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Neuroscience
Letters
584
(2015)
351–355
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Neuroscience
Letters
jo
ur
nal
ho
me
page:
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Short
communication
Task-dependent
modulation
of
regions
in
the
left
temporal
cortex
during
auditory
sentence
comprehension
Linjun
Zhanga,1,
Qiuhai
Yueb,c,1,
Yang
Zhangd,
Hua
Shub,,
Ping
Lie,∗∗
aFaculty
of
Linguistic
Sciences,
Beijing
Language
and
Culture
University,
Beijing,
China
bState
Key
Laboratory
of
Cognitive
Neuroscience
and
Learning,
Beijing
Normal
University,
Beijing,
China
cDepartment
of
Psychology,
Rice
University,
TX,
USA
dDepartment
of
Speech-Language-Hearing
Sciences
and
Center
for
Neurobehavioral
Development,
University
of
Minnesota,
MN,
USA
eDepartment
of
Psychology
&
Center
for
Language
Science,
Pennsylvania
State
University,
PA,
USA
h
i
g
h
l
i
g
h
t
s
The
left
lateral
temporal
cortex
is
sensitive
to
sentence
intelligibility.
The
anterior
and
posterior
STS/MTG
regions
are
involved
in
both
passive
and
active
sentence
comprehension.
The
middle
STS/MTG
regions
respond
to
sentence
intelligibility
only
during
the
active
task.
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
1
August
2014
Received
in
revised
form
27
September
2014
Accepted
30
October
2014
Available
online
3
November
2014
Keywords:
Functional
specialization
Left
lateral
temporal
cortex
Auditory
sentence
comprehension
Task
demands
Independent
component
analysis
a
b
s
t
r
a
c
t
Numerous
studies
have
revealed
the
essential
role
of
the
left
lateral
temporal
cortex
in
auditory
sentence
comprehension
along
with
evidence
of
the
functional
specialization
of
the
anterior
and
posterior
tem-
poral
sub-areas.
However,
it
is
unclear
whether
task
demands
(e.g.,
active
vs.
passive
listening)
modulate
the
functional
specificity
of
these
sub-areas.
In
the
present
functional
magnetic
resonance
imaging
(fMRI)
study,
we
addressed
this
issue
by
applying
both
independent
component
analysis
(ICA)
and
general
linear
model
(GLM)
methods.
Consistent
with
previous
studies,
intelligible
sentences
elicited
greater
activity
in
the
left
lateral
temporal
cortex
relative
to
unintelligible
sentences.
Moreover,
responses
to
intelligi-
bility
in
the
sub-regions
were
differentially
modulated
by
task
demands.
While
the
overall
activation
patterns
of
the
anterior
and
posterior
superior
temporal
sulcus
and
middle
temporal
gyrus
(STS/MTG)
were
equivalent
during
both
passive
and
active
tasks,
a
middle
portion
of
the
STS/MTG
was
found
to
be
selectively
activated
only
during
the
active
task
under
a
refined
analysis
of
sub-regional
contribu-
tions.
Our
results
not
only
confirm
the
critical
role
of
the
left
lateral
temporal
cortex
in
auditory
sentence
comprehension
but
further
demonstrate
that
task
demands
modulate
functional
specialization
of
the
anterior–middle–posterior
temporal
sub-areas.
©
2014
Elsevier
Ireland
Ltd.
All
rights
reserved.
1.
Introduction
Recent
neurolinguistic
work
has
highlighted
the
critical
role
of
the
left
lateral
temporal
cortex
in
auditory
sentence
compre-
hension
[1,13,14,23,30].
Neural
models
for
speech
comprehension
Abbreviations:
fMRI,
functional
magnetic
resonance
imaging;
GLM,
general
lin-
ear
model;
ICA,
independent
component
analysis;
ROI,
region
of
interest;
STS/MTG,
superior
temporal
sulcus
and
middle
temporal
gyrus.
Corresponding
author.
Tel.:
+86
10
58808186.
∗∗ Corresponding
author.
E-mail
addresses:
shuhua.bnu@gmail.com
(H.
Shu),
pul8@psu.edu
(P.
Li).
1L.Z.
and
Q.Y.
contributed
equally
to
this
work.
hold
that
the
left
lateral
temporal
cortex
together
with
the
left
frontal
areas
such
as
par
triangularis
and
par
orbitalis
forms
the
ventral
pathway
responsible
for
auditory-to-meaning
processing
[12,26].
