Consciousness disorders such as prolonged coma and vegetative life in patients with severe stroke , traumatic brain injury and dementia are among the problems for which there is no cure yet. In these situations, aside from supportive treatments and care, little can be done except to wait and hope for a miracle. However, some of the patients who are considered unconscious and unresponsive to external stimuli may actually retain their ability to understand and communicate what is being said. The uncertainty stems from the fact that we still do not know exactly how consciousness is formed. It may be possible to measure the state of consciousness more precisely with high-tech tools than physical examination methods. If these tools reliably enter healthcare practice, they can have serious diagnostic, therapeutic and ethical implications.

Conscious and Unconscious Vision

Agnosia is the loss of the ability to interpret the senses and recognize objects as a result of brain damage. Although patients with visual agnosia cannot consciously see the shape and position of objects, they may pretend to see. If you hold a pencil in front of them and ask if it is in a vertical or horizontal position, they cannot tell, but when asked to reach out with their hands, they can grasp it by positioning and extending their hands according to the position of the pencil. Studies conducted on these patients in the 1990s revealed that there are two different types of image processing in the brain as conscious and unconscious vision (1). In addition, it has inflamed the debates on what constitutes consciousness.

Newly developed techniques for measuring brain activity allow testing theories about what consciousness is, how it is formed, and the boundaries between consciousness and unconsciousness. As our understanding of consciousness increases, new tools may be discovered for the treatment of pathological processes such as brain damage, phobias, and psychiatric illnesses. How the state of consciousness is formed still remains a mystery from a scientific point of view.

What is Consciousness?

Consciousness is considered a subjective experience of the mind. Even a simple robot can unconsciously detect physical properties such as color, temperature, and sound. Consciousness, on the other hand, is the qualitative feelings that constitute a deeper thought, communication and reflection that occur in relation to these perceptions.

Throughout the twentieth century, consciousness studies have been a field of suspicion in science. Studies have focused on observable behaviors and the stimuli that cause them, rather than subjective experiences. Consciousness itself was generally considered beyond the reach of science. This approach changed in the 1990s with technical advances in functional MRI and electroencephalography. Today, mechanisms related to the conscious processing of information are an important field of study.

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Coma and Awareness

One of the cases that improved our understanding of consciousness was a 23-year-old woman who suffered a severe traumatic brain injury due to a traffic accident in 2005 (2). In similar cases, the patient’s eyes are open and there is a sleep-wake cycle, but he does not respond to verbal commands and does not act voluntarily. When the verbal commands and the activity in the brain of the patient, whose clinical status did not change for five months, were examined with functional MRI, surprising findings were obtained. When the patient was asked to imagine playing tennis, activity was observed in the part of his brain called the supplementar motor area. When they were asked to imagine walking home, there was an increase in activity in three areas of the brain associated with memory and movement.

It was an important discovery for neuroscience that some comatose patients showed signs of consciousness. Although these patients seem unresponsive to verbal warnings from doctors and their relatives, they may have the potential to understand and perhaps communicate. Studies after this first study revealed that approximately 10-20% of comatose patients had detectable awareness (3).

Transcranial Magnetic Stimulation

Ways to detect consciousness without the need to give verbal commands to the participants are also being explored. With transcranial magnetic stimulation , “echoes” that can be recorded with EEG can be created in the brain (4). This technique can be likened to tapping to see the thickness of a wall. The repercussions that occur in a dreamless sleeper under general anesthesia are simple. But in the conscious brain, the echoes are complex and spread throughout the cerebral cortex. Perhaps with this method, the state of consciousness can be evaluated in people who cannot see, hear or respond to verbal commands.

Seeing Others’ Dreams

As the tools for detecting consciousness develop, it becomes clear which regions of the brain are more important. The importance of the cerebral cortex for consciousness has been known since the 19th century. Evidence points to the importance of the posterior-cortical region in terms of sensory experiences. In a sleep study conducted in 2017, participants were awakened at night while being monitored with EEG (5). In 30% of wake-ups, participants reported feeling nothing before waking up. Many low-frequency activities were observed in the posterior-cortical region before awakening in those without conscious experience. Those who said they were dreaming had less low-frequency activity and more high-frequency activity. Researchers can determine whether a person is dreaming by observing the posterior-cortical hot zone during sleep.

