures and physiological measures.
Behavioral Measures
Behavioral measures of primary consciousness can be either objective or subjective. Regarding objective measures, knowledge is unconscious if it expresses itself in an indirect test. For example, the ability to pick which item might come next in a series can indicate unconscious knowledge of regularities in sequences. "Strategic control measures" use a person's ability to deliberately use or not use knowledge according to instructions. If they use information despite intentions not to use it, it indicates unconscious knowledge. Post-decision wagering can also be used. In this method, subjects make a first-order discrimination (i.e. a choice) and then place a wager regarding the outcome of the discrimination. Some scientists view this as a direct and objective measure of consciousness, and it can be used with children and animals. However, this method has been argued to be subjective and indirect.Physiological Measures
Event-related cortical potentials (ERPs)Event-related potential
An event-related potential is any measured brain response that is directly the result of a thought or perception. More formally, it is any stereotyped electrophysiological response to an internal or external stimulus....
have been used to assess whether a stimulus
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
is consciously perceived or not. These EEG
EEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
measures either float free of theory, gaining credibility through reliable correlation, or assume a version of integration theory in which the appearance of a particular ERP indicates global availability or locally recurrent processing.
Abundant evidence indicates that consciously perceived inputs elicit widespread brain activation, as compared with inputs that do not reach consciousness.
The dynamic core hypothesis (DCH) proposes that consciousness arises from neural dynamics in the thalamocortical system, as measured by the quantity neural complexity (CN). CN is an information-theoretic measure; the CN value is high if each subset of a neural system can take on many different states, and if these states make a difference to the rest of the system.
The information integration theory of consciousness (IITC) shares with the DCH the idea that conscious experiences provide informative discriminations among a vast repertoire of possible experiences. In the IITC, the quantity phi is defined as the information that is integrated across the informational "weakest link" of a system. Importantly, phi is a measure of the capacity of a neural system to integrate information, whereas CN is a measure of the actual dynamics of the system. A third measure, causal density (CD), measures the fraction of causal interactions among elements of a system that are statistically significant.
Challenges in Measuring
It is important to note that subjective measures are always indirect and can be vulnerable to many biases (e.g., reluctance to report uncertain experiences). Also, because metacognitiveMetacognition
Metacognition is defined as "cognition about cognition", or "knowing about knowing." It can take many forms; it includes knowledge about when and how to use particular strategies for learning or for problem solving...
conscious content assumes primary consciousness but not vice versa, subjective measures risk missing or rejecting the presence of sensory consciousness simply because metacognition isn't observed.
Furthermore, there is the problem of post-decision wagering, which has been criticized because there is a possibility that advantageous wagering could be learned unconsciously; as a result, post-decision wagering would not in fact be considered a conscious behavior. For example, individual differences in risk aversion
Risk aversion
Risk aversion is a concept in psychology, economics, and finance, based on the behavior of humans while exposed to uncertainty....
may lead to variations in wagering performance even with the same underlying conscious phenomenology.
Thus, although behavioral measures are mostly used for assessing which contents are conscious, some brain-based measures seem better suited for measuring conscious level. Objective measures also have their challenges, however. First, objective measures still require a response criterion, for example the decision of whether or not to push a button. Second, they may not even measure consciousness at all because many behavioral proxies, such as forced-choice decision accuracy, are capable of being learned unconsciously.
Primary Consciousness in Lucid Dreams
Hobson asserts that the existence of lucid dreamingLucid dreaming
A lucid dream is a dream in which one is aware that one is dreaming. The term was coined by the Dutch psychiatrist and writer Frederik van Eeden . In a lucid dream, the dreamer can actively participate in and manipulate imaginary experiences in the dream environment. Lucid dreams can seem real and...
means that the human brain can simultaneously occupy two states: waking and dreaming. The dreaming portion has experiences and therefore has primary consciousness, while the waking self recognizes the dreaming and can be seen as having a sort of secondary consciousness
Secondary consciousness
Secondary consciousness, a term coined by Gerald Edelman, is an individual’s accessibility of their past history and future plans, as well as consciousness of their consciousness. The ability allows its possessors to go beyond the limits of the remembered present of primary consciousness. Primary...
in the sense that there is an awareness of mental state. Studies have been able to show that lucid dreaming is associated with EEG power and coherence profiles that are significantly different from both non-lucid dreaming and waking. Lucid dreaming situates itself between those two states. Lucid dreaming is characterized by more 40 Hz power than non-lucid dreaming, especially in frontal regions. Since it is 40 Hz power that has been correlated with waking consciousness in previous studies, it can be suggested that enough 40 Hz power has been added to the non-lucid dreaming brain to support the increase in subjective awareness
Awareness
Awareness is the state or ability to perceive, to feel, or to be conscious of events, objects or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of...
that permits lucidity but not enough to cause full awakening.
Dreaming is thus a virtual reality
Virtual reality
Virtual reality , also known as virtuality, is a term that applies to computer-simulated environments that can simulate physical presence in places in the real world, as well as in imaginary worlds...
experience with a remarkably predictive simulation of external reality. Lucid dreamers may experience primary consciousness (the dream) and secondary consciousness (the waking) separately but simultaneously. Moreover, primary consciousness has recently been proposed by us to be characteristic of dreaming. It remains to be seen whether the enactment of dream behaviors uses the same brain processes as those that mediate those very behaviors in waking, and whether conscious within a dream is governed by the same processes.
Primary Consciousness in Epileptic Seizures
Studies show that it is possible to retain primary consciousness and even secondary consciousnessSecondary consciousness
Secondary consciousness, a term coined by Gerald Edelman, is an individual’s accessibility of their past history and future plans, as well as consciousness of their consciousness. The ability allows its possessors to go beyond the limits of the remembered present of primary consciousness. Primary...
during complex partial epileptic seizures
Complex partial seizure
A complex partial seizure is an epileptic seizure that is associated with bilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. loss of consciousness.-Presentation:...
. One study analyzed 40 patients with complex partial seizures to determine their level of consciousness during seizures. The data acquired was based on patients' subjective descriptions of their experience and descriptions from family members who witnessed the seizures. This study found there was a complete absence of consciousness in only 65% of people during the core period of the seizures. Meanwhile, 35% of seizures included some form of primary consciousness. Five seizure descriptions even reported some form of secondary consciousness, albeit short and intermittent. The level and contents of consciousness during epileptic seizures show considerable variability.
Primary Consciousness in Thirst
In one study, 10 adult males underwent positron emission tomographyPositron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
scans in three different scenarios:
- During generation of moderate thirst by infusion of intravenous hypertonic saline 0.51 M
- After wetting of the mouth with water to remove the sensation of dryness
- 3, 14, 45, and 60 minutes after drinking water to fully quench thirst
The data suggest that the anterior and posterior cingulate cortex
Cingulate cortex
The cingulate cortex is a part of the brain situated in the medial aspect of the cortex. It includes the cortex of the cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus...
as well as the anterior wall of the third ventricle
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
, are major elements of a circuit including thalamic
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
, hippocampal
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, orbitofrontal
Orbitofrontal cortex
The orbitofrontal cortex is a prefrontal cortex region in the frontal lobes in the brain which is involved in the cognitive processing of decision-making...
, insula
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
, and midbrain sites that are needed for the generation of consciousness of thirst.
This study shows that consciousness of some key sensations like thirst is governed by the oldest regions of the brain, which raises the question of whether it is really then possible to say when primary consciousness developed.