PSYCHOLINGUISTIC
“LANGUAGE AND THE BRAIN”
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Lecture : Sinarman Jaya, M.Pd.
Created by
NAME
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NPM
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1.
Mirasti
Hartini
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122 111 0017
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2.
Fiki
Syaputra
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122 111 00
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3.
Kholifatun
Husnah
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122 111 00
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Class
: VI A
GROUP 2
ENGLISH LANGUAGE EDUCATION STUDY PROGRAM
FACULTY OF TEACHER
TRAINING AND EDUCATION
MUHAMMADIYAH UNIVERSITY
OF BENGKULU
2015
Many people
assume the physical basis of language lies in the lips, the tongue, or the
ear. But deaf and mute people can also possess language fully.
People who have no capacity to use their vocal cords may still be able to
comprehend language and use its written forms. And human sign language,
which is based on visible gesture rather than the creation of sound waves, is
an infinitely creative system just like spoken forms of language. But the
basis of sign language is not in the hand, just as spoken language is not based
in the lips or tongue. There are many examples of aphasics who lose both
the ability to write as well as to express themselves using sign-language, yet
they never lose manual dexterity in other tasks, such as sipping with a straw
or tying their shoes.
Language is
brain stuff--not tongue, lip, ear, or hand stuff. The language organ is the
mind. More specifically, the language faculty seems to be located in certain
areas of the left hemispheric cortex in most healthy adults. A special
branch of linguistics, called neurolinguistics, studies the physical
structure of the brain as it relates to language production and comprehension.
Structure of the human brain.
The human brain displays a number of physiological and structural
characteristics that must be understood before beginning a discussion of the
brain as language organ. First, the cerebrum, consisting of a cortex
(the outer layer) and a subcortex, is also divided into two hemispheres
joined by a membrane called the corpus callosum. There are a few
points which must be made about the functioning of these two cerebral
hemispheres.
1) In all
humans, the right hemisphere controls the left side of the body; the left
hemisphere controls the right side of the body. This arrangement--called contralateral
neural control is not limited to humans but is also present in all
vertibrates--fish, frogs, lizards, birds and mammals. On the other hand, in
invertibrates such as worms, the right hemisphere controls the right side, the
left hemisphere controls the left side. The contralateral arrangement of neural
control thus might be due to an ancient evolutionary change which occurred in
the earliest vertibrates over half a billion years ago. The earliest vertibrate
must have undergone a 180° turn of the brain stem on the spinal chord so that
the pathways from brain to body side became crossed. The probability that such
a primordial twist did occur is also born out by the fact that invertibrates
have their main nerve pathways on their bellies and their circulatory organs on
their backs, while all vertibrates have their heart in front and their spinal
chord in back--just as one would expect if the 180° twist of the brain stem
vis-a-vis the body did take place.
2.) Another
crucial feature of brain physiology is that each hemisphere has somewhat unique
functions (unlike other paired organs such as the lungs, kidneys, breasts or
testicles which have identical functions). In other words, hemisphere function
is asymmetrical. This is most strikingly the case in humans, where the
right hemisphere--in addition to controlling the left side of the body--also
controls spatial acuity, while the left hemisphere--in addition to controlling
the right side of the body-- controls abstract reasoning and physical tasks
which require a step-by-step progression. It is important to note that in
adults, the left hemisphere also controls language; even in most left-handed
patients, lateralization of language skills in the left hemisphere is completed
by the age of puberty.
Now, why
should specialized human skills such as language and abstract reasoning have
developed in the left hemisphere instead of the right? Why didn't these skills
develop equally in both hemispheres. The answer seems to combine the principle
of functional economy with increased specialization. In nature, specialization
for particular tasks often leads to physical asymmetry of the body--witness the
lobster's claws--where limbs or other of the body differentiate to perform a
larger variety of tasks with greater sophistication (the same might be said to
have happened in human society with the rise of different trades and the
division of labor).
Because of
this specialization, one hemisphere--in most individuals for some reason it is
the right hemisphere--came to control matters relating to 3D spatial
acuity--the awareness of position in space in all directions simultaneously.
