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Aphasia

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Title: Aphasia


1
Aphasia
  • What is aphasia?
  • Types of aphasia
  • Cognitive neuropsychology and aphasia
  • Syndrome or symptoms?
  • Computational cognitive neuropsychology

2
The forthcoming lectures
  • Take a look at several language processes that
    have interested neuropsychologists (e.g.,
    listening, speaking, reading and writing).
  • Examine neuropsychological data which bear on
    theories about the nature and operation of these
    language processes.
  • Emphasis is on cognitive neuropsychology as a
    research discipline, but practical/clinical
    applications will also be illustrated.
  • Introduce computational neuropsychology.

3
Models of reading
Meaning pathway
zint phonological
Direct pathway
pint surface
4
What kind of language operations?
  • Modular Interactive
  • mandatory, encapsulated non-mandatory
  • domain specific non domain specific
  • Rule based Associative
  • explicit grammatical rules pattern of connections
  • operating on linguistic units operating among
    units
  • symbolic units non symbolic units
  • COGNITIVE BEHAVIOURAL

5
What kind of representations?
  • Semantically transparent Distributed
  • linguistic representations neuron like units with
  • phonemes, syllables, words no immediate referent
  • Morphemes No morphemes
  • Discrete Continuous
  • binary (all or none) activation level
  • words as units words as patterns
  • damage causes total loss partial loss of function
  • TRADITIONAL CONNECTIONIST

6
What is Aphasia?
  • Aphasia is a neurological disorder caused by
    damage to those areas of the brain that are
    responsible for language (frontal/temporal).
  • Primary signs of the disorder include difficulty
    in expressing oneself when speaking, trouble
    understanding speech and difficulty with reading
    and writing.
  • Aphasia is most commonly seen in adults who have
    suffered a stroke but aphasia can also result
    from a brain tumor, infection, head injury or a
    dementia that damages the brain.

7
Sylvian fissure
Sylvian region
Middle cerebral artery
8
Types of aphasia
  • Aphasia can be divided into four categories
  • (1) Expressive aphasia
  • conveying thoughts through speech or writing.
  • (2) Receptive aphasia
  • understanding spoken or written language.
  • (3) Anomic or amnesic aphasia
  • difficulty using the correct names for objects,
    people, places, or events.
  • (4) Global aphasia
  • loss of all comprehension and expression.

9
Differential diagnosis
  • There are two critical features of the language
    produced by aphasic patients
  • Fluent/Non-fluent does language production
    require great effort are there many pauses and
    ums and ers and is the number of words
    produced per unit of time very low?
  • Grammatical/Agrammatical does language
    production lack grammatical structure is it
    mostly just a string of nouns?

10
Brocas aphasia
Brocas area
Motor cortex
  • Speech is non-fluent, slow and laboured.
  • Grammatical structure is absent.
  • Comprehension of morphemes is normal.

Speech (BA45)
Prefrontal cortex
11
Speech sample
  • Doctor Why did you come to hospital?
  • Patient AhMondayah Dad and Pauland
    Dadhospital. Twoahdoctorsand thirty
    minutesand yesahhospital. Wednesdaynine
    oclockdoctors. Two doctorsand ahteeth.
    Yeahfine.

12
Wernickes aphasia
Wernickes area
  • Speech is fluent, but full of neologisms.
  • Grammatical structure is preserved.
  • Comprehension of morphemes is impaired.

Superior temporal gyrus (STG)
Middle temporal gyrus
Inferior temporal gyrus
13
Speech sample
  • Doctor Why did you come to hospital?
  • Patient Never, now mista I wanna tell you this
    happened when happened when he rent. His - kell
    come down here and is - he got ren something. And
    he roden all these arranjen from the pedis on
    from iss pescid.

14
Boston Aphasia Classification System
  • Syndrome approach.
  • Associations of symptoms.
  • Focus is on the location of the lesion.
  • Useful for diagnostic purposes.
  • Rehabilitation?

15
Tell me everything that is happening in this
picture
16
Pathophysiology
  • Aphasia often occurs secondary to almost any type
    of brain injury (stroke,tumour) and usually
    involves the left cerebral hemisphere.
  • Right hemisphere lesions can cause prosodic
    speech errors flat, monotone speech.
  • Language function lateralizes to left hemisphere
    in 96-99 of righthanders and 60 of left handers
    so lefthanders usually develop aphasia after a
    left hemisphere stroke but it is milder.
  • Other left handers show crossed-aphasia.

