As in many areas of science, the rationale behind aphasiology is that we can often gain valuable insights into the workings of a system when that system breaks down. It is hoped, then, that specific malfunctions in the speech of aphasic patients will shed light on the functioning of the unimpaired language system. One of the earliest discoveries in aphasiology was reported by the French neurologist Paul Broca in 1861. It has since been found that patients suffering from Broca's aphasia can generally understand what is said to them, but have considerable difficulty in producing speech.
Sentences tend to be short and are produced intermittently, with long pauses in between.
Broca's aphasia is also characterized by agrammatical sentences which arise from the omission of so-called function words, such as 'the', 'of' and 'to'. Since Broca's pioneering studies, research in aphasiology has implicated several other areas of the brain as potential speech centres. One of the most important, located in the posterior part of the left hemisphere, was named Wernicke's area after Carl Wernicke in 1872. Patients suffering from Wernicke's aphasia possess fluent speech with generally intact grammatical structure. However, the most notable symptom of Wernicke's aphasia is a drastic reduction in the powers of speech comprehension.