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Uncovering the Neuroanatomy of Core Language Systems Using Lesion-Symptom Mapping

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Recent studies have integrated noninvasive brain-imaging methods and advanced analysis techniques to study associations between the location of brain damage and cognitive deficits. By applying data-driven analysis methods to large sets of data on language deficits after stroke (aphasia), these studies have identified the cognitive systems that support language processing—phonology, semantics, fluency, and executive functioning—and their neural basis. Phonological processing is supported by dual pathways around the Sylvian fissure, a ventral speech-recognition component and a dorsal speech-production component; fluent sentence-level speech production relies on a more anterior frontal component, and the semantic system relies on a hub in the anterior temporal lobe and frontotemporal white-matter tracts. The executive function system was less consistently localized, possibly because of the kinds of brain damage tested in these studies. This review synthesizes the results of these studies, showing how they converge with contemporary models of primary systems that support perception, action, and conceptual knowledge across domains, and highlights some divergent findings and directions for future research.
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For more than 150 years, associations between the loca-
tion of brain damage and cognitive deficits have shed
light on the brain systems that are critical for human
cognition and behavior. Contemporary advances in
noninvasive neuroimaging methods and sophisticated
analysis techniques have made it possible to apply this
classic lesion method on a much finer anatomical scale.
Recent research on the neural basis of language using
large data sets from individuals with language deficits
after stroke (aphasia) has provided new insights into
the functional neuroanatomy of the human language
system by identifying the cognitive subsystems that sup-
port language processing and the neural basis of those
subsystems.
The modern version of the lesion method is called
lesion-symptom mapping (Bates etal., 2003; Rorden &
Karnath, 2004) and uses brain scans (MRI or computed
tomography) to localize brain damage (lesions) for each
individual in a group of participants with varying
degrees of deficit. For each small patch of the brain (a
voxel; typically a 1-mm × 1-mm × 1-mm or 3-mm ×
3-mm × 3-mm cube), a lesion-symptom mapping
analysis tests whether people with damage in that patch
have a more severe deficit than people who do not
have damage in that patch (because their brain damage
is in a different location). Lesion-symptom mapping has
been used to examine a wide variety of different cogni-
tive or behavioral symptoms on the basis of one of
three broad approaches. The clinical approach com-
pares participants with different clinical diagnoses, for
example, Broca’s aphasia versus Wernicke’s aphasia.
The theoretical approach compares performance on a
test or measure that is relevant to a particular theory
or hypothesis. For example, a theory about the process-
ing steps involved in word production might identify
speech sound errors, such as saying “girappe” instead
of “giraffe,” as a key symptom to use for lesion-symptom
mapping. The newest approach defines symptoms in a
787486CDPXXX10.1177/0963721418787486Mirman, ThyeCore Language Systems and Lesion-Symptom Mapping
research-article2018
Corresponding Author:
Daniel Mirman, University of Alabama at Birmingham, Department
of Psychology, CH 415, 1300 University Boulevard, Birmingham, AL
35294
E-mail: dan@danmirman.org
Uncovering the Neuroanatomy of
Core Language Systems Using
Lesion-Symptom Mapping
Daniel Mirman and Melissa Thye
Department of Psychology, University of Alabama at Birmingham
Abstract
Recent studies have integrated noninvasive brain-imaging methods and advanced analysis techniques to study
associations between the location of brain damage and cognitive deficits. By applying data-driven analysis methods
to large sets of data on language deficits after stroke (aphasia), these studies have identified the cognitive systems
that support language processing—phonology, semantics, fluency, and executive functioning—and their neural basis.
Phonological processing is supported by dual pathways around the Sylvian fissure, a ventral speech-recognition
component and a dorsal speech-production component; fluent sentence-level speech production relies on a more
anterior frontal component, and the semantic system relies on a hub in the anterior temporal lobe and frontotemporal
white-matter tracts. The executive function system was less consistently localized, possibly because of the kinds of
brain damage tested in these studies. This review synthesizes the results of these studies, showing how they converge
with contemporary models of primary systems that support perception, action, and conceptual knowledge across
domains, and highlights some divergent findings and directions for future research.
Keywords
language, speech, aphasia, neuroimaging, neuropsychology
2 Mirman, Thye
data-driven way—researchers start with many different
measures of cognitive performance and use a statistical
method that combines highly correlated measures to
identify a few scores that capture most of the variability
across all of the measures and likely reflect the underly-
ing cognitive systems. The long-term goal is for these
three approaches to converge: to develop cognitive
theories that explain the observed data-driven syn-
drome clusters in ways that are clinically relevant.
Recent studies from four independent research
groups1 using the data-driven approach have identified
four cognitive systems of language processing and their
associated brain regions: phonology, semantics, fluency,
and executive functions. Figure 1 illustrates how differ-
ent language tasks relate to these four identified sys-
tems. Language tasks rarely rely on a single system—even
seemingly simple language tasks, such as naming com-
mon objects, repeating words, or matching words to
pictures, draw on multiple systems. These systems are
complementary and interactive, working together to
perform everyday language tasks. A key unique contri-
bution of the data-driven approach is that performance
on multiple tasks is combined in order to overcome the
limitations of any single task, thus triangulating the
dissociable underlying cognitive systems. For example,
phonological-discrimination, repetition, and picture-
naming tasks each draw on phonology as well as other
systems, but data-driven methods provide a composite
score that reflects the common latent phonology factor
that underlies performance in all of those tasks and
removes the contribution of other systems. The sub-
stantial convergence across different laboratories, each
using a somewhat different battery of tests and testing
different groups of individuals with aphasia, reveals
that this organization of language processing is quite
robust.
Phonology
The first and most thoroughly described system is pho-
nology: the speech sounds that make up words. Pho-
nological processing is the intermediate step between
higher-level language processes, such as sentence- and
word-level processing, and lower-level auditory percep-
tion and articulation of language. Phonological deficits
include difficulty judging whether two syllables are the
Fluency
Word Finding
Speech Fluency
Naming
Reading & Writing
Repetition
Apraxia of Speech
Sentence Production
Sentence Comprehension
Word-to-Picture Matching
Working Memory
Phonological Discrimination
Semantic Matching
General Cognition
Phonological
Production
Phonological
Recognition Semantics
Executive
Functions
Fig. 1. Schematic depiction of the extent to which various language tasks and deficits (rows) rely on four language
systems (columns): fluency, phonology (separated here into phonological production and phonological recogni-
tion), semantics, and executive functions. Saturation of the cells shows the approximate strength of the relationship
between these systems and language tasks or deficits. Detailed results, including specific tests and factor loadings,
are provided in Table S1 at https://osf.io/6gnvb/.