Thus, in modern humans, artistic ability tends to be centered in various areas
of the right hemisphere.
The left
hemisphere, on the other hand, came to control patterns that progress
step-by-step in a single dimension, such as our sense of time progression, or
the logical steps required in performing feats of manual dexterity such as the
process of fashioning a stone axe. This connects with right-handedness. Most
humans are born with a lopsided preference for performing skills of manual dexterity
with the right hand--the hand controlled by the left hemisphere. The left
hand holds an object in space while the right hand mainpulates that object to
perform tasks which require a step-by-step progression. Obviously, this is a
better arrangement than if both hands were equally clumsy at performing
complex, multi-step tasks, or if both sides of the brain were equally mediocre
at thinking abstractly or at processing information about one's
three-dimensional surroundings. So human hemispheric asymmetry seems to have
developed to serve very practical purposes.
(By the way,
left-handedness seems to be the result of inheritance of two copies of a gene
which does not impart strong right-hand preference. The right-handed gene is
dominant--in 25% of the population has no copy of this gene, presumably 12.5%
percent of these non-handed individuals develop a righthandedness anyway, and
12.5% develop a tendency toward left handedness. At any rate, being left-handed
doesn't seem to have any special effect on language acquistion or learning or
on anything else innate to humans.)
This general
pattern of cognitive asymmetry was probably well established in our hominid
ancestors before the language faculty developed. So why did humans evolve in
such a way that the language faculty normally localized in the left
hemisphere? Why not in the right? Clearly, the reason is that
language, like fashioning a stone axe, is also a linear process: sounds and
words are uttered one after another in a definite progression, not in multiple
directions simultaneously. In the modern human, the feature of monolineal
progression seems naturally to ally language with other left brain skills
such as the ability to perform complex work tasks, or abstract step-by-step
feats of logic, mathematics, or reasoning. Even among natural left-handers (in
about 12.5 % of any human population, language skills are localized in the
cortex of the left hemisphere in all but about 2.5% of the cases. Some of
these are individuals who received damage to the left hemisphere in childhood
which, presumably, prevented language from localizing there; however, we don't
know why language localizes in the right hemisphere of the brain in about one
in fifty healthy adults. Like right or left handedness, it seems to correlate
with nothing else in particular.
How do we
know that the left hemisphere controls language in most adults. There is a
great deal of physical evidence for the left hemisphere as the language center
in the majority of healthy adults.
1) Tests have
demonstrated increased neural activity in parts of the left hemisphere when
subjects are using language. (PET scans--Positron Emission Tomography,
where patient injects mildly radioactive substance, which is absorbed more
quickly by the more active areas of the brain). The same type of tests have
demonstrated that artistic endeavor draws normally more heavily on the neurons
of the right hemispheric cortex.
2) In
instances when the corpus callosum is severed by deliberate surgery to ease epileptic
seizures, the subject cannot verbalize about object visible only in the left
field of vision or held in the left hand.) Remember that in some individuals
there seems to be language only in the right brain; in a few individuals,
there seems to be a separate language center in each hemisphere.)
3.) Another
clue has to do with the evidence from studies of brain damage. A person with a
stroke in the right hemisphere loses control over parts of the left side of the
body, sometimes also suffers a dimunition of artistic abilities. But language
skills are not impaired even if the left side of the mouth is crippled, the
brain can handle language as before. A person with a stroke in the left
hemisphere loses control of the right side of the body; also, 70% of adult
patients with damage to the left hemisphere will experience at least some
language loss which is not due only to the lack of control of the muscles on
the right side of the mouth--communication of any sort is disrupted in a
variety of ways that are not connected with the voluntary muscles of the vocal
apparatus. The cognitive loss of language is called aphasia, and we will
discuss various types of aphasia in great detail tomorrow; only 1% of adults
with damage to the right hemisphere experience any permanent language loss.
Aphasics can
blow out candles and suck on straws, even sing and whistle, but they cannot
produce normal, creative speech in either written, spoken, or gestural
form. Sign language users also store their linguistic ability in the left
hemisphere. If this hemisphere is damaged, they cannot sign properly, even
though they may continue to be able to use their hands for such things as
playing the drums, giving someone a massage, or other non-linguistic hand
movements. Injury to the right hemisphere of deaf persons produces the opposite
effect.