However,
there
is
evidence
that
sub-regions
of
the
left
lateral
temporal
cortex
are
functionally
specialized,
although
the
specific
functions
of
the
different
areas
in
auditory
sentence
com-
prehension
are
still
being
debated.
For
example,
the
posterior
areas
are
considered
to
be
critical
for
semantic
store
at
the
lexical
level,
whereas
the
anterior
regions
are
more
involved
in
combinatorial
semantic
processes
[3,16,23].
There
may
even
exist
subtle
sepa-
ration
of
functions
within
the
left
anterior
temporal
region,
with
the
most
anterior
portion
of
the
superior
temporal
sulcus
and
mid-
dle
temporal
gyrus
(STS/MTG)
primarily
responding
to
syntactic
http://dx.doi.org/10.1016/j.neulet.2014.10.054
0304-3940/©
2014
Elsevier
Ireland
Ltd.
All
rights
reserved.
352
L.
Zhang
et
al.
/
Neuroscience
Letters
584
(2015)
351–355
structure
and
a
region
directly
posterior
to
it
reflecting
the
interac-
tion
of
syntactic
and
semantic
information
[13].
The
existing
studies
on
functional
heterogeneity
of
the
left
lateral
temporal
cortex
have
used
stimulus
manipulations
in
either
a
passive
listening
condition
[1,25,30]
or
active
anomaly
detection/selective
attention
conditions
[10,20,23].
These
studies
adopted
the
strategy
of
comparing
activation
across
different
types
of
stimuli
or
across
active
tasks
to
isolate
semantic
and
syntactic
processing
in
either
passive
or
active
listening
conditions.
While
the
results
helped
to
disentangle
functional
divisions
of
the
sub-regions
in
the
left
lateral
temporal
cortex
and
how
they
were
associated
with
syntactic
and
sentence-level
semantic
processing,
the
previ-
ous
studies
have
not
successfully
addressed
how
task
demands
may
differentially
affect
the
functional
specificity
of
the
sub-regions
in
this
important
brain
area.
To
our
knowledge,
only
one
study
has
made
direct
comparison
between
passive
and
active
sentence
com-
prehension
[11].
By
use
of
sentence
repetition
paradigm,
this
study
reported
null
findings
on
this
issue
as
similar
activation
reductions
were
found
in
the
lateral
aspects
of
STS/MTG
for
the
different
tasks.
In
the
current
study,
we
attempted
to
further
address
whether
and
how
passive
vs.
active
task-related
effects
contribute
to
differ-
ent
activation
patterns
in
various
sub-regions
of
the
left
temporal
cortex
during
auditory
sentence
comprehension.
Of
these
sub-
regions,
the
middle
area
is
of
special
interest
because
functions
of
this
area
in
auditory
sentence
comprehension
have
not
been
clearly
specified,
although
it
is
implicated
as
an
important
part
of
the
ventral
pathway
subserving
semantic
processing
[8].
We
asked
participants
to
listen
to
normal
and
time-reversed
sentences
in
both
passive
and
active
task
conditions.
In
the
passive
listening
task,
participants
were
told
to
listen
to
sentences
carefully
with-
out
overt
responses,
and
in
the
active
comprehension
task,
they
were
instructed
to
comprehend
the
sentences
attentively
and
to
press
a
button
whenever
they
detected
an
anomalous
sentence.
We
first
adopted
probabilistic
independent
component
analysis
(ICA)
[2]
to
identify
the
functional
regions
of
interest
(ROIs)
in
order
to
avoid
the
issues
of
circularity
that
may
characterize
the
traditional
two-step
model-driven
identifications
of
ROIs
[15,29].
And
then
anatomical
parcellation
masks
from
Freesurfer
[7]
were
used
to
create
sub-ROIs
in
order
to
examine
the
possible
functional
het-
erogeneity
of
the
left
lateral
temporal
cortex
that
is
modulated
by
passive
and
active
task
demands.
2.
Materials
and
methods
2.1.
Participants
Twenty
undergraduate
and
postgraduate
students
(11
females)
with
a
mean
age
of
20.8
years
(range
18–25)
participated
in
this
study.
They
were
all
native
Chinese
speakers,
and
were
right-
handed
according
to
a
modified
Chinese
version
of
the
Edinburgh
Handedness
Inventory
[21].
