Folie 1

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(No Transcript)
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Articulation / Motor Control
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The Speech Network
Anterior perisylvian cortex, left SMA Basal
ganglia Cerebellum
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Experiment 1
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Experiment I Introduction
Anterior perisylvian cortex, left
frontal operculum (Initiation) inferior
prefrontal gyrus (Organization) Alexander,
Naeser Palumbo, 1990
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Experiment I Introduction
Anterior perisylvian cortex, left
frontal operculum inferior prefrontal
gyrus precentral gyrus, posterior parts
(execution) precentral gyrus, rostral parts
(planning, sequencing) Penfield Roberts,
1959 Ojeman Mateer, 1979 Deacon, 1992
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Experiment I Introduction
Anterior perisylvian cortex, left
frontal operculum inferior prefrontal
gyrus precentral gyrus left anterior insula
(planning) Dronkers, 1996
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Experiment I Introduction
Anterior perisylvian cortex, left
frontal operculum inferior prefrontal
gyrus precentral gyrus left anterior insula
non-speech orofacial movements vs. simple speech
movements vs. complex speech movements
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Experiment I Methods
Subjects 10 (5 f, 5 m), age 21-32 (median
26.2) healthy, right-handed, native German
Material horizontal tongue movement (HTM) /ta/
(CV) /stra/ (CCCV) /pataka/ (CVCVCV,
non-lexical) /tagebau/ (CVCVCV, lexical)
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Experiment I Methods
Procedure unprosodic (monotonous)
rendition self-paced "comfortable" speaking
rate each item was repeated 4 times for 1
minute seperated by a 1 minute rest periode
(baseline) task 5 tasks (8 minutes each),
randomized order between subjects Speech tasks
were recorded to determine the speaking rate
HTM rate was determined outside the scanner.
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Experiment I Methods
Image acquisition (functional imaging) 1.5 T
whole-body scanner (Siemens Vision) Echo Planar
Imaging (64x64 matrix, FOV 192 mm, TE 46 ms, TR
6 s, a 90º) 28 slices (4 mm thickness, 1 mm gap)
across the complete brain volume
Anatomical reference T1-weighted 3D Turbo Flash
Sequence (MP-Rage) (256x256 matrix, FOV 256 mm,
TE 4 ms, TR 9.7 ms) 128 slices (1.5 mm thickness)
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Experiment I Methods
Image processing (SPM96) movement
correction coregistration (mean EPIs with
anatomical image) spatial normalization (transfo
rmation into Talairach space) smoothing
(Gaussian filter, FWHM 6 mm)
Statistical analysis fixed effects
analysis activation thresholds p lt .001 (voxel
level) p lt .05 (cluster level, corr. for
multiple comparisons)
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Image Processing
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Experiment I Results
Size
Lateralization
HTM
large
bilateral symmetric
CV /ta/
CCCV /stra/
CVCVCV /tagebau/
CVCVCV /pataka/
focused
exclusively left
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Experiment I Results
Syllable production activation restricted to the
anterior and posterior bank of the central
sulcus additional activation in the right
cerebellum during production of /stra/
HTM activation extended to premotor
areas bilateral cerebellar activation
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Experiment I Discussion
Movement fractionation (HTM) poses more
demands on sensorimotor cortex than
nonindividualized motor control (as in
coarticulated /pataka/ and /tagebau/) (cf.
Brooks, 1986). Highly overlearned movements
require less extensive neural activity compared
with untrained movements (cf. Motifee et al.,
1994). Function requiring rapid processing time
show a more focal cerebral organization than
those performed at a more slow tempo (cf. Milberg
Albert, 1991).
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Experiment I Discussion
HTMs require more voluntary effort and
more attentional resources than overlearned
syllables and therefore depend more on premotor
structures. Relatively slow speaking rates might
pose less demands on motor coordination of
articulatory sequences, explaining the lack of
activation in rostro-lateral parts of the
precentral gyrus and in the anterior insula
during syllable production.
