ArticlePDF Available

Bilingual brain training: A neurobiological framework of how bilingual experience improves executive function


Abstract and Figures

Individuals who develop bilingually typically outperform monolinguals on tests of executive functions. This advantage likely reflects enhanced prefrontal function, but the mechanisms that underlie this improvement are still poorly understood. This article describes a theory on the nature of the neural underpinnings of improved executive function in bilinguals. Specifically, we propose that growing up in a bilingual environment trains a gating system in the striatum that flexibly routes information to the prefrontal cortex. This article is divided into three sections. Firstly, literature establishing a three-way connection between bilingualism, executive function, and fronto-striatal loops is summarized. Secondly, a computational model of information processing in the basal ganglia is described, illustrating how the striatal nuclei function to transfer information between cortical regions under prerequisite conditions. Finally, this model is extended to describe how bilingualism may “train the brain,” enabling improved performance under conditions of competitive information selection during information transfer. Theoretical implications and predictions of this theory are discussed.
Content may be subject to copyright.
International Journal of Bilingualism
The online version of this article can be found at:
DOI: 10.1177/1367006912456617
published online 23 August 2012International Journal of Bilingualism
Andrea Stocco, Brianna Yamasaki, Rodion Natalenko and Chantel S Prat
improves executive function
Bilingual brain training: A neurobiological framework of how bilingual experience
Published by:
can be found at:International Journal of BilingualismAdditional services and information for Alerts:
What is This?
- Aug 23, 2012OnlineFirst Version of Record >>
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
International Journal of Bilingualism
0(0) 1 –26
© The Author(s) 2012
Reprints and permission:
DOI: 10.1177/1367006912456617
Bilingual brain training: A
neurobiological framework of how
bilingual experience improves
executive function
Andrea Stocco, Brianna Yamasaki, Rodion
Natalenko and Chantel S Prat
University of Washington, USA
Individuals who develop bilingually typically outperform monolinguals on tests of executive
functions. This advantage likely reflects enhanced prefrontal function, but the mechanisms
that underlie this improvement are still poorly understood. This article describes a theory
on the nature of the neural underpinnings of improved executive function in bilinguals.
Specifically, we propose that growing up in a bilingual environment trains a gating system
in the striatum that flexibly routes information to the prefrontal cortex. This article is
divided into three sections. Firstly, literature establishing a three-way connection between
bilingualism, executive function, and fronto-striatal loops is summarized. Secondly, a
computational model of information processing in the basal ganglia is described, illustrating
how the striatal nuclei function to transfer information between cortical regions under
prerequisite conditions. Finally, this model is extended to describe how bilingualism
may “train the brain,” enabling improved performance under conditions of competitive
information selection during information transfer. Theoretical implications and predictions
of this theory are discussed.
Bilingualism, executive functions, learning, prefrontal cortex, basal ganglia, striatum, inhibition,
It is well known that bilingual individuals outperform monolinguals in a number of tasks
involving executive function (e.g., Bialystok, 1998, 1999, 2004, 2009). The cognitive nature of
this advantage, however, is still debated, and its neural mechanism unspecified. In this paper,
we propose a brain-based computational model of information routing from the striatum to the
frontal cortex that simultaneously explains how bilingualism “trains” the brain and clarifies the
Corresponding author:
Chantel S Prat, Institute for Learning & Brain Sciences (I-LABS), Box 357988, University of Washington, Seattle, WA
98195-7988, USA.
0010.1177/1367006912456617International Journal of BilingualismStocco et al.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
2 International Journal of Bilingualism 0(0)
nature of improved computations in bilinguals. Our explanation links recent developments
from two apparently distinct areas of neuroscience (the neuroscience of bilingualism and the
neuroscience of cognitive flexibility) to support the hypothesis that extensive bilingual experi-
ence reinforces the basal ganglia’s capacity to modulate the flow of signals across cortical
regions. This hypothesis helps unify existing results, explaining a number of apparently contra-
dictory findings in bilingual research, and is supported by recent findings on the neural sub-
strates of executive function. In addition, the use of a neurocomputational model of the basal
ganglia allows us to make predictions about the precise nature of improved information pro-
cessing in bilingual individuals.
This article is divided into three sections. Firstly, literature establishing a three-way connection
between bilingualism, executive function, and the basal ganglia is summarized. Secondly, a com-
putational model of information processing in the basal ganglia is described. This model is extended
to describe how bilingualism may “train the brain” to perform better under conditions of competi-
tive selection during information transfer, thus enabling earlier and improved executive function in
bilingual individuals. Finally, the theoretical implications and predictions of this theory are
Improved executive function in bilinguals
The bilingual advantage on tasks that measure executive function has been well documented
throughout the lifespan (e.g., Bialystok, 2001, 2009; Bialystok, Martin, & Viswanathan, 2005).
For example, children developing bilingually show improved and earlier development of non-
linguistic executive function (Carlson & Meltzoff, 2008), and the effects of aging on declining
executive function are ameliorated in bilingual individual (Bialystok et al., 2005). Studies of
both children and adults show superior performance in a number of tasks that tap into execu-
tive function, such as the Simon task (Bialystok, Craik, Klein, & Viswanathan, 2004), task-
switching paradigms (Prior & MacWhinney, 2010), and tasks that require managing internal
response conflicts (Carlson & Metzoff, 2008). Most of these tasks do not directly assess lin-
guistic competence, and some of them (like the Simon task) are non-verbal in nature. In addi-
tion, research shows that the amount of bilingual experience an individual has (Carlson &
Meltzhoff, 2008) and their ability to control use of their two languages (e.g., Festman, 2012)
are also related to the extent to which improved executive function is observed. The research
suggests, therefore, that a particular linguistic experience, bilingualism, translates into a
domain-general advantage in cognitive function.
“Executive function” is a general name for a number of activities that, to a certain extent, can
be dissociated from one another. Experts in executive function have described at least three
distinct components of performance on executive tasks: inhibition, shifting, and updating (e.g.,
Miyake et al., 2000). These various aspects of executive function have been discussed and
debated in the bilingual research, but no consensus has been reached about which facet (or
facets) is specifically improved in bilinguals. Because increased demands for language selec-
tion and switching in bilinguals overlaps most directly with the inhibition and shifting compo-
nents of executive function, investigations of the executive advantage in bilinguals have
primarily focused on these aspects. Relatively little work has addressed a bilingual advantage
in updating, but one study did report a bilingual advantage on a visually cued recall task involv-
ing an updating component (Carlson & Meltzoff, 2008). In this section, we will provide a brief
overview of the remaining research that links bilinguals’ improved performance on executive
tasks to better inhibitory control and switching processes.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 3
Inhibitory control
One proposed explanation of bilinguals’ advantage in executive function is that it reflects a supe-
rior capacity for inhibitory control, or the capacity of controlling and halting dominant and auto-
matic responses that are strongly associated to environmental stimuli but are not appropriate for
the current task (Miyake et al., 2000). Bilinguals may benefit from additional inhibitory control
because they need to deal with interfering responses from the unwanted language—responses that
are typically activated in parallel with those of the target language (e.g., Bialystok, 2001; Bialystok
& Martin, 2004; Carlson & Meltzoff, 2008; Festman, Rodriguez-Fornells, & Münte, 2010). In an
investigation comparing the performance of bilinguals and monolinguals across three experi-
ments using the Simon task, a non-verbal response competition paradigm (Simon, Acosta,
Mewaldt, & Speidel, 1976), Bialystok and colleagues (2004) presented particularly compelling
evidence that bilingual individuals exhibit advanced inhibitory control. The Simon task requires
participants to respond to a simple visual stimulus with the left or right hand; the response is based
on the stimulus’ color. When the stimulus is presented on a screen position that is opposite to the
response’s hand (i.e., one has to answer with the left hand but the stimulus is presented on the
right), response times increase, implying an additional effort to control the natural tendency to
respond with the hand that is on the same side as the stimulus. Bialystok et al. (2004) found that,
across different experiments and conditions, bilinguals’ response times were less affected by the
spatial interference during incongruent trials, suggesting improved inhibitory control. These
results, however, did not replicate in subsequent experiments (Bialystok, 2006; Bialystok, Martin,
& Viswanathan, 2005).
Colzato et al. (2008) advanced the debate by outlining two possible models for inhibitory pro-
cess in bilinguals: (a) an active model in which inhibition spreads “vertically” from task goals to
the irrelevant responses; and (b) a reactive model where task goals activate both relevant and irrel-
evant response, but inhibition spreads “horizontally” from the relevant to the irrelevant ones.
Colzato et al. (2008) compared the performance of bilinguals and monolinguals across three tasks
that engage different inhibitory models: the stop-response task (Logan & Cowan, 1984), the inhi-
bition-of-return task (Posner & Cohen, 1984), and the attentional blink task (Raymond, Shapiro, &
Arnell, 1992). Bilinguals did not exhibit any advantage over monolinguals in the first two tasks,
but they did show a clear disadvantage in the attentional blink task. In this task, participants
observe a rapid serial visual presentations of simple visual stimuli (e.g., numbers) in which two
targets (e.g., letters) are embedded. While participants can easily detect both targets when they are
either in immediate succession or separated by three or more stimuli, they are typically unable to
report the second target when it is separated from the first by one or two intermediate distractors.
This effect is akin to a temporary “blink” of visual attention. Colzato et al. (2008) found that blink
effects were larger in bilinguals than in monolinguals. The authors interpreted this finding as the
result of inhibition originating from the attention devoted to the first stimulus, therefore favoring
the “reactive” model of inhibition (Colzato et al., 2008). Our model offers a different interpretation
of the results discussed in this section. Specifically, it proposes that the larger blink effect in bilin-
guals is due to the top-down processing of the first stimulus that is mediated by the basal ganglia,
a set of brain nuclei that are particularly important for bilingual language production and override
the automatic visual processing of the second stimulus.
In summary, while improved inhibitory control has been one of the most popular explanations
of improved executive function in bilinguals, a number of recent experimental findings suggest
that this may not be the best characterization of bilinguals’ cognitive advantage (e.g., Bialystok,
2006; Colzato et al., 2008; Festman et al., 2010).
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
4 International Journal of Bilingualism 0(0)
Set shifting
Another possible explanation for improved executive function in bilinguals is that they are better
at the shifting component of complex tasks, or the capacity of flexibly switching back and forth
between multiple tasks, mental operations, or response sets (Miyake et al., 2000). The assumption
behind this hypothesis is that bilingual experience is a linguistic instantiation of task set shifting,
and thus bilinguals’ advantage in executive function reflects improved shifting abilities in general.
In other words, to be a fluent bilingual, individuals need to switch effectively between the appro-
priate grammatical rules and phonological outputs for each of the languages they speak. Thus, it is
conceivable that bilinguals obtain a general benefit from this continuous practice with shifting.
Evidence in this sense can be seen in a study by Festman et al. (2010) that compared the perfor-
mance of a group of bilinguals across different tasks. In this study, participants were initially
required to name pictures alternating between two languages. The number of errors made (i.e.,
failures to switch language) was taken as a measure of their language control ability. The authors
then proceeded to divided the group into “switchers” (less errors, better control) and “non-
switchers” (more errors, worse control), and compared these two subgroups on a number of execu-
tive function tasks. It was found that “switchers” also performed better on all the executive func-
tion tasks, suggesting that having better executive functions is related to the capacity to switch
between languages.
A few studies have specifically compared the set-shifting abilities of bilinguals and monolin-
guals. This line of research has primarily employed task-switching paradigms to investigate shift-
ing abilities. In task-switching experiments, participants shift between two tasks that can be
performed on an identical set of stimuli (e.g., Monsell, 2003). For instance, the experimental stim-
uli might be one-digit numbers, and participants might be required to switch between categorizing
each digit as even or odd (Task 1) or as smaller or larger than five (Task 2). The first trial after
participants switch tasks takes longer than any trial where they are continuing to perform the same
task. The increase in reaction time constitutes the switch cost, which is interpreted as the additional
control needed to prepare for a new set of mental operations. At least two studies (Garbin et al.,
2010; Prior & MacWhinney, 2010) compared bilinguals and monolinguals in a task-switching
paradigm, and found that bilinguals exhibit significantly lower switch costs than monolinguals,
suggesting a more efficient shifting processes.
One of the most intriguing findings in the task-switching literature is the task-switching asym-
metry observed when individuals switch from a more difficult, less automatic task to an easier, or
more automatic, task (e.g., Monsell, 2003). In this condition, a larger switching cost is observed
than when switching from an easier, more automatic task to a more difficult one (e.g., Allport,
Styles, & Hsieh, 1994; Yeung & Monsell, 2003). Interestingly, this asymmetry has a direct coun-
terpart in the bilingual literature: when switching between languages, “unbalanced” bilinguals (i.e.,
bilingual individuals who are more proficient in L1 than L2) find it harder to switch from the less
proficient to the most dominant language, and not vice versa (e.g., Costa & Santesteban 2004).