17
BACS Assessment
  • Spontaneous speech, confrontation naming,
    repetition, reading and writing, comprehension,
    category fluency and letter-fluency (F,A,S, lt8).
  • Spontaneous speech is assessed for fluency.
  • Presence of spontaneous paraphasic errors
    (semantic or phonemic), word-finding pauses,
    circumlocutions (hesitations) and prosody.
  • Some patients have preferential loss of words of
    one category, such as nouns, proper nouns, verbs,
    tools, household objects, body parts.

18
Brocas aphasia
  • Poor naming, repetition, reading and writing with
    semantic paraphasias spared comprehension.
  • Normally caused by damage to the lateral portion
    of the primary motor strip so the patient is
    often hemiplegic on the contralesional side of
    body.
  • The lesion invovles the sylvian region including
    the left opercula, insula, and subjacent white
    matter in the territory of the middle cerebral
    artery.
  • Classical Brocas area BA 44/45 posterior third
    of inferior frontal gyrus transient speech
    apraxia.

19
hat
Hat Name x Repeat x Read x Write x cap
20
Wernickes aphasia
  • Poor naming, repetition, reading and writing are
    often spared but comprehension is impaired.
  • May have a visual field defect (e.g. a
    hemianopia).
  • Tempero-parietal lesion usually involves superior
    temporal gyrus STG posterior to Sylvian fissure.
  • 1. Lexical errors - lesion associated with
    inferior-lateral temporal cortex (middle and
    inferior temporal gyri) and angular gyrus
    (parietal cortex).
  • 2.Phonological errors - lesions of Wernickes
    area proper - posterior STG and supramarginal
    gurus.

21
Conduction aphasia
  • Impaired repetition, with preserved comprehension
    reading and writing and fluent speech although
    there may be problems with confrontation naming.
  • Experimental studies show the ability of aphasics
    to correct their tape-recorded speech Conduit
    d'approche an attempt to correct own errors.
  • Lesion to the actuate fasciculus (AF) which is a
    white matter tract running from the posterior STG
    comprehension to Brocas area speech output.

22
Arcuate fasciculus
Wernickes area
Brocas area
23
Transcortical Motor aphasia no speech output
24
Transcortical aphasias (intact repetition)
  • Motor patients can repeat and comprehend speech
    but have diminished speech output and an
    inability to name caused by damage to frontal
    area BA45 (prefrontal cortex).
  • Sensory patients can repeat and produce fluent
    speech but cannot comprehend speech.
  • Mixed patients can repeat only, i.e., echolalia
    but cannot produce or understand speech.

25
Dynamic aphasia
  • Patient ANG had normal repetition, naming, and
    reading but spontaneous speech impaired.
  • BA45 is involved in the selection of competing
    alternatives for response output (Shallice).
  • Dogs have a good sense of _______
  • Helen reached to dust the _______
  • Robinson et al (1998) argued that ANG had damage
    to a module containing units for the selection of
    competing verbal response units.

26
Dynamic aphasia 2
  • Patient AC had normal repetition, naming, and
    reading but spontaneous speech impaired.
  • BA44 only was damaged

  • ANG AC
  • Design Fluency x v
  • Gesture Fluency x v
  • Robinson et al (2005) argued that HC had damage
    to a module containing units for the selection of
    competing verbal response units.

27
What is the prognosis?
  • The outcome of aphasia is difficult to predict
    given the wide range of variability of the
    condition but some skills are easier to treat.
  • Generally, people who are younger or have less
    extensive brain damage fare better.
  • The location of the injury is also important and
    is another clue to prognosis.
  • In general, patients tend to recover skills in
    language comprehension more completely than those
    skills involving expression.

28
Summary
  • Studies of aphasia have enabled us to develop
    models of normal language processing and to
    identify the necessary cognitive processes.
  • Studies of aphasic patients have shown that the
    syndrome approach to neuropsychology is limited
    in what it can tell us about brain-behaviour
    relationships.
  • Computational cognitive neuropsychology aims to
    understand the behaviour of aphasic patients by
    lesioning connectionist models of language.

29
Glossary
  • Abstract words refer to concepts (love peace).
  • Concrete words refer to physical nouns (cat).
  • Content words Nouns, verbs adjectives open (new
    words can be added).
  • Function words articles, prepositions,
    conjunctions closed class.
  • Mental lexicon store of information about words.
  • Morpheme smallest unit of language that has
    meaning.
  • Orthography visual characteristics of a word.
  • Phonemes smallest unit of sound.
  • Pragmatics context dependent meanings of words.
  • Prosody changes in intonation giving meaning.
  • Semantics the meaning of a word.
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