Ling 411 – 19
New Evidence on Speech
Recognition Areas
and their Functions
Schedule of Presentations
Tu Apr 13
Th Apr 15
Tu Apr 20
Th Apr 22
Delclos
Planum Temp
Banneyer
Categories
Ezell
Lg Dev. (Kuhl)
Ruby Tso
Writing
Rasmussen
2nd language
Bosley
Synesthesia
Brown
Lg&Thought
Koby
Music
Mauvais
LH-RH anat.
Tsai
Tones
Delgado
Amusia
Valuable Lessons from G. Hickok
 The role of Wernicke’s area in speech
production
• Confirms what we have already learned
 Another type of conduction aphasia
 The role of the right hemisphere in
speech perception
 A new explanation of “word deafness”
 The role of Broca’s area and SMG in
phonological working memory
 The role of SMG in speech production and
repetition
On the other hand ..
 One proposal of Hickok is not so good!
• Arcuate fasciculus
 Not a direct connection (acc. to Hickok)
 (later)
Wernicke’s area in speech production
“What I would like to suggest
is that Wernicke was essentially
correct in hypothesizing … that
auditory cortex participates in
speech production …”
(Hickok 2000: 89)
Hickok quotes Wernicke:
Observations of daily speech usage and the
process of speech development indicates the
presence of an unconscious, repeated activation
and simultaneous mental reverberation of the
acoustic image which exercises a continuous
monitoring of the motor images.
Wernicke 1874
Evidence for left pSTP involvement
in speech production
 Erratic speech of Wernicke’s aphasics
 Conduction aphasia from damage to left pSTP
 Intraoperative stimulation of left pSTP
•
•
“distortion and repetition of words and syllables” (Penfield &
Roberts 1959)
N.B.: As in Wernicke’s aphasia
 MSI study shows activity in left pSTG just before
speech production (picture naming) (Levelt et al.
1998)
 fMRI study: similar results – no RH activity shown
(Hickok et al. 1999)
(Hickok 2000: 93-4)
An MSI study from Max Planck Institute
Valuable Lessons from G. Hickok
 The role of Wernicke’s area in speech
production
• Confirms what we have already learned
 Another type of conduction aphasia
 The role of the right hemisphere in
speech perception
 A new explanation of “word deafness”
 The role of Broca’s area and SMG in
phonological working memory
Hickok’s proposal on conduction aphasia
 At least one type of conduction aphasia
results from damage to phonological
processing systems in auditory cortex
which participate both in speech
perception and in speech production
• i.e., Wernicke’s area
 The asymmetry between production
(impaired) and comprehension (spared) can
be explained in terms of different degrees
of lateralization in the … systems that
support (or can support) these functions
(2000: 89)
Why isn’t this Wernicke’s aphasia?
 The area identified by Hickok for
conduction aphasia is Wernicke’s area
• Hickok claims that such damage is responsible
for conduction aphasia
 Conduction aphasia and Wernicke’s aphasia
• In conduction aphasia
 Comprehension is relatively ok
• Hickok claims the RH pSTP also participates in
speech recognition
 Patient is aware of errors in repetition
• Hickok proposes that in Wernicke’s aphasia the
damage extends beyond Wernicke’s area
 MTG (p. 101), (maybe also AG?)
Hickok & Poeppel (2000)
 Left temporal-parietal-occipital junction
area is “typically involved to some extent in
Wernicke’s aphasia, which … has a
prominent post-phonemic component to the
deficit profile. (Toward a functional
neuroanatomy of speech perception, p. 7)
MR template – Wernicke Aphasia (patient I)
Poster
-ior
portio
n of
superior
and
middle
temporal
gyri
MR template – Wernicke Aphasia (patient II)
Superior
temporal
gyrus,
AG,
SMG
Repetition in Wernicke’s aphasia
Repetition in Wernicke’s aphasia
Model for Repetition
 black
Patient’s Response
 blackboard
 shoe
 shoelace
 He parks the car
 He park … he came with
the car. He came with
his car.
