In this lesson, you will learn what the arcuate fasciculus is and where it is located. You will also learn a bit about its general functions and what happens if it is damaged or missing.
The Internet is sometimes called the information superhighway. But it’s not the only one; like the Internet, your own brain is a pretty amazing information superhighway.
Just as all highways have many different routes, connections and bridges, so does your brain.Have you ever seen a brain? It kind of looks like a bunch of squished up worms. The brain is made up of two main components of the brain: gray matter and white matter. The two halves of the brain are referred to as the left and right hemispheres. Scientists have learned a lot about gray and white matter and the two halves of the brain through autopsies and imaging techniques like MRIs, and by studying diseases or conditions associated with brain damage.The arcuate faciculus (AF) is a part of the white matter of the brain.
It is an arched band of white fibers that acts as a bridge between different sections of gray matter that are not directly connected. It can pass along information from one place to another, almost like a shortcut.
The arcuate faciculus (AF ) bridge travels around around a crack in the brain called the Sylvian Fissure. It may connect two regions of the brain called Broca’s area and Wernicke’s area, although there is some controversy.
Imaging suggests AF may also play a role in connecting to other parts of the brain, including Geschwind’s territory, which is a little behind Wernicke’s area.Broca’s area is located in the left posterior frontal lobe, a fancy way of saying the front, middle-bottom of the left hemisphere. Wernicke’s area is located in the left posterior temporal lobe, a fancy way of saying the back middle-bottom of the left hemisphere.
Broca’s Area: Function
To understand the arcuate fasciculus functions, it helps to understand how the Broca’s and Wernicke’s areas work.
Broca’s area is also known as the motor association cortex and is partially responsible for the muscle movement of your mouth when you form words.People with damage to the Broca’s area exhibit problems speaking. They may find it hard to put sentences together and have difficulty with grammar. For example, a person with damage to the Broca’s area may say: ‘I see.
..saw bug fleeing…
flying out window.’ In severe cases, people with damage to the Broca’s area may be unable to speak properly because, even though the muscles in their faces work, they can’t command them to move. Imagine an army that’s ready to fight, but can’t because the general that gives them the orders is missing.
Without orders, the army won’t move.
Wernicke’s Area: Function
Wernicke’s area, the hearing association cortex, is involved in the understanding of language. People with damage to Wernike’s area often speak fluently and are grammatically correct, but what they say is nonsense. For example, someone with damage to Wernicke’s area may say: ‘I played a piano in the ocean and then saw a bird flying upside-down underneath the chair.’ In severe cases, damage to Wernicke’s area may cause total loss of comprehension of both written and spoken words. Those affected can still speak, but they can’t read or understand speech.People with damage to the arcuate fasciculus retain the motor ability of the Broca’s area and the understanding of the Wernicke’s area, but they can’t put the two together.
This results in an ability to understand language but an inability to respond properly to it.
AF Functions ; Imaging
One of the functions of arcuate fasciculus (AF) is the ability to respond to heard speech, or speech processing. The AF is still being studied, and its functions are still coming to light. So how do researchers look at the roles it plays in everyday life without dissecting the brain? Well, there are advanced imaging techniques, like diffusion tensor imaging, that scientists can use to look at neural communication and pinpoint areas in the brain, including the AF.Studies using this technique have determined that the arcuate fasciculus in the right hemisphere plays a role in musicality, especially tone deafness. They have found it may be responsible for distinguishing between pitches and the ability to match sound heard with sound produced, in other words something like the ability to stay on key when singing.
Scientists have also found that lack of myelin sheaths in the arcuate fasciculus can play a role in the voices heard by schizophrenics. Think of myelin sheaths as telephone lines or cell phone towers. Without them, communication between people is slower. Similarly, without myelin sheaths, communication between areas of the brain, such as Wernicke’s and Broca’s, is impaired.In addition, scientists have studied learning in children with differences in the presence of left hemisphere AF. They found that those with a more prominent and functional AF were developmentally faster in language and reading skills than those with lower functioning AF.Overall, studies have found the AF is involved in learning musical structure, categorical learning (organizing objects or ideas, like ‘Windex is bad to drink while water is good’), and grammatical language.
The arcuate fasciculus (AF) is a band of arched white fibers and part of the white matter of the brain that connects separate gray matter regions to one another. It bridges the distance between the Broca’s and Wernicke’s areas past the Sylvian fissure. Broca’s area assists in motor processing, and damage can cause the inability to speak. Wernicke’s area assists in listening comprehension, and damage can cause the inability to understand language.The arcuate fasciculus, which purportedly connects the two areas and others, functions in speech processing. Damage can lead to the understanding of speech, but inability to respond to it.
Other functions of arcuate fasciculus include roles in learning and grammatical knowledge. It can be present in both the left and right hemispheres, and different roles have been discovered for its presence in the two halves.