No
participant
reported
a
history
of
a
hearing,
neurological
or
psychiatric
disorder.
Written
informed
consent
was
obtained
from
all
participants
after
they
were
given
a
complete
description
of
the
study
and
all
received
monetary
com-
pensation
for
their
participation.
The
study
was
approved
by
the
research
ethics
committee
at
Beijing
Normal
University’s
Imaging
Center
for
Brain
Research.
2.2.
Stimulus
material
Two
types
of
stimuli
were
used:
(1)
48
spoken
sentences
in
Mandarin
Chinese,
half
of
which
were
presented
in
the
passive
listening
task
and
the
other
half
in
the
active
comprehen-
sion
task,
and
(2)
time-reversed
versions
of
the
48
sentences.
For
the
first
type,
six
sentences
were
semantically
anomalous
(e.g.,
,
“The
sun
rises
from
the
west
everyday”)
for
both
the
passive
and
the
active
tasks,
intermixed
with
the
remaining
normal
sentences
presented
to
participants.
The
sentences
were
produced
by
a
female
Chinese
native
speaker
and
recorded
in
an
anechoic
chamber
at
a
sampling
rate
of
44.1
kHz.
Each
sentence
consisted
of
10
±
1
Chinese
syllables
with
an
aver-
age
duration
of
2289
ms
(SD
=
115
ms).
For
the
second
type,
the
intelligibility
of
the
speech
was
destroyed
but
the
overall
acous-
tic
complexity
was
preserved,
following
an
established
method
previously
used
by
other
researchers
[17,24].
All
stimuli
were
nor-
malized
for
average
root
mean
square
intensity
amplitude.
2.3.
Functional
magnetic
resonance
imaging
(fMRI)
procedure
and
data
acquisition
Two
runs
of
scanning
were
collected
from
each
participant,
one
for
the
passive
task
and
the
other
for
the
active
task.
The
pas-
sive
and
active
task
runs
were
counterbalanced
across
participants.
Each
run
consisted
of
six
36-s
sentence
blocks,
half
of
which
were
normal
sentence
blocks
and
half
time-reversed
sentence
blocks,
interleaved
with
seven
12-s
silent
resting
blocks.
Each
sentence
block
comprised
eight
sentences
and
before
each
sentence,
a
500-
ms
pure
tone
was
presented
as
a
cue.
The
normal
sentence
blocks
and
time-reversed
sentence
blocks
were
arranged
in
random
order
within
each
run.
The
passive
and
active
task
runs
each
lasted
302
s.
During
the
passive
task
run,
participants
were
required
to
listen
to
the
stimuli
carefully
without
any
explicit
response.
During
the
active
task
run,
they
were
instructed
to
comprehend
the
stimuli
and
make
a
judgment
by
pressing
a
button
when
they
heard
any
seman-
tically
anomalous
sentence.
This
anomaly
detection
paradigm
was
used
to
ensure
that
participants
did
comprehend
each
stimulus
carefully.
Semantically
anomalous
sentences
occurred
in
25%
of
the
total
trials
and
were
not
used
in
the
analysis
to
avoid
measuring
activations
associated
with
error
detection
[23].
Magnetic
resonance
images
were
obtained
on
a
Siemens
Mag-
netom
Trio
Tim
3-T
scanner
at
the
Beijing
normal
university’s
imaging
center
for
brain
research.
Foam
pads
were
used
to
keep
participant’s
head
still
as
far
as
possible
within
the
head
coil.
We
collected
two
sessions
of
fast
echo
planar
imaging
sequence
with
the
following
parameters:
TR
=
2
s,
TE
=
30
ms,
FA
=
90,
matrix
size
=
64
×
64,
voxel
size
=
3.125
×
3.125
×
4
mm3.
Each
session
had
151
volumes
and
each
volume
had
33
slices
to
cover
the
whole
brain.
After
two
EPI
scans,
a
high-resolution
3-dimension
anatomi-
cal
image
was
acquired
using
MPRAGE
sequence
in
axial
plane
with
the
following
parameters:
TR
=
2.53
s,
TE
=
3.45
ms,
FA
=
7,
matrix
size
=
256
×
256,
voxel
size
=
1
×
1
×
1
mm3.
During
the
scanning,
the
auditory
stimuli
were
presented
binaurally
via
MRI-compatible
headphone
SereneSound
(Resonance
Technology
Inc.,
Northridge,
CA,
USA),
which
reduced
the
background
scanner
noise
to
about
70
dB.