This finding provides empirical support that switching between languages for bilinguals involves
some of the same general information-processing principles that operate in non-linguistic task-
switching paradigms. This lends plausibility to the theory that bilinguals’ cognitive advantage
arises because bilingual practice trains the switching sub-component of executive function.
One problem with both the inhibition and switching explanations is that they rely on hypotheti-
cal cognitive constructs that are not well specified at the neural or computational level. For instance,
vastly different computational models can account for the switching costs (Altmann & Gray, 2002;
Gilbert & Shallice, 2002; Schneider & Logan, 2005; Sohn & Anderson, 2001); these models rely
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 5
on different underlying biological mechanisms to explain the nature of changing tasks. The next
two sections will review the most relevant findings about the neural bases of bilingualism and their
connections with the neural bases of executive function.
The neural basis of bilingualism
Differences in cognitive function ultimately result from differences in brain processes. Thus, what-
ever the nature of the bilingual advantage in executive function is, it must be reflected in some
feature or features that characterize the bilingual brain. Investigations of the bilingual brain have
centered around two problems: how multiple languages are represented in the brain, and how they
are controlled in the brain (see Abutalebi & Green, 2007, for a review).
Recent neuroimaging research suggests a great deal of overlap in the representation of multiple
languages (see Abutalebi & Green, 2007, p. 256, Table 1). An abundance of studies (Abutalebi,
2008; Buchweitz, Mason, Hasegawa, & Just, 2009; Chee, Tan, & Thiel, 1999; Dehaene et al.,
1997; Gandour, et al., 2007; Hernandez & Meschyan, 2006; Vingerhoets et al., 2003) showed that
second languages (L2) have a more distributed representation and engage larger cortical areas than
do first languages (L1). Most of these differences, however, can be accounted for by differences in
proficiency levels in the two languages (Abutalebi, 2008; Perani et al., 2003; Yokoyama et al.,
2006). Thus, the general view is that a highly overlapping network of regions is recruited by both
languages, and that eventual differences depend on the recruitment of additional regions (often
prefrontal regions) to compensate for the less automatic control of the second language (Abutalebi
& Green, 2007). An example of the degree of overlap between L1 and L2 comes from a study by
Buchweitz, Shinkareva, Mason, Mitchell, and Just (2012). The authors used machine learning
techniques to investigate the neural substrates of semantic representations of L1 and L2 in profi-
cient English-Portuguese bilinguals. In particular, the authors trained a multi-voxel pattern classi-
fier to correctly associate distinct patterns of activation elicited by words in L1 (e.g., the pattern of
activation elicited by the Brazilian word “Avião”), and found that the same classifier could reliably
recognize the homologous words when presented in L2 (e.g., the English word “Airplane”). This
finding suggests that words in L1 and L2 not only recruit the same brain network to be processed,
but are similarly represented at the neural level.
The fact that L1 and L2 languages share a common neural substrate implies that languages must
compete for access to shared neural resources. Thus, a control mechanism must be operating in the
bilingual brain to monitor and select which language to use. In our opinion, the neural substrates of this
control mechanism are tied to the neural mechanisms of the shifting component in executive function.
Investigations of bilingual language control typically involve translation paradigms, language-
switching paradigms, or language selection paradigms (see Abutalebi & Green, 2008, for a review).
Research has yielded regions of activation that highly overlap with those observed in non-
linguistic cognitive control tasks, such as the prefrontal cortex and the anterior cingulate (e.g.,
Hernandez, Martinez, & Kohnert, 2000; Rodriguez-Fornells et al., 2005). Of particular interest to
our hypothesis, a series of investigations have reported subcortical involvement, specifically the
basal ganglia, during switching or translating paradigms (e.g., Lehtonen et al., 2005; Price, Green,
& von Studnitz, 1999). This research is discussed in more detail in the subsequent section.
The role of the basal ganglia in language
The basal ganglia are a set of interconnected gray matter nuclei located in the middle of the brain.
Together, these nuclei form a complex circuit that, by maintaining a careful balance of inhibitory
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
6 International Journal of Bilingualism 0(0)
Table 1. Comparison of basal ganglia activation foci in neuroimaging studies of bilingualism.
Study Atlas Region
(x, y, z)
Villringer, &
Perani (2003)
L putamen/thalamus –20 8 6
Grammatical judgment
L caudate nucleus –20 0 17
R putamen/thalamus 20 4 0
et al. (2007)
L head of caudate –2 10 14
Language switching vs. non-
switching in the middle of a
L putamen –28 –12 10
R putamen 28 –6 8
R globus pallidum 14 –6 –2
et al. (2007)
L caudate nucleus –16 6 6
Bilingual vs. monolingual in
R caudate nucleus 16 8 12
L caudate nucleus –18 0 22
Bilingual > monolingual in
L caudate nucleus –10 4 4
Naming in L1 > L2R caudate nucleus 14 4 6
R putamen 30 14 10
Garbin et al.
MNI L striatum –16 10 2
Bilinguals > monolinguals in
task switching
Miliivojevic, &
Kirk (2009)
Talairach L caudate tail –15 –31 20
Bilinguals > monolinguals in
Stroop incongruent trials
Ghosh, Basu,
Khushu, &
Kumaran (2009)
R sublobar extra
nuclear, caudate body
14 –2 16
Lexical decision > syllable
Majerus et al.
L caudate tail –12 –30 –18
Low proficiency > high
R caudate tail 22 –38 14
L pallidum –12 0 –4
High proficiency > Low
R pallidum 14 2 –14
Klein, Milner,
Zatorre, Meyer,
& Evans (1995)
Talairach L putamen –15 10 –6
Translation (L1 to L2) vs.
repetition (L1 to L1).
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 7
Study Atlas Region
(x, y, z)
Grogan, Green,
Ali, Crinion, &
Price (2009)
R head of caudate 14 0 16
Correlation between phonemic
task and gray matter volume
L head of caudate –14 10 14
R head of caudate (L2) 16 10 14
Phonemic task > semantic task
L head of caudate (L2) –14 14 10
R head of caudate (L1) 12 –2 16
L head of caudate (L1) –8 4 20
Klein, Watkins,
Zatorre, &
Milner (2006)
L head of caudate –15 13 6
Word repetition minus silent
baseline in L2
L putamen –28 13 -8
Meschyan &
R putamen 24 10 14 L2 > L1 in single word reading
R putamen 26 10 12 L2 > rest in single word reading
Fiebach, Kempe,
& Friederici
L caudate –5 18 3
Correct sentences: Native
speakers vs. non-native
speakers L2 > L1
R caudate 11 15 6
L caudate –7 6 3
Syntactically anomalous
sentences: Native speakers vs.
non-native speakers
R caudate 8 12 9
L caudate –5 6 3
Semantically anomalous
sentences: Native speakers vs.
non-native speakers L2 > L1
R caudate 8 12 9
Price, Green,
& von Studnitz
L putamen/head of
–16 18 0
Translation relative to
reading—increases in
–18 22 16
R putamen/head of
16 26 2
18 14 4
18 8 14
Lehtonen et al.
MNI L globus pallidus –16 4 –4
Sentences translation >
Crinion et al.
L caudate –6 6 8
Language-specific priming
L caudate –4 14 2
Language-specific priming
Klein, Milner,
Zatorre, Meyer,
& Evans (1995)
Talairach L putamen –15 10 –6 L1 to L2 translation
MNI: Montreal Neurological Institute template.
Talairach: Talairach-Tournoux template.
Table 1. (Continued)
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
8 International Journal of Bilingualism 0(0)
and excitatory signals conveyed through parallel pathways, controls the thalamic inputs to the
frontal lobe (Albin, Young, & Penney, 1989; DeLong, 1990). The most important structure within
the basal ganglia is the striatum, which is the largest of the basal ganglia nuclei and constitutes the
input station of the circuit. The striatum receives organized projections from the entire cortex
(Alexander, DeLong, & Strick, 1986), and projects to and modulates the activity of lower-level
nuclei of the basal ganglia, which ultimately control the output of thalamic neurons to the prefron-
tal cortex. Thus, the striatum is in an ideal position to gather information from all the cortical areas
in the brain, and use this information to modulate the subcortical inputs to the prefrontal cortex. In
turn, the prefrontal cortex is the part of the brain that is responsible for higher-level behavior
(Miller, 2000), including working memory (Cohen et al., 1997), planning (Shallice & Burgess,
1991), rule-based behavior (Strange, Henson, Friston, & Dolan, 2001) and, of course, language
(e.g., Just, Carpenter, Keller, Eddy, & Thulborn, 1996).
Until recently, the role of the basal ganglia has been largely disregarded in neuroimaging
investigations of language processes—an example of a more general “cortico-centric myo-
pia” that has characterized the cognitive neurosciences (Parvizi, 2009). However, neuropsy-
chological studies have shown that language impairments such as aphasia, normally associated
with cortical lesions, can also originate from basal ganglia damage (e.g., Brunner, Kornhuber,
Seemüller, Suger, & Wallesch, 1982; D’Esposito & Alexander,1995) or from basal ganglia
abnormalities of genetic origin (e.g., Vargha-Khadem et al., 1998; Watkins et al., 2002). In
addition, an increasing number of contemporary neuroimaging studies have discussed the
relevance of the basal ganglia to language processing, suggesting that this region is substan-
tial for the control of language (e.g., Friederici, 2006; Prat & Just, 2011). To illustrate, we
conducted a review of existing neuroimaging research and found that 16 investigations of the
neural basis of bilingualism reported activation foci within the basal ganglia nuclei under
different conditions (see Table 1). The centroids of these activations in Montreal Neurological
Institute (MNI) coordinates are depicted in Figure 1. Taken together, Figure 1 and Table 1
suggest that basal ganglia activation is often found (although not always discussed and
addressed) in studies of bilingualism. Furthermore, the distribution of the activation foci in
Figure 1 follows a consistent pattern, with the majority of reported foci concentrated on the
head of the caudate nucleus, which crucially receives inputs from (and projects to) the pre-
frontal cortex and has been associated with individual differences in executive function (e.g.,
Prat & Just, 2011).
One explanation for the different contributions of cortical and subcortical structures to lan-
guage processes is that language is underpinned by two processes with distinct neural instantia-
tions: a semantic representation system (which involves the cortex) and a grammatical (or rule
composition) system (which involves subcortical structures: e.g., Paradis, 2004; Ullman 2001a,
2001b; Ullman et al., 1997). This framework largely overlaps with the ideas of language repre-
sentation and control previously discussed; however, the constructs are defined within a mem-
ory framework. Within this framework, lexical information is represented as part of the
declarative memory system, while syntactic knowledge is stored as part of the procedural mem-
ory system. In the human brain, declarative memory is thought to be underpinned by cortical
structures, and in particular with the temporal lobe (for the encoding of information: Squire,
1992, 2004) and the left inferior frontal gyrus (for the retrieval of information: Sohn, Goode,
Stenger, Carter, & Anderson, 2003; Thompson-Schill, D’Esposito, Aguirre, & Farah, 1997).
Procedural memory, on the other hand, is typically associated with the basal ganglia circuit
(Cohen & Squire, 1980; Packard & Knowlton, 2002); thus, this framework establishes a link
between linguistic rule representation and the basal ganglia. Computationally, the distinction
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 9
between dictionary-like semantic knowledge and rule-like procedural knowledge provides an
intuitive and powerful basis for explaining the complex phenomenon of natural language use.
In fact, this dual mechanism has been applied in computational models of language acquisition
(Taatgen & Anderson, 2002), understanding (Lewis & Vasishth, 2005), and language impair-
ments (Stocco & Crescentini, 2005), and is a staple of general-purpose cognitive architectures
such as Adaptive Control of Thought—Rational (ACT-R: Anderson et al., 2004) and Executive
Processes / Interactive Control (EPIC: Meyer & Kieras, 1997).
The idea that syntactic rules can be encoded in the basal ganglia is supported by this cir-
cuit’s involvement in acquiring procedural knowledge (Knowlton, Mangels, & Squire, 1996).
Experiments with animals have shown, for instance, that basal ganglia impairments prevent
the acquisition of stimulus–response associations (e.g., Packard & McGaugh, 1992). In
humans, diseases affecting the basal ganglia (e.g., Parkinson’s or Huntington’s disease)
impair the acquisition of new perceptual-motor skills, such as mirror reading (Cohen &
Squire, 1980) and the acquisition of complex stimulus–response associations (Knowlton
et al., 1996). Thus, experimental and neuropsychological evidence suggest that the basal
ganglia circuit is responsible for learning and applying complex stimulus–response transfor-
mations—a function that is consistent with the application of grammatical rules.
