© 2010
  University of Idaho
  All rights reserved.
  Psychology Dept.
  University of Idaho
  Design - P&D  CTI

First of all, language is the ability to encode signals into some kind of communication sequence.  It’s also different from writing and reading.  Language does not have to be grammatically correct.  In fact, if we go back to early evolutionary times, we did not have much grammar or even major words that we used to communicate, but we were able to communicate in some fashion.  Today, though, humans have an instinctive ability to speak and babble, even as young children.  However, they don’t write and they don’t do other things as well.  However, there’s one specific aspect about language.  That is, languages are learned.  But the capacity to learn the particular language, whatever that language may be, is genetic.

Now, when we look at aspects of language, we need have a little background of language, what it is, and how it works, and where we get this information from that we’re working with today.  The most important source in the study of language has basically been the study of aphasia.  This is caused by brain lesions resulting from some kind of stroke, head trauma, or some other aspects.  As a result of these studies of aphasia, we’ve basically been able to conclude some major things.  First of all, about 96% of all individuals who have language use the left hemisphere for language processing.  That even includes individuals who are left handed. These theorists also found two predominant areas for language.  These are called Broca’s area and Wernicke’s area (which are named after the researchers respectively). 

The earliest model that really examines language is the Wernicke-Geschwind model.  It’s a very early model of language processing and contended that areas of the brain for the majority of language processing basically were in two areas; Wernicke’s area and in Broca’s area.  Both of these areas basically interacted with a particular type of other brain structures that we today call association areas.  Wernicke’s area, as we see in slide five, is located on the posterior rather the superior temporal gyrus.  If you don’t remember where that is, you need to go back and look at DeArmond et al. to kind of get an idea of where it is.  Wernicke’s area is basically concerned with the integration of comprehension of speech.  Broca’s area, on the other hand (as we see in slide six) is adjacent to the precentral gyrus and very near areas that control facial expression, articulation, phonation.  So, it’s going to be very, very close to where structures are located that are going to be extremely important in speech and movement of the face, jaw, mouth, tongue, etc. 

Well in addition to that, these two structures, there is a pathway and this pathway is called the arcuate fasciculus.  Basically the arcuate fasciculus is an axon pathway, and that’s all it is.  Basically connects Wernicke’s and Broca’s areas.  In the Wernicke-Geschwind model, it was considered to be unidirectional.  That is, information went from Wernicke’s area to Broca’s area.  Today we know that it is bi-directional and that information goes back and forth.

The next thing that we see is slide eight.  Slide eight gives us a figure of where all of these areas are located.  As you can see, Broca’s area is down at the very bottom of the frontal lobe in front of the precentral gyrus, while Wernicke’s area is in the superior temporal gyrus.  Of course, the arcuate fasciculus connects the two.  Note that the arcuate fasciculus is underneath the outer layers of cortex and is not a cortical structure.

Today, we look also at newer models of language and speech.  We still include, as we see on slide nine, Wernicke’s and Broca’s areas, but we also know that the Arcuate Fasciculus is bi-directional.  However, while these are important, we also need to know three other areas are also important.  In essence, these areas must work together for good language processing.  So, what are some of these areas?  Well the first set of these areas (as we can see in slide 10) are what we call higher-order association cortex.  These are in the left frontal, left temporal, left parietal lobes.  Basically these are involved with mediating between concepts and language.  So you’re going to have some kind of concept that’s out there, whatever that particular concept is.  Let’s say you’re trying to think of a concept “bird.”  Well, to take that information and put that into a language so you can describe the bird requires a lot of processing from a variety of different structures.

The second area is association cortex which is located in the left insular area or what is also called the Island of Rile.  If we remember from our earlier discussions, the insular cortex is located as follows.  If we took the temporal lobe and kind of lifted it up, and we saw a piece of tissue there, basically that is where the insular cortex is located.  And the left insular cortex is highly related and highly involved with speech articulation. 

The third major set of structures is shown in slide 12 and these are what we call the prefrontal and cingulate areas.  Basically what they do is help with motor control and help mediate between memory and intentional processes.  So, now what we have are three systems interacting together in some kind of language perception and speech production.  As we see here, we have a language implementation system which includes Broca’s, Wernicke’s, the insular cortex, and of course structures within the basal ganglia.  These systems are going to analyze incoming auditory signals.  They activate some kind of conceptual knowledge that we have of auditory things, it insures phonemic and grammatical construction, and ultimately insures some kind of articulatory control. 

A second major system is what we call the mediational system and it’s going to surround the language implementation system.  These include areas of the cortical structures within the temporal, collateral and frontal association areas, but it’s going to work between the implementation system and the conceptual system.

The third major system is what we call the conceptual systems.  Here we have a variety of different regions throughout association cortex.  Basically, these systems are are supporting some kind of conceptual knowledge.  

So, we have several major structures that are involved with speech.  But, there are a few others out there.  These include structures in the left temporal and inferior temporal cortex, insular cortex, supplementary motor areas, and the right cerebral hemisphere.