A
short
pre-test
scanning
was
administered
to
ensure
that
participants
could
hear
the
sentences
clearly
and
the
sound
volume
was
adjusted
to
a
comfortable
level
for
each
participant.
2.4.
Data
analysis
2.4.1.
Preprocessing
and
independent
component
analysis
Functional
image
preprocessing
was
conducted
using
the
AFNI
software
package
[4],
including
the
correction
for
slice
timing
and
head
motion,
alignment
between
functional
images
and
struc-
tural
images,
normalization,
spatial
smoothing
and
scaling.
In
order
to
increase
the
signal
to
noise
ratio,
the
passive
task
run
and
active
task
run
were
concatenated
together
for
each
participant,
and
an
average
concatenated
time
series
was
calculated
across
all
participants
as
the
input
data
for
the
following
ICA
analysis.
L.
Zhang
et
al.
/
Neuroscience
Letters
584
(2015)
351–355
353
A
participant-average
cortical
surface
model
was
created
by
using
Freesurfer
for
display
and
reference
[5,6].
Probabilistic
independent
component
analysis
was
carried
out
using
MELODIC
(Multivariate
Exploratory
Linear
Decomposition
into
Independent
Components)
Version
3.10,
part
of
FSL
(FMRIB’s
Software
Library,
www.fmrib.ox.ac.uk/fsl)
[2].
The
ICA
procedure
resulted
in
28
independent
components
across
the
whole
brain
gray
matter
regions,
each
containing
a
temporal
mode
represent-
ing
its
temporally
dynamic
changes
(time
series)
and
a
spatial
mode
which
consisted
of
voxels
having
the
representative
time
courses
in
its
temporal
mode.
In
order
to
identify
the
independent
com-
ponent
activities
related
to
the
stimuli,
simple
correlation
analyses
were
conducted
between
every
temporal
mode
of
all
the
28
ICs
and
every
ideal
time
series
of
all
types
of
stimuli
was
convolved
with
a
hypothetical
hemodynamic
response
function.
Only
independent
components
significantly
correlated
(p
<
105)
with
any
type
of
stimuli
were
considered
as
the
stimuli-related
components.
Mean-
while,
the
spatially
discrete
cortical
regions
were
identified
in
the
spatial
map
of
each
significantly
temporally-correlated
component
by
thresholding
the
amplitude
of
spatial
map
Z-score
(the
proba-
bility
of
representing
its
temporal
mode
in
that
spatial
map)
at
a
voxel-wise
threshold
(Z
>
3.72,
p
<
104),
corrected
at
cluster-wise
extent
(voxel
size
>
20,
2
×
2
×
2
mm,
p
<
0.005
corrected)
[19,31].
These
spatially
discrete
regions
were
then
used
as
masks
to
extract
regression
coefficient
for
each
stimulus
condition
from
traditional
individual
GLM
analysis.
2.4.2.
Effects
of
stimulus
and
task
analysis
In
order
to
analyze
the
effects
of
stimulus
and
task
within
the
ROIs
identified
by
the
ICA
method,
repeated-measure
ANOVAs
were
conducted
on
the
regression
coefficients
with
stimulus
and
task
as
fixed
factors
and
participant
as
a
random
factor.
Regres-
sion
coefficients
were
estimated
using
standard
GLM
in
AFNI.
Two
regressors
of
interest
for
each
sentence
condition
(normal
sen-
tence
and
time-reversed
sentence),
as
well
as
six
regressors
from
head
motion
parameters
and
one
regressor
from
responses
in
the
active
task
run,
were
modeled
in
GLM.
The
regression
coef-
ficients
(beta
values)
of
each
sentence
condition
for
every
task
were
obtained
from
individual
GLM
analysis.
A
strict
significance
threshold
(p
<
0.01)
for
any
main
effect
or
interaction
was
used
to
control
for
Type
I
error
due
to
the
multiple
tests.
In
order
to
exam-
ine
whether
functional
specialization
of
the
sub-areas
in
the
left
lateral
temporal
cortex
is
modulated
by
tasks,
the
anatomical
par-
cellation
masks
from
Freesurfer
[7]
were
applied
in
creating
the
sub-ROIs.
Then
the
differences
in
intelligibility
contrast
coefficients
were
calculated
for
each
sub-ROI
between
the
passive
and
active
tasks.