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Experiment I Discussion
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Experiment 2
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Experiment II Introduction
Lateralization effects
Speech motor control shows a predominantly left-si
ded hemodynamic response (anterior
insula, dorsolateral premotor area, posterior
pallidum)
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Experiment II Introduction
Lateralization effects
Speech motor control shows a predominantly left-si
ded hemodynamic response 'Inner speech' elicits a
further lateralization effect (rather exclusive
activation of the left precentral
gyrus) Paulesu, Connely Frith, 1995 Wildruber,
Ackermann Klose, 1996 Ackermann et al., 1998
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Experiment II Introduction
Lateralization effects
Speech motor control shows a predominantly left-si
ded hemodynamic response 'Inner speech' elicits a
further lateralization effect Singing (melody
processing) depends critically upon right-hemisphe
re structures Peretz, 1990 Gordon Bogen,
1974 Epstein, Meador Loring, 1999
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Experiment II Introduction
Lateralization effects
Speech motor control shows a predominantly left-si
ded hemodynamic response 'Inner speech' elicits a
further lateralization effect Singing (melody
processing) depends critically upon right-hemisphe
re structures Lateralized activation of the right
precentral gyrus during silent reproduction of a
tune Wildgruber, Ackermann Klose, 1996
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Experiment II Methods
Subjects 18 (9 f, 9 m), age 22-63 (median
39) healthy, right-handed, native German
Material continuous recitation of the month of
the year - overt - covert non-lyrical tune
(W.A. Mozart, Eine kleine Nachtmusik) - overt -
covert
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Experiment II Methods
Procedure self-paced "comfortable" production
rate (overt speech, Jan.-Dez. mean 5.6s, s.d.
1.3s overt singing 6.9s, s.d. 1.1s) each
task was applied 12 times (visual
stimulation) seperated by rest periodes 24 sec
onset-to-onset interval between activation
phases tasks were applied in randomized order
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Experiment II Methods
Image acquisition (functional imaging) 1.5 T
whole-body scanner (Siemens Vision) Echo Planar
Imaging (64x64 matrix, FOV 192 mm, TE 39 ms, TR
3 s, a 90º) 28 slices (4 mm thickness, 1 mm gap)
across the complete brain volume
Anatomical reference T1-weighted 3D Turbo Flash
Sequence (MP-Rage) (256x256 matrix, FOV 256 mm,
TE 4 ms, TR 9.7 ms) 128 slices (1.5 mm thickness)
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Experiment II Methods
Image processing (SPM96) movement
correction coregistration (mean EPIs with
anatomical image) spatial normalization (transfo
rmation into Talairach space) smoothing
(Gaussian filter, FWHM 10 mm)
Statistical analysis overt speech vs. overt
singing and vice versa overt vs. covert speech
and overt vs. covert singing activation
thresholds p lt .001 (voxel level) p lt .05
(cluster level, corr. for multiple comparisons)
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Experiment II Results
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Experiment II Results
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Experiment II Results
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Experiment II Discussion
The left anterior intrasylvian cortex
mediates coordination and sequencing of speech
articulation (cf. Ojemann, 1983 Dronkers,
1996). These processes occur in cooperation with
the cerebellum (Ackermann Hertrich,
1997). Besides propositional content, verbal
utterances convey paralinguistic aspects
(speaker's mood and attitudes. The insula has
interconnections with auditory, somatosensory,
premotor and limbic regions - the neuroanatomic
prerequisites of a device integrating linguistic
and paralinguistic information.
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Experiment II Discussion
In analogy, the right intrasylvian cortex might
support the temporo-spatial coordination of vocal
musculature according to a given melody template,
and the emotions and attitudes of the
singer. Bilateral overactivation of the insula
as observed in stuttering (Fox, Ingham Ingham,
1996) could reflect compensatory enhancement of
the assumed intrasylvian temporo-spatial
coordination device.
