Agnosia
Contents:
Description:
Agnosia is the disturbance of different types of perception arising at damage of a cerebral cortex and the nearest subcrustal structures.
Agnosia reasons:
Agnosia is connected with defeat secondary (projective ассоциационных) the departments of a cerebral cortex which are a part of cortical level of analizatorny systems.
Causes damage to primary (projective) departments of bark only elementary disorders of sensitivity (disturbance of touch visual functions, painful and tactile sensitivity, decrease in hearing). At defeat of secondary departments of bark of big hemispheres elementary sensitivity at the person remains, however he loses ability to the analysis and synthesis of the arriving information that leads to disturbance of different types of perception.
Agnosia symptoms:
Distinguish several main types of agnosia:
visual;
tactile;
acoustical.
Visual agnosias arise at defeat of secondary departments of occipital bark. They are shown that the person - at sufficient safety of visual acuity - cannot learn objects and their images (subject agnosia), to distinguish space signs of objects, the main space coordinates (space agnosia); it breaks process of an identification of persons at safety of perception of objects and their images (agnosia on faces, or a prozopagnoziya), ability to classify colors at safety of color sight (color agnosia) is broken, ability to distinguish letters (alphabetic agnosia) is lost, the volume of at the same time perceived objects (simultaneous agnosia) is sharply reduced.
The nature of visual agnosias is defined by the party of defeat and localization of the center within secondary cortical fields of occipital departments of big hemispheres and parietal and temporal areas adjoining to them.
Tactile agnosias arise at defeat of secondary cortical fields of a parietal lobe of the left or right hemisphere and are shown in the form of frustration of an identification of objects to the touch (astereoagnoziya) or in disturbance of recognition of parts of own body, disturbance of a body scheme (somatoagnoziya).
Acoustical agnosias arise at defeat of secondary cortical fields of a temporal share. At defeat of temporal bark of the left hemisphere acoustical or slukhorechevy agnosia is shown in the form of disturbance of phonemic hearing, i.e. disturbance of ability to distinguish speech sounds that leads to an alalia; at defeat of temporal bark of the right hemisphere (right-handed persons) have actually acoustical agnosia - impossibility of recognition of familiar not musical sounds and noise (for example, bark of dogs, a scratch of steps, rain noise, etc.) or an amusia - impossibility of recognition of familiar melodies, disorder of ear for music.
