Hallucinations: definition, causes, and symptoms

The perception is the process by which living beings capture information from the environment with the in order to process it and acquire knowledge about it, being able to adapt to the situations that we live.

However, in many cases, whether or not there is a metal disorderPerceptions are produced that do not correspond to reality, and these perceptual alterations can be grouped into distortions or deceptions, mainly.

While in perceptual distortions a real stimulus is abnormally perceived, in perceptual delusions there is no stimulus that triggers the perceptual process. The clearest example of this last type of perceptual alteration is hallucinations.

Hallucinations: defining the concept

The concept we just mentioned, hallucination, has evolved throughout history and its description has been enriched over the years. Hallucination can be considered as a perception that occurs in the absence of a stimulus that triggers it, having who suffers the feeling that it is real and that it occurs without the subject being able to control it (this characteristic being shared with obsessions, delusions and some illusions).

Although they are generally indicators of mental disorder (being a diagnostic criterion of the schizophrenia and may appear in other disorders, such as during manic episodes or during depressions), hallucinations can also appear in many other cases, such as neurological disorders, substance use, epilepsy, tumors and even in non-pathological situations of high anxiety or stress (in the form of nervous paroxysm by the object of our anxiety, for example).

An example of hallucination

Let's see an example below to help us understand what a hallucination is

“A young man comes to see a psychologist. There, he indicates to his psychologist that he has come to him because he is very afraid. Initially he is reluctant to speak with the professional, but throughout the interview he confesses that the reason for being in his consultation is in that every time he looks in the mirror he hears a voice that speaks to him, insulting him, saying that he will not achieve anything in life and stating that he should disappear".

This example is a fictitious case in which the supposed patient has perceived a stimulus that does not really exist from a specific situation (looking in the mirror). The young man has really had that perception, being for him a very real phenomenon that he cannot direct or control.. In this way, we can consider that it has all the aforementioned characteristics.

However, not all hallucinations are always the same. There is a wide variety of typologies and classifications, among which the one that refers to the sensory modality in which they appear stands out. Furthermore, they do not all appear in the same conditions, and there are also multiple variants of the hallucinatory experience.

Types of hallucinations according to sensory modality

If we classify the hallucinatory experience according to the sensory modality in which they appear, we can find several categories.

1. Visual hallucinations

First you can find the visual hallucinations, perceived through the sense of sight. In this case the subject sees something that does not exist in reality. These stimuli can be very simple, such as flashes or lights. However, more complex elements such as characters, animated beings or vivid scenes can be seen.

It is possible that these elements are visualized with different measures than those that would be perceived to be these real stimuli, called Lilliputian hallucinations in the case of smaller perceptions and Gulliverian in the case of seeing them enlarged. Within visual hallucinations there is also autoscopy, in which a subject sees himself from the outside of their body, in a way similar to that reported by patients with experiences close to the death.

Visual hallucinations are especially frequent in organic conditions, trauma and substance use, although they also appear in certain mental disorders.

2. Auditory hallucinations

Regarding auditory hallucinations, in which the perceiver hears something unreal, it can be simple noises or elements with complete meaning such as human speech.

The clearest examples are hallucinations in the second person, in which, as in the example described above, a voice speaks to the subject, hallucinations in the third person in which voices are heard that speak of the individual himself between them or imperative hallucinations, in which the individual hears voices that order him to do or stop doing something. Hallucinations of this sensory modality are the most frequent in mental disorders, especially in paranoid schizophrenia.

3. Hallucinations of taste and smell

When it comes to the senses of taste and smell, hallucinations in these senses are rare and they are usually related to the consumption of drugs or other substances, in addition to some neurological disorders such as temporal lobe epilepsy, or even tumors. They also appear in schizophrenia, usually related to delusions of poisoning or persecution.

4. Haptic hallucinations

The haptic hallucinations are those that refer to the sense of touch. This typology includes a large number of sensations, such as those of temperature, pain or tingling (the latter being called paresthesias, and highlighting among them a subtype called dermatozoal delirium in which you have the sensation of having small animals in the body, being typical of substance use such as cocaine).

Apart from these, related to the senses, two more subtypes can be identified.

In the first place, the kinesthetic or somatic hallucinations, which cause perceived sensations regarding the organs themselves, normally associated with strange delusional processes.

In the second and last place, kinesthetic or kinesthetic hallucinations refer to sensations of movement of the own body that are not produced in reality, being typical of Parkinson's patients and the consumption of substances.

As already mentioned, regardless of where they are perceived, it is also useful to know how they are perceived. In this sense we find different options.

Different modes of false perception

The so-called functional hallucinations are unleashed in the presence of a stimulus that triggers another, this time hallucinatory, in the same sensory modality. This hallucination occurs, begins and ends at the same time as the stimulus that originates it. An example would be the perception of someone who perceives the tune of the news every time he hears the noise of the traffic.

The same phenomenon occurs in reflex hallucinationOnly this time the unreal perception occurs in a different sensory modality. This is the case in the above example.

The extracampine hallucination It occurs in cases where the false perception occurs outside the perceptual field of the individual. That is, something beyond what could be perceived is perceived. An example is seeing someone behind a wall, with no other information that could suggest their existence.

Another type of hallucination is the absence of perception of something that exists, called negative hallucination. However, in this case the behavior of the patients is not influenced as if they perceived that there is nothing, so that in many cases it has come to doubt that there is a real lack of perception. An example is the negative autoscopy, in which the person does not perceive himself when looking in a mirror.

Finally, it is worth noting the existence of pseudo-hallucinations. These are perceptions with the same characteristics as hallucinations with the exception that the subject is aware that they are unreal elements.

Why does a hallucination occur?

We have been able to see some of the main modalities and types of hallucinations but, Why do they occur?

Although there is no single explanation in this regard, various authors have tried to shed light on this type of phenomenon, some of the most accepted being those who consider that the hallucinating subject mistakenly attributes his internal experiences to external factors.

An example of this is the theory of metacognitive discrimination of Slade and Bentall, according to which the hallucinatory phenomenon is based on the inability to distinguish real from imaginary perception. These authors consider that this ability to distinguish, which is created and can be modified through learning, may be due to an excess of activation by stress, lack or excess of environmental stimulation, high suggestibility, the presence of expectations as to what is going to be perceived, among Other options.

Another example, focused on auditory hallucinations, is the Hoffman's subvocalization theory, which indicates that these hallucinations are the subject's perception of their own subvocal speech (that is, our voice internal) as something alien to himself (theory that has generated therapies to treat auditory hallucinations with certain effectiveness). However, Hoffman considered that this fact was not due to a lack of discrimination, but to the generation of involuntary internal discursive acts.

Thus, hallucinations are ways of "reading" reality in the wrong way, as if there were elements that are really there even though our senses seem to indicate otherwise. However, in the case of hallucinations our sensory organs work perfectly, what changes is the way our brain processes information that arrives. Normally this means that our memories are mixed with sensory data in a way anomalous, joining visual stimuli experienced previously to what is happening to our around.

For example, this is what happens when we spend a lot of time in the dark or blindfolded so that our eyes do not register anything; the brain begins to invent things because of the anomaly that supposes not to receive data through this sensory pathway while awake.

The brain that creates an imaginary environment

The existence of hallucinations reminds us that we do not just record data about what is happening around us, but that our nervous system has the mechanisms to "build" scenes that tell us what is happening around us. Some diseases can trigger hallucinations in an uncontrolled way, but these are part of our day to day, even if we do not realize it.

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