Hallucinations: definition, causes, and symptoms

Why do some people suffer hallucinations? What happens in their brains?

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

However, in many cases, whether or not there is a mental disorder, there are perceptions 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 perceived in an anomalous way, in perceptual deceptions 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 have just mentioned, hallucinationThe term "hallucination" has been evolving 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.The sufferer has the sensation 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 schizophrenia and may appear in other disorders, such as during manic episodes or during depression), hallucinations can also appear in many other cases, such as neurological disorders, substance abuse, 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

Here is an example to help us understand what is a hallucination

"A young man arrives at a psychologist's office. There, he tells his psychologist that he has come to him because he is very afraid. Initially he is reluctant to talk to the professional, but throughout the interview he confesses that the reason for being in his consulting room is that every time he looks in the mirror he hears a voice talking to him, insulting him, saying that he will never achieve anything in life and saying 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 concrete situation (looking in the mirror). The young man has really had this perception, being for him a very real phenomenon that he can neither direct nor control.. In this way, we can consider that it has all the characteristics mentioned above.

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. Moreover, they do not all appear under 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

In the first place we can find the visual hallucinationsperceived 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 can be seen, such as characters, animated beings or vivid scenes.

It is possible that these elements are visualized with different measures to those that would be perceived if these stimuli were real, being called Lilliputian hallucinations in the case of smaller perceptions and Gulliverian in the case of seeing them enlarged. Visual hallucinations also include autoscopy, in which a subject sees himself from outside his body, in a manner similar to that reported by patients with near-death experiences.

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

2. Auditory hallucinations

With regard to auditory hallucinationsAuditory hallucinations, in which the perceiver hears something unreal, 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 above, a voice speaks to the subject, hallucinations in the third person in which voices are heard speaking of the individual or imperative hallucinations, in which the individual hears voices ordering him to do or not to do something. Hallucinations of this sensory modality are the most frequent in mental disorders, especially in schizophrenia.especially in paranoid schizophrenia.

3. Taste and smell hallucinations

As far as the senses of taste and smell are concerned, hallucinations in these senses are more frequent in mental disorders, especially in paranoid schizophrenia, hallucinations in these senses are not very frequent and are usually related to the consumption of drugs or other substances, in addition to some neurological disorders such as temporal lobe epilepsy, or even in 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 temperature, Pain or tingling (the latter being called paresthesias, and highlighting among them a subtype called dermatozoic delirium in which there is 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.

Firstly, cenesthetic or somatic hallucinations, which cause sensations perceived with respect to one's own organs, normally linked to strange delirious processes.

Second and lastly, kinesthetic hallucinations refer to sensations of movement of one's own body that are not produced in reality, being typical of Parkinson's disease and substance abuse patients.

As already mentioned, apart from 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 triggered by the presence of a stimulus that triggers another stimulus, this time hallucinatory, in the same sensory modality. This hallucination is produced, 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 television news every time he hears the noise of the traffic.

The same phenomenon occurs in the reflex hallucinationThe only difference is that this time the unreal perception occurs in a different sensory modality. This is the case in the example given above.

The extracampus hallucination occurs in cases where the false perception occurs outside the perceptual field of the individual. That is to say, something beyond what could be perceived is perceived. An example is seeing someone behind a wall, without other data that could make one think of his existence.

Another modality of hallucination is the absence of perception of something that exists, denominated negative hallucination. However, in this case the behavior of the patients is not influenced as if they perceive that there is nothing, so that in many cases it has come to be doubted that there is a real lack of perception. An example is the negative autoscopyin which the person does not perceive him/herself when looking into a mirror.

Finally, it is worth mentioning the existence of pseudohallucinations. These are perceptions with the same characteristics as hallucinations with the exception that the subject is aware that these are unreal elements.

Why does a hallucination occur?

We have seen some of the main modalities and types of hallucinations, but why do they occur? why do they occur?

Although there is no single explanation, several authors have tried to shed light on this type of phenomena, some of the most accepted ones being those who consider that the subject who hallucinates erroneously attributes his internal experiences to external factors..

An example of this is Slade and Bentall's theory of metacognitive discrimination, according to which the hallucinatory phenomenon is based on the inability to distinguish real from imaginary perception. These authors consider that this capacity of distinction, which is created and can be modified through learning, may be due to an excess of activation due to 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-type hallucinations, is the Hoffman's theory of subvocalizationwhich indicates that these hallucinations are the subject's perception of one's own subvocal speech (i.e., one's internal voice) as something alien to oneself (a theory that has generated therapies to treat auditory hallucinations with some effectiveness). However, Hoffman considered that this was not due to a lack of discrimination, but to the generation of involuntary internal speech acts.

Thus, hallucinations are ways of "reading" reality erroneously, 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 in which our brain processes information. what changes is the way in which our brain processes the incoming information. information that arrives. Normally, this means that our memories are mixed with sensory data in an anomalous way, linking previously experienced visual stimuli to what is happening around us.

For example, this is what happens when we spend a long time in the dark or blindfolded so that our eyes do not register anything; the brain starts to make things up because of the anomaly of not receiving sensory data while awake.

The brain creating an imaginary environment

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

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