Fundamentals of Neuroscience/Language

Type classification: this is a lesson resource.

Subject Classification: this is a neuroscience resource.

Goals

The Rosetta Stone is a good example of the intricacies that characterize each unique human language.

• To learn the major brain areas responsible for accomplishing the many complex tasks involved in language
• To understand the mechanisms behind communication and comprehension
• To learn the unique aspects of human biology which permit high-level language abilities

Characteristics of language

Although the idea of language may appear hard to define, it is in fact nothing more than a systematic method of communication. Communication can take a wide range of forms: everything from spoken words to body gestures to written symbols. In each case, the expression carries with it some kind of meaning- whether it be the definition of the word, or an emotion conveyed by body language or simply sign language, or written sentences or mathematical equations. However, what distinguishes humans from other species is a grasp on sophisticated verbal and written communication.

This cross-section shows the basic anatomy of speech production.

While it may seem like a routine occurrence, having a simple conversation is in fact an immensely complicated feat on the neurological level. Almost every aspect of cognition must work together in order to comprehend what the other person is saying, and then rapidly compute in order to respond back. This task involves short term memory to remember what the other person just said, hearing in order to extract ideas out of sound vibrations, then higher cognitive steps to analyze the structure and meaning of speech, and finally the formulation of a reply which must be converted into coordinated muscle movements of the mouth and vocal chord. All of this must take place in less than a third of a second. This makes language one of the most complicated and cognitively-intensive processes known, which is a major factor of why its mastery is so rare among living organisms.

Verbal communication

The primary brain regions involved in language. Broca's area is in blue, Wernicke's area is in green, the primary auditory cortex is near the pink spot, and the remaining yellow and orange patches are Geschwind's territory.

After all of the necessary auditory processing of information is completed, the next challenge for the brain is to put those sounds together into a cohesive unit that can be understood. The first step in this process occurs as the message leaves the primary auditory cortex and enters a region called Wernicke's area. Here raw sounds are matched with their corresponding linguistic counterparts in order to form the basic skeleton of a sentence. Even at this lowest level however, the brain is already beginning alternate pathways responsible for formulating an appropriate reply. Next there is Geschwind's territory, which is located just above Wernicke's area, and is central in combining the individual units of language it receives into coherent sentences and phrases. Finally, neurons from Geschwind's territory fan out to other cortical regions for further interpretative steps, one of which occurs at a frontal lobe region known as Broca's area. It is here that the task of speech production begins to take shape and get refined.

Once the final touches before articulation are made, Broca's area must activate a certain sequence of neurons connected to the muscles of the jaw, tongue, and mouth. These need to be coordinated in just the right way so that when air exits the larynx, it is vibrated to form the specific phonemes, or sound units, of the desired words. The process then repeats with second person, who must now decode what they are hearing and formulate a response themselves.

Written communication

As an example of just one model of the complex process of language, this diagram indicates a vastly simplified representation of how different cortical regions interact.

It should be noted that of all the brain regions discussed so far, all of them are located almost exclusively on the left hemisphere. The left hemisphere of the brain is specialized for tasks like language much more than the right, which is comparably better at tasks such as spatial navigation or rote behavior. Although the process of writing emerged far later in human development and has no immediate precedent elsewhere in the animal kingdom, in practice it uses much of the same brain pathways as speech. Interestingly enough, even Broca's area is active during reading, even though no audible speech is being produced. One important difference is that during reading and writing much more of the temporal lobe is activated since memories of what certain symbols (i.e. words) mean must be retrieved.