Core Language Systems and Lesion-Symptom Mapping 3
same or different, difficulty judging whether two words
rhyme or not, and difficulty repeating a word or non-
word. Several of the reports also differentiated between
articulation-production of speech sounds and recogni-
tion of speech sounds. This distinction requires using
measures that are specific to deficits in phonological
production or perception rather than measures that
reflect both (e.g., repetition requires both correct per-
ception and production; see Table S1 at https://osf
.io/6gnvb/).
Deficits in the phonological-production subsystem
are associated with damage in a dorsal pathway primar-
ily involving inferior parietal and frontal regions (Fig.
2a, darker green). Deficits in the phonological-
recognition subsystem are associated with damage in
a ventral pathway extending from the posterior to ante-
rior superior temporal lobe (Fig. 2a, lighter green). This
dual-stream architecture of the phonological system
broadly aligns with the contemporary view of the com-
putational neuroanatomy of speech processing (Hickok
& Poeppel, 2007). These two subsystems interact and
work together: The goal of speech production is par-
ticular speech sounds, so the speech-perception system
plays an important role in setting speech-production
targets and monitoring articulation (Hickok, 2012).
When speech perception and production were not dis-
sociated, a general phonological factor was identified
and associated with damage along the superior
temporal sulcus, including Heschl’s gyrus and planum
temporale. This region, where the two phonological
subsystems come into contact, may be critical for the
auditory-motor transformations involved in setting audi-
tory targets and monitoring speech programs.
Semantics
The second system is semantics: conceptual knowledge
about objects and the meanings of words. Semantic
knowledge about an object includes what that object
looks and sounds like, how it acts and how we act on
or with it, the emotions it evokes in us, and so forth.
This knowledge is distributed across modality-specific
perceptual, motor, and emotional systems and inte-
grated in convergence zones or hubs (Barsalou, Simmons,
Barbey, & Wilson, 2003; Meyer & Damasio, 2009; Rogers
etal., 2004). Semantic deficits are most often exhibited
in comprehension tasks such as matching words or sen-
tences to pictures or judging whether two words are
synonyms, but they can also affect nonverbal tasks such
as matching related pictures (e.g., whether a pyramid
goes with a palm tree or a pine tree).
Deficits in the semantic system are associated with
anterior temporal lobe damage (Fig. 2a, yellow), includ-
ing the temporal pole and the midanterior portions of
the middle and superior temporal gyri. For comprehen-
sion tasks, this is the continuation of the ventral stream:
ab
Fig. 2. Brain regions critical for language processing. The neuroanatomy of core language systems (a) is shown on the lateral surface of
the left hemisphere: semantics (yellow), fluency (red), and phonology (green; lighter green shows the phonological recognition system,
whereas darker green shows the phonological production system; the two systems overlap in the posterior portions of the Sylvian fissure
and the superior temporal gyrus). White-matter tracts particularly important for language processing are shown in (b): arcuate fasciculus
(red), inferior fronto-occipital fasciculus (green), and uncinate fasciculus (blue). A more detailed description of the brain regions involved
in each system, including peak voxel coordinates, is provided in Table S2 at https://osf.io/6gnvb/.
4 Mirman, Thye
The progression from posterior to anterior temporal
regions corresponds to the progression from recogniz-
ing speech sounds and syllables to recognizing words
and comprehending what those words mean (see also
DeWitt & Rauschecker, 2012). This progression aligns
with extensive evidence that the anterior temporal lobe
is a critical hub for integrating semantic knowledge
that is distributed across modality-specific systems
(Binder & Desai, 2011; Lambon Ralph, Jefferies,
Patterson, & Rogers, 2017; Patterson, Nestor, & Rogers,
2007).
Poststroke semantic deficits are also associated with
damage to white-matter pathways, particularly the infe-
rior fronto-occipital fasciculus and the uncinate fascicu-
lus (Fig. 2b), which appear to be critical for effective
functioning of the distributed semantic system. Damage
to white-matter bottlenecks—regions where multiple
tracts come together—is particularly disruptive (Griffis,
Nenert, Allendorfer, & Szaflarski, 2017; Mirman, Chen,
etal., 2015; Mirman, Zhang, Wang, Coslett, & Schwartz,
2015). This is, presumably, because these bottlenecks
are locations where even a small amount of damage
can disrupt multiple tracts, producing broad semantic
network dysfunction (for a computational approach see
L. Chen, Lambon Ralph, & Rogers, 2017).
Fluency
The third system, which was identified in a subset of
the studies, is fluency: the ability to produce connected
speech rapidly and smoothly. This requires rapid coor-
dination of multiple processes (e.g., Nozari & Faroqi-Shah,
2017; Wilson et al., 2010), including articulatory-
phonological planning and execution, which corre-
sponds to the phonological production system discussed
above, and retrieving words to fit the semantic and
syntactic constraints, which corresponds to the seman-
tic system discussed above (see also Q. Chen, Middleton,
& Mirman, 2018). The data-driven studies identified a
distinct fluency system that corresponds to planning
and structuring sentences, including syntax and work-
ing or short-term memory. People with deficits in this
sentence-level planning and structuring system tend to
produce shorter utterances, slower speech (fewer words
per minute), and less grammatically complex sentences
(e.g., fewer embedded clauses). They also tend to make
more syntactic omissions, such as omitting closed class
words (determiners, prepositions, etc.) or producing
incomplete sentences. However, sentence-comprehension
deficits are not strongly associated with this system, sug-
gesting that it is more closely related to sentence-level
planning and execution rather than general syntactic
processing (see also Linebarger, Schwartz, & Saffran,
1983; Thothathiri, Kimberg, & Schwartz, 2012).