Figure 1. Locations of basal ganglia foci of activations in 16 neuroimaging studies of bilingualism (see Table
1 for references). The foci of activations are overlaid on the Montreal Neurological Institute (MNI) Colin 27
template (Sagittal view, x = –20). Different colors (color online only) represent results from different studies;
dots of the same color represent distinct foci of activation reported in the same paper (e.g., in two different
contrasts). Stereotactic coordinates that were originally given in the Talairach-Tourneaux system were
converted to the MNI system using the non-linear transformation algorithm provided in the GingerALE
software (Eickhoff et al., 2009).
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
10 International Journal of Bilingualism 0(0)
The basal ganglia and the bilingual brain
This declarative/procedural framework can be usefully applied to explain the proficiency-related
differences between L1 and L2 in late bilinguals. While learning a second language, grammatical
rules are more likely to be encoded explicitly, and thus retrieved and held in working memory dur-
ing language tasks. This additional activity would be reflected in larger activation of prefrontal
regions for L2 compared to L1. With increasing practice, however, grammatical rules for L2 would
be eventually stored in the basal ganglia in the form of procedural rules, thus reducing the differ-
ence between L1 and L2 (Paradis, 2004; Ullman, 2001b). This view is confirmed by the fact that,
in bilingual individuals with degenerative disorders of the basal ganglia such as Parkinson’s dis-
ease, greater impairment is found in the language spoken with higher proficiency, whereas less
impairment is observed in the language spoken with less proficiency (Zanini, Tavano, & Fabbro,
2010; Zanini et al., 2004; see Fabbro, 2001, for a review).
However, experimental and neuropsychological evidence suggest that, in the bilingual brain,
the basal ganglia play the additional role of controlling which language to use. For instance, bilin-
gual patients with injuries spanning the basal ganglia circuit show a pathological tendency to
switch back and forth between languages (Fabbro, 2001). This neuropsychological evidence is also
corroborated by experimental investigations; for instance, direct stimulation of the left striatum
(the largest nucleus of the basal ganglia) during open-skull surgery causes spontaneous language
switching (Robles, Gatignol, Capelle, Mitchell, & Duffau, 2005).
One important neuroimaging study conducted by Crinion et al. (2006; see also Friederici,
2006, for a discussion of this study’s implications) examined the nature of automatic language
switching by using a priming paradigm. In the experiment, bilinguals responded to words that
were preceded by either semantically related or unrelated primes. More importantly, the prime
word was presented in either the same language as the target word, or in a different language.
Noticeably, the authors did not compare L1 against L2, but instead used priming to investigate
the nature of language processing when a language switch (L1 or L2) is processed. Semantic
priming crosses the language boundary, so that seeing the prime word “Salmon” in English still
results in a decreased response time for the target word “Trout” in German (“Forelle”). The
priming effect was significant in a distributed cortical network involving most of the brain
regions that were recruited by the task. The only exception to this rule was a region in the left
striatum. Semantically related words reduced activation in this region only when they were in
the same language. In other words, the priming effect in the striatum was selectively modulated
by the specific language input.
Crinion et al.’s (2006) finding suggests that the striatum is involved in monitoring which lan-
guage is in use. It is conceivable that damage to this structure impairs a specific brain circuit that
controls which language is used, thus explaining the neuropsychological symptoms described
above. Friederici (2006) recognized the connection between this putative function of language
selection and the established role of the basal ganglia circuit in selecting motor programs (e.g.,
Albin et al., 1989).
In summary, investigations of the nature of language processing in bilinguals have shown that dif-
ferent languages are represented in highly overlapping cortical networks, especially when one
accounts for different levels of proficiency and exposure. The basal ganglia seem to play a role
both in controlling language selection and in subsequent application of rules. Importantly, in the
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 11
bilingual brain, this subcortical circuit is involved in a specific function (i.e., switching or translat-
ing between languages) that is analogous to the facet of executive function, where bilinguals seem
to excel (i.e., switching between tasks or response sets). The next section will describe the func-
tions of this circuit in more detail and their relevance for executive function and shifting.
The basal ganglia and executive function
How might practice with language switching in bilinguals provide an advantage in executive func-
tion? We propose that the critical link between bilingual experience and improved executive func-
tion arises with training of the fronto-striatal loops, which are involved in both language control
and executive function.
The basal ganglia are primarily known for their role in learning and skill acquisition (Knowlton
et al., 1996; see Packard & Knowlton, 2002, for a review). However, this circuit has been impli-
cated in a larger number of higher-level cognitive functions, including working memory (McNab
& Klingberg, 2008), decision making (Montague, King-Casas, & Cohen, 2006; Tom, Fox, Trepel,
& Poldrack, 2007), language (Frederici, 2006; Prat & Just, 2011; Ullman, 2001a, 2001b), planning
(Monchi, Petrides, Strafella, Worsley, & Doyon, 2006), and reasoning (Frank, Seeberger, &
O’Reilly, 2004; Stocco & Anderson, 2008).
Of particular interest to the theory presented herein, the basal ganglia have also been pro-
posed to play a role in the shifting component of executive function. Some evidence of this
comes from deficits observed in patients with diseases such as Parkinson’s and Huntington’s
disease, which selectively damage the basal ganglia. Patients with Parkinson’s disease, for
instance, have problems switching to new rules in the Wisconsin Card Sorting Task (Gotham,
Brown, & Marsden, 1988; Owen, Roberts, Hodges, & Robbins, 1993). In this task, participants
go through a deck of cards with colored symbols and are required to put them in piles according
to a specific rule. The rule itself is not revealed explicitly; instead, participants need to rely on
the yes/no feedback from the experimenter to know whether putting a card in a particular pile
(e.g., the pile with all red symbols) is a correct move. Unpredictably, the experimenter some-
times changes the sorting rule (switching from color to shape), so that participants have to learn
a different criterion for piling up the cards.
Both Parkinson’s (e.g., Rogers et al., 1998) and Huntington’s (e.g., Aron et al., 2003)
patients exhibit impairments when shifting to new task rules in standard task-switching para-
digms, again suggesting a specific involvement of the basal ganglia in the control of alternat-
ing behavioral rules. Additional evidence can be found in a number of neuroimaging studies,
which report basal ganglia activation in healthy populations during task-switching experi-
ments (Cools, Clark, & Robbins, 2004; Crone, Wendelken, Donohue, & Bunge 2006; Gu et
al., 2008; Sohn, Ursu, Anderson, Stenger, & Carter, 2000). Finally, a critical link between set
shifting, the basal ganglia, and bilingualism is reported in one neuroimaging investigation of
task switching (Garbin et al., 2010). The authors compared the brain activation of bilinguals
and monolinguals while performing a task-switching paradigm. The paradigm was designed
to be non-linguistic, with the two tasks involving classifying colored shapes according to
either their shape (e.g., circle or square) or their color (e.g., orange or blue). Consistent with
previous findings (e.g., Prior & MacWhinney, 2010), bilinguals showed a reduced switching
cost (e.g., reduced increase in latency) when switching between tasks. Most importantly,
however, the size of the switch costs was negatively associated with the activity of the left
caudate nucleus in bilinguals, suggesting that successful recruitment of this nucleus results
in faster switches. The same correlation was not observed in monolinguals, suggesting that
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
12 International Journal of Bilingualism 0(0)
one crucial difference between the bilingual and the monolingual brain is that the bilingual
brain relies on the left caudate to switch between tasks, while the monolingual brain does not
(Garbin et al., 2010).
In summary, the literature suggests a three-way connection between executive function, the
basal ganglia, and bilingualism. Bilinguals exhibit behavioral advantages in executive func-
tion, which reflect, in part, superior cognitive control in switching between different rule-
based behaviors. This superior control ability relies on the basal ganglia, a set of nuclei that
are crucially involved in both switching between different task sets and in switching between
languages. Two questions arise at this point. (a) What is the mechanism by which the basal
ganglia contribute to linguistic and behavioral switching? (b) Can we use this information to
better understand how growing up in a bilingual environment trains the brain in a way that
generalizes to non-linguistic executive function? The next two sections will attempt to provide
answers to both questions.
Identifying basal ganglia computations in task and language switching
To understand the mechanism behind improved executive function in bilinguals, one must first
specify the neural computations that take place in the basal ganglia. Specifically, we must deter-
mine whether the same neural computations are involved both in the control and switching between
languages and in the control and switching between other, non-linguistic, tasks. In addition, we
must determine how this circuit is shaped by practice and, in particular, how domain-specific train-
ing (i.e., speaking two languages) generates a domain-general benefit (i.e., improved executive
One way to better understand the computations of a specific neural circuit is by generating a
computational model of the circuit. Biologically based models are particularly useful, because
they provide a direct connection between anatomical structure and function (e.g., O’Reilly &
Munakata, 2000). Because of their elaborate patterns of connectivity with the cortex, and their
wide involvement in cognitive functions, several models of the basal ganglia have been gener-
ated (see Cohen & Frank, 2009; Gillies & Arbuthnott, 2000, for reviews), and some consensus
has emerged about the basic nature of their computations. According to several of these models,
the basal ganglia provide a complex and flexible mechanism to control information flow to the
prefrontal cortex. In many recent models (e.g., Amos, 2000; Frank, Loughry, & O’Reilly, 2001;
Gurney, Prescott, & Redgrave, 2001; O’Reilly & Frank, 2006; Stocco, Lebiere, & Anderson,
2010) this “gating” of signals to the prefrontal cortex is performed by monitoring all possible
incoming signals from the cortex, and then using the internal inhibitory connections within the
basal ganglia to suppress those signals that are not of interest. The signals of interest are then
selected and routed to the prefrontal cortex.
This paper adopts one such model, the Conditional Routing Model proposed by Stocco, Lebiere,
and Anderson (2010), as a framework for understanding the role of basal ganglia function in the
bilingual brain. This model offers a number of advantages over other models. Firstly, it provides a
detailed account of both how signals are gated to the prefrontal cortex and of how rule-based
behaviors can be encoded in the basal ganglia. Secondly, this model provides a means to explain
the activity of the striatum in terms of the execution of abstract “IF–THEN” rules. Finally, the
model is biologically plausible and incorporates all of the known inhibitory and excitatory connec-
tions between the basal ganglia, the thalamus, and the cortex. These features are important because
they can potentially explain both how the appropriate language outputs and grammar processes are
selected and switched in the bilingual brain.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 13
The conditional routing model
According to the conditional routing model, the basal ganglia operate as a system that imposes
order over the highly overlapping exchange of signals between networks of cortical regions. In the
absence of basal ganglia interventions, the flow of signals across the network is determined by the
relative strength of cortico-cortical projections. Such relative strength is in turn shaped by previous
practice and reward contingencies, and under normal conditions is sufficient to produce effective
behavior. However, during learning (where preexisting cortical networks cannot accomplish the
task at hand) or in situations where predetermined or automatized cognitive routines cannot accom-
plish a task goal (such as in a task-switching paradigm), the basal ganglia shape behavior by prior-
itizing different signals and overriding preexisting cortico-cortical connections.
This idea is visually summarized in Figure 2. Figure 2(a) illustrates a situation where a single
prefrontal area (the “target”) receives competing signals from three different regions (the “sources”)
at the same time. As an example, these regions are placed in the frontal (A), parietal (B), and tem-
poral (C) lobes. These three regions contain different types of information, and the “target” pre-
frontal area must select a signal from only one of them. Since the prefrontal cortex lies at the apex
of a hierarchy of converging pathways (e.g., Miller, 2000), such a conflict situation (where multi-
ple signals compete to affect a single region) must not be uncommon. In the absence of basal
ganglia routing, the relative strength of these projections, shaped by previous experience and
reward contingencies, is sufficient to prioritize signals and produce efficient behavior. In Figure
2(a), the relative strength of cortico-cortical projections is represented by the different lines, with
dashed lines indicating weaker connections and solid lines depicting stronger ones. In this hypo-
thetical situation, Region B in the parietal lobes is sending the signal that will have the largest
influence on the prefrontal target region.