 It goes between two
others
 It went two cars …
between the cars
Valuable Lessons from G. Hickok
 The role of Wernicke’s area in speech
production
• Confirms what we have already learned
 Another type of conduction aphasia
 The role of the right hemisphere in
speech perception
 A new explanation of “word deafness”
 The role of Broca’s area and SMG in
phonological working memory
Hickok’s proposal on speech perception
 The primary substrate for speech perception
is the posterior temporal plane (pSTP)
•
pSTP – Heschl’s gyrus plus planum temporale
 Conduction aphasia can result from damage
to exactly this area in left hemisphere
 Apparent paradox:
• Comprehension is preserved in conduction aphasia
 Explanation:
• Speech perception is subserved by pSTP in both
hemispheres
(2000: 90)
RH involvement in speech perception
Isolated RH
 Evidence from tests of isolated RH
• Split-brain studies
• Wada test
•
•
 Sodium amytol, sodium barbitol
Discrimination of speech sounds
Comprehension of syntactically simple speech
(Hickok 2000: 92)
Caution – Split-Brain Studies
 These patients are generally epileptics
 Usually the onset of seizures is several to
many years before the surgery
 Often the onset of seizures was during
childhood
 Therefore the brain has had time to adapt
– perhaps reorganize some linguistic
functions
RH involvement in speech perception
Intra-operative recording
 Evidence from intraoperative recording
 Sites found in STG of both hemispheres for
• Phoneme clusters
• Distinguishing speech from backwards speech
• Distinguishing mono- from polysyllabic words
(Hickok 2000: 92-3)
RH involvement in speech perception
Imaging
 Evidence from imaging
•
•
•
PET
fMRI
MEG
•
More activity in LH
 Subjects passively listen to speech
 Both hemispheres show activity
 Some evidence for differential contributions of
the two hemispheres (Hickok & Poeppel, another
publication)
(Hickok 2000: 93)
Some findings w.r.t. RH speech perception
 Vowel qualities
 Intonation
 Tones in tone languages
Valuable Lessons from G. Hickok
 The role of Wernicke’s area in speech
production
• Confirms what we have already learned
 Another type of conduction aphasia
 The role of the right hemisphere in
speech perception
 A new explanation of “word deafness”
 The role of Broca’s area and SMG in
phonological working memory
Word Deafness
 Also known as pure word deafness
 Profound speech comprehension deficit
•
•
Inability to hear words as words
Like Wernicke’s aphasia, but worse
 Wernicke’s aphasics have some speech
perception ability
 Geschwind: disconnection of Wernicke’s area
from speech input
 Hickok’s alternative: Damage to pSTP of both
hemispheres
 Speech production similar to that in
conduction aphasia (Hickok 2000: 94)
•
Paraphasia
More on word deafness
“… word deafness is the only aphasic
syndrome dominated by a profound deficit
in speech perception. …none of the left
unilateral-lesion-based aphasic syndromes
have a speech perception deficit as a major
component of the syndrome, which in turn
further supports the view that speech
perception is mediated bilaterally.”
Hickok 2000: 92
Valuable Lessons from G. Hickok
 The role of Wernicke’s area in speech
production
• Confirms what we have already learned
 Another type of conduction aphasia
 The role of the right hemisphere in
speech perception
 A new explanation of “word deafness”
 The role of Broca’s area and SMG in
phonological working memory
Phonological working memory
“… Broca’s area and the SMG are involved in speech
perception only indirectly through their role in phonological working memory which may be recruited during
the performance of certain speech perception tasks.”
Hickok 2000: 97
“The sound-based system interfaces not only with the
conceptual knowledge system, but also with frontal
motor systems via an auditory-motor interface system
in the inferior parietal lobe. This circuit is the primary
substrate for phonological working memory, but also
probably plays a role in volitional speech production.
Hickok 2000: 99
But ..
 One proposal of Hickok is not so good!
• Arcuate fasciculus
• Hickok’s assertion:
“… this auditory cortex-SMG-Broca’s area circuit
replaces the notion of a direct sensory-motor link
via the arcuate fasciculus. Connectivity studies in
nonhuman primates is consistent with the claim that
there is not a direct … connection between auditory
cortex and the ventral posterior frontal lobe…
“… auditory cortex … in the macaque monkey … does
project to the parietal lobe which in turn projects
to ‘Broca’s area.’ ”
2000:99
Arcuate Fasciculus
 The macaque monkey’s brain is not
the same as the human brain
 The macaque monkey has no language!
 Better to rely on anatomical studies
of the human brain.
Arcuate fasciculus in primates
Asif Ghazanfar, Nature Neuroscience 11:4.382-384, April 2008
Benson and Ardila on conduction
aphasia
“… a single type of aphasia may have distinctly
different loci of pathology. Both conduction
aphasia and transcortical motor aphasia are
examples of this inconsistency.” (117)
(See also p. 135)
Hannah Damasio on conduction aphasia
“Conduction aphasia is associated with left perisylvian
lesions involving the primary auditory cortex…, a portion
of the surrounding association cortex…, and to a variable
degree the insula and its subcortical white matter as well
as the supramarginal gyrus (area 40). Not all of these
regions need to be damaged in order to produce this type
of aphasia. In some cases without involvement of auditory
and insular regions, the compromise of area 40 is
extensive…. In others, the supramarginal gyrus may be
completely spared and the damage limited to insula and
auditory cortices … or even to the insula alone….”
