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1.  ERP correlates of letter identity and letter position are modulated by lexical frequency 
Brain and language  2013;125(1):11-27.
The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (Experiment 1) and lexical decision (Experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition.
PMCID: PMC3612367  PMID: 23454070
visual-word recognition; position coding; ERPs; word-frequency; transposed-letter effects
2.  The Role of Age of Acquisition on Past Tense Generation in Spanish-English Bilinguals: an fMRI study 
Brain and language  2013;125(1):28-37.
At its most basic sense, the sensorimotor/emergentist (S/E) model suggests that early second language (L2) learning is preferentially reliant upon sensory and motor processes, while later L2 learning is accomplished by greater reliance on executive abilities. To investigate the S/E model using fMRI, neural correlates of L2 age of acquisition were examined by employing a past-tense generation task on 22 L2 proficient bilinguals. Early bilinguals preferentially recruited left hemisphere sensorimotor regions involved in motoric control and articulation. In contrast, later learners, to a greater degree, engaged regions involved in executive cognitive control and lexical access. The data support the notion that early L2 learners devote neural resources to motor control during lexical retrieval. In contrast, later L2 learners recruit executive control mechanisms to generate the past tense. These data are consistent with the S/E model of bilingual language learning, and serve as an extension of cognitive control theories.
PMCID: PMC3624750  PMID: 23454071
Bilingualism; Age of Acquisition; Sensorimotor; Cognitive Control; fMRI
3.  Impairment of script comprehension in Lewy body spectrum disorders 
Brain and language  2013;125(3):330-343.
A disabling impairment of higher-order language function can be seen in patients with Lewy body spectrum disorders such as Parkinson's disease (PD), Parkinson's disease dementia (PDD), and dementia with Lewy bodies (DLB). We focus on script comprehension in patients with Lewy body spectrum disorders. While scripts unfold sequentially, constituent events are thought to contain an internal organization. Executive dysfunction in patients with Lewy body spectrum disorders may interfere with comprehension of this internal structure. We examined 42 patients (30 non-demented PD and 12 mildly demented PDD/DLB patients) and 12 healthy seniors. We presented 22 scripts (e.g., “going fishing”), each consisting of six events. Pilot data from young controls provided the basis for organizing associated events into clusters and arranging them hierarchically into scripts. We measured accuracy and latency to judge the order of adjacent events in the same cluster versus adjacent events in different clusters. PDD/DLB patients were less accurate in their ordering judgments than PD patients and controls. Healthy seniors and PD patients were significantly faster to judge correctly the order of highly associated within-cluster event pairs relative to less closely associated different-cluster event pairs, while PDD/DLB patients did not consistently distinguish between these event-pair types. This relative insensitivity to the clustered-hierarchical organization of events was related to executive impairment and to frontal atrophy as measured by volumetric MRI. These findings extend prior work on script processing to patients with Lewy body spectrum disorders and highlight the potential impact of frontal/executive dysfunction on the daily lives of affected patients.
PMCID: PMC3940934  PMID: 23566691
Parkinson's disease; Parkinson's disease dementia; Dementia with Lewy bodies; Frontal cortex; Executive function; Scripts; Organization; Discourse; Volumetric MRI
4.  The ability to tap to a beat relates to cognitive, linguistic, and perceptual skills 
Brain and language  2013;124(3):225-231.
Reading-impaired children have difficulty tapping to a beat. Here we tested whether this relationship between reading ability and synchronized tapping holds in typically-developing adolescents. We also hypothesized that tapping relates to two other abilities. First, since auditory-motor synchronization requires monitoring of the relationship between motor output and auditory input, we predicted that subjects better able to tap to the beat would perform better on attention tests. Second, since auditory-motor synchronization requires fine temporal precision within the auditory system for the extraction of a sound’s onset time, we predicted that subjects better able to tap to the beat would be less affected by backward masking, a measure of temporal precision within the auditory system. As predicted, tapping performance related to reading, attention, and backward masking. These results motivate future research investigating whether beat synchronization training can improve not only reading ability, but potentially executive function and basic auditory processing as well.
