Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: How does agnosia affect the brain?
Agnosia is the inability to process sensory information. Often there 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.[1] It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream.[2] Agnosia only affects a single modality,[3] such as vision or hearing.[4] More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.[5]
Integrative agnosia is a sub-disease of agnosia, meaning the lack of integrating perceptual wholes within 
knowledge. Integrative agnosia can be assessed by several experimental tests such as the Efron shape test, which 
determines the specificity of the disease being Integrative. 
This disease is often caused by brain trauma, producing medial ventral lesions to the extrastriate cortex. Affecting this region of the brain produces learning impairments: the inability to 
integrate parts such as spatial distances or producing visual images from short or long-term memory.
Visual agnosia occurs after damage to visual association cortex or to parts of the ventral stream of vision, known as the "what pathway" of vision for its role in object recognition. This occurs even when no damage has been done to the eyes or optic tract that leads visual information into the brain; in fact, visual agnosia occurs when symptoms cannot be explained by such damage. Damage to specific areas of the ventral stream impair the ability to recognize certain categories of visual information, such as the case of prospagnosia. Patients with visual agnosia generally do not have damage to the dorsal stream of vision, known as the "where pathway" of vision because of its role determining object's position in space, allowing individuals with visual agnosia to show relatively normal visually guided behavior.
Agnosia can result from strokes, dementia, or other neurological disorders. It may also be trauma-induced by a head injury, brain infection, or hereditary. Additionally, some forms of agnosia may be the result of developmental disorders.[4] Damage causing agnosia usually occurs in either the occipital or parietal lobes of the brain. Although one modality may be affected, cognitive abilities in other areas are preserved.[4]
An agnosia that affects hearing, "auditory sound agnosia", is broken into subdivisions based on level of processing impaired, and a "semantic-associative" form is investigated within the auditory agnosias.
Each patient that suffers from apperceptive agnosia does not have brain damage in exactly the same area. However, brain damage in proximity to the occipital lobe is largely correlated with the patterns of deficit seen in apperceptive agnosics. For example, patient JB suffered extensive damage to the parietal-occipital areas to the left cerebral hemisphere leading to his deficit in the ability to name distinguish between structurally similar object.
Holographic models of memory and consciousness may be related to several brain disorders involving disunity of sensory input within a unified consciousness, including Charles Bonnet Syndrome, Disjunctive Agnosia, and Schizophrenia. Charles Bonnet Syndrome patients experience two vastly different worlds within one consciousness. They see the world that psychologically normal people perceive, but also a simplified world riddled with Pseudohallucination. These patients can differentiate these two worlds easily. Since dynamic core and global workspace theories insist that a distinct area of the brain is responsible for consciousness, the only way a patient would perceive two worlds was if this dynamic core and global workspace were split. But such does not explain how different content can be perceived within one single consciousness since these theories assume that each dynamic core or global workspace creates a single coherent reality. The primary symptom of Disjunctive Agnosia is an inconsistency of sensory information within a unified consciousness. They may see one thing, but hear something entirely incompatible with that image. Schizophrenics often report experiencing thoughts that do not seem to originate from themselves, as if the idea was inserted exogenously. The individual feels no control over certain thoughts existing within their consciousness.
Phonagnosia (from Ancient Greek φωνή "phone", "voice" and γνῶσις "gnosis", "knowledge") is a type of agnosia, or loss of knowledge, that involves a disturbance in the recognition of familiar voices and the impairment of voice discrimination abilities in which the affected individual does not suffer from comprehension deficits. Phonagnosia is an auditory agnosia, an acquired auditory processing disorder resulting from brain damage, other auditory agnosias include cortical deafness and auditory verbal agnosia also known as pure word deafness.
Patient TH was in the early stages of dementia and was affected by mirror agnosia. While TH was looking into a mirror, the researcher held an object behind TH in such a way so it was reflected in the mirror. Due to his belief that mirrors represent a separate place, TH tried to reach into the mirror to retrieve the object rather than reaching over his shoulder. TH’s mirror agnosia accounts for the development of the delusional idea. Because not all patients with mirror agnosia develop the delusion, there needs to be the presence of a second factor that explains why TH does not reject his delusional belief that the object is inside the mirror. Neuropsychological testing showed TH had an impaired right hemisphere. He displayed poor visual memory and visuoconstructional problems but still had basic visuoperceptual skills, a normal intelligence, typical vocabulary, and average semantic ability. These issues are indicative of significant right hemisphere dysfunction, specifically in the right dorsolateral prefrontal cortex. Because of such cranial impairments, TH was unable to use logic to reject his delusional beliefs based on implausibility. From this case study, researchers concluded that while not all patients with mirror agnosia develop mirrored-self misidentification, when mirror agnosia is paired with right hemisphere damage of the belief evaluation system, the delusion will develop.