Figure 2. A visual illustration of the role of the basal ganglia in controlling how information is routed in
the cortex. (a) Because of the large number of incoming projections, the prefrontal cortex receives many
concurrent signals from different cortical areas; under normal conditions, the region with the strongest
cortico-cortical connections (region B, continuous line) is more likely to successfully affect the prefrontal
region than other regions with weaker connection (regions A and C, dotted lines). (b) The basal ganglia
can modify the flow of signals through the cortex by selecting a different pathway (from region B, thicker
continuous line) and enhancing its strength through the fronto-striatal loops.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
14 International Journal of Bilingualism 0(0)
Under certain situations, however, behavior must be flexibly modified and adapted to perform
novel tasks, and the same cortical input region must shift its priority to inputs from another region
or regions (e.g., when switching tasks requires attending to a new set of features of the stimuli, or
when switching languages requires applying a new set of rules for parsing sentences). According
to the conditional routing model, this change in behavior is mediated by the basal ganglia. In par-
ticular, the model suggests that the basal ganglia circuit can enhance signals coming from a selected
source region, thus increasing the probability of this source’s signal to influence the behavior of the
target region despite otherwise weaker cortico-cortical connections. The name “Conditional
Routing” refers precisely to these circumstances, which can be seen as imposing new routes of
information transfer between cortical regions when specific circumstances (or “conditions”) arise.
An instance of conditional routing is depicted in Figure 2(b), which illustrates a hypothetical situ-
ation in which the basal ganglia are routing information from Region C in the temporal lobe to the
target area, thus amplifying the signal and reprioritizing the cortico-cortical connections such that
Region C is now influencing the target area rather than Region B. In Figure 2(b), the effect of the
basal ganglia is illustrated by the thicker line from the temporal region to the target, which replaces
the previously weaker (dotted) line.
This process is made possible by the internal organization of the basal ganglia, and in particular
of the striatum. According to Stocco, Lebiere, and Anderson (2010), the striatum is internally
organized in a way that mirrors the cortico-cortical network, so that “routing” a signal corresponds
to activating one particular set of neurons that would eventually activate the corresponding cortico-
cortical projection. Importantly, the authors have shown that the routing activity of the basal gan-
glia can be understood as the execution of conditional rules (i.e., rules of the form “IF … THEN
…”). The conditional routing mechanism of this framework has essential implications for the two
cognitive functions that are discussed in this paper, namely executive functions and language. The
next sections will provide a brief overview of these implications.
Conditional routing, executive functions, and language
As outlined above, there is experimental evidence that connects the basal ganglia to the shifting
component of executive function (Yehene, Meiran, & Soroker, 2008). Within the conditional rout-
ing framework, such shifting results naturally from the capacity of the basal ganglia to modify the
course of information flow within the cortex (e.g., Amos, 2000; Stocco, Lebiere & Anderson,
According to the conditional routing framework, the importance of basal ganglia function to
language arises in part because of the complexity of linguistic rules. Complex rules pose a natural
challenge to established cortico-cortical pathways, because they may require flexible activation of
particular pathways under specific circumstances. In addition, grammatical rules often depend on
complex dependencies between their terms. Take, for instance, the relatively simple English rule
for pluralization, which can be stated as: “IF X is the singular form and you want to use the plural
form, THEN add -s to X.Applying this rule requires knowing the specific conditions under which
it can be applied (for instance, it does not apply to the word “sheep”), mapping the proper word to
the variable X, and applying an invariant constant term (“-s”). The conditional routing model pre-
dicts that, with learning, grammatical rules become permanently stored in the basal ganglia in the
form of patterns of synaptic strengths that determine signal routing (Stocco, Lebiere & Anderson,
Thus, the conditional routing model can explain why the impact of basal ganglia lesions on
language depends on proficiency (Fabbro, 2001; Zanini et al., 2004). With practice, rules become
encoded in the basal ganglia in abstract form, and can be applied whether or not an explicit,
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 15
conscious representation of the rule exists in the cortex. The model also explains why damage to
the basal ganglia would impair precisely these types of automated rule-based behaviors, while
sparing to a greater extent behaviors where the rules are explicitly encoded and represented in the
cortex (for example, how to pluralize nouns in a less-proficient second language).
The conditional routing model also makes specific predictions about the nature of linguistic
errors and mistakes that occur in basal ganglia patients. In particular, the model predicts that com-
plex transformations, requiring simultaneous integration of many sources of information, will
require the computations of the striatum, whereas the more direct stimulus–response mappings can
be handled by cortico-cortical connections. Because of this dual representation, the model predicts
that basal ganglia lesions should impair the production of sentences that require complex gram-
matical transformations (because they rely on learned patterns in the striatum), but spare those
structures that are highly familiar and automatic, such as idiomatic expressions (because their fixed
structure remains stored within cortico-cortical connections). Consistent with this prediction,
patients with language impairments due to basal ganglia lesions exhibit impoverished grammar in
their native language and produce a large amount of language automatisms (Brunner et al., 1982;
Code, 1994). While the idea that the basal ganglia encode syntactic rules is common to other
accounts (e.g., Paradis, 2004; Ullman, 2001a), the prediction that familiarity predicts the extent to
which the basal ganglia will be involved is specific to the conditional routing model.
The connection between language and executive function can be fully appreciated when one
notices that, within the conditional routing model, language and executive function share a com-
mon set of computations that rely on the basal ganglia circuitry. In particular, the capacity of shift-
ing between tasks and mental sets and the capacity of applying complex rules both depend on the
ability of the basal ganglia to properly and timely route the appropriate signals within the network
of regions involved in a task. Thus, even if distinct cognitive functions (e.g., language and execu-
tive functions) are underpinned by different brain networks, they still rely on the basal ganglia
when the communication between different regions needs to be organized according to some com-
plex and non-habitual template. This common ground is central to our theory about how practice
within one cognitive function (i.e., managing two languages in the case of bilingualism) can have
positive effects on the other (i.e., executive functions).
Conditional routing and bilingualism
To understand how being raised bilingually “trains the brain” in a way that gives rise to improved
executive function, one must first explain how bilingualism shapes the basal ganglia circuit. From
the point of view of the conditional routing framework, bilingual language experience imposes two
concurrent challenges on the basal ganglia circuit. The first is that representation of the two lan-
guages needs to be kept distinct, despite the overlapping contexts and information they share.
Think, for instance, of an Italian-English bilingual; both languages have morphological rules to
mark the plural, but the two rules are different. Deciding which rule to apply depends only on the
specific intended language output. According to the conditional routing model, the striatum is nec-
essary to select the appropriate rule based on a specific linguistic context (IF the desired output is
English, THEN add “s” to the target noun to pluralize). Recent research has also provided evidence
that the basal ganglia are important for maintaining distinct representations of words between lan-
guages (Crinion et al., 2006). In Crinion’s experiment, the striatum was the only region that showed
language-specific priming effects (i.e., it was the only region where reduced activation was only
observed for semantically related words presented in the same language). As the authors acknowl-
edged, this effect implies that the activity of the striatal neurons is modulated by language, consist-
ent with its role in discriminating between linguistic contexts. Additional support for this can be
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
16 International Journal of Bilingualism 0(0)
found in research showing that direct electrical stimulation of the striatum causes spontaneous and
uncontrolled switches between L1 and L2 (Robles et al., 2005).
Thus, for bilinguals, the basal ganglia (and in particular the striatum) face increasing
demands to select appropriate rules and representations, and to switch between rules and repre-
sentations depending on the intended language. Much like switching tasks, switching between
languages requires the capacity to override the signals from a network of brain regions that are
still active. In many ways, it is even more difficult than the standard task-switching paradigm
as it requires switching between two “tasks” (L1 and L2) that are largely automatic and whose
neural underpinnings are significantly overlapping. Due to this pressure, we propose that effi-
cient practice in two or more languages has the side effect of increasing the ability of the basal
ganglia to exert control over established cortico-cortical connections, resulting in the ability to
flexibly reroute signals to the frontal cortex. Note that we chose the word “override,” instead of
“inhibit,” to characterize this process. This choice reflects the fact that, at the neural level,
“inhibition” refers to the active reduction of a particular signal’s strength. The basal ganglia-
based mechanism outlined here does not perform “inhibition” in this sense, and relies instead
on the timely strengthening of otherwise weaker signals to modify the way information is trans-
ferred between different regions of the brain.
In summary, the conditional routing framework predicts that bilingual practice capitalizes on
two key functions of the basal ganglia—the capacity of selecting the appropriate rules in response
to very specific conditions and the capacity of overriding habitual responses encoded within cor-
tico-cortical connections. These functions are also important in tasks that demand executive func-
tions, such as those that rely on maintaining a top-down goal in the face of distracting information
(e.g., the Stroop Task) and those that rely on “shifting” from one determined set of responses to
Empirical support
In the previous sections, we have outlined a framework for understanding the mechanisms by
which bilingual language practice provides an advantage in executive function. The framework
assumes that this advantage is mediated by the basal ganglia and, in particular, that it results from
the strengthening of the ability of the basal ganglia to prioritize information flow to the prefrontal
cortex, and override cortico-cortical connections. This framework allows for the generation of
several predictions, some of which are supported in existing data from other researchers, and oth-
ers that we are currently investigating.
Perhaps the most interesting prediction concerns situations where the model predicts a dis-
advantage for bilinguals. By predicting that the bilinguals’ advantage occurs in terms of a
strengthening of the influx of basal ganglia at the disadvantage of cortico-cortical projections,
our framework implicitly lays out conditions where bilingual performance should be inferior to
monolinguals. One can conceive of the difference between striato-cortical and cortico-cortical
connections as a difference between endogenous and exogenous control (Monsell, 2003) or,
alternatively, as a difference between top-down and bottom-up attentional processes. The
research described in the first section of the paper provides extensive evidence that bilinguals
are better at exerting top-down control, but are they really worse at capitalizing on bottom-up
processes? There is some evidence that this is, indeed, the case. For instance, as seen above,
Colzato et al. (2008) reported that bilinguals exhibit inferior performance in the attentional
blink task. Successful performance in this task depends on capturing perceptual information
flowing in at a fast pace, and missing the second target (during the “blink”) might be caused by
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 17
interference from top-down processes that are still processing the first stimulus. That is, notic-
ing the second target requires suspending, or blocking, the top-down processing that has been
initiated on the first target (see Taatgen et al., 2007, for a model of this task that is consistent
with this interpretation).
This top-down processing bias is also apparent in the second experiment by Colzato et al.
(2008), where the authors compared monolinguals and bilinguals in an inhibition-of-return para-
digm. In this paradigm, participants have to attend a stimulus appearing at a particular location. A
cue appearing at the same location before the stimulus has the effect of increasing the response
reaction time at short Stimulus Onset Asynchronies (SOAs); this fact is usually explained in terms
of an automatic inhibition of the previously attended location. The authors reasoned that, if bilin-
guals’ advantage were due to improved inhibitory control, the effect of inhibition of return should
be larger in bilinguals, but the prediction was not confirmed. According to our framework, bilin-
guals’ top-down bias should have the effect of speeding up the response times overall (because of
the facilitation in setting up the appropriate response set) and actually reducing the effect of the
cue (because of the better capacity of ignoring bottom-up information). Colzato’s data (see Figure
4, p. 307) suggests that this is, indeed, the case.
Another example of increased top-down control in bilinguals comes from Experiments 2 and
3 in Bialystok et al.’s (2004) paper. In this paper, the authors compared bilinguals and monolin-
guals in variants of the Simon task. Remember that in the Simon task participants have to respond
to the color of the stimulus (e.g., red or green) with the appropriate hand, and ignore its location
(left or right). Across different conditions bilinguals showed smaller Simon effects (i.e., smaller
costs for responding with the hand to the opposite side of the stimulus), which can be explained
as evidence for either better inhibition or for better capacity for ignoring irrelevant perceptual
information. In Experiments 2 and 3, however, the authors modified the Simon task by doubling
the number of colors of the stimuli. In this condition, the stimuli could have four possible colors
(e.g., red, green, yellow, and blue); participants had to respond with the left hand for two out of
four possible colors (e.g., red and yellow), and with the right hand for the other two (e.g., green
and blue). Thus, instead of selecting between two alternative rules (“if green then press left” and
“if red then press right”), participants have to manage four possible rules, some of which entail
the same response (e.g., “if red then press right” and “if yellow then press right”). In this modi-
fied paradigm, bilinguals showed virtually no increased cost for the additional number of rules,
while monolinguals were significantly slower than in the traditional, two-rule version. Our
framework can easily account for these findings as a result of the bilinguals’ better capacity for
rapidly selecting the relevant task rules. An alternative explanation is that bilingual participants
had better working memory capacity. The bilingual and monolingual groups, however, were
equated for working memory span across two working memory tasks (the alpha span and the
sequencing span tasks), thus making our account preferable.
In summary, our framework is consistent not only with the data that show a superiority of bilin-
guals in switching tasks and managing interference, but also with a number of previously puzzling
findings from experiments that used tasks that were designed to examine different components of
executive function, such as attentional blink and inhibition of return.
