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Clinical Features Of Mental Diseases: Disorders Of Perception, Memory, Intelligence, Consciousness And More

Updated on February 20, 2014

Hallucination As A Perception Disorder



From the previous hub, we analysed the disorders of affect and cognition. Under the cognition disorders are those of thinking which was already discussed in the previous hub (just click on the previous hub in the slide slow beneath this one to go through it). Now, we will discussed the remaining cognitive disorders.

Disorders Of Perception

Hallucination, illusions, macropenia and micropsia are the common disorders of perception. “Hallucinations” are vivid sensory experiences occurring in the absence of any external stimuli or object. These are experienced in the field of the special sense organs. Thus the hallucinations may be “auditory”, “visual”, “Olfactory”, “gustatory” and “haptic” or “tactile”. In auditory hallucination, the patient hears noises or voices without any external auditory stimuli. Similarity in “visual hallucinations” objects are seen without any appropriate visual stimuli. In “olfactory hallucinations” smells are experienced when really there are no such smells outside. The same is true of gustatory and tactile hallucinations as well.

“Illusion” refers to misrecognition of objects. A rope may be interpreted as a snake or a shadow of a tree may appear as a ghost. The illusion can be corrected by verifying the truth by closer examination. In “micropsia”, the object or figures appear smaller than what they actually are, and in “macropsia” it is the reverse.

Amnesia As A Disorder Of Memory


Disorders of memory

Memory includes registration, retention and recollection of events. Events initially registered are retained and stored in the memory centers and are recalled later according to the needs. The common disorder of memory is “amnesia” which denotes loss of memory. Amnesia may be global and progressive of selective for certain events only. Loss of memory may be for immediate events (loss of retention) or recent or remote events. The gap in the memory may be filled up by fabricated events. This is called “confabulation”. The inability to forget events is called “hyperamnesia”.

Dementia As A Disorder Of Intelligence


Disorder Of Intelligence

“Dementia” and mental “subnormality” are the common disorders in this group. Intelligence is the capacity of an individual to think rationally to act purposefully and to adjust adequately to his surroundings. Intelligence grows and develops with physical growth and maturation. When the intelligence is not proportionately grown and developed, mental retardation results. When dementia develops, the normally acquired intelligence deteriorates abnormally. Intelligence is expressed in terms of intelligence quotient (IQ). The average IQ is 100 + 16. In dementia and mental abnormality, the IQ is considerably reduced.

Disorder Of Disorientation


Disorders Of Consciousness, Orientation, Attention And Concentration

Disorders Of Consciousness

The disorders of consciousness include clouding, confusion, stupor, and coma. Functional psychiatric symptoms develop in a clear conscious setting. On the other hand, if the symptoms are found to supervene on the impaired state of consciousness, an organic illness has to be considered. In psychogenic fainting, there is no real loss of consciousness. Eg, hysterical loss of consciousness.

Disorders Of Orientation

Orientation is the appreciation of one’s own temporal and personal relation at a given moment. “Disorientation” is the disorder of orientation. Disorientation may pertain to time, place or persons. It may be found in delirium.

Disorders Of Attention And Concentration

Distractability is the disorder in which the attention is fleeting. Fluctuating levels of attention are found in organic brain syndromes.



Disorder Of Conation

Conation is represented by the motor activity. The disorders of motor activity may include decreased, increased, and repetitive activity and disorders of posture. The condition is called psychomotor retardation when the motor activity is decreased. In stupor, the motor activity is reduced to a minimum. When motor activity is increased it is termed psychomotor overactivity. Motor activity is increased to a maximum in states of excitement. Repetitive motor activity includes stereotypy, mannerism, perseveration, echopraxia and echolalia.

Stereotype refers to a monotonous repetition of an activity. Mannerism also is a repetitive activity but is not monotonously repeated and often goes with normal personality.


The repetition of the previous activity inspite of the patient’s effort to move on to a new activity is called perseveration. Echopraxia denotes repetition of an activity just seen. Echolalia denotes repetition of words just heard.

Posture Disorder


Disorder Of Posture

Waxy flexibility (flexibilitas cerea) is a disorder of posture. It refers to the maintenance of imposed postures for long periods of time, however, awkward they may be. Negativism which is also another motor disorder refers to the performance of a given stimulus.

Finally, somatic symptoms are also cognitive importance of huge psychiatric effects. Symptoms such as headache, blindness, limping, diarrhea, loss of appetite or other symptoms pertaining to any system may be present in mental diseases, either alone or in combination with psychiatric symptoms.

© 2014 Funom Theophilus Makama


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