Experiments on healthy
individuals with both hemispheres intact.
4.) In 1949
it was discovered that if sodium amytal is injected into the left carotid
artery, which services blood to the left hemisphere, language skills are temporarily
disrupted. If the entire left hemisphere is put to sleep, a person can
think but cannot talk.
5.) If an
electrical charge is sent to certain areas of the left hemisphere (exactly
which areas we will discuss tomorrow), the patient has difficulty talking or
involuntarily utters a vowel-like cry (although the production of
specific speech sounds has never been induced by electrical charge). An
electrical charges to the right hemisphere produces no such effect.
6.) Musical
notes and tones are best perceived through the left ear (which is connected to
the spacial-acuity-controlling right hemisphere. In contrast, the right ear
better perceives and processes the sounds of language, even linguistic tones
(any form with meaning); the right ear takes sound directly to the left
hemisphere language center.
7.) When
repeating after someone, most individuals have a harder time tapping with the
fingers of the right hand than with the left hand. /Perform this experiment in
class./
8.) The
language centers in the left hemisphere of humans actually make the left
hemisphere bulge out slightly in comparison to the same areas of the right
hemisphere. This is easily seen without the aid of the microscope. For this
reason, some neurolinguists have called humans the lopsided ape.
Some paleontologists claim to have found evidence for this left-hemispheric
bulging in Homo neanderthalus and Homo erectus skulls.
Other
primates also possess a left perisylvian area of the brain, but it doesn't seem
to be involved in their communication. Animal communication seems in fact
to be controlled by the subcortical areas of the animal brain, much like human
vocalizations other than language--laughter, sobbing, crying, as well as
involuntary, word-like exclamations which do form part of language--are
controlled in humans in the subcortex, a phylogenetically older portion of the
brain that is involved with emotions and reflex responses.
Tourette's
syndrome, which produces random and involuntary emotive reflex responses,
including vocalizations This type of disorder, which often affects language
use, is caused by a disfunction in the subcortex. There is no filter which
prevents the slightest stimulus from producing a vocal response, sometimes of
an inappropriate manner using abusive language or expletives. These words are
involuntary and often the affected individual is not even aware of uttering
them (like "um" in many individuals) and only realizes it when video
is played back.
This syndrome
is not so much a language disorder per se as a disorder of the filters on the
adult emotional reflex system--a kind of expletive hiccup. True language is
housed in the cortex of the left hemisphere, not in the subcortical area that
controls involuntary responses.
What can language
disorders tell us about the brain's language areas?
Certain types
of brain damage can affect language production without actually eliminating
language from the brain. A stroke that damages the muscles of the vocal
apparatus may leave the abstract cognitive structure of language intact--as
witnessed by the fact that right hemisphere stroke victims often understand
language perfectly well and write it perfectly with their right hand--although
their speech may be slurred due to lack of muscle control. We have also seen
that certain disorders involving the subcortex--the seat of involuntary
emotional response--may have linguistic side effects, such as in some cases of
Tourette's syndrome.
But what
happens when the areas of the brain which control language are affected
directly, and the individual's abstract command of language is affected? We
will see that language disorders can shed a great deal of light on the enigma
of the human language instinct.
SLI. One rare
language disorder seems to be inborn rather than the result of damage to a
previously normal brain. I have said that children are born with a
natural instinct to acquire language, the so-called LAD; however, a tiny
minority of babies are born with an apparent defect in this LAD.
Certain
families appear to have a hereditary language acquisition disorder, labeled specific
language impairment, or SLI. Children born with this disorder
usually have normal intelligence, perhaps even high intelligence, but as
children they are never able to acquire language naturally and effortlessly.
