Aphasia (Linguish)
Aphasia is an impairment of language affecting the ability to use or comprehend speech. Aphasia usually results from brain injury, most often connected with a stroke. It can range from mild to severe. Although the play Linguish posits a virus that affects that same part of the brain, no known virus communicates the condition. There are three common forms of aphasia in Linguish, anomic aphasia, Broca’s aphasia, and Wernicke’s aphasia, all defined below. Also, Linguish references symptoms such as eidetic memory (never associated with real life aphasia), echolalia (something sometimes found in aphasics, but not commonly considered a part of the disease), and a Tourette’s-like desire to use certain words (also something sometimes found in aphasics)

Anomic Aphasia
A type of aphasia characterized by the ongoing inability to name things or find the words the aphasic seeks. These aphasics are able to comprehend well, but are forced to rely on circumlocution in order to convey their meaning. In Linguish, a connection is also made between this sort of aphasia and an inability to comprehend multiple meanings—a phenomenon that has precedent among case studies.

Asperger’s
Asperger’s is sometimes referred to as high functioning autism. All those with Asperger’s, by definition, have a normal IQ. Often, Asperger’s is not diagnosed till later in life, though increasingly it is being diagnosed early. Those with Asperger’s have difficulty in social interaction, tend to be considered eccentric, and often have monomanias. However, they are able to function in the world of the more neurotypical. It is named after Hans Asperger, who originally described it in Vienna in 1944. Many people with Asperger's consider their condition a difference rather than a disorder, and wish to choose for themselves what they will be, and how they are to be seen.

Autism (Tabula Rasa, The Boy Who Wanted to be a Robot)
A developmental neurological condition, usually appearing by age three, which is characterized by a difficulty in social communication and interaction. Most interests tend to be reclusive, and often the interests are fixated on a single subject matter. Autistics usually exhibit stimming—repetitive, self stimulating behavior such as rocking or tapping. Language development is often delayed. Autistics also often display great sensitivity to outside stimuli, such as noises. Sometimes autism is accompanied by great facility in math or music or memory.

Broca’s Aphasia
A form of aphasia marked primarily in a difficulty expressing oneself. Those suffering from Broca’s Aphasia are likely to struggle with every word, and utterances of more than four words running are unusual. Vocabulary is difficult to access. However, the ability to comprehend speech can be unaffected. It is sometimes referred to as “non-fluent aphasia.”

Capgras’ Syndrome (Impostors)
A neurological condition in which the person affected believes that some person or persons have been replaced by an exact double. The syndrome is caused by the inability to access the emotional connection to the person who is believed to have been replaced, though visual recognition is not impaired. Thus, those with Capgras may see their husband, wife, child, parent or friend, but will state that the person does not “feel” like the same person. The delusion may extend to many people, or it may be centered on one person. It may even be centered on the very individual suffering the delusion—some people with Capgras have become convinced that the face they see in the mirror is that of a doppelganger. However, these delusions are purely neurological, not psychological.

Creutzfeldt-Jakob Disease (CJD)
A form of degenerative dementia that is inevitably fatal, usually within a year. It can be inherited or caught virally, or it can occur for no known reason. There is some correlation thought to be between the virus and Mad Cow Disease. They are both considered prion diseases—diseases communicated through infectious proteins.

Dementia (Doctors Jane and Alexander)
A condition marked by the deterioration of mental abilities, such as the ability to remember, judge, or concentrate, resulting from an organic cause within the brain. This condition is often, though not exclusively, associated with old age. Sometimes it is accompanied by emotional disturbance and personality changes. Alzheimer’s Disease and Creutzfeldt-Jakob Disease are both forms of dementia, though some dementia, such as that exhibited in Doctors Jane and Alexander, can be the result of a stroke.

Echolalia
The repetition of another person’s speech in a meaningless and often involuntary manner. Echolalia can exist is schizophrenics, as well as sometimes occurring in aphasics and people suffering from Tourette’s Syndrome. Sometimes it is attached to mimicry of tone or body language. Interestingly, personal pronouns can sometimes switch.

Eidetic Memory
The ability to recall things extremely accurately, especially when it comes to visual images. Some well known people said to have this ability are Bobby Fischer, Claude Monet, and Nicola Tesla, and others mentioned in the entry on synesthesia, below.

Korsakov's Syndrome
A type of amnesia characterized by the inability to recall any recent events although long term memory is intact. The amnesia can be retrograde, dating back at times to years before the onset. Other cognitive abilities are usually well preserved. Korsakov’s syndrome is most often caused by thiamine deficiency as a result of alcohol abuse (or possibly malnutrition or malabsorbtion), although it can also be caused by head injury, heavy metal poisoning or tumors.

Meniere's Disease
A disorder of the inner ear, characterized by idiopathic damage to the vestibucochlear nerve (one of the twelve cranial), which is halved between the vestibular and the acoustic. It can lead to vertigo, tinnitus, loss of hearing, and a sense of fullness in the ear.

Synesthesia (The Taste of Blue)
A condition in which the real information collected by one sense results additionally in a sensation or perception in a sense other than the one being stimulated. Thus, sounds can be perceived to have colors, colors can be perceived to have taste or smell, etc. Much like the character in The Taste of Blue, people who have synesthesia have been known to have eidetic memory—two well known cases of that sort are Valdimir Nabokov and the subject of A. R. Luria’s Mind of a Mnemonist.

Tourette’s Syndrome (Syndrome, Welcome to Tourettaville!)
A neurological condition characterized by compulsive motor or vocal tics that are frequent and repetitive. The most known of these tics is the compulsion to say curse words, though the vocal tics are not limited to this, and often someone with Tourette’s may not have that particular compulsion at all. Sometimes Tourette’s is described as the sensation of being “sped up”, and the reflexes of those with Tourette’s Syndrome tend to be much faster than those of people who do not have the syndrome.

Wernicke’s Aphasia
A form of aphasia often referred to as “fluent aphasia,” because those with this type of aphasia can speak at length. However, their speech is often nonsensical, resembling a stream of consciousness filled with irrelevant phrases and sometimes including made up words. When someone with Wernicke’s aphasia is read a transcript of his or her own speech, the aphasic is often shocked at the contents. Comprehension of others people’s speech is also profoundly and negatively effected.