Associative agnosia
Encyclopedia
People with associative agnosia
Agnosia
Agnosia is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss...

fail in assigning meaning to an object, animal or building that they can see clearly. Most cases have injury to the occipital
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...

 and temporal
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....

 lobes and the critical site of injury appears to be in the left occipital-temporal region, often with involvement of the splenium
Splenium
The posterior end of the corpus callosum is the thickest part, and is termed the splenium .It overlaps the tela chorioidea of the third ventricle and the mid-brain, and ends in a thick, convex, free border....

 of the corpus callosum
Corpus callosum
The corpus callosum , also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication...

. The clinical "definition" of the disorder is when an affected person is able to copy/draw things that they cannot recognize. The disorder appears to be very uncommon in a "pure" or uncomplicated form and is usually accompanied by other complex neuropsychological problems such as impaired language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

 or memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

. The affected individual may not realize that they have a visual problem and may complain of becoming "clumsy" or "muddled" when performing familiar tasks such as setting the table or simple DIY.

There has been debate about whether the fundamental problem in associative agnosia implicates
  • Higher-order visual perception
    Visual perception
    Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...

     - perhaps in integrating the parts of an object into a structured whole
  • A disconnection syndrome - a failure of linking vision and perception with language
  • Damage to a modality-specific meaning process (semantic system).


Any or all of these interpretations may be appropriate for an individual patient but the same explanation will not necessarily work for all.

Evidence in favor of the semantic hypothesis can be inferred from studies showing that affected people can often show partial knowledge of the things they cannot recognize - such as knowing that an object is a container but not being able to determine whether it is a jug or a mug. They may also have difficulties in deciding whether two different visual forms (visual synonyms) are "the same" - for example, they may be unable to determine that a wine glass and a tumbler are more alike than a tumbler and a vase.

See also

  • Agnosia
    Agnosia
    Agnosia is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss...

  • Visual agnosia
    Visual agnosia
    Visual agnosia is the inability of the brain to make sense of or make use of some part of otherwise normal visual stimulus and is typified by the inability to recognize familiar objects or faces...

  • Apperceptive agnosia
    Apperceptive agnosia
    Apperceptive Agnosia is the visual disorder that renders a person unable to recognize objects. It is also known as visual space agnosia. Distinction between shapes is difficult, although other aspects of vision, such as ability to see detail and colour, remain intact. Recognition of, copying and...

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