They are born with their window of opportunity already closed to natural
language acquisition. These children grow up without succeeding in acquiring
any consistent grammatical patterns. Thus, they never command any language
well--even their native language. As children and then as adults, their speech
in their native language is a catalog of random grammatical errors, such as: It's
a flying birds, they are. These boy eat two cookie. John is work in the
factory. These errors are random, not the set patterns of an alternate
dialect: the next conversation the same SLI-afflicted individual might
say This boys eats two cookies. These sentences, in fact, were
uttered by a British teenager who is at the top of his class in mathematics; he
is highly intelligent, just grammar blind. SLI sufferers are
incapable of perfecting their skills through being taught, just as some people
are incapable of being taught how to draw well or how to see certain colors.
This is the best proof we have that the language instinct most children are
born with is a skill quite distinct from general intelligence.
Because SLI
occurs in families and seems to have no environmental cause whatsoever, it is
assumed to be caused by some hereditary factor--probably a mutant, recessive
gene that interferes with or impairs the LAD. The precise gene which causes SLI
has yet to be located.
First, humans
are born with the innate capacity to acquire the extremely complex, creative
system of communication that we call language. We are born with a language
instinct, which Chomsky calls the LAD (language acquisition device).
This language aptitude is completely different from inborn reflex responses to
stimuli as laughter, sneezing, or crying. The language instinct seems to
be a uniquely human genetic endowment: nearly all children exposed to
language naturally acquire language almost as if by magic. Only in rare
cases are children born without this magical ability to absorb abstract
syntactic patterns from their environment. These children are said to
suffer from Specific Language Impairment, or SLI. It is
thought that SLI is caused by a mutant gene which disrupts the LAD.
The LAD
itself, of course, is probably the result of the complex interaction of many
genes--not just one--and the malfunction of some single key gene simply
short-circuits the system. For example, a faulty carburetor wire may prevent an
engine from running, but the engine is more than a single carburetor wire. Many
thousands of genes contribute to the makeup of the human brain--more than to
any other single aspect of the human body. To isolate the specific set of genes
that act as the blueprint for the language organ is something no one has even
begun to do.
Second, the
natural ability for acquiring language normally diminished rapidly somewhere
around the age of puberty. There is a critical age for acquiring fluent
native language. This phenomenon seems to be connected with the lateralization
of language in the left hemisphere of most individuals--the hemisphere
associated with monolinear cognition (such as abstract reasoning and step-by
step physical tasks) and not the right hemisphere, which is associated with 3D
spatial acuity, artistic and musical ability. Unlike adults, children
seem to be able to employ both hemispheres to acquire language. In other words,
one might say that children acquire language three-dimensionally while adults
must learn it two dimensionally.
Third and
finally, in most adults the language organ is the perisylvian area of the
left hemispheric cortex. Yesterday we discussed the extensive catalog of
evidence that shows language is usually housed in this specific area of the
brain. Only the human species uses this area for communication. The
signals of animal systems of communication seem to be controlled by the
subcortex, the area which in humans controls similar inborn response signals
such as laughter, crying, fear, desire, etc.
We
know which specific areas of the left hemisphere are involved in the production
and processing of particular aspects of language. And we know this
primarily from the study of patients who have had damage to certain parts of
the left hemispheric cortex. Damage to this area produces a condition called aphasia,
or speech impairment (also called dysphasia in Britain). The study of language
loss in a once normal brain is called aphasiology.
Aphasia is
caused by damage to the language centers of the left hemisphere in the region
of the sylvian fissure. Nearly 98% of aphasia cases can be traced to
damage in the perisylvian area of the left hemisphere of the cerebral
cortex. Remember, however, that in the occasional individual language is
localized elsewhere; and in children language is not yet fully localized.
Strokes cause
85% of all aphasia cases; other causes include cerebral tumors and lesions. One
in 200 people experiences aphasia, with males more at risk. Gradual recovery is
possible in 40% of adult cases; pre-pubescent children are much more likely to
recover from aphasia, with the language faculty localizing in another,
unaffected area of the brain, usually the perisylvian cortex of the right
hemisphere. Generally, the more extensive the injury, the greater the
likelihood of permanent damage.