So, what about the left temporal and inferior temporal cortex?  Basically these structures are allowing you to access to words and note categories of things.  But, it’s not just the actions but it’s the relationships.  It’s kind of figuring out that there are certain categories out there.  For example if you go and damage Broadman’s area 38, you have difficulty recalling names of unique places but not for common things.  While, if you damage areas 20 and 21, you have difficulty recalling particular names of both unique and common names.  Finally, if you have left posterior or inferior temporal cortical damage, you can’t recall particular word items, such as of tools, but you can recall words of natural or unique things.  So, what I’m trying to drive at you here is this.  When you talk about speech and language articulation, different systems and different structures are extremely important for very specific things, and by damaging these cortical structures, you may have a specific set of symptoms.  So, when you use neuropsychological test batteries, these are kinds of symptoms that will come out and not be demonstrated in things such as a MRI, FMRI, or SQUID or CAT scans.

The next major structure is what we call Insular cortex.  We’ve talked about insular cortex a little bit before.  Again, it’s important for planning or coordinating articulatory movements for speech.  Basically, when you have damage, you have difficulty pronouncing particular phonemes in proper order.  However, you have no difficulty perceiving the speech sounds and you even can recognize your own errors when you can find the words.  But you have the problems producing it.  Here’s the classic example.  You have an instructor that’s talking about something in class, and they have a difficulty pronouncing a particular type of phoneme that’s out there (some word of some sort).  They recognize they have a problem with this wording or phrasing but they have problems figuring out how to produce it.  So, they recognize they have the problem but they can’t actually solve the problem.

Another major structure that’s important to speech is the frontal cortex.  Again these are going to include things such as supplementary motor cortex and the angulate cingulated region which is also called area 24.  It’s extremely important for many higher cortical functions including the initiation and maintenance of speech.  It’s also very, very important in relation to attention and emotion.  As you can see here, there’s a variety of different symptoms that can occur when you damage this structure.  For example, you can impair the initiation of particular types of movement, called echinesia.  Or, you can have speech stopping (basically mutism).  Patients with either of these conditions cannot communicate by words, by gestures or even by facial expressions.  Now, again, it’s not aphasia.  So, when you talk about left frontal cortical damage, basically what you’re talking about is an impairment of a particular drive to communicate.  That is, you don’t communicate at all using a variety of different techniques, whereas in aphasia, you are trying to communicate, you just have difficulty doing so.

Now when we talk about all of the structures within speech systems, usually what we talk about is the left hemisphere.  As we’ve talked about, the left hemisphere basically is important for about 96% of us.  Well, what about the right hemisphere, doesn’t it do anything?  Well, the right hemisphere, as we can see in slide 20, is extremely, extremely important as well. Basically, the right hemisphere is important for communicative and emotional stress.  It is also and probably more important in relation to timing and imitation of particular words.  Basically, when you have right anterior lesions, that is, in the front, you produce inappropriate intonation.  Whereas, if you have the right posterior lesions, you have difficulty interpreting the emotional tones of another person’s speech.  So, the other person might be angry, but you interpret them as being happy, mellow, and having a good time.

Pragmatics, as we also see in slide 21, is also involved with the right hemisphere.  With damage, you have extreme difficulty incorporating sentences and coherent, and kind of language.  Basically, what you begin to do is use conversations that are inappropriate to particular situations.  So, as we see here with some of the examples, you don’t understand a person’s particular jokes.  Since most jokes are relatively not good, it makes them a little more difficult to understand.  In essence, we also use inappropriate language in a particular social situation.  For example you start swearing and cursing and sort of other things within some particular environment which would not be appropriate, like church.

Now we’ve talked now about a variety of different structures.  I want to kind of end up here with this.  In this section, by talking about some specific speech disorders (including aphasias), what we can see here is there’s a variety of different types.  We will talk about these in much more detail when we get into the disorder section of the class. But as you can see here, there’s a wide variety of different types of speech disorders, and there’s different types of other communication disorders as well.

In general, what I’d like you to remember when we talk about speech and language disorders and speech is that there are a lot of different structures involved.  You need to remember this, all you need to damage is one particular structure and you can have damage to the speech system.  So think about this.  Think about a person who has had a cerebral vascular accident, basically a stroke, and that stroke has been relatively large.  Well if you have that, you might have major problems with a variety of different types of speech areas.  As a consequence of that, you will show very specific symptoms.  On the other hand, if you have a tumor that is starting to grow and is growing relatively rapidly, you might begin to have specific speech symptoms as well.  As a result of that, that would cause you to have some alarm and then get some kind of follow up.  Again, you may see some of these problems with particular types of physical types of examination such as with an MRI (especially if you’re having a tumor of some sort).  However, neuro-psychological test batteries are more effective in a diagnosing these problems because it is more defined and more sensitive to different types of damage that we have out there.  So, even though we always say go to a doctor and assorted other things for a particular type of disorder, we need to recognize that a lot of neuropsychological problems and brain problems can actually be diagnosed (in some cases) a lot better with a neuropsychological test battery than with more traditional medical types of examination, such as MRIs.

Well that concludes this section and I hope you’ve enjoyed it.  In the next section we continue on and look at other types of systems, so until then, we hope you have a good day.