Perception is a complex system of processes for receiving and transforming information which gives a possibility to the body to fulfil the function of reflection of objective reality and orientation in the visual environment. Perception together with sensation, synthesises the starting point of the process of cognition, giving a body the suitable sensory material; perception is somehow mediated by the process of activity of thinking and is verified by practice.
The mechanism of perception depends on correct functioning of receptors (sense organs) and analysers (central organs) consisting of a number of transformers (ganglia), through which energy being received from the external world is transformed into a substrate for mental function of perception; this mechanism also depends on the current state of consciousness and attention as well as on social experience. Dysfunctions of central perception mechanisms are of particular importance, especially if no complete loss of functions, but only pathological changes leading to a distortion of the sensory experience and to so-called deception of the senses, which are the main mental insanity associated with disorders in the area of perception.
HALLUCINATIONS
The scientific understanding and definition of hallucinations has developed in the process of the historical development of this psychiatry problem study. The original, common meaning of the word "alucinatio" translated from Latin corresponds to such concepts as "senseless chatter", "pipe dreams", and "empty ravings". In the Renaissance in France, J. Fernell used the term "hallucinations" in the section "Pathology" of his treatise "Universal Medicine" (1554), where eye diseases were described. He explained: Greek called hallucination with the term "parorhasis"; it means "visual impairment". According to J. Fernell, for a hallucination, there is the morbid lemon-yellow colouration of the cornea, or it becomes red and inflamed. It is obvious that a common, utilitarian understanding of the word "hallucinations" gradually starts to have a scientific meaning,