Perception and its disorders

Perception is the process of becoming aware of what is presented through sensory organs. Imagery refers to an experience within the mind that is often without a sense of reality. Eidetic imagery is that which is very detailed and intense. Pareidolia is state in which real and unreal images exist side by side.

Illusions

Pseudoillusion denotes distorted perception of objects which occurs when the overall level of sensory stimulation is reduced. For example, a bush can be misperceived as a man in poor lighting at a distance, where the misperception is corrected by coming closer. Illusions appear mainly in conditions of qualitative disturbances of consciousness (ie delirious states, intoxications). Unlike pseudoillusions, illusions lack insight. For example, a patient may mistake a doctor as a member of his family.

Hallucinations

Hallucinations refer to perception without any obvious stimulus of the sensory organs, and these cannot be distinguished from reality. If the patient can distinguish hallucinations from reality, then the term pseudohallucinations should be used. Elementary hallucination are for experiences such as whistles and flashes. Complex hallucinations refer to hearing voices or music, and seeing people. Hallucinations can be defined by sensory modality, such as auditory, visual, gustatory, etc. Extracampine hallucinations are outside our field of perception. Inadequate hallucinations come from non-sensory organs, ie hearing through a tooth, smelling through fingers. Intrapsychic hallucination are disturbances of thinking Typical for schizophrenia, these are experiences where strange ideas are inserted into one's mind. Hypnagogic hallucinations are not pathological, referring to the experience of falling asleep.

References

• Raboch J., Pavlovský P. at al.: Basic Psychopathological Terms and Psychiatric Diagnoses, Karolinum Praha 2004