This paper provides a comprehensive explanation of the nature of the cognitive advantage that
bilinguals exhibit in tasks that require executive function. The proposed theory is that the
advantage resides in an increased ability of the signals originating in the striatum to influence
the activity of the prefrontal cortex, thus reducing the more automated contributions of other
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
18 International Journal of Bilingualism 0(0)
cortical areas. This theory is based on two types of evidence: (a) Evidence that the basal ganglia
circuit, and in particular the striatum, is responsible for language selection in bilinguals; and (b)
evidence that the same region plays a crucial role in the very same type of tasks where bilin-
guals outperform monolinguals. In support of this theory, we have described a computational
model of how the basal ganglia control and route signals to prefrontal cortex, and propose that
extensive language-switching practice in bilinguals strengthens the ability of this system to
reroute, or override, cortico-cortical connections, resulting in the empirically observed cogni-
tive advantages in bilinguals.
Understanding the costs of bilingualism
Our proposed framework can be tested and extended in a number of ways.
For instance, it can be used to predict not only those cases in which bilinguals exhibit superior
performance over monolinguals, but also the situations in which bilinguals are at a disadvantage
over monolinguals. This has been demonstrated in a number of linguistic tasks, such as those meas-
uring lexical retrieval and verbal fluency (see Bialystok & Feng, 2009, for an example). Our frame-
work can explain these findings in terms of practice effects; because they speak two languages,
bilinguals cannot reach the level of performance within one language that can be reached by mono-
linguals. In addition, at the retrieval level, bilinguals have more interference than monolinguals,
with multiple lexical representations sharing an underlying semantic structure.
Crucially, however, our framework predicts conditions where monolinguals should outperform
bilinguals in non-linguistic tasks. In particular, we expect that their bias in favor of top-down process-
ing over bottom-up processing would make bilingual individuals less reactive to sudden contextual
or perceptual changes that require immediate changes of behavior. Imagine, for instance, an everyday
multitasking condition, such as driving and talking to a cell phone. Our framework predicts that bilin-
guals would be better at performing both tasks concurrently (as indexed, for instance, by measures of
lane deviation in the driving task and memory for conversation in the cell phone task), but less reac-
tive to sudden changes in the outside world (for instance, slower at responding to a pedestrian sud-
denly stepping into the street ahead of them). We see this as an interesting avenue for future research.
Implications for neuroimaging research
The conditional routing framework can also be used to generate testable predictions at the neural
level. In particular, it highlights the importance of the striatum as the source of differential abilities
to bilinguals. The framework predicts, therefore, that activity of the basal ganglia should exert
increased control over the prefrontal cortex in bilinguals. Such differences can be tested using
Dynamic Causal Modeling (Friston, Harrison, & Penny, 2003), a methodology that permits com-
paring the strength of the causal effect exerted by one region on another. It is also conceivable that
bilingual practice would result in a measurable increase in the functional connectivity between the
striatal nuclei and other language centers (such as Broca’s area) or non-linguistic cognitive areas,
such as the dorsal prefrontal cortex. A preliminary analysis of this hypothesis has been attempted
by Luk, Bialystok, Craik, and Grady (2011) and has yielded positive results, which were also con-
firmed by more direct measures of structural connectivity, including Diffusor Tensor Imaging.
The case of multilingualism
This paper has primarily discussed how managing two languages produces long-lasting
changes in behavior and brain circuitry when compared to managing one language. But what
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 19
can the model say of multilingual individuals (i.e., individuals who speak more than two lan-
guages)? Our framework makes two qualitative predictions on this topic. The first prediction
is that the behavioral and neural effects of bilingualism should be increased in multilingual-
ism. This prediction arises because the specific operations that “train” the bilingual brain (i.e.,
switching between languages and overriding intrusive signals from the unwanted language)
occur more frequently (and thus are more practiced) in multilinguals than in bilinguals. In
other words, an individual that manages three languages in his/her ordinary life needs to
switch language more often than an individual who uses only two languages. Furthermore,
each linguistic operation of a multilingual needs to override not one, but two or more unwanted
languages. Thus, in multilinguals, the amount of interference at any given point is greater than
in bilinguals. Within the conditional routing model, this implies that the strength of the fronto-
striatal connections needs to be even more enhanced to manage the increasing bottom-up
interference. Thus, successful control of many languages should result in an even stronger
top-down processing bias (behaviorally) and stronger effect of the basal ganglia on prefrontal
activation (neurally).
At the same time, one should not expect these effects to grow linearly with the number of
languages spoken by an individual. While a bilingual individual needs to cope with processing
difficulties and neural-level conflicts that a monolingual never faces, a multilingual individual
can largely use the same brain circuitry that is enhanced in bilingual practice. The specific brain
circuit that resolves language conflict in bilinguals is already in place for multilinguals, and
while it might need to be “tuned up” to deal with additional interference, it does not require the
same amount of reorganization that is necessary to move from speaking one language to speak-
ing two languages. In summary, our model predicts that the behavioral and neural consequences
of bilingualism (both positive and negative) should be magnified in multilingualism, but that
these effects should follow a law of diminishing returns, with the mastering of each additional
language yielding increasingly reduced benefits. This is a testable prediction, which we are
currently investigating.
Bilingualism as brain training
Finally, our framework allows for the application of what we have learned from bilinguals to
other domains. Specifically, we can adapt bilingual practice as a means to improve cognitive
performance or rehabilitate cognitive decline. It is possible that extensive training in task
switching produces general cognitive benefits. A great deal has been written about brain train-
ing; typically, the results are very domain specific with limited generalization to other domains.
As an extreme example, with 230 hours of practice Ericsson, Chase, and Faloon (1980) were
able to increase one’s subject digit span from 7 to 79 items; in other memory tests, however, the
same participant’s performance improved only modestly. Bilingualism is one of the very few
practices that results in general cognitive benefits that have been assessed and replicated.
Interestingly, one of the few “brain training” experiments that elicited general cognitive
improvements (Jaeggi, Buschkuehl, Jonides, & Perrig, 2008) involved a training regimen that
required participants to perform two N-back tasks at the same time, with visually presented and
aurally presented stimuli. This training task presents the same characteristics of bilingual prac-
tice, including internal control of switching between similar tasks, top-down resistance to inter-
ference, and dual tasking. Ultimately, an improved understanding of the mechanisms underlying
bilingual brain training could lead to widespread applications for improvement in general cog-
nitive functions.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
20 International Journal of Bilingualism 0(0)
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit
Abutalebi, J. (2008). Neural aspects of second language representation and language control. Acta
Psychologica, 128, 466–478.
Abutalebi, J., Annoni, J. M., Zimine, I., Pegna, A. J., Seghier, M., Lee-Jahnke, H., & Khateb, A. (2007).
Language control and lexical competition in Bilinguals: An event-related fMRI study. Cerebral Cortex,
18, 1496–1505.
Abutalebi, J., & Green, D. (2007). Bilingual language production: The neurocognition of language represen-
tation and control. Journal of Neurolinguistics, 20, 242–275.
Abutalebi, J., & Green, D. W. (2008). Control mechanisms in bilingual language production: Neural evidence
from language-switching studies. Language and Cognitive Processes, 23, 557–582.
Abutalebi, J., Simona, M., Anonni, J. M., Moro, A., Cappa, S., & Perani, D. (2007). The neural cost of the
auditory perception of language switches: An event-related functional magnetic resonance imaging study
in bilinguals. The Journal of Neuroscience, 27, 13762–13769.
Albin, R. L., Young, A. B., & Penney, J. B. (1989). The functional anatomy of basal ganglia disorders. Trends
in Neurosciences, 12, 366–375.
Alexander, G., DeLong, M., & Strick, P. (1986). Parallel organization of functionally segregated circuits link-
ing basal ganglia and cortex. Annual Review of Neuroscience, 9, 357–381.
Allport, D. A., Styles, E. A., & Hsieh, S. (1994). Shifting attentional set: Exploring the dynamic control of
tasks. In C. Umiltà & M. Moscovitch (Eds.), Attention and performance XV: Conscious and nonconscious
information processing (pp. 421–452). Hillsdale, NJ: Erlbaum.
Altmann, E. M., & Gray, W. D. (2002). Forgetting to remember: the functional relationship of decay and
interference. Psychological Science, 13, 27–33.
Amos, A. (2000). A computational model of information processing in the frontal cortex and basal ganglia.
Journal of Cognitive Neuroscience, 12, 505–519.
Anderson, J. R., Bothell, D., Byrne, M., Douglass, S., Lebiere, C., & Qin, Y. (2004). An integrated theory of
the mind. Psychological Review, 111, 1036–1060.
Aron, A. R., Watkins, L., Sahakian, B. J., Monsell, S., Barker, R. A., & Robbins, T. W. (2003). Task-set
switching deficits in early-stage Huntington’s disease: implications for basal ganglia function. Journal of
Cognitive Neuroscience, 15, 629–642.
Bialystok, E. (1998). The relationship between bilingualism and the development of cognitive processes in
problem solving. Applied Psycholinguistics, 19, 69-85.
Bialystok, E. (1999). Cognitive complexity and attentional control in the bilingual mind. Child Development,
70, 636–644.
Bialystok, E. (2001). Bilingualism in development: Language, literacy and cognition. New York: Cambridge
University Press.
Bialystok, E. (2006). Effect of bilingualism and computer video game experience on the Simon task. Canadian
Journal of Experimental Psychology, 60, 68–79.
Bialystok, E. (2009). Bilingualism: The good, the bad, and the indifferent. Bilingualism: Language and
Cognition, 12, 3–11.
Bialystok, E., Craik, F. I., Klein, R., & Viswanathan, M. (2004). Bilingualism, aging, and cognitive control:
Evidence from the Simon Task. Psychology and Aging, 19, 290–303.
Bialystok, E., & Feng, X. (2009). Language proficiency and executive control in proactive interference:
Evidence from monolingual and bilingual children and adults. Brain and Language, 109, 93–100.
Bialystok, E., & Martin, M. (2004). Attention and inhibition in bilingual children: Evidence from the dimen-
sional change card sort task. Developmental Science, 7, 325–339.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 21
Bialystok, E., Martin, M. M., & Viswanathan, M. (2005). Bilingualism across the lifespan: The rise and fall
of inhibitory control. International Journal of Bilingualism, 9, 103–119.
Brunner, R. J., Kornhuber, H. H., Seemüller, E., Suger, G., & Wallesch, C. W. (1982). Basal ganglia participa-
tion in language pathology. Brain and Language, 16, 281–299.
Buchweitz, A., Mason, R. A., Hasegawa, M., & Just, M. A. (2009). Japanese and English sentence reading
comprehension and writing systems: An fMRI study of first and second language effects on brain activa-
tion. Bilingualism: Language and Cognition, 12, 141–151.
Buchweitz, A., Shinkareva, S. V., Mason, R. A., Mitchell, T. M., & Just, M. (2012). Identifying bilingual
semantic neural representations across languages. Brain and Language, 120(3), 282–289.
Carlson, S. M., & Meltzoff, A. N. (2008). Bilingual experience and executive functioning in young children.
Developmental Science, 11, 282–298.
Chee, M. L., Tan, E. L., & Thiel, T. (1999). Mandarin and English single word processing studied with func-
tional magnetic resonance imaging. The Journal of Neuroscience, 19, 3050–3056.
Code, C. (1994). Speech automatism production in aphasia. Journal of Neurolinguistics, 8, 135–148.
Cohen, J. D., Perlstein, W. M., Braver, T. S., Nystrom, L. E., Noll, D. C., Jonides, J., & Smith, E. E. (1997).
Temporal dynamics of brain activation during a working memory task. Nature, 386, 604-608.
Cohen, M. X., & Frank, M. J. (2009). Neurocomputational models of basal ganglia function in learning,
memory and choice. Behavioural Brain Research, 199, 141–156.
Cohen, N. J., & Squire, L. R. (1980). Preserved learning and retention of pattern-analyzing skill in amnesia:
dissociation of knowing how and knowing that. Science, 210, 207–210.
Colzato, L. S., Bajo, M. T. T., van den Wildenberg, W., Paolieri, D., Nieuwenhuis, S., La Heij, W., & Hommel,
B. (2008). How does bilingualism improve executive control? A comparison of active and reactive inhibi-
tion mechanisms. Journal of Experimental Psychology: Learning, Memory, and Cognition, 34, 302–312.
Cools, R., Clark, L., & Robbins, T. W. (2004). Differential Responses in Human Striatum and Prefrontal
Cortex to Changes in Object and Rule Relevance. The Journal of Neuroscience, 24(5), 1129–1135.
Costa, A., & Santesteban, M. (2004). Lexical access in bilingual speech production: Evidence from language
switching in highly proficient bilinguals and L2 learners. Journal of Memory and Language, 50, 491–511.
Crinion, J., Turner, R., Grogan, A., Hanakawa, T., Noppeney, U., Devlin, J. T., …Price, C. J. (2006). Language
control in the bilingual brain. Science, 312, 1537–1540.
