Agnosia - Types

Types

Name	Description
Akinetopsia	Also known as Cerebral akinetopsia is associated with the inability to perceive visual motion. One cause of cerebral akinetopsia is lesions outside the striate cortex.
Anosognosia	This is the inability to gain feedback about one's own condition and can be confused with lack of insight but is caused by problems in the feedback mechanisms in the brain. It is caused by neurological damage and can occur in connection with a range of neurological impairments but is most commonly referred to in cases of paralysis following stroke. Those with Anosognosia with multiple impairments may even be aware of some of their impairments but completely unable to perceive others.
Apperceptive visual agnosia	Patients are unable to distinguish visual shapes and so have trouble recognizing, copying, or discriminating between different visual stimuli. Unlike patients suffering from associative agnosia, those with apperceptive agnosia are unable to copy images.
Associative visual agnosia	Patients can describe visual scenes and classes of objects but still fail to recognize them. They may, for example, know that a fork is something you eat with but may mistake it for a spoon. Patients suffering from associative agnosia are still able to reproduce an image through copying.
Astereognosis	Also known as Somatosensory agnosia is connected to tactile sense - that is, touch. Patient finds it difficult to recognize objects by touch based on its texture, size and weight. However, they may be able to describe it verbally or recognize same kind of objects from pictures or draw pictures of them. Thought to be connected to lesions or damage in somatosensory cortex.
Auditory agnosia	Auditory agnosia has been recognized since 1877. With Auditory Agnosia there is difficulty distinguishing environmental and non-verbal auditory cues including difficulty distinguishing speech from non-speech sounds even though hearing is usually normal. There are two types of auditory agnosia: semantic associative and discriminative agnosia. Semantic associative agnosia is associated with lesions to the left hemisphere, where as discriminative agnosia is associated with lesions to the right hemisphere.
Auditory verbal agnosia	Also known as Pure Word Deafness (PWD) This presents as a form of meaning 'deafness' in which hearing is intact but there is significant difficulty recognising spoken words as semantically meaningful.
Autotopagnosia	Is associated with the inability to orient parts of the body, and is often caused by a lesion in the parietal part of the posterior thalmic radiations.
Cerebral achromatopsia	Also known as Color agnosia involves having difficulty categorizing colours, as well as recognizing colours. Cerebral achromatopsia is usually caused by neurological damage. There are two regions of the brain which specialize for color recognition, areas V4 and V8. If there is a unilateral lesion to area V4, a loss of color perception will result known as hemiachromatopsia.
Cortical deafness	Refers to people who do not perceive any auditory information but whose hearing is intact.
Environmental Agnosia	It is the inability to locate a specific room or building that one is familiar with, as well as the inability to provide directions for how to arrive at a particular location. These individuals experience difficulty with learning routes. This form of agnosia is often associated with lesions to the bilateral or right hemisphere posterior regions. It is also associated with prosopagnosia and Parkinson's disease.
Finger agnosia	Is the inability to distinguish the fingers on the hand. It is present in lesions of the dominant parietal lobe, and is a component of Gerstmann syndrome.
Form agnosia	Patients perceive only parts of details, not the whole object.
Integrative agnosia	Usually a patient has a form of associative agnosia or appreceptive agnosia. However, in the case of integrative agnosia a patient falls in between a form of associative and appreceptive agnosia. This is where one has the ability to recognize elements of something but yet be unable to integrate these elements together into comprehensible perceptual wholes.
Pain agnosia	Also referred to as Analgesia, this is the difficulty perceiving and processing pain; thought to underpin some forms of self injury.
Phonagnosia	Is the inability to recognize familiar voices, even though the hearer can understand the words used.
Prosopagnosia	Also known as faceblindness and facial agnosia: Patients cannot consciously recognize familiar faces, sometimes even including their own. This is often misperceived as an inability to remember names.
Pure alexia	Inability to recognize text. Patients with Pure alexia often have damage to their corpus callosum, as well as damage to the left visual association areas. Pure alexia involves not being able to read printed material, but these individuals still have the ability to write. Individuals with pure alexia usually read words letter by letter. However, individuals with pure alexia show a frequency effect. They are able to read high frequency words better and faster than they can read low frequency words.
Semantic agnosia	Those with this form of agnosia are effectively 'object blind' until they use non-visual sensory systems to recognise the object. For example, feeling, tapping, smelling, rocking or flicking the object, may trigger realisation of its semantics (meaning).
Social-Emotional Agnosia	Sometimes referred to as Expressive Agnosia, this is a form of agnosia in which the person is unable to perceive facial expression, body language and intonation, rendering them unable to non-verbally perceive people's emotions and limiting that aspect of social interaction.
Tactile agnosia	Impaired ability to recognize or identify objects by touch alone.
Time agnosia	Is the loss of comprehension of the succession and duration of events.
Topographical disorientation	Also known as Topographical agnosia or Topographagnosia, is a form of visual agnosia in which a person cannot rely on visual cues to guide them directionally due to the inability to recognize objects. Nevertheless, they may still have an excellent capacity to describe the visual layout of the same place. Patients with topographical agnosia have the ability to read maps, but become lost in familiar environments.
Visuospatial dysgnosia	This is a loss of the sense of "whereness" in the relation of oneself to one’s environment and in the relation of objects to each other. It may include constructional apraxia, topographical disorientation, optic ataxia, ocular motor apraxia, dressing apraxia, and right-left confusion.
Visual agnosia	Is associated with lesions of the left occipital lobe and temporal lobes. Many types of visual agnosia involve the inability to recognize objects.

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