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PPA and Semantic Dementia

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Title: PPA and Semantic Dementia


1
PPA and Semantic Dementia
2
Picks Disease
  • Six patients with language impairment and
    temporal lobe atrophy

3
Lund-Manchester CriteriaNeurology 1998 51
1546-1554
  • Frontotemporal Lobar Degeneration
  • Frontal variant FT dementia
  • Progressive nonfluent dsyphasia
  • Semantic Dementia

wide range of neuropathological entities
4
  • FvFTD
  • Best viewed in terms of known frontal lobe
    symptomatology

5
  • Orbitobasal disinhibition, poor impulse,
    antisocial

6
  • Medial frontal-cingulate apathy (although very
    common in AD)
  • Dorsolateral disorders of executive function

7
Distinguishing FTD from ADPhonology,syntax and
grammar well preserved in AD
  • Stereotypical behaviours
  • Change in food preferences, Kluver-Bucy like
    behaviour
  • NPI
  • PPA phonemic paraphasias are common, rare in AD
  • phonemic or literal paraphasias, in which the
    response differs from the correct word by one
    letter or sound, such as saying "shammer" for
    "hammer."

8
Semantic Dementia (Snowden 1989)
  • Semantic memory (Warrington 1975)
  • Term applied to the component of long-term memory
    which contains the permanent representation of
    our knowledge about things in the world facts,
    concepts and words
  • Culturally shared, acquired early in life.

9
Wernickes area
  • Gateway for linking the sensory patterns of words
    to the distributed associations that encode their
    meaning.

10
Semantic Dementia (Snowden 1989)
  • Affects fundamental aspects of language, memory
    and object recognition.

11
Semantic Framework
Verbal access
Visual access
Multi-modal semantic system common knowledge
Sounds, smells, tactile
Actions Real object use

12
Semantic Dementia
  • Progressive anomia, not an aphasia, but a loss of
    semantic memory.
  • Impaired naming, word comprehension, object
    recognition and understanding of concepts.
  • characterized by preserved fluency and impaired
    language comprehension phonologically and
    syntactically correct

13
Assessement
  • Category fluency
  • Generation of definitions
  • Lion it has little legs and big ears, they
    sleep a lot, see them in shops
  • Word-picture matching
  • Famous faces test
  • Normal episodic memory, normal visuospatial
    skills

14
  • Nature of errorSemantic-type naming
    errorsinitially within-category, elephant for
    hippopotamus, then superordinate dog for
    everything, then animal
  • Profound and complete anomia
  • Circumlocutions and semantic paraphasias
  • semantic paraphasias, in which the wrong word is
    produced, one that is usually related to the
    target (eg, "pliers" for "hammer").

15
  • Nature of errorImpaired general knowledge
    patients complain of memory loss.
  • Whats your favourite food?-
  • food, food, I wish I knew what that was.
  • Patient JL, aged 60, company director
  • frightened by a snail in his backyard, and
    thought a goat a strange creature.

16
  • Phonology and syntax striking preserved
  • Surface dyslexia difficulty reading and spelling
    irregular words eg Reading PINT to rhyme with
    flint, mint etc

Loss of semantic support necessary for correct
pronunciation, creating a phonologically
plausible error( regularization Error)
17
SD and memory
  • Can relate details ( in a rather anomic fashion)
    of recent events, but there is impaired recall of
    distant life events.

18
Memory what we know
  • Patients with lesions to the hippocampus and
    related structures show severe impairments to new
    learning and a temporally limited retrograde
    amnesia.

19
  • What about patients who may show the converse
    neuroanatomical lesion (i.e., focal damage to the
    temporal neocortex sparing the hippocampal
    system)?

20
  • What about patients who may show the converse
    neuroanatomical lesion (i.e., focal damage to the
    temporal neocortex sparing the hippocampal
    system).
  • show the converse pattern of memory impairment,
    that is to say, preservation of recent and loss
    of distant memories.

21
SD and memory
  • SD can relate details ( in a rather anomic
    fashion) of recent events, but there is impaired
    recall of distant life events.
  • Alzheimer's disease more typical temporally
    graded loss (poor recall of recent memories)

22
Amnesic Alzheimer's disease patient with
hippocampal atrophy (H) accompanied by a mild
degree of general neocortical atrophy.
23
  • R. B., who had bilateral lesions limited to the
    CA1 region of the hippocampus although he showed
    a relatively severe anterograde memory
    impairment, R. B. demonstrated a retrograde
    amnesia of no more than 1 or 2 years.