Fluency deficits are associated with damage in the
insula and inferior frontal and precentral areas (Fig. 2a,
red). This is anterior to the region associated with pho-
nological production deficits and may reflect a higher
level of speech-production planning and coordination,
that is, sentence- or utterance-level planning rather than
word- or syllable-level planning or articulation of indi-
vidual speech sounds. Related research also suggests
that fluency deficits are associated with middle frontal
gyrus damage and frontal white-matter damage
(Basilakos etal., 2014; Catani etal., 2013; Fridriksson,
Guo, Fillmore, Holland, & Rorden, 2013; Rogalski etal.,
2011; Wilson etal., 2010), including the anterior seg-
ment of the arcuate fasciculus (Fig. 2b, red) and the
frontal aslant tract, which connects superior and inferior
portions of the frontal lobe. The frontoparietal speech-
production system is neuroanatomically similar to the
frontoparietal system for the production of skilled tool-use
actions (e.g., Brandi, Wohlschlager, Sorg, & Hermsdorfer,
2014; Johnson-Frey, 2004). Anterior-to-posterior progres-
sion within the speech-production planning system aligns
with general theories about the hierarchical organization
of frontal planning systems (Botvinick, 2008) in which
more anterior regions are responsible for higher-level
planning and maintenance of tasks and goals (e.g., making
a cup of coffee, or producing a full sentence or narrative)
and more posterior regions are responsible for lower-level
planning of individual actions involved in accomplishing
those tasks or goals (e.g., scooping coffee grounds into
the coffee maker or sugar into the cup, or saying a single
word).
Executive Functions
The final factor, which was identified in a subset of the
studies, is executive functioning: cognitive abilities,
such as planning, reasoning, cognitive flexibility, cogni-
tive control, and selective attention (e.g., Jurado &
Rosselli, 2007), that are not specific to language but are
important for language processing. Lacey, Skipper-
Kallal, Xing, Fama, and Turkeltaub (2017) reported that
executive function deficits were associated with damage
in middle frontal gyrus (dorsolateral prefrontal cortex)
and posterior frontal white matter, but the other studies
did not converge on a consistent lesion correlate. This
may be because (a) some of the regions that are critical
to executive functions are outside the territory of the
middle cerebral artery, so they are unlikely to be dam-
aged by strokes that affect language processing, and
(b) the executive function system is distributed across
both hemispheres of the brain, so damage within the
left hemisphere may not be sufficiently strongly associ-
ated with executive function deficits. Thus, executive
functions may be impaired in poststroke aphasia, but
Core Language Systems and Lesion-Symptom Mapping 5
the relationship between executive functions and lan-
guage remains unclear (see also Fedorenko, 2014).
Conclusions and Future Directions
Two systems form the core of spoken language: pho-
nology and semantics. The phonological system has
two subcomponents organized in dual pathways around
the Sylvian fissure, a dorsal-stream production compo-
nent and a ventral-stream recognition component,
which is consistent with contemporary dual-stream
models of speech recognition and production (Hickok,
2012; Hickok & Poeppel, 2007). The semantic system
is broadly distributed and relies on a hub in the anterior
temporal lobe and frontotemporal white-matter tracts,
which is consistent with the current theories and neu-
rocomputational models of semantic cognition (Lambon
Ralph etal., 2017). Fluent speech-production deficits
are primarily associated with frontal damage, anterior
to the regions where damage is associated with single-
word phonological-production deficits. This suggests
that language production may rely on the same com-
putational and neural systems that support other kinds
of hierarchical, sequential action planning and execu-
tion (Botvinick, 2008; Hickok, 2012; see also Weiss
etal., 2016). A key overarching theme is that language
processing is situated in the context of primary systems
that support perception, action, and conceptual knowl-
edge across domains.
Two psycholinguistic constructs have not emerged in
these data-driven lesion-symptom mapping studies. One
is the lexicon—a mental inventory of words. It may be
that the lexicon is an emergent property of interactions
between phonological and semantic systems rather than
a discrete system. The other is syntax—knowledge of a
language’s grammatical rules. Although often associated
with nonfluent aphasia, fluency (rapid and smooth pro-
duction of connected speech) is neither necessary nor
sufficient for syntax. In fact, substantial syntax knowl-
edge is preserved in so-called agrammatism (e.g., Line-
barger etal., 1983), and syntax deficits in aphasia may
be a result of a more general reduction in cognitive
resources (e.g., Caplan, Michaud, & Hufford, 2013).
The clinical relevance of data-driven lesion-symptom
mapping studies has yet to be established, although there
is potential for improved diagnosis, stronger integration
with neural systems, and clearer guidance for treatment
selection. Ideally, a new data-driven classification system
would make contact with the outcome that is of utmost
importance for people with aphasia and for their clini-
cians—functional communication—but it is not yet clear
how these systems relate to the ability to communicate
in real-world settings. In addition, data-driven methods
are necessarily limited by the data that are driving them.
Pragmatic aspects of language and communication were
not assessed in any of these studies, and fluency, written
language, and executive functions were only minimally
assessed, and not in all of the studies.
Finally, lesion-symptom mapping methods are con-
tinuing to develop and evolve. A new generation of
multivariate methods captures the contributions of mul-
tiple brain regions more effectively (Pustina, Avants,
Faseyitan, Medaglia, & Coslett, 2018; Zhang, Kimberg,
Coslett, Schwartz, & Wang, 2014). Updating the classic
lesion method, contemporary lesion-symptom mapping
leverages advanced neuroimaging, statistical, and
machine-learning techniques to identify brain regions
that are critical for specific cognitive functions. Data-
driven lesion-symptom mapping has recently revealed
the core systems that support language function and
their neural basis and informed theoretical accounts of
language in ways that are clinically meaningful.
Recommended Reading
Dronkers, N. F., Ivaonova, M. V., & Baldo, J. V. (2017). What
do language disorders reveal about brain-language rela-
tionships? From classic models to network approaches.
Journal of the International Neuropsychological Society,
23, 741–754. A review of how language disorders have
elucidated the neural basis of language.
Hickok, G., & Small, S. L. (Eds.). (2016). Neurobiology of lan-
guage. San Diego, CA: Academic Press. An encyclopedic
collection of short chapters covering the neurobiology
of language.
Karnath, H.-O., Sperber, C., & Rorden, C. (2018). Mapping
human brain lesions and their functional consequences.
NeuroImage, 165, 180–189. doi:10.1016/j.neuroim
age.2017.10.028. A somewhat more technical overview of
lesion-symptom mapping.
