Aphasiology is the study of language impairment usually resulting from brain damage, due to neurovascular accident—hemorrhage, stroke—or associated with a variety of neurodegenerative diseases, including different types of dementia.
[citation needed] First described by the French neurologist Paul Broca in the nineteenth century, expressive aphasia causes the speech of those affected to display a considerable vocabulary but to show grammatical deficits.
[citation needed] Receptive aphasia was originally described by the German neurologist Karl Wernicke, a contemporary of Broca.
If the damage extends posteriorly, visual connections are disrupted, and the patient will have difficulty understanding written language.
[citation needed] Another less commonly known aphasia is global aphasia, which generally manifests itself after a stroke affecting an extensive portion of the brain occurs, including infarction of both divisions of the middle cerebral artery and generally both Broca's area and Wernicke's area.
[citation needed] Primary progressive aphasia is a rare disorder where people slowly lose their ability to talk, read, write, and comprehend what they hear in conversation over a period of time.
[8] The nineteenth century marked the most important time in the evolution of aphasiology, beginning with the works of Franz Josef Gall.
Gall is the founder of the more modern localization theory and is the origin of the idea of a language center in the brain.
However, supporting evidence for the theory that language had its own anatomical representation was not found until the case study of Mr. Leborgne, also known as Tan, by Paul Broca in 1861.
The discovery of what is now known as Broca's area was followed years later by Carl Wernicke's famous work, 'The Symptom-Complex of Aphasia: A Psychological Study on an Anatomical Basis' in 1874.