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.
Anosognosia, a lack of awareness of the deficit, is common and can cause therapeutic resistance. In some agnosias, such as prosopagnosia, awareness of the deficit is often present; however shame and embarrassment regarding the symptoms can be a barrier in admission of a deficiency. Because agnosias result from brain lesions, no direct treatment for them currently exists, and intervention is aimed at utilization of coping strategies by patients and those around them. Sensory compensation can also develop after one modality is impaired in agnostics
Visual agnosia, or visual-form agnosia, is a brain disorder that produces an inability to recognize objects. This disorder often arises after damage to the ventral stream.
Social-emotional agnosia, also known as emotional agnosia or expressive agnosia, is the inability to perceive facial expressions, body language, and voice intonation. A person with this disorder is unable to non-verbally perceive others' emotions in social situations, limiting normal social interactions. The condition causes a functional blindness to subtle non-verbal social-emotional cues in voice, gesture, and facial expression. People with this form of agnosia have difficulty in determining and identifying the motivational and emotional significance of external social events, and may appear emotionless or agnostic (uncertainty or general indecisiveness about a particular thing). Symptoms of this agnosia can vary depending on the area of the brain affected. Social-emotional agnosia often occurs in individuals with schizophrenia and autism. It is difficult to distinguish from, and has been found to co-occur with, alexithymia.
Since the early days of aphasia research, the relationship between auditory agnosia and speech perception has been debated. Lichtheim (1885) proposed that auditory agnosia is the result of damage to a brain area dedicated to the perception of spoken words, and consequently renamed this disorder from ‘word deafness’ to ‘pure word deafness’. The description of word deafness as being exclusively for words was adopted by the scientific community despite the patient reported by Lichtheim’s who also had more general auditory deficits. Some researchers who surveyed the literature, however, argued against labeling this disorder as pure word deafness on the account that all patients reported impaired at perceiving spoken words were also noted with other auditory deficits or aphasic symptoms. In one review of the literature, Ulrich (1978) presented evidence for separation of word deafness from more general auditory agnosia, and suggested naming this disorder “linguistic auditory agnosia” (this name was later rephrased into “verbal auditory agnosia”). To contrast this disorder with auditory agnosia in which speech repetition is intact (word meaning deafness), the name “word sound deafness” and “phonemic deafness” (Kleist, 1962) were also proposed. Although some researchers argued against the purity of word deafness, some anecdotal cases with exclusive impaired perception of speech were documented. On several occasions, patients were reported to gradually transition from pure word deafness to general auditory agnosia/cerebral deafness or recovery from general auditory agnosia/cerebral deafness to pure word deafness.
Auditory agnosia is a form of agnosia that manifests itself primarily in the inability to recognize or differentiate between sounds. It is not a defect of the ear or "hearing", but rather a neurological inability of the brain to process sound meaning. It is caused by bilateral damage to the anterior superior temporal gyrus, which is part of the auditory pathway responsible for sound recognition, the auditory "what" pathway . Persons with auditory agnosia can physically hear the sounds and describe them using unrelated terms, but are unable to recognize them. They might describe the sound of some environmental sounds, such as a motor starting, as resembling a lion roaring, but would not be able to associate the sound with "car" or "engine", nor would they say that it "was" a lion creating the noise. All auditory agnosia patients read lips in order to enhance the speech comprehension. It is yet unclear whether auditory agnosia (also called general auditory agnosia) is a combination of milder disorders, such auditory verbal agnosia (pure word deafness), non-verbal auditory agnosia, amusia and word meaning deafness), or a mild case of the more severe disorder, cerebral deafness. So far, 203 patients with auditory perceptual deficits due to CNS damage were reported in the medical literature, of which 183 diagnosed with general auditory agnosia or word deafness, 34 with cerebral deafness, 51 with non-verbal auditory agnosia-amusia and 8 word meaning deafness (for a list of patients see).
Visual agnosia is an impairment in recognition of visually presented objects. It is not due to a deficit in vision (acuity, visual field, and scanning), language, memory, or intellect. While cortical blindness results from lesions to primary visual cortex, visual agnosia is often due to damage to more anterior cortex such as the posterior occipital and/or temporal lobe(s) in the brain. There are two types of visual agnosia: apperceptive agnosia and associative agnosia.