3.
Results
3.1.
Behavioral
data
For
the
active
task
runs,
behavioral
responses
of
all
the
participants
approached
ceiling-level
performance
(mean
accu-
racy
=
99%),
indicating
that
the
participants
maintained
vigilance
during
the
task
and
that
the
anomaly
detection
paradigm
success-
fully
directed
participants’
attention
to
semantic
integration
of
the
sentences.
3.2.
Intelligibility
and
task
effects
Of
the
twenty-eight
independent
components
decomposed
by
ICA
analysis,
five
components
were
identified
as
stimulus-
related
(significantly
correlated
with
any
type
of
sentences),
which
was
confirmed
by
t-tests
on
simple
correlations
between
time
modes
of
components
and
hemodynamic
response
function
for
Table
1
Independent
components
correlated
with
stimuli
(p
<
105).
IC#
Regions
EV
(%)
t-value
All
stimuli
Sentence
Reversed
3
HG
(b),
STG
(b),
STS
(b),
precentral
(r)
5.09
28.75
6.61
8.00
6
ATL
(b),
ITG
(b)
3.92
34.65
8.40
6.97
9
MTG
(b),
STS
(b),
precentral
(b),
SMA
(b),
MCC
(b)
IFG
p.tri
(l),
IFG
p.orb
(l),
MFG
(l),
Insula
lobe
(l),
3.39
9.52
13.45
27
SFG
(b),
calcarine
(b),
MCC
(r),
thalamus
(l),
SPL
(l),
MFG
(l),
MOG
(l)
1.56
10.02
28
ACC
(b),
insular
lobe
(b),
MFG
(b),
orbital
(r)
1.45
4.71
IC#:
independent
component
number;
EV:explained
variance;
HG:Heschl’s
gyrus;
STG:superior
temporal
gyrus;
STS:superior
temporal
sulcus;
ATL:anterior
temopral
lobe;
ITG:inferior
temoral
gyrus;
MTG:middle
temporal
gyrus;
SMA:supplementary
motor
area;
MCC:middle
cingulate
cortex;
IFG
p.tri:inferior
frontal
gyrus
par
triangularis;
IFG
p.orb:par
orbitalaris;
MFG:middle
frontal
gyrus;
SFG:superior
frontal
gyrus;
SPL:
superior
parietal
lobule;
MOG:middle
occipital
gyrus;
ACC:anterior
cingulate
cortex;
(l):left
hemisphere;
(r):
right
hemisphere;
(b):both
hemispheres;
-:no
significant
correlation.
Fig.
1.
Stimuli
by
task
ANOVA
analyses
within
all
stimuli-related
clusters.
354
L.
Zhang
et
al.
/
Neuroscience
Letters
584
(2015)
351–355
different
stimulus
models
(see
Table
1).
The
five
components
explained
15.41%
of
the
variance
in
the
data.
The
five
components
contained
in
total
31
discrete
clusters
dis-
tributing
over
the
bilateral
temporal
and
frontal
regions.
These
clusters
were
used
as
ROIs
to
further
examine
response
patterns
in
different
regions
with
regard
to
intelligibility
and
task
demands.
As
shown
in
Fig.
1,
a
large
cluster
in
the
left
lateral
temporal
cortex
and
two
clusters
in
the
bilateral
insular
lobe
showed
a
significant
main
effect
of
stimulus,
indicating
their
sensitivities
to
sentence
intelligibility
(normal
sentences
>
time-reversed
sentences)
in
both
passive
and
active
tasks.
In
the
bilateral
superior
temporal
gyri
including
Heschl’s
gyri,
there
was
only
a
significant
stimulus
by
task
interaction
effect
with
time-reversed
sentences
eliciting
stronger
activation
than
normal
sentences
in
the
passive
task
and
an
oppo-
site
pattern
of
activation
in
the
active
task.
A
cluster
in
the
dorsal
part
of
the
left
inferior
frontal
cortex
showed
a
significant
main
effect
of
task
(active
>
passive)
and
stimulus
by
task
interaction
with
normal
sentences
eliciting
stronger
activation
than
time-reversed
sentences
only
in
the
active
task.
