Broca's Aphasia

Speech is produced in the posterior region of the cerebral cortex. One can communicate via speech a memory from the past, current environmental conditions, or a novel concept one makes within the imagination. When a person actually says something, thoughts, memories, and sensory perceptions are converted into speech in areas of the frontal lobe (Carlson, 1999). Specifically, the region responsible for speech production is Broca's area (located in the frontal lobe), named after the French physician who localized the region after examining patients who had speech production deficits resulting from damage to the inferior left frontal lobe (Stillings et al., 1995). Such deficits are now called Broca's aphasia. It is important to note, however, that Broca's area is not the sole source of what is comprehensively known as Broca's aphasia. Damage includes Broca's area, as well as areas nearby in the frontal lobe and subcortical white matter. Neuroimaging shows that damage to the neocortex and the head of the caudate nucleus are also involved in Broca's aphasia (Carlson, 1999).

Broca's aphasia is characterized by three separate deficits, including agrammatism, anomia, and impaired speech articulation (Carlson, 1999). One who has Broca's aphasia speaks with great difficulty. Speech is slow, and sounds are often rearranged or slurred (Stillings et al., 1995). Broca's aphasia can relate to written, signed, auditory, or vocal material. All parts of language, including the morphological (sounds), lexical (sounds or words with meaning), and grammatical levels (rules of grammar), can be affected (Bradshaw & Mattingley, 1995). Patients have greater difficulty producing function words, and less difficulty with content words. Function words have little meaning, and serve functions regarding grammatical structure (such as a preposition), while content words (for example nouns), convey meaning (Carlson, 1999). Broca's aphasia overall has several aspects of complexity.

One characteristic deficit of Broca's aphasia is called agrammatism. Agrammatism deals with grammatical devices. Patients have difficulty either comprehending or using the appropriate verb endings to words, or confuse word order. Although Broca's aphasia is defined as a disorder of production, comprehension is also impaired when word order is confused. For example, when subjects are shown two pictures of close meaning, along with the sentence that describes one of the pictures, patients have difficulty pointing to the correct picture. Patients confused the appropriate objects of actions. For example, in the sentence "The girl is laughing at the boy," a patient would have difficulty picking between a picture of a girl laughing at a boy, or a boy laughing at a girl (Carlson, 1999). Such sentences are usually reversible sentences. When the object and the subject are nouns that can fill one another's role, a person can reverse them and the sentence still makes sense, though the meaning is changed (Kosslyn & Koenig, 1995). When the grammar is not understood within the sentence, the meaning is also lost, hence the deficit in comprehension.

Anomia, or nomical aphasia, is another symptom among Broca's aphasic patients. Anomia literally means "without name." Patients with anomia have difficulty in remembering the proper word to describe an attribute, action, or object (Carlson, 1999). Patients have more trouble with infrequent words, or words not used in everyday language. One with anomia may give a detailed definition of a word in with ease, yet be unable recall the actual word. The patient may know exactly what he or she desires to say, yet (especially when talking about objects or actions) they cannot "find" the right word. Anomic patients often use circumlocutions, where inaccessible words are replaced with similar words or phrases that are more common (Kosslyn & Koenig, 1995). A patient with anomia can describe a picture and not be able to name it, yet when the word is said aloud by someone else, the anomic patient can easily point to the corresponding picture. When given the first phoneme of a word (the first unit of sound with meaning), patients can think of the appropriate word more easily, and often the words produced by a patient are phonologically close to, or sound like, the correct word. According to cognitive theory, all of these characteristics appear to suggest that in associative memory (memory for the association between events, objects, words, etc.), the semantic information (general knowledge) and the correct representation of the word are activated and intact. Yet the pathways for speech output are either not activated, damaged, or could not be used to generate output instructions. Such damage to the neural connections of associative memory can lead to losing information that is associated with a word, or malfunctioning of the processes that activate that specific information (Kosslyn & Koenig, 1995). Anomia is a main symptom of all forms of aphasia. A Broca's patient can easily be distinguished, because their speech is not eloquent or fluid, and they use words such as "uh" as they struggle to find the correct word (Carlson, 1999). Besides anomia, Broca's aphasia patients also have articulation difficulty.

A Broca's patient has a characteristic deficit in articulation, evidenced when he or she modifies the sequence of sounds or mispronounces words. The area of the brain responsible for articulation is the left precentral gyrus of the insula (which is located in the cerebral cortex below the temporal, frontal, and parietal opercula, and is primarily responsible for integrating information of the autonomic nervous system). The patient is often aware that the articulation is wrong, and will attempt to remedy the error, since comprehension of speech and reading is normal among those with pure aphasic articulation problems (Carlson, 1999; Kosslyn & Koenig, 1995).

Apraxia of speech may be at the root of articulation problems. Apraxia of speech is an impairment in programming the movements of the physical body parts needed to produce the sounds of speech (e.g., the throat, tongue, and lips) (Carlson, 1999). In other words, the movement execution subsystem is impaired thereby affecting the articulation of complex linguistic sounds. The problem may also stem from not being able to produce the desired sound from memory. Like anomia, the problem might be traced to damage in memory, leading to a disruption in speech output pathways (Kosslyn & Koenig, 1995).

Certain symptoms of Broca's aphasia may be directly related to muscular movements that articulate words. This is evidenced by the fact that the muscles used for articulation are controlled by the portion of the primary motor cortex that is connected to the "inferior caudal left frontal lobe (including Broca's area)" (Carlson, 1999, p.386). Besides the primary motor cortex, the cerebellum may be involved in certain symptoms of Broca's aphasia. A function of the cerebellum is to coordinate movements related to exact timing. The ability to speak is certainly a quickly executed movement of skill. Cerebellum damage can cause agrammatism and imprecise enunciation (Carlson, 1999).

Therefore, even though the above-mentioned aspects of Broca's aphasia are usually caused by damage to Broca's area or areas close by, damage to other areas of the brain can cause the same problems. The brain is a complex entity, and one symptom or deficit cannot be automatically assigned to one particular area in the brain. Aside from the intricate subject of Broca's aphasia speech production deficits, the arguably more complex process of speech comprehension is also subject to damage. Such deficits in speech articulation and related production fall under the category of Wernicke's aphasia.