But we have
seen that language is a complex of interacting components--consonants and
vowels, nouns and verbs, content words and function words, syntax and
semantics. Could it be that these components are housed in particular sub-areas
of the left hemisperic perisylvian cortex? We haven't pinpointed whether
nouns are stored separately from verbs, or where the fricative sounds are
stored. There is no conclusive proof for that type of specialization of
brain tissue. But there is compelling evidence to believe that two
special aspects of language structure are processed by different sub-areas of
the language center. We know this because damage to specific areas of the
peresylvian area produces two basic types of aphasia.
Each of these
two types of language loss is associated with damage to a particular sub-region
of the perisylvian area of the left hemispheric cortex.
(1861) Paul
Broca discovered Broca's area (located in the frontal portion of the
left perisylvian area) which seems to be involved in grammatical processing.
(While parsing sentences such as fat people eat accumulates, there is a
measurable burst of neural activity in Broca's area when the last word is
spoken.) Broca's area seems to process the grammatical structure rather than
select the specific units of meaning. It seems to be involved in the
function aspect rather than the content areas of language)
Broca's
aphasia involves difficulty in speaking. For this reason it is also
known as emissive aphasia. Broca's aphasics can comprehend but have
great difficulty replying in any grammatically coherent way. They tend to
utter only isolated content words on their own. Grammatical and syntactic
connectedness is lost. Speech is a labored, irregular series of content words
with no grammatical morphemes or sentence structure. (Read example)
Grammar rules as well as function morphemes are lost. Broca's aphasia is also
known as agrammatic aphasia. Grammar is destroyed; the lexicon more or
less preserved intact.
(1875) Karl
Wernicke: Wernicke's area (in the lower posterior part of the
perisylvian region) controls comprehension, as well as the selection of content
words. When this area is specifically damaged, a very different type of
aphasia usually results, one in which the grammar and function words are
preserved, but the content is mostly destroyed.
Since Wernicke's
aphasia involves difficulty in comprehension, in extracting meaning from a
context, it is also known as receptive aphasia. Wernicke's aphasics easily
initiate long-winded, fluent nonsense, but don't seem able to respond
specifically to their interlocutor (unlike Broca's aphasics, who can understand
but the have difficulty replying). Wernicke's aphasics often talk incessantly
and tend to utter whole volumes of grammatically correct nonsense with
relatively few content words or with jibberish words like
"thingamajig" or "whatchamacallit" instead of true
content words. (Read example.) Because Wernicke's aphasia patients
can utter whole monologs of such contentless grammatical babble, hardly letting
their interlocutor get a word in edgewise, their affliction is also known as jargon
aphasia.
The normal human mind uses both areas in unison when speaking. Apparently,
normal adults use the neurons of Wernicke's area to select sounds or
listemes. We use the neurons of Broca's area to combine these units
according to the abstract rules of phonology and syntax--the elements in
language which have function but no specific meaning-- to produce utterances.
![]() Paul Broca |
![]() Tan’s brain |
When Broca autopsied Tan’s brain, he found a sizable
lesion in the left inferior frontal cortex. Subsequently, Broca studied eight
other patients, all of whom had similar language deficits along with lesions in
their left frontal hemisphere. This led him to make his famous statement that
“we speak with the left hemisphere” and to identify, for the first time, the
existence of a “language centre” in the posterior portion of the frontal lobe
of this hemisphere. Now known as Broca’s area, this was in fact the first area
of the brain to be associated with a specific function—inthiscase,language.
Ten years later, Carl Wernicke, a German neurologist, discovered another part of the brain, this one involved in understanding language, in the posterior portion of the left temporal lobe. People who had a lesion at this location could speak, but their speech was often incoherent and made no sense.
Ten years later, Carl Wernicke, a German neurologist, discovered another part of the brain, this one involved in understanding language, in the posterior portion of the left temporal lobe. People who had a lesion at this location could speak, but their speech was often incoherent and made no sense.
![]() Carl Wernicke |
![]() Brain with a lesion causing Wernicke’s aphasia |
Wernicke's
observations have been confirmed many times since. Neuroscientists now agree
that running around the lateral sulcus (also known as the fissure of
Sylvius) in the left hemisphere of the brain, there is a sort of neural loop
that is involved both in understanding and in producing spoken language.
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