Mesulam, M.-M., Rogalski, E. J., Wieneke, C., Hurley, R. S.,
Geula, C., Bigio, E. H., . . . Weintraub, S. (2014). Primary
progressive aphasia and the evolving neurology of the
language network. Nature Reviews Neurology, 10, 554–
569. doi:10.1038/nrneurol.2014.159. A review of progres-
sive language deficits that result from neurodegenerative
diseases (primary progressive aphasia), which offers a
different perspective on the neuroanatomy of language.
Wilson, S. M. (2017). Lesion-symptom mapping in the study
of spoken language understanding. Language, Cognition
and Neuroscience, 32, 891–899. doi:10.1080/23273798.201
6.1248984. An accessible overview of the lesion-symptom
mapping method.
Action Editor
Randall W. Engle served as action editor for this article.
ORCID iDs
Daniel Mirman https://orcid.org/0000-0001-5472-0220
Melissa Thye https://orcid.org/0000-0002-6383-6361
6 Mirman, Thye
Acknowledgments
A preliminary version of this summary was presented at the
2016 American Speech-Language-Hearing Association Con-
vention (Philadelphia, Pennsylvania). We thank Peter Turkel-
taub, Ajay Halai, and Matthew Lambon Ralph for providing
the statistical maps of their results, which allowed us to more
accurately describe their findings.
Declaration of Conflicting Interests
The author(s) declared that there were no conflicts of interest
with respect to the authorship or the publication of this
article.
Funding
Preparation of this article was supported by the University of
Alabama at Birmingham.
Note
1. The four research groups were based in Philadelphia,
Pennsylvania (Mirman, Chen, etal., 2015; Mirman, Zhang, etal.,
2015); Columbia and Charleston, South Carolina (Fridriksson
et al., 2016, 2018); Washington, DC (Lacey etal., 2017); and
Manchester, England (Butler, Lambon Ralph, & Woollams, 2014;
Halai, Woollams, & Lambon Ralph, 2017).
References
Barsalou, L. W., Simmons, W. K., Barbey, A. K., & Wilson, C. D.
(2003). Grounding conceptual knowledge in modality-
specific systems. Trends in Cognitive Sciences, 7, 84–91.
Basilakos, A., Fillmore, P. T., Rorden, C., Guo, D., Bonilha,
L., & Fridriksson, J. (2014). Regional white matter dam-
age predicts speech fluency in chronic post-stroke apha-
sia. Frontiers in Human Neuroscience, 8, Article 845.
doi:10.3389/fnhum.2014.00845
Bates, E., Wilson, S. M., Saygin, A. P., Dick, F., Sereno, M. I.,
Knight, R. T., & Dronkers, N. F. (2003). Voxel-based
lesion-symptom mapping. Nature Neuroscience, 6, 448–
450. doi:10.1038/nn1050
Binder, J. R., & Desai, R. H. (2011). The neurobiology of
semantic memory. Trends in Cognitive Sciences, 15, 527–
536. doi:10.1016/j.tics.2011.10.001
Botvinick, M. M. (2008). Hierarchical models of behavior
and prefrontal function. Trends in Cognitive Sciences, 12,
201–208. doi:10.1016/j.tics.2008.02.009
Brandi, M.-L., Wohlschlager, A., Sorg, C., & Hermsdorfer, J.
(2014). The neural correlates of planning and executing
actual tool use. The Journal of Neuroscience, 34, 13183–
13194. doi:10.1523/JNEUROSCI.0597-14.2014
Butler, R. A., Lambon Ralph, M. A., & Woollams, A. M. (2014).
Capturing multidimensionality in stroke aphasia: Mapping
principal behavioral component to neural structures.
Brain, 137, 3248–3266.
Caplan, D., Michaud, J., & Hufford, R. (2013). Dissociations
and associations of performance in syntactic compre-
hension in aphasia and their implications for the nature
of aphasic deficits. Brain & Language, 127, 21–33.
doi:10.1016/j.bandl.2013.07.007
Catani, M., Mesulam, M. M., Jakobsen, E., Malik, F., Martersteck,
A., Wieneke, C., . . . Rogalski, E. J. (2013). A novel frontal
pathway underlies verbal fluency in primary progressive
aphasia. Brain, 136, 2619–2628. doi:10.1093/brain/awt163
Chen, L., Lambon Ralph, M. A., & Rogers, T. T. (2017). A
unified model of human semantic knowledge and its
disorders. Nature Human Behaviour, 1, Article 0039.
doi:10.1038/s41562-016-0039
Chen, Q., Middleton, E., & Mirman, D. (2018). Words fail:
Lesion-symptom mapping of errors of omission in post-
stroke aphasia. Journal of Neuropsychology. Advance
online publication. doi:10.1111/jnp.12148
DeWitt, I., & Rauschecker, J. P. (2012). Phoneme and word
recognition in the auditory ventral stream. Proceedings of
the National Academy of Sciences, USA, 109, E505–E514.
doi:10.1073/pnas.1113427109
Fedorenko, E. (2014). The role of domain-general cogni-
tive control in language comprehension. Frontiers in
Psychology, 5, Article 335. doi:10.3389/fpsyg.2014.00335
Fridriksson, J., den Ouden, D.-B., Hillis, A. E., Hickok, G.,
Rorden, C., Basilakos, A., . . . Bonilha, L. (2018). Anatomy
of aphasia revisited. Brain. Advance online publication.
doi:10.1093/brain/awx363
Fridriksson, J., Guo, D., Fillmore, P. T., Holland, A., & Rorden,
C. (2013). Damage to the anterior arcuate fasciculus pre-
dicts non-fluent speech production in aphasia. Brain,
136, 3451–3460. doi:10.1093/brain/awt267
Fridriksson, J., Yourganov, G., Bonilha, L., Basilakos, A.,
Den Ouden, D.-B., & Rorden, C. (2016). Revealing the
dual streams of speech processing. Proceedings of the
National Academy of Sciences, USA, 113, 15108–15113.
doi:10.1073/pnas.1614038114
Griffis, J. C., Nenert, R., Allendorfer, J. B., & Szaflarski, J. P.
(2017). Damage to white matter bottlenecks contrib-
utes to language impairments after left hemispheric
stroke. NeuroImage: Clinical, 14, 552–565. doi:10.1016/j
.nicl.2017.02.019
Halai, A. D., Woollams, A. M., & Lambon Ralph, M. A.