Crone, E., Wendelken, C., Donohue, S., & Bunge, S. (2006). Neural evidence for dissociable components of
task-switching. Cerebral Cortex, 16, 475–486.
Dehaene, S., Dupoux, E., Mehler, J., Cohen, L., Paulesu, E., Daniela, P., & Bihan, D. (1997). Anatomical vari-
ability in the cortical representation of first and second language. NeuroReport, 8, 3809–3815.
DeLong, M. (1990). Primate models of movement disorders of basal ganglia origin. Trends in Neurosciences,
13, 281–285.
D’Esposito, M., & Alexander, M. (1995): Subcortical aphasia: Distinct profiles following left putaminal hem-
orrhage. Neurology, 45, 38–41.
Eickhoff, S. B., Laird, A. R., Grefkes, C., Wang, L. E., Zilles, K., & Fox, P. T. (2009). Coordinate-based
activation likelihood estimation meta-analysis of neuroimaging data: a random-effects approach based on
empirical estimates of spatial uncertainty. Human Brain Mapping, 30, 2907–2926.
Ericsson, K. A., Chase, W. G., & Faloon, S. (1980). Acquisition of a memory skill. Science, 208, 1181–1182.
Fabbro, F. (2001). The bilingual brain: Cerebral representation of languages. Brain and Language, 79,
Festman, J. (2012). Language control abilities of late bilinguals. Bilingualism: Language and Cognition,
15(3), 580–593.
Festman, J., Rodriguez-Fornells, A., & Münte, T. F. (2010). Individual differences in control of language
interference in late bilinguals are mainly related to general executive abilities. Behavioral and Brain
Functions, 6, 1–12.
Frank, M. J., Loughry, B., & O’Reilly, R. C. (2001). Interactions between frontal cortex and basal ganglia in
working memory: A computational model. Cognitive, Affective & Behavioral Neuroscience, 1, 137–160.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
22 International Journal of Bilingualism 0(0)
Frank, M. J., Seeberger, L. C., & O’Reilly, R. C. (2004). By carrot or by stick: Cognitive reinforcement learn-
ing in Parkinsonism. Science, 306, 1940–1943.
Friederici, A. D. (2006). What’s in control of language? Nature Neuroscience, 9, 991-992.
Friston, K. J., Harrison, L., & Penny, W. (2003). Dynamic causal modelling. NeuroImage, 19, 1273–1302.
Gandour, J., Tong, Y., Talavage, T., Wong, D., Dzemidzic, M., Xu, Y., …Lowe, M. (2007). Neural basis of
first and second language processing of sentence-level linguistic prosody. Human Brain Mapping, 28,
Garbin, G., Sanjuan, A., Forn, C., Bustamante, J. C., Rodriguez-Pujadas A., Belloch, V., & Avila, C.
(2010). Bridging language and attention: Brain basis of the impact of bilingualism on cognitive control.
NeuroImage, 52, 1272–1278.
Ghosh, S., Basu, A., Khushu, S., & Kumaran, S. S. (2009). Cortical activity modulation of language process-
ing by dynamic optimization of task complexity and functional restrictions. Nature Precedings. Retrieved
Gilbert, S. J., & Shallice, T. (2002). Task switching: a PDP model. Cognitive Psychology, 44, 297–337.
Gillies, A., & Arbuthnott, G. (2000). Computational models of the basal ganglia. Movement Disorders, 15,
Gotham, A. M., Brown, R. G., & Marsden, C. D. (1988). ‘Frontal’ cognitive function in patients with
Parkinson’s disease ‘on’ and ‘off Levodopa. Brain, 111, 299–321.
Grogan, A., Green, D. W., Ali, N., Crinion, J., & Price, C. J. (2009). Structural correlates of semantic and
phonemic fluency ability in first and second languages. Cerebral Cortex, 19, 2690–2698.
Gu, B.-M., Park, J.-Y., Kang, D.-H., Lee, S. J., Yoo, S. Y., Jo, H. J., … Kwon, J. S. (2008). Neural correlates
of cognitive inflexibility during task-switching in obsessive-compulsive disorder. Brain, 131, 155–164.
Gurney, K., Prescott, T. J., & Redgrave, P. (2001). A computational model of action selection in the basal
ganglia. I. a new functional anatomy. Biological Cybernetics, 84, 401–410.
Hernandez, A. E., Martinez, A., & Kohnert, K. (2000). In search of the language switch: An fMRI study of
picture naming in Spanish–English bilinguals. Brain and Language, 73, 421–431.
Hernandez, A. E., & Meschyan, G. (2006). Executive function is necessary to enhance lexical processing in a
less proficient L2: Evidence form fMRI during picture naming. Bilingualism: Language and Cognition,
9, 177–188.
Jaeggi, S. M., Buschkuehl, M., Jonides, J., & Perrig, W. J. (2008). Improving fluid intelligence with training
on working memory. Proceedings of the National Academy of Sciences, 105, 6829–6833.
Just, M. A., Carpenter, P. A., Keller, T. A., Eddy, W. F., & Thulborn, K. R. (1996). Brain activation modulated
by sentence comprehension. Science, 274, 114–116.
Klein, D., Milner, B., Zatorre, R. J., Meyer, E., & Evans, A. (1995). The neural substrates underlying word
generation: A bilingual functional-imaging study. Proceedings of the National Academy o Sciences of the
United States of America, 92, 2899–2903.
Klein, D., Watkins, K. E., Zatorre, R. J., & Milner, B. (2006). Word and nonword repetition in bilingual sub-
jects: A PET study. Human Brain Mapping, 27, 153–161.
Knowlton, B. J., Mangels, J. A., & Squire, L. R. (1996). A neostriatal habit learning system in humans.
Science, 273, 1399–1402.
Lehtonen, M., Laine, M., Niemi, J., Thomson, T., Vorobyev, V. A., & Hughdal, K. (2005). Brain correlates of
sentence translation in Finnish-Norwegian bilinguals. NeuroReport, 16, 607–610.
Lewis, R. L., & Vasishth, S. (2005). An activation-based model of sentence processing as skilled memory
retrieval. Cognitive Science, 29, 375–419.
Logan, G. D., & Cowan, W. B. (1984). On the ability to inhibit thought and action: A theory of an act of con-
trol. Psychological Review, 91, 295–327.
Luk, G., Bialystok, E., Craik, F. I. M., & Grady, C. (2011, April). Experience-induced changes in brain struc-
tures and functions: Influence of lifelong bilingualism. Poster presented at the 18th Annual meeting of the
Cognitive Neuroscience Society, San Francisco, CA.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 23
Majerus, S., Belayachi, S., DeSmedt, B., Leclercq, A. L., Martinez, T., Schmidt, C., & Maquet, P. (2008).
Neural networks for short-term memory for order differentiate high and low proficiency bilinguals.
Neuroimage, 42, 1698–1713.
McNab, F., & Klingberg, T. (2008). Prefrontal cortex and basal ganglia control access to working memory.
Nature Neuroscience, 11, 103–107.
Meschyan, G., & Hernandez, E. (2006). Impact of language proficiency and orthographic transparency on
bilingual word reading: An fMRI investigation. Neuroimage, 29, 1135–1140.
Meyer, D. E., & Kieras, D. E. (1997). A computational theory of executive cognitive processes and multiple-
task performance. 1. Basic Mechanisms. Psychological Review, 104, 3–65.
Miller, E. K. (2000). The prefrontal cortex and cognitive control. Nature Reviews Neuroscience, 1, 59–65.
Miyake, A., Friedman, N. P., Emerson, M. J., Witzki, A. H., Howerter, A., & Wager, T. D. (2000). The unity
and diversity of executive functions and their contributions to complex “frontal lobe” tasks: A latent vari-
able analysis. Cognitive Psychology, 41, 49–100.
Monchi, O., Petrides, M., Strafella, A. P., Worsley, K. J., & Doyon, J. (2006). Functional role of the basal
ganglia in the planning and execution of actions. Annals of Neurology, 59, 257–264.
Monsell, S. (2003). Task switching. Trends in Cognitive Sciences, 7, 134–140.
Montague, P. R., King-Casas, B., & Cohen, J. D. (2006). Imaging valuation models in human choice. Annual
Review of Neuroscience, 29, 417–448.
O’Reilly, R. C., & Frank, M. J. (2006). Making working memory work: a computational model of learning in
the prefrontal cortex and basal ganglia. Neural Computation, 18, 283–328.
O’Reilly, R. C., & Munakata, Y. (2000). Computational explorations in cognitive neuroscience. Cambridge,
MA: MIT Press.
Owen, A. M., Roberts, A. C., Hodges, J. R., & Robbins, T. W. (1993). Contrasting mechanisms of impaired
attentional set-shifting in patients with frontal lobe damage or Parkinson’s disease. Brain, 116, 1159–1175.
Packard, M. G., & Knowlton, B. J. (2002). Learning and memory functions of the basal ganglia. Annual
Review of Neuroscience, 25, 563–593.
Packard, M. G., & McGaugh, J. L. (1992). Double dissociation of fornix and caudate nucleus lesions on acqui-
sition of two water maze tasks: Further evidence for multiple memory systems. Behavioral Neuroscience,
106, 439–446.
Paradis, M. (2004). A neurolinguistic theory of bilingualism. Amsterdam, the Netherlands: John Benjamin
Parvizi, J. (2009). Corticocentric myopia: old bias in new cognitive sciences. Trends in Cognitive Sciences,
13, 354–359.
Perani, D., Abutalebi, J., Paulesu, E., Brambati, S. Scifo, P. Cappa, S., & Fazio, F. (2003). The role of age of
acquisition and language usage in early, high-proficient bilinguals: An fMRI study during verbal fluency.
Human Brain Mapping, 19, 170–182.
Posner, M. I., & Cohen, Y. (1984). Components of visual orienting. In H. Bouma & D. G. Bouwhuis (Eds.),
Attention and performance: Control of language processes (pp. 531–556). Hillsdale, NJ: Erlbaum.
Prat, C. S., & Just, M. A. (2011). Exploring the cortical dynamics underpinning individual differences in
sentence comprehension. Cerebral Cortex, 21, 1747–1760.
Price, C. J., Green, D., & von Studnitz, R. A. (1999). Functional imaging study of translation and language
switching. Brain, 122, 2221–2236.
Prior, A., & MacWhinney, B. (2010). A bilingual advantage in task switching. Bilingualism: Language and
Cognition, 13, 253–262.
Raymond, J. E., Shapiro, K. L., & Arnell, K. M. (1992). Temporary suppression of visual processing in an
RSVP task: an attentional blink? Journal of experimental psychology: Human perception and perfor-
mance, 18, 849-860.
Robles, S. G., Gatignol, P., Capelle, L., Mitchell, M. C., & Duffau, H. (2005). The role of dominant striatum
in language: a study using intraoperative electrical stimulations. Journal of Neurology, Neurosurgery &
Psychiatry, 76, 940-946.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
24 International Journal of Bilingualism 0(0)
Rodriguez-Fornells, A., van der Lugt, A., Rotte, M., Britti, B., Heinze, H.-J. J., & Münte, T. F. (2005). Second
language interferes with word production in fluent bilinguals: brain potential and functional imaging evi-
dence. Journal of Cognitive Neuroscience, 17, 422–433.
Rogers, R. D., Sahakian, B. J., Hodges, J. R., Polkey, C. E., Kennard, C., & Robbins, T. W. (1998). Dissociating
executive mechanisms of task control following frontal lobe damage and Parkinson’s disease. Brain, 121,
Rueschemeyer, S. A., Fiebach, C. J., Kempe, V., & Friederici, A. D. (2005). Processing lexical semantic and
syntactic information in first and second language: fMRI evidence from German and Russian. Human
Brain Mapping, 25, 266–286.
Schneider, D. W., & Logan, G. D. (2005). Modeling task switching without switching tasks: a short-term
priming account of explicitly cued performance. Journal of Experimental Psychology: General, 134,
Shallice, T., & Burgess, P. W. (1991). Deficits in strategy application following frontal lobe damage in man.
Brain, 114, 727–741.
Simon, J. R., Acosta, E., Jr., Mewaldt, S. P., & Speidel, C. R. (1976). The effect of an irrelevant directional cue
on choice reaction time: Duration of the phenomenon and its relation to stages of processing. Perception
& Psychophysics, 19, 16–22.
Sohn, M. H., & Anderson, J. R. (2001). Task preparation and task repetition: two-component model of task
switching. Journal of Experimental Psychology: General, 130, 764–778.
Sohn, M.-H., Goode, A., Stenger, V. A., Carter, C. S., & Anderson, J. R. (2003). Competition and representa-
tion during memory retrieval: Roles of the prefrontal cortex and the posterior parietal cortex. Proceedings
of the National Academy of Sciences of the United States of America, 100, 7412–7417.