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Experiment 3
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Experiment III Introduction
Speaking rate clinical observations
Basal ganglia dysfunction leads to normal
or increased speaking rate (hypophonia).
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Experiment III Introduction
Speaking rate clinical observations
Basal ganglia dysfunction leads to normal
or increased speaking rate (hypophonia). Atactic
dysarthria (with cerebellar origin)
is characterized by slowed speaking rate
and lengthening of unstressed syllables (voice
tremor and irregular pitch shifts).
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Experiment III Introduction
Speaking rate clinical observations
Basal ganglia dysfunction leads to normal
or increased speaking rate (hypophonia). Atactic
dysarthria (with cerebellar origin)
is characterized by slowed speaking rate
and lengthening of unstressed syllables (voice
tremor and irregular pitch shifts). Lesions to
the motor cortex or the corticobulbar tracts may
result in spastic dysarthria with slowed speaking
rate (hypernasality, tongue retraction etc.).
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Experiment III Methods
Subjects 10 (5 f, 5 m), age 22-32 healthy,
right-handed, native German
Material oral diadochokinesis, syllable
/ta/ repetition rates 2.5, 4.0 and 5.5
Hz covert speech production
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Experiment III Methods
Procedure repetition rate paced via
earphones 8 blocks of 50 sec. per session,
alternating rest and task condition 3
sessions, one for each frequency condition
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Experiment III Methods
Image acquisition (functional imaging) 1.5 T
whole-body scanner (Siemens Vision) Echo Planar
Imaging (64x64 matrix, FOV 192 mm, TE 39 ms, TR
5 s, a 90º) 27 slices (4 mm thickness, 1 mm gap)
across the complete brain volume
Anatomical reference T1-weighted 3D Turbo Flash
Sequence (MP-Rage) (256x256 matrix, FOV 256 mm,
TE 4 ms, TR 9.7 ms) 128 slices (1.5 mm thickness)
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Experiment III Methods
Image processing (SPM96) movement
correction coregistration (mean EPIs with
anatomical image) spatial normalization (transfo
rmation into Talairach space) smoothing
(Gaussian filter, FWHM 10 mm)
Statistical analysis (SPM99) activation vs.
respective baseline parametric analysis of rate-
and time-dependent effects activation
thresholds p lt .001 (voxel level) p lt .05
(cluster level, corr. for multiple comparisons)
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Experiment III Results
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Experiment III Results
height threshold p lt .001 (uncorr.), no
thresholding at cluster level
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Experiment III Discussion
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Experiment III Discussion
Asymmetry of basal ganglia activation towards the
left putamen is in accordance with clinical
observations of disordered articulation and
reduced voice volume after left-sided subcortical
infarction (Alexander et al., 1987). Decreased
response within the putamen during
fastest production rate is supported by clinical
obeservations of accelerated speech tempo in
patients with basal ganglia dysfunction
(Ackermann Ziegler, 1991).
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Experiment III Discussion
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Experiment III Discussion
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Experiments
Articulation / Motor Control
The speech network
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Introduction
left-sided functional dominance for speech motor
control clinical observation lesion of the left
capsula interna causes speech disorders, lesion
of the right cortico-bulbar tracts does
not complete recovery within days or weeks
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Methods
Subject male, age 38 CVA in the left capsula
interna dysarthria, hemiparesis complete
recovery after 9 days
Procedure overt and covert speech
production measurements 4 and 35 days post
CVA movement correction, coregistration and
statistical data analysis using SPM99
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Results
overt speech significant lateralization effects
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Results
covert speech significant lateralization effects
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Discussion
Cortical re-organization of speech motor
control after unilateral lesions in the left
hemisphere. Compensatory activation of the right
motor cortex (and left cerebellum). Right motor
cortex is part of an alternative
activation pathway in speech motor control which
becomes inhibited during functional
lateralization of speech/ language processing.