As in many other agnosias, those with the disorder have difficulty recognizing their errors and often do not correct themselves.
There is no known treatment for finger agnosia. Typically, finger agnosia does not present difficulties in daily life. In most cases, visual guidance can help with any difficulty in distinguishing or moving the appropriate finger.
Agnosia is the inability to recognize certain objects, persons or sounds. Agnosia is typically caused by damage to the brain (most commonly in the occipital or parietal lobes) or from a neurological disorder. Treatments vary depending on the location and cause of the damage. Recovery is possible depending on the severity of the disorder and the severity of the damage to the brain. Many more specific types of agnosia diagnoses exist, including: associative visual agnosia, astereognosis, auditory agnosia, auditory verbal agnosia, prosopagnosia, simultanagnosia, topographical disorientation, visual agnosia etc.
Associative visual agnosias are generally attributed to anterior left temporal lobe infarction, caused by ischemic stroke, head injury, cardiac arrest, brain tumour, brain hemorrhage, or demyelination. Environmental toxins and pathogens have also been implicated, such as, carbon monoxide poisoning or herpes encephalitis and infrequent developmental occurrences have been documented.
Questions to answer: How does this affect material choice? Does the brain have unique phages that act differently and may affect materials thought to be biocompatible in other areas of the body?
Damage to the left hemisphere of the brain has been explicitly implicated in the associative form of visual agnosia. Goldberg suggested that the associative visual form of agnosia results from damage to the ventral stream of the brain, the occipito-temporal stream, which plays a key role in object recognition as the so-called "what" region of the brain, as opposed to the "where," dorsal stream.
Musical agnosias may be categorized based on the process which is impaired in the individual. Apperceptive music agnosia involves an impairment at the level of perceptual analysis involving an inability to encode musical information correctly. Associative music agnosia reflects an impaired representational system which disrupts music recognition. Many of the cases of music agnosia have resulted from surgery involving the middle cerebral artery. Patient studies have surmounted a large amount of evidence demonstrating that the left side of the brain is more suitable for holding long-term memory representations of music and that the right side is important for controlling access to these representations. Associative music agnosias tend to be produced by damage to the left hemisphere, while apperceptive music agnosia reflects damage to the right hemisphere.
Loss of object recognition is called "visual object agnosia". There are two broad categories of visual object agnosia: apperceptive and associative. When object agnosia occurs from a lesion in the dominant hemisphere, there is often a profound associated language disturbance, including loss of word meaning. 
Object recognition is a complex task and involves several different areas of the brain – not just one. If one area is damaged then object recognition can be impaired. The main area for object recognition takes place in the temporal lobe. For example, it was found that lesions to the perirhinal cortex in rats causes impairments in object recognition especially with an increase in feature ambiguity. Neonatal aspiration lesions of the amygdaloid complex in monkeys appear to have resulted in a greater object memory loss than early hippocampal lesions. However, in adult monkeys, the object memory impairment is better accounted for by damage to the perirhinal and entorhinal cortex than by damage to the amygdaloid nuclei. Combined amygdalohippocampal (A + H) lesions in rats impaired performance on an object recognition task when the retention intervals were increased beyond 0s and when test stimuli were repeated within a session. Damage to the amygdala or hippocampus does not affect object recognition, whereas A + H damage produces clear deficits. In an object recognition task, the level of discrimination was significantly lower in the electrolytic lesions of globus pallidus (part of the basal ganglia) in rats compared to the Substantia- Innominata/Ventral Pallidum which was in turn worse compared to Control and Medial Septum/Vertical Diagonal Band of Broca groups; however, only globus pallidus did not discriminate between new and familiar objects. These lesions damage the ventral (what) pathway of the visual processing of objects in the brain.
Agnosia is "the loss or diminution of the ability to recognize familiar objects or stimuli usually as a result of brain damage". There are several different kinds of agnosia that affect every one of our senses, but the two most common related to speech are speech agnosia and phonagnosia.
Apperceptive agnosia is a failure in recognition that is due to a failure of perception. In contrast, associative agnosia is a type of agnosia where perception occurs but recognition still does not occur. When referring to apperceptive agnosia, visual and object agnosia are most commonly discussed; This occurs because apperceptive agnosia is most likely to present visual impairments. However, in addition to visual apperceptive agnosia there are also cases of apperceptive agnosia in other sensory areas.
Some of the causes of integrative agnosia include stroke, traumatic brain injury, Alzheimer's disease, an anoxic episode following myocardial infarction, and progressive multifocal leukoencephalopathy.