Broca's area in the context of "Brodmann area 45"

A gesture is a form of nonverbal communication or non-vocal communication in which visible bodily actions communicate particular messages, either in place of, or in conjunction with, speech. Gestures include movement of the hands, face, or other parts of the body. Gestures differ from physical non-verbal communication that does not communicate specific messages, such as purely expressive displays, proxemics, or displays of joint attention. Gestures allow individuals to communicate a variety of feelings and thoughts, from contempt and hostility to approval and affection, often together with body language in addition to words when they speak. Gesticulation and speech work independently of each other, but join to provide emphasis and meaning.

Gesture processing takes place in areas of the brain such as Broca's and Wernicke's areas, which are used by speech and sign language. In fact, language is thought by some scholars to have evolved in Homo sapiens from an earlier system consisting of manual gestures. The theory that language evolved from manual gestures, termed Gestural Theory, dates back to the work of 18th-century philosopher and priest Abbé de Condillac, and has been revived by contemporary anthropologist Gordon W. Hewes, in 1973, as part of a discussion on the origin of language.

Wernicke's area (/ˈvɛərnɪkə/; German: [ˈvɛɐ̯nɪkə]), also called Wernicke's speech area, is one of the two parts of the brain that are linked to speech, the other being Broca's area. It is involved in the comprehension of written and spoken language, in contrast to Broca's area, which is primarily involved in the production of language. It is traditionally thought to reside in Brodmann area 22, located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of right-handed individuals and 70% of left-handed individuals.

Damage caused to Wernicke's area results in receptive, fluent aphasia. This means that the person with aphasia will be able to fluently connect words, but the phrases will lack meaning. This is unlike non-fluent aphasia, in which the person will use meaningful words, but in a non-fluent, telegraphic manner.

Phrenology is a pseudoscience that involves the measurement of bumps on the skull to predict mental traits. It is based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules. It was said that the brain was composed of different muscles, so those that were used more often were bigger, resulting in the different skull shapes. This provided reasoning for the common presence of bumps on the skull in different locations. The brain "muscles" not being used as frequently remained small and were therefore not present on the exterior of the skull. Although both of those ideas have a basis in reality, phrenology generalizes beyond empirical knowledge in a way that departs from science. The central phrenological notion that measuring the contour of the skull can predict personality traits is discredited by empirical research. Developed by German physician Franz Joseph Gall in 1796, the discipline was influential in the 19th century, especially from about 1810 until 1840. The principal British centre for phrenology was Edinburgh, where the Edinburgh Phrenological Society was established in 1820.

Phrenology is today recognized as pseudoscientific. The methodological rigor of phrenology was doubtful even for the standards of its time, since many authors already regarded phrenology as pseudoscience in the 19th century. There have been various studies conducted that discredited phrenology, most of which were done with ablation techniques. Marie-Jean-Pierre Flourens demonstrated through ablation that the cerebrum and cerebellum accomplish different functions. He found that the impacted areas never carried out the functions that were proposed through phrenology. Paul Broca also discredited the idea when he discovered and named the "Broca's area": the patient's ability to produce language was lost while their ability to understand language remained intact, due to a lesion on the left frontal lobe. He concluded that this area of the brain was responsible for language production. Between Flourens and Broca, the claims to support phrenology were dismantled. Phrenological thinking was influential in the psychiatry and psychology of the 19th century. Gall's assumption that character, thoughts, and emotions are located in specific areas of the brain is considered an important historical advance toward neuropsychology. He contributed to the idea that the brain is spatially organized, but not in the way he proposed. There is a clear division of labor in the brain but none of which even remotely correlates to the size of the head or the structure of the skull. It contributed to some advancements in understanding the brain and its functions.

Paul Pierre Broca (/ˈbroʊkə/, also UK: /ˈbrɒkə/, US: /ˈbroʊkɑː/, French: [pɔl bʁɔka]; 28 June 1824 – 9 July 1880) was a French physician, anatomist and anthropologist. He is best known for his research on Broca's area, a region of the frontal lobe that is named after him. Broca's area is involved with language. His work revealed that the brains of patients with aphasia contained lesions in a particular part of the cortex, in the left frontal region. This was the first anatomical proof of localization of brain function.

Broca's work contributed to the development of physical anthropology, advancing the science of anthropometry, and craniometry, in particular, the now-discredited practice of determining intelligence. He was engaged in comparative anatomy of primates and humans and proposed that Negroes were an intermediate form between apes and Europeans. He saw each racial group as its own species and believed racial mixing eventually led to sterility.

Expressive aphasia (also known as Broca's aphasia) is a type of aphasia characterized by partial loss of the ability to produce language (spoken, manual, or written), although comprehension generally remains intact. A person with expressive aphasia will exhibit effortful speech. Speech generally includes important content words but leaves out function words that have more grammatical significance than physical meaning, such as prepositions and articles. This is known as "telegraphic speech". The person's intended message may still be understood, but their sentence will not be grammatically correct. In very severe forms of expressive aphasia, a person may only speak using single word utterances. Typically, comprehension is mildly to moderately impaired in expressive aphasia due to difficulty understanding complex grammar. A better way to describe aphasia is fluent or non-fluent rather than "expressive" or "receptive" given the typical presence of both expressive and receptive language deficits in all subtypes of aphasia.

It is caused by acquired damage to the frontal regions of the brain, such as Broca's area. Expressive aphasia contrasts with receptive aphasia, in which patients are able to speak in grammatical sentences that lack semantic significance and generally also have trouble with comprehension. Expressive aphasia differs from dysarthria, which is typified by a patient's inability to properly move the muscles of the tongue and mouth to produce speech. Expressive aphasia also differs from apraxia of speech, which is a motor disorder characterized by an inability to create and sequence motor plans for conscious speech.

In the study of language processing, Carl Wernicke created an early neurological model of language, that later was revived by Norman Geschwind. The model is known as the Wernicke–Geschwind model.

1. For listening to and understanding spoken words, the sounds of the words are sent through the auditory pathways to area 41, which is the primary auditory cortex (Heschl's gyrus). From there, they continue to Wernicke's area, where the meaning of the words is extracted.
2. In order to speak, the meanings of words are sent from Wernicke's area via the arcuate fasciculus to Broca's area, where morphemes are assembled. The model proposes that Broca's area holds a representation for articulating words. Instructions for speech are sent from Broca's area to the facial area of the motor cortex, and from there instructions are sent to facial motor neurons in the brainstem, which relay movement orders to facial muscles.
3. In order to read, information concerning the written text is sent from visual areas 17, 18, and 19 to the angular gyrus (area 39) and from there to Wernicke's area, for silent reading or, together with Broca's area, for reading out loud.

This model is now obsolete. Nevertheless, it has been very useful in directing research and organizing research results, because it is based on the idea that language consists of two basic functions: comprehension, which is a sensory/perceptual function, and speaking, which is a motor function.
However, the neural organization of language is more complex than the Wernicke–Geschwind model of language suggests. The localization of speech in Broca's area is one of the weakest points of this model.