(1998: 47)
CT template – Conduction Aphasia (patient I)
CT template – Conduction Aphasia (patient II)
Left
auditory
cortex
and
insula
Kurt Goldstein on Conduction Aphasia
 Kurt Goldstein
(1878-1965)
•
•
•
German
Studied with Wernicke
Influenced by Gestalt psychology (Koffka 1935)
•
•
Became the best-known spokesman for this approach
Important publication in 1948
•
•
Not the arcuate fasciculus but a central area
Proposed the term ‘Central Aphasia’
 Adopted a “holistic” approach
 Criticized the Wernicke-Lichtheim view of
conduction aphasia
 Now we see that there are really three kinds of
conduction aphasia
Three types of conduction aphasia
 Damage to arcuate fasciculus
• The classical one
 Proposed by Wernicke and Lichtheim
 Doubted by Hickok
• But Hickok is wrong!
 Damage to SMG
• Proposed by Goldstein
• Supported by Hickok
 Damage to Wernicke’s area
• New proposal of Hickok
 Possible 4th type: Damage to insula
More on RH Linguistic Functions
 Inference, Metaphor
 Coarse coding
 Music
Possible bases for RH/LH difference
 Higher ratio of white to gray matter in RH
• Therefore, higher degree of connectivity in RH
 Difference in dendritic branching
 Different density of interneurons
 Evoked potentials (EEG) are more diffuse
over the RH than over LH
Beeman 257
Anatomical differences between LH and RH
 Geschwind & Levitsky (1968)
• 100 brain specimens examined
• Planum temporale
•
 Larger in LH: 65%
 Larger in RH: 11%
 About the same, both sides: 24%
Correlates with shape of Sylvian fissure
 Shorter horizontal extent in RH
Goodglass 1993:60
Experiments (described by Beeman)
 Words presented to rvf-LH or lvf-RH
 RH more active than LH
• Synonyms
• Co-members of a category: table, bed
• Polysemy: FOOT1 – FOOT2
• Metaphorically related connotations
• Sustains multiple interpretations
 LH about same as RH
• Other associations: baby-cradle
 LH more active than RH
• Choose verb associated with noun
Patients with brain-damage
 Some patients with LH damage
• Can’t name fruits but can say that they are
fruits
 Patients with RH damage
• Impaired comprehension of metaphorical
•
statements
More difficulty producing words from a
particular semantic category than producing
words beginning with a particular letter (258)
Imaging studies
 When listening to spoken discourse,
cerebral blood flow increases in
• Wernicke’s area
• Broca’s area
• RH homologues of Wernicke’s and Broca’s areas
 More cerebral blood flow in RH when
subjects read sentences containing
metaphors than literal sentences
Experiments on speech perception
 Dichotic listening – normal subjects
• Right ear (i.e. LH) advantage for distinctions of
•
•
 Voicing
 Place of articulation
Left hear (RH) advantage for
 Emotional tone of short sentences
Sentences presented in which only intonation
could be heard
 RH advantage for identifying sentence type –
declarative, question , or command
Experiments on speech perception
 Split brain patients
• They hear a consonant
• Then written representations are presented
• ‘Point to the one you heard’
• rvf-LH exhibited strong advantage
Patients with right-brain damage
 Posterior RH lesions result in deficits in
interpreting emotional tone
 Anterior RH lesions abolish the ability to
control the production of speech intonation
Split-brain studies
 Isolated RH has ability to read single
words
• But not as fast nor as accurate as LH
• Ability declines with increasing word length
• Lexical context does not assist letter
identification
 In Japanese subjects
• RH is better at reading kanji than kana
• LH is better at reading kana
Musical abilities and the hemispheres








Pitch, melody, intensity, harmony, etc. in RH
Rhythm in LH
Absolute pitch (if present) in LH temporal plane
Musicians’ ability to analyze chord structures in LH
Appreciation of chord harmony in RH
Discrimination of local melody cues more in LH
Timbre discrimination in anterior right temporal lobe
Melody recognition in anterior right temporal lobe
Evidence from results of brain lesions/surgery,
from dichotic listening experiments, from
Wada test experiments, and from imaging
end