Sohn, M.-H., Ursu, S., Anderson, J. R., Stenger, V. A., and Carter, C. S. (2000). The role of prefrontal cortex
and posterior parietal cortex in task switching. Proceedings of the National Academy of Sciences, 97,
Squire, L. R. (1992). Declarative and nondeclarative memory: Multiple brain systems supporting learning and
memory. Journal of Cognitive Neuroscience, 4, 232–243.
Squire, L. R. (2004). Memory systems of the brain: a brief history and current perspective. Neurobiology of
Learning and Memory, 82, 171–177.
Stocco, A., & Anderson, J. R. (2008). Endogenous control and task representation: An fMRI study in alge-
braic problem-solving. Journal of Cognitive Neuroscience, 20, 1300–1314.
Stocco, A., & Crescentini, C. (2005). Syntactic comprehension in agrammatism: A computational model.
Brain and Language, 95, 127–128.
Stocco, A., Lebiere, C., & Anderson, J. R. (2010). Conditional routing of information to the cortex: A model
of the basal ganglia’s role in cognitive coordination. Psychological Review, 117, 541–574.
Strange, B. A., Henson, R. N. A., Friston, K. J., & Dolan, R. J. (2001). Anterior prefrontal cortex mediates rule
learning in humans. Cerebral Cortex, 11, 1040–1046.
Taatgen, N. A., Juvina, I., Herd, S., Jilk, D., & Martens, S. (2007). Attentional Blink: an internal traffic jam?
In R. Lewis & T. Polk (Eds.), Proceedings of the Eight International Conference on Cognitive Modeling
(pp. 91–96 ST - Attentional Blink: an internal traffic). New York, NY: Psychology Press.
Taatgen, N. A., & Anderson, J. R. (2002). Why do children learn to say “Broke”? A model of learning the past
tense without feedback. Cognition, 86, 123–155.
Thompson-Schill, S. L., D’Esposito, M., Aguirre, G. K., & Farah, M. J. (1997). Role of left inferior prefron-
tal cortex in retrieval of semantic knowledge: A reevaluation. Proceedings of the National Academy of
Sciences of the United States of America, 94, 14792–14797.
Tom, S. M., Fox, C. R., Trepel, C., & Poldrack, R. A. (2007). The neural basis of loss aversion in decision-
making under risk. Science, 315, 515–518.
Ullman, M. T. (2001a). A neurocognitive perspective on language: The declarative/procedural model. Nature
Reviews Neuroscience, 2, 717–726.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
Stocco et al. 25
Ullman, M. T. (2001b). The neural basis of lexicon and grammar in first and second language: the declarative/
procedural model. Bilingualism: Language and Cognition, 4, 105–122.
Ullman, M. T., Corkin, S., Coppola, M., Hickok, G., Growdon, J. H., Koroshetz, W. J., & Pinker, S. (1997).
A neural dissociation within language: Evidence that the mental dictionary is part of declarative memory,
and that grammatical rules are processed by the procedural system. Journal of Cognitive Neuroscience,
9, 266–276.
Vargha-Khadem, F., Watkins, K. E., Price, C. J., Ashburner, J., Alcock, K. J., Connelly, A., …Passingham, R.
E. (1998). Neural basis of an inherited speech and language disorder. Neurobiology, 95, 12695–12700.
Vingerhoets, G., Borsel, J. V., Tesink, C., Noort, M., Deblaere, K., Seurinck, R., …Achten, E. (2003).
Multilingualism: An f MRI study. NeuroImage, 20, 2181–2196.
Waldie, K. E., Badzakova-Trajkov, G., Miliivojevic, B., & Kirk I. J. (2009) Neural activity during Stroop col-
our-word task performance in late proficient bilinguals: A functional magnetic resonance imaging study.
Psychology & Neuroscience, 2, 125–136.
Wartenburger, H. R., Abutalebi, J., Cappa, S. F., Villringer, A., & Perani, D. (2003). Early setting of grammati-
cal processing in the bilingual brain. Neuron, 37, 159–170.
Watkins, K. E., Vargha-Khadem, F., Ashburner, J., Passingham, R. E., Connelly, A., Friston, K. J., & Gadian,
D. G. (2002). MRI analysis of an inherited speech and language disorder: Structural brain abnormalities.
Brain, 125, 465–478.
Yehene, E., Meiran, N., & Soroker, N. (2008). Basal ganglia play a unique role in task switching within the
Frontal-Subcortical circuits: Evidence from patients with focal lesions. Journal of Cognitive Neuroscience,
20, 1079–1093.
Yeung, N., & Monsell, S. (2003). Switching between tasks of unequal familiarity: the role of stimulus-attribute
and response-set selection. Journal of Experimental Psychology: Human Perception and Performance,
29, 455–469.
Yokoyama, S., Okamoto, H., Miyamoto, T., Yoshimoto, K., Kim, J., Iwata, K., …Kawashima, R. (2006).
Cortical activation in the processing of passive sentences in L1 and L2: An fMRI study. NeuroImage, 30,
Zanini, S., Tavano, A., & Fabbro, F. (2010). Spontaneous language production in bilingual Parkinson’s dis-
ease patients: Evidence of greater phonological, morphological and syntactic impairments in native lan-
guage. Brain and Language, 113, 84-89.
Zanini, S., Tavano, A., Vorano, L., Schiavo, F., Gigli, G. L., Aglioti, S. M., & Fabbro, F. (2004). Greater
syntactic impairments in native language in bilingual Parkinsonian patients. Journal of Neurology,
Neurosurgery, and Psychiatry, 75, 1678–1681.
Author biographies
Andrea Stocco is a Research Assistant Professor in the Department of Psychology and at the Institute for
Learning and Brain Sciences at the University of Washington. His research uses the combination of func-
tional neuroimaging and computational models to investigate the nature of higher-level cognitive processes.
He is particularly interested in the role of the basal ganglia in cognitive flexibility.
Briana Yamasaki is a first-year graduate student in the Department of Psychology at the University of
Washington. In collaboration with Drs Prat and Stocco, her research investigates the nature of improved
executive functions in individuals who develop bilingually.
Rodion Natalenko is an honors student in the Department of Psychology at the University of Washington,
working at the Cognition and Cortical Dynamics Laboratory in collaboration with Drs Prat and Stocco. His
research interests include individual differences in cognitive styles and their implications for information
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
26 International Journal of Bilingualism 0(0)
Chantel S Prat is an Assistant Professor in the Department of Psychology and at the Institute for Learning
and Brain Sciences at the University of Washington. Her research uses multiple methodologies to explore the
biological basis of individual differences in cognitive abilities, with an emphasis on language comprehension.
Recently, in collaboration with Dr Stocco, she has begun a series of investigations of the biological basis of
improved executive functioning in bilinguals.
at Universitaetsbibliothek Potsdam on August 28, 2012ijb.sagepub.comDownloaded from
... How do bilinguals do this? The literature this chapter reviews shows that over a lifetime of usage, bilinguals rely on several networks including the salience network (Seeley et al., 2007) during language acquisition and training, and perhaps also in high language diversity contexts, when proactive control is paramount and this observation is entirely in keeping with the neurobiological framework developed by Stocco et al (2014) who focused on the role of the basal ganglia in gating access to the frontal lobes via the frontostriatal loops. Later, as bilinguals achieve greater mastery of their second language, they express greater bilateral connectivity between the inferior frontal gyri of the frontoparietal control network (Vincent et al., 2008). ...
... In many studies of young adult bilinguals, a common finding is increased bilateral connectivity between (usually) the inferior frontal gyri than monolingual controls or less advanced bilinguals. At first glance, this pattern appears incongruous with models of bilingualism arguing for shifts in activity from frontal to posterior and subcortical regions (Grant et al., 2014;Grundy et al., 2017;Stocco et al., 2014). Higher connectivity however implies distributed load, and reduced burden on any single brain region, and this may also be interpreted as a hallmark of neural efficiency. ...
... Increased posterior connectivity fits with models of neural efficiency (e.g., Grant et al., 2014;Grundy et al., 2017;Stocco et al., 2014). Interestingly, later age of onset, also predicted higher fractional anisotropy (FA) or white matter integrity in the corpus callosum, possibly as managing the languages was an ongoing challenge requiring greater intervention from the salience network and had not yet become automatic. ...
Full-text available
Four patterns describe how bilingualism affects the functional connectivity of the brain. First, a general observation across most of the studies I surveyed was that bilinguals tended to have higher functional connectivity when compared to monolinguals. Second, increased connectivity with the salience network, a set of regions including the anterior cingulate cortex, the bilateral insula, and subcortical regions is often associated with language training or language diversity where proactive attention to content is paramount. Third, to the degree that individuals have greater exposure or mastery of a second language, (greater proficiency and an earlier or simultaneous age of acquisition) and can rely more on reactive control, studies often show greater bilateral connectivity between the inferior frontal gyri. This is also sometimes associated with decreased activation of frontal regions implying distributed load and greater neural efficiency. The distributed neural pattern in young adulthood may also explain how bilingual older adults are able to sustain their cognition at levels of neuropathology most monolinguals cannot endure. Fourth, in studies that examined anticorrelations between task and rest networks, bilinguals tended to have more distinct (e.g., modular organization), and more strongly anticorrelated task-positive and default-mode networks, and this was often correlated with cognitive control.
... This gating system could dynamically regulate the flow of information to the prefrontal cortex, a brain region implicated in cognitive control. [6]. Besides, a structural MRI study shows that bilingualism is associated with increased gray matter volume in frontal, parietal and temporal regions among adults, which is involved in cognitive control and language processing [7]. ...
Full-text available
Linguistic code-switching is a common phenomenon among bilinguals that requires extensive executive control to manage two languages. However, limited research has specifically examined whether frequent code-switching enhances cognitive inhibition as measured by the Stroop test. Understanding this relationship has important implications for harnessing bilingual advantages in inhibition and executive functioning. Therefore, this study aimed to investigate whether bilingual adolescents who engage in code-switching demonstrate improved cognitive inhibition compared to monolingual peers. Participants were 81 Chinese-English bilinguals aged 14-18, who were assigned to English reading, Chinese reading, or mixed language reading groups. Participants then completed Stroop tests. Results revealed the mixed language group had significantly faster response times on incongruent Stroop trials compared to both monolingual groups, indicating enhanced cognitive inhibition from code-switching. No significant difference emerged between the English and Chinese groups, implying monolingual reading in either language does not differentially impact inhibition.
... . The cortical (black) and subcortical-cortical pathways (grey) of the bilingual language control network. For a detailed description of the role of the basal ganglia in subcortical-cortical connections see Stocco et al. (2014). PFC: Prefrontal cortex; ACC: Anterior cingulate cortex; Pre-SMA: Pre-supplementary motor área; BG: Basal ganglia; IPL: Inferior parietal lobule The role of the IPLs (including the supramarginal gyrus) in language control has been related to biasing language selection away from the language not in use (the left IPL) and biasing selection toward the language in use (the right IPL). ...
The field of neuropsychology can contribute to bilingualism research from a multidisciplinary perspective that ranges from psycholinguistics and brain imaging studies. While the psycholinguistic approach provides the outlook on linguistic processes in experimental study of patients with brain damage, neural models define the underlying brain areas of such processes and help to predict language deficits in said patients. Current neural models of bilingualism do not provide accurate predictions of deficits in bilinguals with brain damage since they have not been tested in a systematic way. However, they do offer a roadmap for the underlying cognitive and linguistic processes of bilingual language control and speech production. In this chapter, I propose how a neurolinguistic approach to bilingualism might be implemented in neuropsychology by including: (a) the application of traditional methods of cognitive (neuro)psychology to the field of bilingualism, such as dissociations, (b) the use of psycholinguistic methods, and (c) how neurodegenerative diseases may be a neuropsychological paradigm in which one can study bilingual language processes.
... The latter children were also fluent in English, rendering them bilingual. Bilingualism, in turn, is associated with superior EF (Stocco et al., 2014). Hence, the group difference regarding language abilities may have made it more difficult to detect mindfulness-related benefits for EF. ...
Full-text available
The present study examined whether both dispositional mindfulness without mindfulness training and mindfulness resulting from longer-term mindfulness training are positively associated with pre-adolescents' well-being, via enhanced executive functioning (EF) and emotion regulation. EF was assessed in a GoNoGo task via behavioral performance and event-related potentials. Study 1 (N = 62) investigated associations of dispositional mindfulness without mindfulness training with EF, well-being and emotion regulation; longitudinal Study 2 with an active control group compared the effects of long-term mindfulness training (N = 28) with a positive psychology intervention (N = 15). Dispositional mindfulness without training was associated with lower EF, unrelated to emotion regulation and the relationship with well-being was mixed. Long-term mindfulness training was positively related to EF and well-being (reduced negative affect), but was uncorrelated with emotion regulation and mindfulness scores. Taken together, long-term mindfulness training was found to have mixed effects. Further research is required in this area.