24
Semantic dementia patient with severe focal
atrophy of the left temporal lobe see arrow,
right-hand side of MRI scan) involving the pole,
inferior, and middle temporal gyri with relative
sparing of the hippocampal complex (H) and of
the superior temporal gyrus.
25
SD
  • In most cases, neuroradiological studies reveal
    selective damage to the inferolateral temporal
    gyri(inferior and middle) of one or both temporal
    lobes, with sparing of the hippocampi,
    parahippocampal gyri, and subiculum.
  • Note AD inferior and middle temporal gyri

26
Disrupted temporal lobe connections in SD
Mummery CJ et al. Brain 1999, 122 61-73
  • PPT SEMANTIC TASK VISUAL TASK
  • COWhorsebear. CUCUMBERtomatocorn

27
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SD Reduced activity in Left inferior temporal
gyrus (BA 37) Known for specific naming
deficits or anomia Region is presumed to be
structurally intact, but functioning abnormally
due to reduced input from anterior temporal
lobe.
29
Temporal lobe regions engaged during normal
speech comprehension Crinion JT et al.Brain,
Vol. 126, No. 5, 1193-1201, May 2003
  • Processing of speech is obligatory!
  • Aphasic stroke patients importance of the
    posterior temporal and inferior parietal cortex.
  • SD anterior and ventral temporal lobe cortex may
    be central to word comprehension

30
Experiment
  • Reversed versions of the narratives, (same
    acoustic complexity as forward speech) expected
    to control for early acoustic processing of the
    speech signal in both left and right superior
    temporal cortex.
  • Contrastspeech comprehension

31
Results
  • Comprehension is dependent on anterolateral and
    ventral left temporal regions.

32
Patient with SD
33
  • M. put orange juice in his lasagna and on another
    occasion, brought the lawnmower up to the
    bathroom when he was asked for a ladder

34
Test autobiographical information (e.g., an
event that occurred at secondary school) across
three life periods childhood, early adulthood,
and recent life
  • Graham KS Hodges JR. Neuropsychology. 1997 Vol.
    11, No. 1, 77-89Differentiating the Roles of the
    Hippocampal Complex and the Neocortex in
    Long-Term Memory Storage

35
  • The results suggest that the preservation of
    recently acquired autobiographical memories is
    restricted to the most recent 5 years, and, in
    particular, one patient, only from the last 1 1/2
    years.
  • Medial temporal lobe structures do not store or
    index memories for long periods of time, for
    example, decades.

36
SD and memory
  • In contrast to the time-limited role played by
    the hippocampus, a crucial site for the storage
    of our knowledge of the world and our past
    autobiographical experiences is the temporal
    neocortex.

37
Memory
  • As direct connections form within the neocortex,
    remembering the experienced event becomes less
    dependent on the medial temporal lobe structures
    and, therefore, more resistant to hippocampal
    damage.

38
Memory Hippocampal Function
  • Hippocampus does not itself store memories but
    acts as an orienting system, flagging the need
    for the neocortex to form a new representation (
    Alvarez Squire, 1994 ).
  • Storage of an experienced event as a process
    initially reliant on the hippocampal system,
    before gradual changes in the neocortex allow the
    memory to be stored permanently

39
In Alzheimers disease
  • Significant episodic memory impairment due to
    functional disconnection of hippocampus

40
In Alzheimers disease
  • Significant episodic memory impairment due to
    functional disconnection of hippocampus
    (transentorhinal limbic)
  • Even early, may be significant semantic
    impairment due to temporal neocortex involvement.
  • (NB Category dissasociation natural vs
    artefactual)

41
Memory
  • Temporal memory system for semantic facts, and
    medial memory system for episodic memories is an
    oversimplification.
  • Neuropsychologia 2002
  • Snowden JS, Neary D
  • Relearning of verbal labels in semantic dementia

42
  • Semantic knowledge about the world is more than a
    static storehouse of words and objects
    represented by a set of abstract properties. It
    includes personalised, experience-based
    knowledge.

43
  • Descriptive information about the meaning of the
    item
  • The stimulus picture of a duck was the same type
    of thing as the china duck ornament in her own
    conservatory and the same as the ducks that she
    sees on the pond when she walks in her local
    park. A line drawing of a rolling-pin was
    described as the same sort of object as the long
    glass rolling-pin in her kitchen drawer, which
    she had used in the past to make pastry to put on
    the top of pies.

44
  • 20 pictures,all of which the patient had
    consistently failed to name on the pre-test
    assessments.
  • Recall at 2 weeks and 4 months

45
  • Episodic memories specific temporal and spatial
    context.
  • Object information, represented by temporal
    neocortex, is linked with temporal and spatial
    information, represented by other brain regions.
  • This linking of (weak) word/object information
    with (strong) spatial and temporal information
    that provides the basis for patients' relative
    preservation of autobiographical memories.

46
  • In semantic dementia the most context-free levels
    of knowledge (constituting traditional notions of
    semantic memory) are most compromised.
  • In contrast, patients may retain knowledge tied
    to specific experiences or routines

47
  • Episodes gradually, over many years, take on the
    properties of semantic memory (i.e., resemble
    general knowledge by becoming independent of
    specific temporal and spatial contexts).

48
  • Butters and Cermak (1986)
  • a detailed case study of a patient with
    Korsakoff's syndrome,
  • "knowledge of public events and personal
    experiences from the 1930s and 1940s may be part
    of semantic memory whereas public and personal
    happenings from the past decade may still be
    associated with specific spatial and temporal
    contexts

49
  • A more appropriate compartmentalisation might be
    between context-free (neocortical) and
    context-bound (medial temporal) memories. The
    latter is characterised by the drawing together
    of distinct aspects of information (item, time,
    space) from distant cortical sites and includes
    both semantic and episodic characteristics.

