Broca’s area is an anatomical functional unit of the human brain. Even the smallest lesions of this cerebral cortical area result in measurable performance deficits or cognitive deficits.
What is Broca’s area?
Broca’s area was named after a French anthropologist and neurosurgeon. Paul Broca was born in 1824 and died in Paris in 1880. It is to his basic science that we owe the current knowledge of the brain area named after him. In established medical but also lay usage, Broca’s area is often referred to as Broca’s center, Broca’s speech center, or even the so-called motor speech center. It refers to a well-defined anatomical section on a person’s cerebral cortex that can be assigned to speech motor function. Paul Broca discovered the functioning of this important brain area through a patient he studied himself named Monsieur Tan. The articulation ability of this patient, i.e. his ability to form speech, was limited to the syllable Tan. However, apart from this disturbance in speech articulation, this patient showed no other limitations in speech comprehension.
Anatomy and Structure
The anatomy and structure of Broca’s center had also been described previously by Paul Broca himself. When Broca learned of the death of his patient with the specific speech disorder, he was permitted to perform an autopsy himself. In doing so, Broca focused primarily on certain sections of the brain in which he suspected the cause of his patient’s limited ability to articulate. Brain anatomically, Broca was presented with the picture of an extensive lesion in the cortex area of the cerebrum, which today is referred to as Broca’s area. Today, this motor speech center can also be very accurately visualized and differentiated from other brain regions by imaging techniques such as computed tomography or magnetic resonance imaging. These imaging techniques are particularly diagnostic for the detection of functional disorders of Broca’s area. At that time, Broca only made assumptions about the task area of the brain area named after him, but today it is considered certain that this brain anatomical structure is the area of syntactic language processing. Broca’s area is located in the cerebral hemisphere, usually in the left hemisphere in right-handed people and in the right hemisphere in left-handed people. The exact anatomical location is the area of the partes triangularis et opercularis within the so-called inferior frontal gyrus.
Function and tasks
Tasks and functions of Broca’s area are directly associated with the generation and processing of human language expression. Without the specialized brain cells of this motor speech center, proper speech processing is not possible. As a rule, the affected person does not notice this at first until other people point it out to him. Broca’s area, in turn, receives input on afferent nerve commands from the higher-level Wernicke’s center. If Broca’s area is damaged, the nerve impulses arriving from there cannot be processed further. It is now considered scientifically established that Broca’s speech center mediates the integration of speech production, as well as semantic understanding or sensory input. The nervous commands of Broca’s area are projected to special nerve nodes, the basal ganglia, where the fine modulation of motor programs finally takes place. If the physiological functions for speech processing and speech transmission are impaired, then the cause does not necessarily lie in Broca’s area itself, but possibly in the upstream large cerebral arteries, which supply Broca’s area with blood and oxygen. If the disturbance of Broca’s area is not caused by a lesion, the cause is often to be found in an occlusion of the ateria praerolandica. This artery is anatomically a branch of the middle large cerebral artery, ateria media cerebri, and serves primarily to supply nutrients and oxygen to Broca’s speech center. Arteriosclerosis in these important brain vessels therefore repeatedly leads to noticeable restrictions in the function of Broca’s area, especially in older people.
Diseases
If not only Broca’s area but also other anatomic units associated with it for language mediation are pathologically altered, then complex neurologic examinations are necessary to accurately determine the origin of a speech aphasia. Pathologic processes of Broca’s area can result in minute lesions to complete destruction of this brain region. The nature and extent of the inability to properly process and reproduce speech is directly dependent on the extent of the lesions. Pathological changes of Broca’s region are based on the one hand on the consequences of a stroke or on the other hand they are the consequence of intracranial space-occupying lesions, for example malignant brain tumors. Whether the cause of the lesion in Broca’s region is an ischemic insult, i.e. a stroke, or a brain tumor, is initially irrelevant for the symptoms, but it is relevant for the therapy. This is always aimed at eliminating the cause of a lesion, which unfortunately is not always successful, especially in the case of extensive findings, so that patients have to suffer from a certain speech disorder for the rest of their lives. Any pathological change in Broca’s region leads to the clinical picture known as Broca’s aphasia. The result is halting, slowed speech, the formation of only short sentences in telegram style, and sound confusion. In addition, affected patients regularly report that they have to make a great effort to speak. Even if speech comprehension is less impaired, however, problems frequently exist when function words, such as “his,” “herself,” or “her,” must be assigned within linguistic communication.