(2017). Using principal component analysis to capture
individual differences within a unified neuropsychologi-
cal model of chronic post-stroke aphasia: Revealing the
unique neural correlates of speech fluency, phonology
and semantics. Cortex, 86, 275–289. doi:10.1016/j.cortex
.2016.04.016
Hickok, G. S. (2012). Computational neuroanatomy of speech
production. Nature Reviews Neuroscience, 13, 135–145.
doi:10.1038/nrn3158
Hickok, G. S., & Poeppel, D. (2007). The cortical organiza-
tion of speech processing. Nature Reviews Neuroscience,
8, 393–402.
Johnson-Frey, S. H. (2004). The neural bases of complex tool
use in humans. Trends in Cognitive Sciences, 8, 71–78.
doi:10.1016/j.tics.2003.12.002
Jurado, M. B., & Rosselli, M. (2007). The elusive nature of
executive functions: A review of our current understand-
ing. Neuropsychology Review, 17, 213–233. doi:10.1007/
s11065-007-9040-z
Lacey, E. H., Skipper-Kallal, L. M., Xing, S., Fama, M. E.,
& Turkeltaub, P. E. (2017). Mapping common aphasia
Core Language Systems and Lesion-Symptom Mapping 7
assessments to underlying cognitive processes and their
neural substrates. Neurorehabilitation & Neural Repair,
31, 442–450. doi:10.1177/1545968316688797
Lambon Ralph, M. A., Jefferies, E., Patterson, K., & Rogers, T. T.
(2017). The neural and computational bases of seman-
tic cognition. Nature Reviews Neuroscience, 18, 42–55.
doi:10.1038/nrn.2016.150
Linebarger, M. C., Schwartz, M. F., & Saffran, E. M. (1983). Sensitivity
to grammatical structure in so-called agrammatic aphasics.
Cognition, 13, 361–392. doi:10.1016/0010-0277(83)90015-X
Meyer, K., & Damasio, A. (2009). Convergence and diver-
gence in a neural architecture for recognition and mem-
ory. Trends in Neurosciences, 32, 376–382. doi:10.1016/j
.tins.2009.04.002
Mirman, D., Chen, Q., Zhang, Y., Wang, Z., Faseyitan, O. K.,
Coslett, H. B., & Schwartz, M. F. (2015). Neural organization
of spoken language revealed by lesion-symptom
mapping. Nature Communications, 6, Article 6762. doi:10
.1038/ncomms7762
Mirman, D., Zhang, Y., Wang, Z., Coslett, H. B., & Schwartz,
M. F. (2015). The ins and outs of meaning: Behavioral
and neuroanatomical dissociation of semantically-driven
word retrieval and multimodal semantic recognition in
aphasia. Neuropsychologia, 76, 208–219. doi:10.1016/j
.neuropsychologia.2015.02.014
Nozari, N., & Faroqi-Shah, Y. (2017). Investigating the origin
of nonfluency in aphasia: A path modeling approach
to neuropsychology. Cortex, 95, 119–135. doi:10.1016/j
.cortex.2017.08.003
Patterson, K. E., Nestor, P. J., & Rogers, T. T. (2007). Where
do you know what you know? The representation of
semantic knowledge in the human brain. Nature Reviews
Neuroscience, 8, 976–987. doi:10.1038/nrn2277
Pustina, D., Avants, B. B., Faseyitan, O. K., Medaglia, J., &
Coslett, H. B. (2018). Improved accuracy of lesion to
symptom mapping with multivariate sparse canonical cor-
relations. Neuropsychologia, 115, 154–166. doi:10.1016/j
.neuropsychologia.2017.08.027
Rogalski, E. J., Cobia, D., Harrison, T. M., Wieneke, C.,
Thompson, C. K., Weintraub, S., & Mesulam, M.-M. (2011).
Anatomy of language impairments in primary progres-
sive aphasia. The Journal of Neuroscience, 31, 3344–3350.
doi:10.1523/JNEUROSCI.5544-10.2011
Rogers, T. T., Lambon Ralph, M. A., Garrard, P., Bozeat,
S., McClelland, J. L., Hodges, J. R., & Patterson, K. E.
(2004). Structure and deterioration of semantic memory:
A neuropsychological and computational investigation.
Psychological Review, 111, 205–235.
Rorden, C., & Karnath, H.-O. (2004). Using human brain
lesions to infer function: A relic from a past era in the
fMRI age? Nature Reviews Neuroscience, 5, 813–819.
Thothathiri, M., Kimberg, D. Y., & Schwartz, M. F. (2012).
The neural basis of reversible sentence comprehension:
Evidence from voxel-based lesion symptom mapping in
aphasia. Journal of Cognitive Neuroscience, 24, 212–222.
doi:10.1162/jocn_a_00118
Weiss, P. H., Ubben, S. D., Kaesberg, S., Kalbe, E., Kessler,
J., Liebig, T., & Fink, G. R. (2016). Where language meets
meaningful action: A combined behavior and lesion anal-
ysis of aphasia and apraxia. Brain Structure & Function,
221, 563–576. doi:10.1007/s00429-014-0925-3
Wilson, S. M., Henry, M. L., Besbris, M., Ogar, J. M., Dronkers,
N. F., Jarrold, W., . . . Gorno-Tempini, M. L. (2010). Connected
speech production in three variants of primary progres-
sive aphasia. Brain, 133, 2069–2088. doi:10.1093/brain/
awq129
Zhang, Y., Kimberg, D. Y., Coslett, H. B., Schwartz, M. F., &
Wang, Z. (2014). Multivariate lesion-symptom mapping
using support vector regression. Human Brain Mapping,
35, 5861–5876. doi:10.1002/hbm.22590
... Data-driven statistical methods like factor analysis and principal components analysis (PCA) use correlations among measures to group them into latent factors or components and calculate composite scores for those factors. Several studies have focused on measures of connected speech and used factor analysis to identify clusters of measures that suggest common underlying components 5,[35][36][37] (for recent reviews of factor analysis approaches in contemporary aphasia research see 38,39 ). A key factor analysis study 5 of spontaneous speech in 274 individuals with aphasia identified 6 latent factors that accounted for 52% of the variance, with substantial overlap between some of the factors. ...