50
PPA
  • "a slowly progressing aphasic disorder without
    the additional intellectual and behavioral
    disturbances of dementia"
  • Memory, judgment, executive function intact.
  • Mesulam, M. M. (1982). Slowly progressive aphasia
    without generalized dementia. Annals of
    Neurology, 11, 592-598, and
  • Mesulam, M.M. (2001). Primary Progressive
    Aphasia. Annals of Neurology, 49, 425-432.

51
PPA
  • 1. Insidious onset and gradual progression of
    word-finding, object-naming, or word
    comprehension impairments as manifested during
    spontaneous conversation or as assessed through
    formal neuropsychological testing of language.
  • 4. Absence of significant apathy, disinhibition,
    forgetfulness for recent events, visuospatial
    impairment, visual recognition deficits, or
    sensorimotor dysfunction within the initial 2
    years of illness.
  • 5. Acalculia and ideomotor apraxia can be present
    even in the first 2 years. Mild constructional
    deficits and perseveration (eg, as assessed by
    the go no-go task) are also acceptable as long as
    neither visuospatial deficits nor disinhibition
    influence daily living activities.

52
Classification?
  • Cases of SD often included under PPA When free
    of face and object recognition deficits, semantic
    dementia constitutes a subtype of PPA with poor
    comprehension of verbal semantics.
  • Annals of Neurology53, 2003. Pages 35-49
  • Primary progressive aphasia PPA and the language
    network

53
PPA vs SD?
  • Aphasia in PPA can be fluent
  • there is not a single type of language
    dysfunction that is pathognomonic for PPA
  • the term SDdesignates a prominent fluent
    aphasia with impaired comprehension in the
    presence of of prominent defects of visual
    recognition (or perception).
  • But also used to refer to PPA subtype with fluent
    speech and impaired comprehension
  • Mesulam, M.M. (2001). Primary Progressive
    Aphasia. Annals of Neurology, 49, 425-432.

54
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56
Semantic dementia patient with severe focal
atrophy of the left temporal lobe see arrow,
right-hand side of MRI scan) involving the pole,
inferior, and middle temporal gyri with relative
sparing of the hippocampal complex (H) and of
the superior temporal gyrus.
57
PPA vs SD?
  • Hodges
  • SD is fluent, PPA is not
  • SD deteriorate fast, PPA slow.
  • Primary disorder is verbal, visual component is
    not obligatory (visuospatial tests are normal)

58
Brocas
  • Generation of articulatory sequences so that
    thoughts can be turned into statements with
    correct phonology and syntax.
  • Dysfunction leads to impaired articulation, word
    order, grammar.
  • Phonology sound structure
  • Syntax sentence order and structure

59
PPA
  • Anomia is (nearly) universal in PPA
  • Anomia can emerge with either fluent or
    non-fluent speech
  • PPA with agrammatism, frequently impaired
    fluency, telegraphic speech
  • Rare lexical lacunes, which become increasingly
    common
  • school? What does school mean?

60
PPA
  • Comprehension excellent, except for grammatically
    complex sentences the lion was eaten by the
    tiger vs the tiger ate the lion
  • Progress to mutism

61
Annals of NeurologyVolume 53, Issue 1, 2003.
Pages 35-49Sreepadma P. Sonty, BA 1, M.-Marsel
Mesulam, MD 1 2 3, Cynthia K. Thompson, PhD 1 2
4, Nancy A. Johnson, PhD 1 3, Sandra Weintraub,
PhD 1 3, Todd B. Parrish, PhD 1 5, Darren R.
Gitelman, MD 1 2 5
  • Sample of PPA patients with impaired word finding
    but preserved comprehension of conversational
    speech

62
Annals of NeurologyVolume 53, Issue 1, 2003.
Pages 35-49
  • fMRI.
  • Judgment of pairs of words
  • Phonological task React if words were homonyms
    (ie, had identical pronunciation but dissimilar
    orthography and meaning).
  • Semantic taskReact if words in a pair were
    synonyms (ie, had a very similar meaning but
    dissimilar orthography and phonology).

63
Annals of NeurologyVolume 53, Issue 1, 2003.
Pages 35-49
  • PPA patients
  • Activation in fusiform gyrus, precentral gyrus,
    and intra-parietal sulcus.
  • May be a compensatory spread of language-related
    neural activity

64
  • Word reading is a highly learned, automatic task.
  • In PPA, this process may lose its automaticity
    and may become increasingly more dependent on
    laborious grapheme-to-phoneme transformations,
    such as those that are necessary for reading
    unfamiliar pseudowords.
  • .

65
PPA Pathology
  • 60 neuronal loss with gliosis lacking in
    distinctive histopathological features.
  • 20 Alzheimer's disease.
  • Some of these patients have an unusual
    perisylvian and temporal neocortical distribution
    of neurofibrillary tangles, which occasionally
    spares medial temporal lobe structures.
  • Another 20 show the tau-positive,
    intracytoplasmic bodies of Pick's disease.
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