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It is clear that consciousness is not related to a single region of the brain. Various neurons and neural pathways are involved in the process. According to functional MR imaging results, there is a more complex pattern and constantly changing, coordinated signaling in healthy people compared to people under minimal conscious state or anesthesia (6).

Exiting a Coma with a Thalamus Ultrasound

People with traumatic brain injury may be the first to benefit from studies on consciousness. Based on the important role that the thalamus plays in consciousness, a 25-year-old person who was in a coma for 19 days due to a traffic accident was able to be awakened in a study in which the thalamus was stimulated with a non-surgical (non-invasive) method using ultrasound (7). This result may be purely coincidental. However, other studies by the same team suggest that ultrasound stimulation of the thalamus may make a difference in vegetative or minimally conscious patients.

Overcoming Fears

Consciousness research can also provide new approaches in the treatment of anxiety, phobias and post-traumatic stress disorder. Exposure therapy, the standard method for treating phobias, is based on confronting people with what scares them the most. The dropout rate is 50% or more because it is irritating. Alternatively, it may be possible to reprogram the unconscious by activating specific brain areas with a technique based on fMRI. In a study in which 17 people participated, participants were asked to enlarge a point that appeared on the computer screen with any mental focus method (8). The more they can enlarge the point, the higher the amount of money they receive for participating in the study. What the participants didn’t know was that the point was only detected in previous studies,

In the subjects, who were able to activate the relevant brain regions without thinking about animals such as spiders and snakes, which became a source of fear over time, the stress responses measured by sweating in the palms of the hands decreased when they encountered the images of these animals. The activity of the amygdala, the part of the brain involved in response to threats, also decreased. With this technique, the brain’s fear response was unconsciously reprogrammed. Although there was a decrease in physical symptoms, there was no change when people were asked about their feelings about spiders or snakes.

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Overcoming fears may require targeting both conscious and unconscious neuronal pathways. Unconscious pathways originate from the amygdala. However, motivational responses to threats cannot be regarded as fear itself. The conscious experience of fear is related to emotional interpretation and cognitive awareness of a particular situation. The resulting experience is not amygdala-centered. The difference is evident in blind people who cannot consciously perceive visual stimuli but act as if they can . When faced with a threat, their amygdala is activated and they show associated physical responses, but they do not feel fear.

Psychiatric Disorders and Consciousness Studies

This disconnection may explain why drugs for anxiety are not always as effective as expected. Based on animal experiments, these drugs that target circuits in the amygdala can affect a person’s behavior; for example, it can make it easier for them to participate in social events by reducing their timidity. But these drugs may not reduce the conscious experience of fear. Future treatments can be designed to act on both the unconscious and conscious levels.

Another area of ​​interest of consciousness research is mental health problems such as schizophrenia, obsessive-compulsive disorder and depression. These diseases may be caused by problems at the unconscious level or by the conflict of the unconscious with the conscious. Hallucinations, the experience of feeling things that are not there, are among the symptoms of schizophrenia. The neural basis of hallucinations is tested with a virtual reality program that uses machine learning to simulate the visual hallucination experience in healthy individuals (9). Experiments showed that these hallucinations were similar to those experienced by those using psychedelic drugs. The effects of psychedelic drugs also provide important clues for investigating the neural bases of consciousness. If the mechanism of hallucinations is understood, the associated parts of the brain can be manipulated,

Consciousness During General Anesthesia

Many people become conscious during general anesthesia. Although these people cannot move or speak, they can hear voices and feel pain. This traumatic experience is sometimes the subject of lawsuits for doctors and other healthcare professionals in the USA. Alternative ways of detecting consciousness can reduce such traumas. In addition, guidelines are being developed for communicating with unresponsive patients.

As a result, studies on consciousness are at the center of neuroscience today compared to the twentieth century. The emergence of techniques that can show the real-time functioning of the brain is the main factor in this. Understanding how consciousness occurs not only satisfies thousands of years of curiosity, but may pave the way for new treatments for many neurodegenerative and psychiatric diseases.

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