... Several recent studies have applied this approach and identified consistent dissociations between fluency, semantic, phonological, and executive deficits 39 . In these studies, the fluency components had high loadings from composite measures of spontaneous speech production (e.g., fluency scores from aphasia assessments such as the Western Aphasia Battery and Comprehensive Aphasia Test) and coarse measures of fluency (such as words per minute and mean length of utterance). ...
... We sought to balance detailed measures of narrative speech with key anchors (aphasia severity, semantic deficit, phonological deficit). The present study included fewer grammatical measures than prior PCA studies of QPA and fluency35,37,57 , but compared to other PCA studies of aphasia39,41 it included more grammatical measures and fewer other measures. This fills an important gap in the literature by identifying how aspects of connected speech production are related to or independent of those key anchors. ...
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Deficits in fluent speech production following left hemisphere stroke are a central concern because of their impact on patients’ lives and the insight they provide about the neural organization of language processing. Fluent speech production requires the rapid coordination of phonological, semantic, and syntactic processing, so this study examined how deficits in connected speech relate to these language sub-systems. Behavioural data (N = 69 participants with aphasia following left hemisphere stroke) consisted of a diverse and comprehensive set of narrative speech production measures and measures of overall severity, semantic deficits, and phonological deficits. These measures were entered into a principal component analysis with bifactor rotation – a latent structure model where each item loads on a general factor that reflects what is common among the items, and orthogonal factors that explain variance not accounted for by the general factor. Lesion data were available for 58 of the participants and each factor score was analysed with multivariate lesion-symptom mapping. Effects of connectivity disruption were evaluated using robust regression with tract disconnection or graph theoretic measures of connectivity as predictors. The principal component analysis produced a four-factor solution that accounted for 70.6% of the variance in the data, with a general factor corresponding to overall severity and length and complexity of speech output (Complexity factor), a Lexical Syntax factor, and independent factors for Semantics and Phonology. Deficits in Complexity of speech output were associated with a large temporo-parietal region, similar to overall aphasia severity. The Lexical Syntax factor was associated with damage in a relatively small set of fronto-parietal regions, that may reflect recruitment of control systems to support retrieval and correct usage of lexical items that primarily serve a syntactic rather than semantic function. Tract-based measures of connectivity disruption were not statistically associated with the deficit scores after controlling for overall lesion volume. Language network efficiency and average clustering coefficient within the language network were significantly associated with deficit scores after controlling for overall lesion volume. These results highlight overall severity as the critical contributor to fluent speech in post-stroke aphasia, with a dissociable factor corresponding to Lexical Syntax.
... Despite this, People With Aphasia (PWA) rarely receive extensive cognitive assessment, meaning data on individual cognitive skills in this patient population is scarce. Evidence suggests that executive functions may be impaired in post-stroke aphasia, but the relationship between language and executive functions is difficult to tease apart (see Fedorenko, 2014) and studies have not been able to converge on the underlying lesions correlates of executive functions in PWA (Mirman and Thye, 2018). ...
... The neural basis of aphasia is commonly explored by linking behavioural assessment with brain lesion data. This has resulted in some distinct brain-behaviour relationships for various language domains, however studies have not been able to converge on a consistent lesion correlate of higher-level executive functions (Mirman and Thye, 2018), either because non-language assessments were not included (Mirman et al., 2015;Kümmerer et al., 20132013) or were only included in a limited scope (Butler et al., 20142014;Halai et al., 2017;Tochadse et al., 2018) though see Lacey et al. (2017). More recently, the neural correlates of non-language cognitive domains in aphasia have been explored by Schumacher et al. (2019Schumacher et al. ( , 2020 and Alyahya et al. (2020), whose findings are discussed below. ...
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Aphasia is an acquired disorder caused by damage, most commonly due to stroke, to brain regions involved in speech and language. While language impairment is the defining symptom of aphasia, the co-occurrence of non-language cognitive deficits and their importance in predicting rehabilitation and recovery outcomes is well documented. However, people with aphasia (PWA) are rarely tested on higher-order cognitive functions, making it difficult for studies to associate these functions with a consistent lesion correlate. Broca’s area is a particular brain region of interest that has long been implicated in speech and language production. Contrary to classic models of speech and language, cumulative evidence shows that Broca’s area and surrounding regions in the left inferior frontal cortex (LIFC) are involved in, but not specific to, speech production. In this study we aimed to explore the brain-behaviour relationships between tests of cognitive skill and language abilities in thirty-six adults with long-term speech production deficits caused by post-stroke aphasia.Our findings suggest that non-linguistic cognitive functions, namely executive functions and verbal working memory, explain more of the behavioural variance in PWA than classical language models imply. Additionally, lesions to the LIFC, including Broca’s area, were associated with non-linguistic executive (dys)function, suggesting that lesions to this area are associated with non-language-specific higher-order cognitive deficits in aphasia. Whether executive (dys)function – and its neural correlate in Broca’s area – contributes directly to PWA’s language production deficits or simply co-occurs with it, adding to communication difficulties, remains unclear. These findings support contemporary models of speech production that place language processing within the context of domain-general perception, action and conceptual knowledge. An understanding of the covariance between language and non-language deficits and their underlying neural correlates will inform better targeted aphasia treatment and outcomes.
... Nowadays, researchers can map behavioral symptoms to brain lesions in vivo, due to high-quality structural magnetic resonance imaging. This approach, called lesion-symptom mapping (LSM, [25][26][27]), can be further combined with electrophysiological methods to provide a comprehensive account of plastic reorganization following focal damage. ...
Chapter
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... Мы предполагаем, что одним из механизмов нарушения слухового восприятия у детей с умственной отсталостью является задержка функционального созревания структур мозга, в первую очередь -левого полушария. Восприятие и воспроизведение речи задействуют множество мозговых структур, включенных в сеть с ядром, состоящим из трех анатомических образований: верхняя височная извилина (извилина Гешля, зона Вернике), медиальная височная извилина, нижняя лобная извилина (зона Брока) (Friederici, 2011;Marslen-Wilson & Welsh, 1978;Mirman & Thye, 2018). При этом указанные структуры связаны пучками, образующими вентральный и дорсальный пути (Keitel & Gross, 2016). ...
