Transcript University of Split Danica Škara, PhD e

University of Split
Danica Škara, PhD
e-mail: [email protected]
Office hours: Tuesday, 14:00-15:00h
PSYCHOLINGUISTICS AND COGNITIVE
ASPECTS OF LANGUAGE
Week 2: LANGUAGE AND THE BRAIN
THE HUMAN BRAIN
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The human brain is the center of the human
nervous system and is a highly complex organ. It has
the same general structure as the brains of other
mammals, but is over three times as large as the brain
of a typical mammal. Especially expanded are the
frontal lobes, which are involved in executive
functions such as self-control, planning, reasoning, and
abstract thought.
The portion of the brain devoted to vision is also
greatly enlarged in human beings.
Neurons
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The human brain has been estimated to contain 50–100
billion (1011) neurons, of which about 10 billion (1010)
are cells. These cells pass signals to each other via
approximately 100 trillion (1014)synaptic connections.
What does the brain do?
It receives and transmits messages to other parts of our
body. It accepts a fllod of information about the world
around your various senses (seeing, hearing, smelling,
tasting and touching).
Neuron structure
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Millions of sensory receptors detect changes, called
stimuli, which occur inside and outside the body. They
monitor such things as temperature, light, and sound
from the external environment.
Sensory input is converted into electrical signals called
nerve impulses that are transmitted to the brain. There
the signals are brought together to create sensations, to
produce thoughts, or to add to memory.
Each neuron has three basic parts: cell body (soma),
one or more dendrites, and a single axon.
Neurons transmit nerve messages.
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Brain message travel between neurons in just one
thousandth of a second. Each time you have a new
thought or memory, a new brain connection is made
between two or more brain cells.
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The neural network in the human brain is formed by
the genetic code acting as a framework, and by
individual development.
Long-term memory is either achieved by changes on
the synapses (more strength connections) or by
changes of functional units (new cell assemblies).
A connection can become stronger when the same
path is used often, the other way round a connection
that is rarely used will weaken.
LANGUAGE IN THE BRAIN
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The ability of humans to speak and to
understand speech requires an enormous
amount of brain resources. These resources
have to manage information about many
thousands of words and many syntactic
constructions and their interconnections.
This complex combination of brain structure
can be called the brain’s linguistic system.
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We use language to talk about an enormous range of
different kinds and aspects of human experience, all
of which also have representations in the brain.
The linguistic system must therefore occupy a central
position in mental structure, connected to the
cognitive systems that register all those other
experiences.
Lateralization
Left-brain/Right-brain
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The human brain is split into two hemispheres.
The left hemisphere controls any muscular
activity on the right side of the human body and
the right hemisphere operates vice versa.
We know that there are small differences in the
sizes of some regions in the two hemispheres.
These differences may form the basis for the
first major brain specialization for language –
lateralization of language to the left hemisphere.
Functions of hemispheres
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The two hemispheres are thought to contribute
to the processing and understanding of
language:
the left hemisphere: rapid language processing,
lexical, syntactic processing, phonemic
processing
the right hemisphere: higher level processing,
discourse processing, prosodic information
Location of two brain areas that play a critical role
in language: Broca’s area and Wernicke’s area
Broca’s area
The first language area within the left hemisphere to
be discovered is Broca's area, named after Paul Broca,
who discovered the area while studying patients with
aphasia, a language disorder.
 Deficits associates with brain damage:
Broca’s area
 Disturbance of speech production
 Agrammatic speech
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For example, in the following passage, a Broca's
aphasic patient is trying to explain how he came
to the hospital for dental surgery:
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Yes... ah... Monday... er... Dad and Peter H... (his own
name), and Dad.... er... hospital... and ah...
Wednesday... Wednesday, nine o'clock... and oh...
Thursday... ten o'clock, ah doctors... two... an'
doctors... and er... teeth... yah.[
Wernicke's area
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The second language area to be discovered is
called Wernicke's area, after Carl Wernicke, a
German neurologist who discovered the area
while studying patients who had similar
symptoms to Broca's area patients but damage
to a different part of their brain.
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Individuals with Wernicke's aphasia may speak in long
sentences that have no meaning, add unnecessary
words, and even create new "words" (neologisms).
For example, someone with Wernicke's aphasia may
say, "You know that smoodle pinkered and that I want
to get him round and take care of him like you want
before", meaning "The dog needs to go out so I will
take him for a walk".
They have poor auditory and reading comprehension,
and fluent, but nonsensical, oral and written
expression. Individuals with Wernicke's aphasia usually
have great difficulty understanding the speech of both
themselves and others and are therefore often
unaware of their mistakes.