Broca's area of the brain
Broca's area is located in the left inferior frontal cortex and is associated with language outputs.
the discovery of Broca's area
Broca's area was first discovered by Paul Broca, a French neuroscientist, who discovered a brain lesion in a deceased patient that was unable to produce language, despite having the ability to understand language.
The area of the lesion is now known as Broca's area and is located in the left inferior frontal cortex.
Wernicke's area of the brain
Wernicke's area is located in the left superior posterior temporal lobe and is associated with the comprehension of words.
the discovery of Wernicke's area.
Wernicke's area was first discovered by Carl Wernicke, a German neurologist, who discovered lesions in the brains of deceased patients that could speak, but the words were completely incoherent.
The area of the lesions is now known as Wernicke's area and is located in the left superior posterior temporal lobe.
What is the name given to the large bundle of nerves that connects Broca's area and Wernicke's area?
the arcuate fasciculus
The arcuate fasciculus connects these two areas, creating a neural language loop.
the neural loop involved with producing and understanding spoken language
The neural loop includes Broca's area, Wernicke's area, and the neural connection between the two, formed by the arcuate fasciculus.
This loop is often called the neural language loop.
What is unique about the location of the inferior parietal lobe?
The inferior parietal lobe is located at the junction between the auditory, visual, and somatosensory cortices of the brain.
the inferior parietal lobe
The inferior parietal lobe can simultaneously process different types of stimuli, (including auditory, sensorimotor, and visual), allowing the brain to understand the many properties of language, such as sound, appearance, and function.
What are two noteworthy evolutionary facts regarding the inferior parietal lobe?
Two noteworthy evolutionary facts regarding the inferior parietal lobe are:
- It is one of the last brain structures to develop, explaining the late development of reading and writing skills in children.
- It was one of the last brain structures to have developed over the course of evolution.
the Geschwind-Wernicke model of language
The Geschwind-Wernicke model of language states that each component of language (perception, comprehension, production) is controlled by a specific structure in the brain, and the structures are connected in a very specific way.
This model was the first language model proposed and although it explains many functions, it also has many limitations.
the Mesulam model of language
The Mesulam model proposes a hierarchy of brain networks that processes information by level of complexity, and that brain structures and their connections are not fixed, but rather vary according to the task to be performed.
This model makes up for many of the limitations found in the Geschwind-Wernicke model.
What skills are affected by a parieto-occipital lesion?
A parieto-occipital lesion causes a person to be unable to read or write, while retaining the ability to speak.
What skills are affected by a Wernicke's area lesion?
Wernicke's area lesions causes a person to be unable to read and understand spoken language.
Brain lateralization is the phenomenon in which a skill or function is preferably controlled by one side of the brain over the other, causing the hemispheres to have specialized functions.
What are the two most lateralized functions of the human brain?
motor control and language
What brain hemisphere is considered the dominant hemisphere in regard to language?
In the majority of people, the left hemisphere is dominant for language.
For most people, the right hemisphere plays a more supplemental role.
What is the role of the right hemisphere in language capabilities?
The right hemisphere processes the pragmatics of language, or the ability to understand things that are implicitly signified.
Understanding language functions such as metaphors, sarcasm, and tones of voice are all pragmatic functions processed by the right hemisphere.
With regard to brain lateralization, is there a direct relationship between motor control and language lateralization?
Motor control lateralization (handedness) seems to have some influence over language lateralization; however, there is no direct relationship, as the correlation does not exist for all people.
With respect to motor control, a right-handed person is left brain lateralized and a left-handed person is right brain lateralized.
What percentage of right-handed people are also left-lateralized with respect to language?
Approximately 92-96% of right-handed people are also left-lateralized with respect to language.
People that are right-handed show left hemisphere dominance for motor control.
What percentage of left-handed people are also right-lateralized with respect to language?
Some studies cite that only 15% of left-handed people are also right lateralized with respect to language.
Other studies say that nearly 70% of left-handed people show equal capabilities in both hemispheres.
People that are left-handed show right hemisphere dominance for motor control.
What are two major physical brain asymmetries concerning language capabilities?
- A longer and more shallow lateral sulcus on the dominant hemisphere
- A temporal planum on the dominant hemisphere
the temporal planum
The temporal planum is a physical asymmetry of the brain in which the superior surface of one hemisphere's temporal lobe is much larger, denoting the dominant hemisphere with respect to language.
In 65% of individuals the temporal planum is located on the left hemisphere.
Wada's test is a procedure done to determine a person's language lateralization within the brain.
A Wada's test involves anesthetizing one brain hemisphere at a time. If the anesthetized hemisphere results in the patient's inability to produce or understand language, then that hemisphere is the patient's dominant language hemisphere.
When is a Wada's test performed?
A Wada's test is useful in preparation for brain surgery, in which the surgeon locates exactly which areas of a patient's brain control language.
In this way, a surgeon can avoid brain areas that would disrupt the patient's language capabilities.
Dysphasia is a language development abnormality, associated with malfunctions in the areas of the brain that process language.
Dysphasic children hear properly, but often have a difficult time understanding the meaning of words or sentences, and making their own speech understandable.
Aphasia is a language disorder acquired as a result of brain damage to a person that had previously mastered a language.
Aphasia can be caused by stroke, injury, a tumor, or a neurological degenerative disease.
Articulation disorders are a type of dysphasia characterized by an error in the movement of the mouth or tongue.
Examples include lisping and the inability to form consonant sounds.
Dyslexia is a type of dysphasia that consists of difficulties in reading or writing. Dyslexic people may confuse similar sounds or letters, reverse letters or words, or completely substitute certain words for others.
Some studies show that nearly 5-10% of the population suffers from varying degrees of dyslexia.
Broca's aphasia is caused by lesions to Broca's area and results in speech issues including slow speech, the inability to recall certain words, a difficulty in forming verbs, and trouble distinguishing the subject from the object.
Language understanding is generally well preserved in people with Broca's aphasia.
Wernicke's aphasia is caused by a lesion to Wernicke's area and results in reduced understanding of spoken or written language, as well as jumbled and incomprehensible speech.
Global aphasia is caused by lesions to both Broca's and Wernicke's areas, and leads to the total loss of the ability to understand, speak, read, or write language.
Conduction aphasia results in difficulty repeating words or phrases, despite retaining both language comprehension and spontaneous oral communication skills.
It is still unknown which areas of the brain correspond to conduction aphasia.
Anomic aphasia results in difficulty recalling certain words, despite retaining both oral expression and syntactic structure skills.
People with anomic aphasia generally suffer from damage to their parietal lobes.
At what age do most babies speak their first word?
At approximately 10 months most babies speak their first word.
A baby's first word is most commonly "mama" or "dada".
At what age to children generally have a complete understanding of the spoken language?
By age 2, most children have a nearly complete understanding of the language they hear.
At this age, most children can form 2-3 word sentences, and are beginning to develop language syntax skills.