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Theories expounding the neural relationship between speech and singing range from sharing neural circuitry, to relying on opposite hemispheres. Yet, hodological studies exploring their shared and distinct neural networks remain scarce. In this study, we combine a white matter connectometry approach together with comprehensive and naturalistic appraisal of verbal expression during spoken language production and singing in a sample of individuals with post-stroke aphasia. Our results reveal that both spoken language production and singing are mainly supported by the left hemisphere language network and projection pathways. However, while spoken language production mostly engaged dorsal and ventral streams of speech processing, singing was associated primarily with the left ventral stream. These findings provide evidence that speech and singing share core neuronal circuitry within the left hemisphere, while distinct ventral stream contributions explain frequently observed dissociations in aphasia. Moreover, the results suggest prerequisite biomarkers for successful singing-based therapeutic interventions.
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Lesion-symptom mapping (LSM) studies have revealed brain areas critical for naming, typically finding significant associations between damage to left temporal, inferior parietal and inferior fontal regions and impoverished naming performance. However, specific subregions found in the available literature vary. Hence, the aim of this study was to perform a systematic review and meta-analysis of published lesion-based findings, obtained from studies with unique cohorts investigating brain areas critical for accuracy in naming in stroke patients at least 1 month post-onset. An anatomic likelihood estimation (ALE) meta-analysis of these LSM studies was performed. Ten papers entered the ALE meta-analysis, with similar lesion coverage over left temporal and left inferior frontal areas. This small number is a major limitation of the present study. Clusters were found in left anterior temporal lobe, posterior temporal lobe extending into inferior parietal areas, in line with the arcuate fasciculus, and in pre- and postcentral gyri and middle frontal gyrus. No clusters were found in left inferior frontal gyrus. These results were further substantiated by examining five naming studies that investigated performance beyond global accuracy, corroborating the ALE meta-analysis results. The present review and meta-analysis highlight the involvement of left temporal and inferior parietal cortices in naming, and of mid to posterior portions of the temporal lobe in particular in conceptual-lexical retrieval for speaking.
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Impaired object naming is a core deficit in post-stroke aphasia, which can manifest as errors of commission – producing an incorrect word or a non-word – or as errors of omission – failing to attempt to name the object. Detailed behavioural, computational, and neurological investigations of errors of commission have played a key role in the development of neurocognitive models of word production. In contrast, the neurocognitive basis of omission errors is radically underspecified despite being a prevalent phenomenon in aphasia and other populations. The prevalence of omission errors makes their neurocognitive basis important for characterizing an individual's deficits and, ideally, for personalizing treatment and evaluating treatment outcomes. This study leveraged established relationships between lesion location and errors of commission to investigate omission errors in picture naming. Omission error rates from the Philadelphia Naming Test for 123 individuals with post-stroke aphasia were analysed using support vector regression lesion-symptom mapping. Omission errors were most strongly associated with left frontal and mid-anterior temporal lobe lesions. Computational model analysis further showed that omission errors were positively associated with impaired semantically driven lexical retrieval rather than phonological retrieval. These results suggest that errors of omission in aphasia predominantly arise from lexical–semantic deficits in word retrieval and selection from a competitor set.
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A major challenge in understanding the origin of clinical symptoms in neuropsychological impairments is capturing the complexity of the underlying cognitive structure. This paper presents a practical guide to path modeling, a statistical approach that is well-suited for modeling multivariate outcomes with a multi-factorial origin. We discuss a step-by-step application of such a model to the problem of nonfluency in aphasia. Individuals with aphasia are often classified into fluent and nonfluent groups for both clinical and research purposes, but despite a large body of research on the topic, the origin of nonfluency remains obscure. We propose a model of nonfluency inspired by the psycholinguistic approach to sentence production, review several bodies of work that have independently suggested a relationship between fluency and various elements in this model, and implement it using path modeling on data from 112 individuals with aphasia from the AphasiaBank. The results show that word production, comprehension, and working memory deficits all contribute to nonfluency, in addition to syntactic impairment which has a strong and direct impact on fluency. More generally, we demonstrate that a path model is an excellent tool for exploring complex neuropsychological symptoms such as nonfluency.
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Wernicke (1900, as cited in G. H. Eggert, 1977) suggested that semantic knowledge arises from the interaction of perceptual representations of objects and words. The authors present a parallel distributed processing implementation of this theory, in which semantic representations emerge from mechanisms that acquire the mappings between visual representations of objects and their verbal descriptions. To test the theory, they trained the model to associate names, verbal descriptions, and visual representations of objects. When its inputs and outputs are constructed to capture aspects of structure apparent in attribute-norming experiments, the model provides an intuitive account of semantic task performance. The authors then used the model to understand the structure of impaired performance in patients with selective and progressive impairments of conceptual knowledge. Data from 4 well-known semantic tasks revealed consistent patterns that find a ready explanation in the model. The relationship between the model and related theories of semantic representation is discussed.
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Damage to the white matter underlying the left posterior temporal lobe leads to deficits in multiple language functions. The posterior temporal white matter may correspond to a bottleneck where both dorsal and ventral language pathways are vulnerable to simultaneous damage. Damage to a second putative white matter bottleneck in the left deep prefrontal white matter involving projections associated with ventral language pathways and thalamo-cortical projections has recently been proposed as a source of semantic deficits after stroke. Here, we first used white matter atlases to identify the previously described white matter bottlenecks in the posterior temporal and deep prefrontal white matter. We then assessed the effects of damage to each region on measures of verbal fluency, picture naming, and auditory semantic decision-making in 43 chronic left hemispheric stroke patients. Damage to the posterior temporal bottleneck predicted deficits on all tasks, while damage to the anterior bottleneck only significantly predicted deficits in verbal fluency. Importantly, the effects of damage to the bottleneck regions were not attributable to lesion volume, lesion loads on the tracts traversing the bottlenecks, or damage to nearby cortical language areas. Multivariate lesion-symptom mapping revealed additional lesion predictors of deficits. Post-hoc fiber tracking of the peak white matter lesion predictors using a publicly available tractography atlas revealed evidence consistent with the results of the bottleneck analyses. Together, our results provide support for the proposal that spatially specific white matter damage affecting bottleneck regions, particularly in the posterior temporal lobe, contributes to chronic language deficits after left hemispheric stroke. This may reflect the simultaneous disruption of signaling in dorsal and ventral language processing streams.
