Aphasia

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Aphasia

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

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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.

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Models of reading
Meaning pathway
zint phonological
Direct pathway
pint surface
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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

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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

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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.

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Sylvian fissure
Sylvian region
Middle cerebral artery
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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.

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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?

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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
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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.

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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
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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.

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Boston Aphasia Classification System

• Syndrome approach.
• Associations of symptoms.
• Focus is on the location of the lesion.
• Useful for diagnostic purposes.
• Rehabilitation?

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Tell me everything that is happening in this
picture
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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.

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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.

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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.

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hat
Hat Name x Repeat x Read x Write x cap
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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.

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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.
  

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Arcuate fasciculus
Wernickes area
Brocas area
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Transcortical Motor aphasia no speech output
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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.

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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.

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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.

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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.

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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.

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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.