Aphasias and Language Centers

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Aphasias and Language Centers
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Aphasia A primary disturbance in the
comprehension or production of speech, caused by
brain damage. Lateralization Verbal behavior is
lateralized to the left side of the brain, which
is specialized for analysis of sequences of
stimuli (comprehension) and control of sequences
of voluntary movement (production). Speech
comprehension and production is sequential. Of
course, if the right hemisphere were damaged,
people would find it difficult to talk about maps
and prosody (the use of changes in intonation
and emphasis to convey meaning in speech beyond
that specified by words) would suffer. Speech
Production The posterior hemispheres of the brain
are responsible for having something to say. The
frontal lobes convert the perceptions, memory,
and thoughts into speech. Brocas area A
region of frontal cortex, located just below the
base of the left primary motor cortex, that is
necessary for normal speech production.
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Brocas area contains motor memories of the
sequences of muscular movements that are needed
to articulate words. Talking involves
coordination movements of the lips, tongue, jaw,
and vocal cords. Indeed, Brocas area is
directly connected to the motor primary motor
cortex, which controls the muscles for
speech. Brocas aphasia Damage to Brocas area
and nearby structures result in Brocas aphasia,
a disorder characterized by slow, laborious and
nonfluent speech. The posterior hemispheres have
something to say, but the frontal hemisphere
makes it difficult to express the words. Brocas
aphasics are aware of their deficit. The
afflicted mispronounce many words, but what they
do say is meaningful. They mostly have difficulty
with function words (a, the, some, in, or about),
which have important grammatical structures. The
words they do manage to say are usually content
words (desk, orange, toss, clock), words that
convey meaning, such as nouns, verbs, or
adjectives.
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While Brocas aphasia patients have great
difficulty with speech production, speech
comprehension is much less impaired. The three
major speech deficits involved in Brocas aphasia
are agrammatism, anomia, and articulation
difficulties. Agrammatism difficulty in using
grammar. Loss of function words and grammatical
markers and auxillaries (-ed and I have gone).
Agrammatism disrupts understanding of word order,
making it difficult for them to see the meaning
behind some sentences. (Area responsible for
grammatical structure, word order, function
words, and word ending is damaged) Anomia
Difficulty finding words. They frequently omit
words, use inappropriate words, and say uh
(making it obvious that they are searching for
the correct word). (Area responsible for
selection of particular words is
damaged) Difficulty with articulation
Mispronunciation of words and altering sequences
of sounds. (Area responsible for control of
sequences of speech muscle movements is damaged)
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• Damage to the left precentral gyrus of the
  insula results in Apraxia of speech impairment
  of ability to program movement of tongue, lips,
  and throat. Pronunciation of words causes
  activation of the left anterior insula.
• Speech Comprehension
• Wernickes area- located in the middle and
  posterior portion of the superior temporal gyrus
  of the left hemisphere. Contains memories for
  sequences of sounds.
• Wernickes aphasia Description
• Characterized by poor speech comprehension and
  production of meaningless, though fluent and
  unlabored, speech. Their speech sounds
  grammatical. It has function words, verb tenses,
  and subordinate clauses, but they use little
  content words. What results is string of words
  that dont make sense.
• They are unaware of their deficit.

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Wernickes aphasia Analysis Because Wernickes
area is in the auditory association cortex it is
called receptive aphasia. There are three
abilities that become disrupted Recognition of
spoken words, comprehension of the meaning of
words, and ability to convert thoughts into
words. 1. Recognition Pure Word Deafness Pure
word deafness arises from left temporal lobe
damage, that results in impaired auditory word
recognition. These patients can understand
nonspeech sounds and can even recognize emotion
in speech, but they cannot understand the speech
itself. Furthermore, their own speech is
unimpaired. 2. Comprehension Transcortical
Sensory Aphasia Failure to comprehend meaning of
words and produce meaningful speech, produced by
damage beyond Wernickes area that surrounds the
posterior part of the lateral fissure (the
posterior language area). The posterior language
area is the place for interchange between the
auditory representation of words and the meaning
of word. Transcortical sensory aphasia damage
to posterior language area. These aphasics can
recognize words (they can repeat the words), but
they cant comprehend the meaning, nor generate
their own meaningful speech. Wernickes Aphasia
Pureword Deafness Transortical Sensory
Aphasia.
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• What is meaning?
• The meaning of a word is defined by particular
  memories associated with it.
• These memories are stored in the association
  cortices of the brain.
• The hippocampal formation ties related memories
  together. (i.e. The word tree contains sound
  memories in the auditory association cortex,
  visual memories in the visual association cortex,
  sensory memories in the somatosensory association
  cortex, etc.)
• We hear a word and Wernickes area recognizes
  the sequences of sounds that make up the words.
  Wernickes area is connected to the posterior
  language area, which is further connected to the
  areas of the brain that contain memories of
  words. Wernickes area is also connected to
  Brocas area via the arcuate fasciculus, which
  sends information about the sounds of words.
• Conduction aphasia Characterized by
  meaningful, fluent speech relatively good
  comprehension but very poor repetition.
  Although, they can repeat words with meaning,
  just not nonsense words.

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Conduction aphasics have damage to the articulate
fasciculus, which simply conveys speech sounds
from Wernickes area to Brocas area. We use this
to repeat unfamiliar words Brocas Area
Articulate Fasciculus
Wernickes Area Brocas Area
Posterior Language area
Wernickes Area
sound
meaning
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Anomic Aphasia (word amnesia) Fluent, grammatical
speech, excellent comprehension, but they have
difficulty finding the appropriate words, and use
circumlocution (saying things in a roundabout
way).
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