... We used the Unified Bilingual Experience Trajectory (UBET) framework ( DeLuca et al., 2020 ) as a basis for our predictions and experience measures. The UBET framework is based on previous findings and models, specifically the Adaptive Control Hypothesis (ACH) ( Abutalebi and Green, 2016 ;Green and Abutalebi, 2013 ), the Conditional Routing Model (CRM) ( Stocco et al., 2014 ;Stocco et al., 2010 ), the Bilingual Anterior to Posterior and Subcortical Shift (BAPSS) framework ( Grundy et al., 2017 ) and the Dynamic Restructuring Model (DRM) ( Pliatsikas, 2020 ). These models stress different aspects of bilingualism and how these affect various brain areas involved in cognitive control. ...
Bilinguals have often, but not always, been found to outperform monolinguals on domain-general attentional control. Inconsistent findings have been argued to stem, at least partly, from treating bilingualism as a uniform category and from not considering how neural adaptations to bilingual experiences modulate behavioural outcomes. The present study investigated how patterns of language experience, including language switching behaviour, duration and intensity/diversity of bilingual language use, influence the brain processes underlying cognitive control, and how these in turn translate to cognitive control performance. We examined reaction times and spectral dynamics of the electroencephalograms (EEG) of two-hundred-and-thirty-nine participants (about 70% bilinguals) with diverse language experiences during two cognitive control paradigms testing interference suppression (flanker and Simon task). Using structural equation modelling, we found that different bilingual experience factors were related with neurocognitive measures, which in turn were related with behavioural interference effects, for the flanker but not the Simon task. More specifically, increased frequency of language switching and intensity / diversity of bilingual language usage was negatively related to induced top-down control measures (especially midline-frontal theta), which in turn was beneficial for interference control. In contrast, duration of bilingual engagement correlated negatively with evoked bottom-up control measures (especially P3) and was therefore detrimental to interference control. We demonstrate here for the first time how the different factors of bilingual experience lead to different neural adaptations which impact behavioural outcomes. SIGNIFICANCE STATEMENT: Like other intensive experiences, bilingualism leads to brain adaptations. It results in structural changes in language areas, and, due to demands on language control, in brain areas associated with domain-general cognitive control. Related to this, bilinguals often outperform monolinguals on cognitive control tasks. But what is often ignored is that bilingualism is a multi-dimensional phenomenon, with variations such as diversity of language usage and duration of language use. The present large-scale study of neural functioning in bilingualism revealed for the first time how individual differences in bilingual experience lead to adaptations to brain functioning which in turn affect cognitive control behaviour. It exemplifies how the complexity of individual experiences plays a fundamental role in brain function.
... It has also been well established that an individual's languages are concurrently active irrespective of whether only one is being used at any given time (Kroll, Bobb, Misra & Guo, 2008;Wu & Thierry, 2010). Accordingly, suppression of non-target language(s) is a regular cognitive activity for bi/multilinguals, which is thought to enhance executive function beyond the domain of language (Abutalebi & Green, 2007;Stocco, Yamasaki, Natalenko & Prat, 2014). Such cognitive control may be heightened in individuals living in highly linguistically diverse contexts such as South Africa, explaining why we did not observe group differences in IC. ...
Full-text available
English is imposed as the language of instruction in multiple linguistically diverse societies where there is more than one official language. This might have negative educational consequences for people whose first language (L1) is not English. To investigate this, 47 South Africans with advanced English proficiency but different L1s (L1-English vs. L1-Zulu) were evaluated in their listening comprehension ability. Specifically, participants listened to narrative texts in English which prompted an initial inference followed by a sentence containing an expected inference or an unexpected but plausible concept, assessing comprehension monitoring. A final question containing congruent or incongruent information in relation to the text information followed, assessing the revision process. L1-English participants were more efficient at monitoring and revising their listening comprehension. Furthermore, individual differences in inhibitory control were associated with differences in revision. Results show that participants’ L1 appears to supersede their advanced English proficiency on highly complex listening comprehension.
Inferencing is defined as 'the act of deriving logical conclusions from premises known or assumed to be true', and it is one of the most important processes necessary for successful comprehension during reading. This volume features contributions by distinguished researchers in cognitive psychology, educational psychology, and neuroscience on topics central to our understanding of the inferential process during reading. The chapters cover aspects of inferencing that range from the fundamental bottom up processes that form the basis for an inference to occur, to the more strategic processes that transpire when a reader is engaged in literary understanding of a text. Basic activation mechanisms, word-level inferencing, methodological considerations, inference validation, causal inferencing, emotion, development of inferences processes as a skill, embodiment, contributions from neuroscience, and applications to naturalistic text are all covered as well as expository text, online learning materials, and literary immersion.
Multilingualism affects cognitive, behavioral, and neural function across the lifespan. Here, we review the neuroimaging literature on bilingualism, multilingualism, and executive functions, focusing on three multilingual groups who rely on language control to varying degrees to overcome competition from other languages: third-language learners, multilingual adults, and simultaneous interpreters. In third-language learners, changes in brain regions underlying executive functions occur during the early stages of acquiring another language. In multilingual adults, effects of language experience reflect a qualitative difference between monolingual and multilingual processing rather than cumulative effects of increased linguistic knowledge. In simultaneous interpreters, changes in gray matter volume and white matter integrity are found in areas underlying language selection and executive functions, reflecting neural efficiency due to experience with rapid translation. The implications of these findings for our understanding of multilingualism and the value of moving beyond the monolingual–bilingual dichotomy are discussed.
Bilingualism is a ubiquitous global phenomenon. Beyond being a language experience, bilingualism also entails a social experience, and it interacts with development and learning, with cognitive and neural consequences across the lifespan. The authors of this volume are world renowned experts across several subdisciplines including linguistics, developmental psychology, and cognitive neuroscience. They bring to light bilingualism’s cognitive, developmental, and neural consequences in children, young adults, and older adults. This book honors Ellen Bialystok, and highlights her profound impact on the field of bilingualism research as a lifelong experience. The chapters are organized into four sections: The first section explores the complexity of the bilingual experience beyond the common characterization of “speaking multiple languages.” The next section showcases Ellen Bialystok’s earlier impact on psychology and education; here the contributors answer the question “how does being bilingual shape children’s development?” The third section explores cognitive and neuroscientific theories describing how language experience modulates cognition, behavior, and brain structures and functions. The final section shifts the focus to the impact of bilingualism on healthy and abnormal aging and asks whether being bilingual can stave off the effects of dementia by conferring a “cognitive reserve.”
Full-text available
Bilinguals employ both global and local control mechanisms to manage coactivated languages that compete for selection, yet little is known about how they operate on morphosyntactic information. The current study investigated bilingual language control mechanisms for a morphosyntactic production task. Across two experiments, 48 early Spanish-English bilinguals completed rapid instructed task learning paradigms with priming-in-item-recognition manipulations that investigated the extent to which parallel activation was observed across languages and across rules of the same type within a language. The results from the current experiments showed that it was more difficult to reject incorrect responses in the correct target language than to reject incorrect responses that contained the correct grammatical manipulation executed in the nondesired language. These results suggest that global control at the level of target language selection is more effective than local control processes during a bilingual morphosyntactic manipulation. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
Full-text available
Language, regarded as a hierarchical cognitive code activated by functional operational modes of the brain by most neuropsychologists, is characterized by increased cognitive load in successively higher levels of processing. Language comprehension is posited to be executed through symbolic-iconic information being encoded neurally as modulated phenomena, and can be studied _in vivo_ by functional brain imaging. Using a lexical decision-making task in conjunction with syntactic error correction that effectively isolated the regulatory neural substrate of processing structural-functional information, and minimizing the possible confounds of gender and proficiency, functional magnetic resonance imaging (fMRI) was performed on bilingual volunteers to ascertain the attentional modulation of second language lexical and sentence processing. Our results indicate that while a right posterior cingulate gyrus-precuneus-lingual gyrus-cerebellar loop processes lexical information, the left inferior and middle frontal cortices are critically involved in the implementation of a structural-functional decision-making procedural loop in mediating second language comprehension.
Full-text available
The switch cost (the disadvantage of performing a new task vs. a repeated task) has been attributed to lack of preparation for the switched task or priming of the repeated task. These sources were examined by manipulating foreknowledge of task transition (repeat or switch), response-to-stimulus interval (RSI), and practice level. Regardless of foreknowledge, the cost decreased with RSI and practice. The reduction was greater with foreknowledge than with no foreknowledge, and the amount of switch cost did not depend on foreknowledge. These results suggest that the switch cost with foreknowledge may consist of both inadequate preparation and repetition benefit but the switch cost with no foreknowledge may reflect repetition benefit only. An ACT-R (adaptive control of thought-rational) model was proposed, accommodating both preparation and priming effect with 2 independent processes: conflict resolution among productions and decay of chunk activation.
Full-text available
Despite a need for rule learning in everyday life, the brain regions involved in explicit rule induction remain undetermined. Here we use event-related functional magnetic resonance imaging to measure learning-dependent neuronal responses during an explicit categor-ization task. Subjects made category decisions, with feedback, to exemplar letter strings for which the rule governing category membership was periodically changed. Bilateral fronto-polar prefrontal cortices were selectively engaged following rule change. This activation pattern declined with improving task performance reflecting rule acquisition. The vocabulary of letters comprising the exemplars was also periodically changed, independently of rule changes. This exemplar change modulated activation in left anterior hippocampus. Our finding that fronto-polar cortex mediates rule learning supports a functional contribution of this region to generic reasoning and problem-solving behaviours.
Full-text available
Twelve patients with focal damage of the frontal cortex and 12 patients with mild, medicated, early stage Parkinson's disease switched between letter- and digit=naming tasks on every second trial of a task-switching paradigm. Compared with age- and IQ-matched control performance, patients with left-sided, but not right-sided, frontal damage exhibited markedly increased time costs associated with these predictable switches only when there was a general incidence of interference or 'crosstalk' between the tasks, and particularly so when the available task cues were relatively weak and arbitrary. The same patients also showed evidence of an increased sensitivity to the facilitatory and inhibitory effects of previous processing, when required to switch between tasks. Both groups of patients (with left- or right-sided frontal damage) exhibited slow, disorganized performance early in practice. In contrast to these frontal effects, the Parkinson's disease patients showed little indication of larger time costs of task switches but they did show progressive increases in the error costs, while age- and IQ-matched control subjects showed reductions. We propose that while both left and right frontal cortical areas are involved in the organization of cognitive and motor processes in situations involving novel task demands, only the left frontal cortex is involved in the dynamic reconfiguring between already-established task-sets, and specifically, that it is the site of an executive mechanism responsible for the modulation of exogenous task-set activity. Finally, dopaminergic transmission, along the nigrostriatal pathway, may be implicated in sustaining various cognitive and motor processes over prolonged periods, including the operation of those executive control mechanisms that accomplish reconfiguring between task-sets.
A new theoretical framework, executive-process interactive control (EPIC), is introduced for characterizing human performance of concurrent perceptual-motor and cognitive tasks. On the basis of EPIC, computational models may be formulated to simulate multiple-task performance under a variety of circumstances. These models account well for reaction-time data from representative situations such as the psychological refractory-period procedure. EPIC's goodness of fit supports several key conclusions: (a) At a cognitive level, people can apply distinct sets of production rules simultaneously for executing the procedures of multiple tasks; (b) people's capacity to process information at "peripheral" perceptual-motor levels is limited; (c) to cope with such limits and to satisfy task priorities, flexible scheduling strategies are used; and (d) these strategies are mediated by executive cognitive processes that coordinate concurrent tasks adaptively.
The neural systems underlying translation and language switching were investigated using PET. Proficient German–English adult bilinguals were scanned whilst either translating or reading visually presented words in German (L1), English (L2) or alternating L1/L2. We refer to alternating L1/L2 as `switching'. The results revealed contrasting patterns of activation for translation and switching, suggesting at least partially independent mechanisms. Translation, but not switching, increased activity in the anterior cingulate and subcortical structures whilst decreasing activation in several other temporal and parietal language areas associated with the meaning of words. Translation also increased activation in regions associated with articulation (the anterior insula, cerebellum and supplementary motor area) arguably because the reading response to the stimulus must be inhibited whilst a response in a different language is activated. In contrast, switching the input language resulted in activation of Broca's area and the supramarginal gyri, areas associated with phonological recoding. The results are discussed in terms of the cognitive control of language processes.