Unlike
the
dorsal
activation
pat-
tern,
a
cluster
in
the
ventral
part
of
the
left
inferior
frontal
cortex
and
two
clusters
near
the
medial
superior
frontal
region
had
a
sig-
nificant
main
effect
of
stimulus
(normal
sentences
>
time-reversed
sentences)
and
stimulus
by
task
interaction
with
active
task
only
increasing
activation
of
the
normal
sentences
but
not
the
time-
reversed
sentences.
In
a
tiny
cluster
of
the
left
insular
cortex,
there
were
only
significant
stimulus
(normal
sentences
>
time-reversed
sentences)
and
task
(active
>
passive)
main
effects,
but
no
stimulus
by
task
interaction.
3.3.
Functional
heterogeneity
of
the
left
lateral
temporal
cortex
The
cluster
in
the
left
lateral
temporal
cortex
was
very
large
covering
a
wide
range
of
anterior,
middle,
and
posterior
temporal
regions.
In
order
to
find
out
whether
activation
patterns
of
vari-
ous
sub-regions
was
modulated
by
task
demands
during
auditory
sentence
comprehension,
we
created
sub-ROIs
by
using
the
left
STS
mask
from
Freesurfer
anatomical
parcellation
and
anterior-
posterior
gradient
mask
along
y-axis
direction
(Talairach
standard
space)
[28],
and
then
tested
task
by
sub-ROIs
interaction.
The
results
showed
that
the
sub-ROIs
by
task
interaction
was
significant
(F(7,133)
=
5.38,
p
<
0.001),
indicating
that
responses
to
sentence
intelligibility
in
these
sub-regions
were
differentially
modulated
by
passive/active
task
demands
although
all
the
sub-areas
in
the
large
cluster
discriminate
between
intelligible
and
unintelligible
sen-
tences.
Paired
sample
t-test
further
revealed
that
task-modulated
intelligibility
effect
was
only
observed
in
the
middle
parts
(y
coordi-
nates
of
the
sub-ROIs:
0.5
y
40.5;
t(19)
2.564,
p
<
0.05),
but
not
in
either
the
anterior
or
posterior
parts
of
the
left
lateral
tem-
poral
cortex
(anterior
part,
y
=
9.5;
t(19)
=
1.598,
p
>
0.1;
posterior
parts,
y
=
50.5,
60.5;
t(19)
=
1.054,
0.947,
p
>
0.3)
Fig.
2.
Fig.
2.
Task
effects
on
the
processing
of
intelligible
sentences
along
the
left
supe-
rior
temporal
sulcus.
Left:
sub-ROIs
with
each
marked
in
a
different
color;
right:
intelligibility
effect
with
the
y
scale
representing
beta
values.
4.
Discussion
Although
multiple
methodological
approaches
have
identified
the
left
lateral
temporal
cortex
as
one
of
the
most
important
areas
responsible
for
sentence-level
speech
comprehension,
there
remain
substantial
disagreements
in
the
literature
with
respect
to
the
precise
functions
of
its
sub-regions
[1,12,13,23,25,30].
Specif-
ically,
it
is
unclear
whether
and
how
functions
of
the
various
sub-regions
are
modulated
by
passive/active
task
demands
dur-
ing
auditory
sentence
comprehension.
To
address
this
issue,
we
combined
ICA
and
GLM
analyses
of
fMRI
data
to
elucidate
the
sub-
areas
of
the
left
lateral
temporal
cortex
respectively
involved
in
the
passive
and
active
processing
of
sentence
intelligibility.
Consistent
with
previous
research,
a
large
cluster
of
the
left
lateral
temporal
cortex
but
not
the
primary
auditory
cortex
showed
greater
activity
for
intelligible
relative
to
unintelligible
sentences,
reflecting
its
crit-
ical
role
in
sentence
comprehension.
Further
analyses
revealed
that
the
anterior
and
posterior
sub-regions
of
the
left
lateral
temporal
cortex
were
equally
activated
during
both
passive
and
active
com-
prehension,
whereas
the
middle
sub-regions
were
only
activated
during
the
active
task.
These
findings
indicate
that
the
anterior-
middle-posterior
sub-areas
of
the
left
lateral
temporal
cortex
are
differentially
affected
by
passive
and
active
task
demands
during
sentence
comprehension.
Previous
studies
have
provided
evidence
implicating
functional
separation
between
the
anterior
and
posterior
sub-regions
of
the
left
lateral
temporal
cortex
in
speech
intelligibility.
Evidence
from
semantic
dementia
has
led
some
researchers
to
emphasize
the
role
of
the
anterior
regions
in
word-level
semantic
processes
[25,27],
while
other
researchers
have
highlighted
the
role
of
posterior
regions
for
storage
of
lexical
representations
based
on
functional
imaging
data
[12,22].
Moreover,
the
anterior
regions
have
been
found
to
contribute
to
combinatorial
semantic
and
syntactic
com-
putations
because
the
anterior
but
not
the
posterior
areas
are
more
active
when
listening
to
sentences
than
to
word
lists
and
pseu-
doword
sentences
[9,14].
While
many
studies
have
examined
the
anterior
and
posterior
sub-regions,
few
have
investigated
the
func-
tional
role(s)
of
the
middle
regions
in
sentence
comprehension.
The
mid-STS/MTG
regions,
especially
in
the
left
hemisphere,
have
been
suggested
to
be
involved
in
phoneme
recognition
processes
and
represent
an
intermediate
processing
stage
in
which
combi-
nations
of
phonemes
activate
semantic
representations
of
single
words
[13,18].
In
contrast
to
studies
that
have
focused
on
the
functional
dif-
ferentiation
of
the
sub-regions
of
the
left
lateral
temporal
cortex
in
semantic,
syntactic
and
phonological
processes
per
se,
our
study
was
designed
to
provide
new
insights
into
the
functional
similar-
ity
or
specialization
of
the
anterior–middle–posterior
sub-areas.
We
demonstrated
their
different
activation
patterns
in
passive
and
active
sentence
comprehension
tasks.
On
the
one
hand,
a
small
anterior
region
and
large
posterior
regions
were
sensitive
to
sen-
tence
intelligibility
irrespective
of
task
demands,
which
implicates
the
essential
role
of
the
anterior
and
posterior
regions
in
sentence
comprehension.
On
the
other
hand,
a
large
portion
of
the
middle
regions
occupying
the
majority
of
the
STS/MTG
cluster
showed
intelligibility
effect
only
in
the
active
but
not
the
passive
task,
which
reflects
its
role
in
controlled
semantic
processing
of
sen-
tences.
It
is
clear
from
these
results
that
functional
similarity
and
specialization
of
these
sub-regions
is
task-dependent
during
sen-
tence
comprehension.
Our
results
suggest
when
investigating
the
neural
substrates
for
sentence
comprehension
and
integrating
the
data
with
the
literature,
researchers
need
to
take
into
account
task-dependent
functional
modulation
of
individual
brain
regions
and
possible
discrepancies
due
to
differences
in
the
tasks
of
inter-
est.
Given
the
mounting
evidence
pointing
to
different
roles
of
the
sub-regions
of
the
left
lateral
temporal
cortex
in
phonemic,
L.
Zhang
et
al.
/
Neuroscience
Letters
584
(2015)
351–355
355
semantic
and
syntactic
processing,
future
studies
can
be
designed
to
investigate
how
phonemic/semantic/syntactic
processes
are
differentially
susceptible
to
attentional
processing
demands
and
how
the
interactions
between
task
demands
and
linguistic
pro-
cessing
modulate
functional
similarity
and
specialization
of
these
sub-regions
in
order
to
elucidate
brain
systems
underlying
the
pro-
cessing
of
intelligible
speech.
5.
Conclusion
In
sum,
our
fMRI
data
indicate
the
existence
of
two
classes
of
sub-regions
in
the
left
lateral
temporal
cortex
that
are
dif-
ferentially
sensitive
to
sentence
intelligibility
depending
on
the
demands
of
the
listening
task.
First,
the
anterior
and
posterior
sub-regions
respond
similarly
to
intelligibility
of
spoken
sen-
tences
regardless
of
task
demands.
Second,
the
middle
sub-regions
selectively
respond
to
controlled
processing
of
intelligibility
that
requires
overt
behavioral
response.
Thus,
functional
heterogene-
ity
of
the
left
lateral
temporal
cortex
and
specialization
of
the
anterior–middle–posterior
sub-areas
are
modulated
by
task
demands
during
auditory
sentence
comprehension.
Acknowledgements
This
research
was
supported
by
Program
for
New
Century
Excel-
lent
Talents
in
University
(NCET-13-0691),
the
Natural
Science
Foundation
of
China
(31271082),
and
the
Natural
Science
Foun-
dation
of
Beijing
(7132119).
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