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Semantic cognition refers to our ability to use, manipulate and generalize knowledge that is acquired over the lifespan to support innumerable verbal and non-verbal behaviours. This Review summarizes key findings and issues arising from a decade of research into the neurocognitive and neurocomputational underpinnings of this ability, leading to a new framework that we term controlled semantic cognition (CSC). CSC offers solutions to long-standing queries in philosophy and cognitive science, and yields a convergent framework for understanding the neural and computational bases of healthy semantic cognition and its dysfunction in brain disorders.
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In most cases, aphasia is caused by strokes involving the left hemisphere, with more extensive damage typically being associated with more severe aphasia. The classical model of aphasia commonly adhered to in the Western world is the Wernicke-Lichtheim model. The model has been in existence for over a century, and classification of aphasic symptomatology continues to rely on it. However, far more detailed models of speech and language localization in the brain have been formulated. In this regard, the dual stream model of cortical brain organization proposed by Hickok and Poeppel is particularly influential. Their model describes two processing routes, a dorsal stream and a ventral stream, that roughly support speech production and speech comprehension, respectively, in normal subjects. Despite the strong influence of the dual stream model in current neuropsychological research, there has been relatively limited focus on explaining aphasic symptoms in the context of this model. Given that the dual stream model represents a more nuanced picture of cortical speech and language organization, cortical damage that causes aphasic impairment should map clearly onto the dual processing streams. Here, we present a follow-up study to our previous work that used lesion data to reveal the anatomical boundaries of the dorsal and ventral streams supporting speech and language processing. Specifically, by emphasizing clinical measures, we examine the effect of cortical damage and disconnection involving the dorsal and ventral streams on aphasic impairment. The results reveal that measures of motor speech impairment mostly involve damage to the dorsal stream, whereas measures of impaired speech comprehension are more strongly associated with ventral stream involvement. Equally important, many clinical tests that target behaviours such as naming, speech repetition, or grammatical processing rely on interactions between the two streams. This latter finding explains why patients with seemingly disparate lesion locations often experience similar impairments on given subtests. Namely, these individuals' cortical damage, although dissimilar, affects a broad cortical network that plays a role in carrying out a given speech or language task. The current data suggest this is a more accurate characterization than ascribing specific lesion locations as responsible for specific language deficits.awx363media15705668782001.
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Lesion to symptom mapping (LSM) is a crucial tool for understanding the causality of brain-behavior relationships. The analyses are typically performed by applying statistical methods on individual brain voxels (VLSM), a method called the mass-univariate approach. Several authors have shown that VLSM suffers from limitations that may decrease the accuracy and reliability of the findings, and have proposed the use of multivariate methods to overcome these limitations. In this study, we propose a multivariate optimization technique known as sparse canonical correlation analysis for neuroimaging (SCCAN) for lesion to symptom mapping. To validate the method and compare it with mass-univariate results, we used data from 131 patients with chronic stroke lesions in the territory of the middle cerebral artery, and created synthetic behavioral scores based on the lesion load of 93 brain regions (putative functional units). LSM analyses were performed with univariate VLSM or SCCAN, and the accuracy of the two methods was compared in terms of both overlap and and displacement from the simulated functional areas. Overall, SCCAN produced more accurate results - higher dice overlap and smaller average displacement - compared to VLSM. This advantage persisted at different sample sizes (N=20-131) and different multiple comparison corrections (false discovery rate, FDR; Bonferroni; permutation-based family wise error rate, FWER). These findings were replicated with a fully automated SCCAN routine that relied on cross-validated predictive accuracy to find the optimal sparseness value. Simulations of one, two, and three brain regions showed a systematic advantage of SCCAN over VLSM; under no circumstance could VLSM exceed the accuracy obtained with SCCAN. When considering functional units composed of multiple brain areas VLSM identified fewer areas than SCCAN. The investigation of real scores of aphasia severity (aphasia quotient and picture naming) showed that SCCAN could accurately identify known language-critical areas, while VLSM either produced diffuse maps (FDR correction) or few scattered voxels (FWER correction). Overall, this study shows that a multivariate method, such as, SCCAN, outperforms VLSM in a number of scenarios, including functional dependency on single or multiple areas, different sample sizes, different multi-area combinations, and different thresholding mechanisms (FWER, Bonferroni, FDR). These results support previous claims that multivariate methods are in general more accurate than mass-univariate approaches, and should be preferred over traditional VLSM approaches. All the methods described in this study are available in the newly developed LESYMAP package for R.
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Background: Understanding the relationships between clinical tests, the processes they measure, and the brain networks underlying them, is critical in order for clinicians to move beyond aphasia syndrome classification toward specification of individual language process impairments. Objective: To understand the cognitive, language, and neuroanatomical factors underlying scores of commonly used aphasia tests. Methods: Twenty-five behavioral tests were administered to a group of 38 chronic left hemisphere stroke survivors and a high-resolution magnetic resonance image was obtained. Test scores were entered into a principal components analysis to extract the latent variables (factors) measured by the tests. Multivariate lesion-symptom mapping was used to localize lesions associated with the factor scores. Results: The principal components analysis yielded 4 dissociable factors, which we labeled Word Finding/Fluency, Comprehension, Phonology/Working Memory Capacity, and Executive Function. While many tests loaded onto the factors in predictable ways, some relied heavily on factors not commonly associated with the tests. Lesion symptom mapping demonstrated discrete brain structures associated with each factor, including frontal, temporal, and parietal areas extending beyond the classical language network. Specific functions mapped onto brain anatomy largely in correspondence with modern neural models of language processing. Conclusions: An extensive clinical aphasia assessment identifies 4 independent language functions, relying on discrete parts of the left middle cerebral artery territory. A better understanding of the processes underlying cognitive tests and the link between lesion and behavior may lead to improved aphasia diagnosis, and may yield treatments better targeted to an individual's specific pattern of deficits and preserved abilities.
Article
Significance Relatively recently, the concept of dual route neural architecture, where dorsal and ventral brain regions process information synergistically, has been applied to study of speech processing. Although a large body of work has investigated these streams in relation to human speech processing, there is little consensus regarding specific cortical regions implicated. Relying on extensive behavioral and neuroimaging data from a large sample of stroke survivors, we used a data-driven approach to localize regions crucial for motor–phonological and lexical–semantic aspects of speech processing. Results revealed distinct anatomical boundaries between a dorsal frontoparietal stream supporting a form-to-articulation pathway and a ventral temporal–frontal stream supporting a form-to-meaning pathway. This study shows clear division between two processing routes underlying human speech.