States of Consciousness: Everything You Need to Know About the 3 Levels of Consciousness

You’ve surely heard of the different states of consciousness. They can often seem like mysterious and complicated concepts for people outside the cognitive sciences, but this guide will explain everything you need to know!

Understanding the States of Consciousness.  Photo by Cristofer Jeschke on Unsplash
Understanding the States of Consciousness. Photo by Cristofer Jeschke on Unsplash

What is Consciousness?

The state of consciousness, or consciousness, can be defined as the state in which our higher neurocognitive functions such as attention, perception, language, executive functions, memory and coordination are active. This state occurs when the subject is aware of their mental and physical state and the environment that surrounds them.

Being conscious means having an experience—the subjective experience, the phenomenon of seeing an image, hearing a sound, having a thought, or feeling an emotion. Even when we “daydream” or when we dream in sleep, we are still experiencing a form of consciousness.

Consciousness only fades in deep sleep, in states of general anesthesia, or in other states that we will see later; states in which we experience nothing. In order to be conscious, the correct functioning of certain brain structures is necessary.

Although experiences are private, we can deduce that people have a conscious state if they are in a waking state and act with intentionality.

The level or state of consciousness is usually assessed by scoring visual, auditory, verbal, and motor functions using standardized scales. Consciousness is also assessed by asking participants to perform behaviors in response to simple questions (“Press this button or look up if you see a face in this photo“).

However, awareness may exist in the absence of behavioral responses. For example, in the minimally conscious state, patients are alert and aware, although they do not offer any apparent response. 

The state of consciousness is a concept that has two major components:

  • The level of alertness (the level, or state of consciousness)
  • The awareness of the environment and of oneself (content of consciousness).

You need to be in a waking state to have consciousness (with the exception of the REM state).

Levels of Consciousness

In the first level or state of consciousness, a difference is established between focusing attention outwards, towards the environment; and focusing it inwards, towards oneself (self-awareness). 

It is assumed that to direct attention inward or outward, an organism must be alert. If an organism is not alert, it is unconscious, and there is no information processing. The states where there is no consciousness are coma and deep sleep.

1 – Level of “Alertness”:

At the first level or state of consciousness, when someone is alert but not conscious, an organism will experience perceptions, sensations, thoughts, etc., but will not be aware of this experience. The organism will be totally immersed in the experience and will be a thoughtless actor of its environment. Most animals are at this level of consciousness. This level emphasizes the processing of external stimulation, without including the person himself as an object of knowledge, which is necessary to move and interact in the environment.

Vegetative patients are at the first level of alert. Patients are awake, awake from coma, but do not show “voluntary” interaction with the environment. These patients have their eyes wide open but, by definition, they are not aware of themselves or their surroundings.

They usually make faces, cry, or smile, although never in response to external stimulation; they move their eyes, head, and limbs automatically and without meaning. The vegetative state is frequently, but not always, chronic. If medical care (artificial hydration and nutrition) is provided, patients can survive for years.

The next level refers to the “first person perspective” or “subjective perspective; and it involves body awareness, which enables spatial navigation.

2 – Level of “Self-awareness”:

The next level or state of consciousness, “self-awareness” refers to the ability to be the object of our own attention. It occurs when we attend to our internal world and become reflective observers of ourselves. The organism is then aware that it is alert and experiencing specific mental events, emitting behaviors, etc. A language-proficient child might verbalize things like “I feel tired.”

3 – Level of “Meta-self-awareness”:

A final level of consciousness is the “meta-self-awareness”—being aware that one is self-aware. This state represents a logical extension of the previous level. While a subject with self-awareness would say “I am hungry”, a subject with meta-self-consciousness would say “I am aware that I am hungry.”

States of Consciousness: How Do You Know that Patients are Completely Unconscious?

Some authors propose that a grimace or response to pain shows flashes of some state of consciousness. When a diagnosis is made with insufficient care, up to one in three vegetative patients may actually be conscious – even if it is in a state of “minimally conscious”.

The diagnostic error can be explained in part by the difficulties in detecting signs of consciousness in patients with changing levels of activity, attention, and perception.

The latest Functional Neuroimaging studies are measuring neural activity at rest and during external stimulation (for example, before painful stimuli) in these patients, showing lower values.

Studies using anesthetic drugs have shown a reduction in brain activity to half normal values. Similar reductions in activity have been observed in deep sleep, although brain metabolism returns to normal waking values in the REM sleep state.

In the vegetative state—the “waking without consciousness” state—activity also drops to about 50% of normal values.

Therefore, the relationship between global levels of brain function and the presence or absence of consciousness is not absolute. It seems that certain areas of the brain are more important than others for its emergence. 

Various neuroimaging studies have attempted to identify the regions that show dysfunction in subjects in a vegetative state compared to healthy conscious subjects. These studies have identified dysfunction not in one region, but in a broad fronto-parietal network, known to be active “by default,” in subjects at rest.

Can Patients in a Vegetative State of Consciousness Feel or Suffer from Something?

An important question, due to its health implications, is whether patients in a vegetative state have residual pain perception.

Studies using high intensity electrical stimulation, which is experienced as painful in healthy patients, show activation in low-level areas (brain stem, thalamus, and primary somatosensory cortex) in vegetative patients. 

Interestingly, high-level areas of pain perception (secondary somatosensory cortices, insular, posterior parietal, and anterior cingulate) were not activated.

Similarly, auditory stimulation activates auditory areas but not high-level areas in vegetative patients.

In summary, vegetative patients still show brain activation, but it appears to be limited to low-level areas (subcortical and cortical), and they appear to show a disconnection of the fronto-parietal network related to consciousness.

It is a great challenge to behaviorally distinguish patients in a vegetative state from patients in a minimally conscious state because both are, by definition, non-communicative.

Functional Neuroimaging can be of great value to objectively differentiate activation patterns in the face of external stimulation. Recently, Schiff et al. used fMRI to study patients in a minimally conscious state and their results revealed activation in language areas in response to auditory stimulation of personal narratives, something that does not occur in patients in a vegetative state.

In conclusion, the use of Functional Neuroimaging techniques can improve our characterization of survivors of severe brain damage, not only in the diagnostic aspect, but also to differentiate them in terms of treatment, predict their evolution, and improve decisions in the last phases of the life.

Other Dissociated States of Consciousness

The vegetative state is not the only one that shows dissociation between the level of alertness and the level of consciousness. In other states, patients are alert, but show an automatic and behavior:

Epilepsy and State of Consciousness

Absences of consciousness appear as short episodes (between 5-10 seconds), in which they show fixed gaze and lack of response, often accompanied by blinking. Functional Magnetic Resonance studies have shown massive deactivation in areas related to consciousness. Temporal lobe epilepsy can also alter consciousness. The lack of response usually lasts several minutes, and patients may show manual and oral automatisms. 

Sleepwalking and State of Consciousness

This is an abnormal condition that occurs during deep sleep. It is another example of a transitory lack of response, with a partially preserved level of alertness and semi-intentional behavior, such as walking.

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