PMCID: PMC3594434  PMID: 23400117
reading; auditory perception; attention; rhythm
5.  Age, Sex, and Verbal Abilities Affect Location of Linguistic Connectivity in Ventral Visual Pathway 
Brain and language  2013;124(2):184-193.
Previous studies have shown that the strength of connectivity between regions can vary depending upon the cognitive demands of a task. In this study, the location of task-dependent connectivity from the primary visual cortex (V1) was examined in 43 children (ages 9–15) performing visual tasks; connectivity maxima were identified for a visual task requiring a linguistic (orthographic) judgment. Age, sex, and verbal IQ interacted to affect maxima location. Increases in age and verbal IQ produced similar shifts in maxima location; in girls, connectivity maxima shifted primarily laterally within the left temporal lobe, whereas the shift was primarily posterior within occipital cortex among boys. A composite map across all subjects shows an expansion in the area of connectivity with age. Results show that the location of visual/linguistic connectivity varies systematically during development, suggesting that both sex differences and developmental changes in V1 connectivity are related to linguistic function.
PMCID: PMC3572208  PMID: 23376366
fMRI; connectivity; development; language; IQ; sex; reading
6.  Individual differences in neural regions functionally related to real and imagined stuttering 
Brain and language  2013;124(2):153-164.
Recent brain imaging investigations of developmental stuttering show considerable disagreement regarding which regions are related to stuttering. These divergent findings have been mainly derived from group studies. To investigate functional neurophysiology with improved precision, an individual-participant approach (N = 4) using event-related functional magnetic resonance imaging and test-retest reliability measures was performed while participants produced fluent and stuttered single words during two separate occasions. A parallel investigation required participants to imagine stuttering or not stuttering on single words. The overt and covert production tasks produced considerable within-subject agreement of activated voxels across occasions, but little within-subject agreement between overt and covert task activations. However, across-subject agreement for regions activated by the overt and covert tasks was minimal. These results suggest that reliable effects of stuttering are participant-specific, an implication that might correspond to individual differences in stuttering severity and functional compensation due to related structural abnormalities.
PMCID: PMC3625940  PMID: 23333668
stuttered words; mental imagery; brain imaging; fMRI; reliability
7.  Mouse vocal communication system: are ultrasounds learned or innate? 
Brain and language  2013;124(1):10.1016/j.bandl.2012.10.002.
Mouse ultrasonic vocalizations (USVs) are often used as behavioral readouts of internal states, to measure effects of social and pharmacological manipulations, and for behavioral phenotyping of mouse models for neuropsychiatric and neurodegenerative disorders. However, little is known about the neurobiological mechanisms of rodent USV production. Here we discuss the available data to assess whether male mouse song behavior and the supporting brain circuits resemble those of known vocal non-learning or vocal learning species. Recent neurobiology studies have demonstrated that the mouse USV brain system includes motor cortex and striatal regions, and that the vocal motor cortex sends a direct sparse projection to the brainstem vocal motor nucleus ambiguous, a projection thought be unique to humans among mammals. Recent behavioral studies have reported opposing conclusions on mouse vocal plasticity, including vocal ontogeny changes in USVs over early development that might not be explained by innate maturation processes, evidence for and against a role for auditory feedback in developing and maintaining normal mouse USVs, and evidence for and against limited vocal imitation of song pitch. To reconcile these findings, we suggest that the trait of vocal learning may not be dichotomous but encompass a broad set of behavioral and neural traits we call the continuum hypothesis, and that mice possess some of the traits associated with a capacity for limited vocal learning.
PMCID: PMC3886250  PMID: 23295209
ultrasonic vocalization; vocal learning; song system; mouse communication; motor cortex; deafening; call convergence; nucleus ambiguus
8.  Early gray-matter and white-matter concentration in infancy predict later language skills: A whole brain voxel-based morphometry study 
Brain and language  2012;124(1):34-44.
Magnetic Resonance Imaging (MRI) brain scans were obtained from 19 infants at 7 months. