Agnosia is characteristically modality-specific; the patient who fails to recognized material presented though a particular sensory channel such as vision, can do so successfully in another channel e.g. touch, hearing.
The term ‘agnosia’ should be restricted to situation in which recognition impairment are confined to one sensory modality, for example, vision, or audition or touch. When recognition defects extend across two or more modalities, the appropriate designation is ‘amnesia’.
The term coined by Freud in 1891, means literally ‘absence of knowledge’, but its precise critical definition continues to be a subject of debate.
There are two kinds of agnosia:
*Apperceptive agnosia – define as a failure to construct a coherent structural percept of an object, as shown by the ability to draw or identify.
*Associative agnosia – In associative agnosia, however, the person could copy a drawing but not identify it or determine its meaning.
What is agnosia?
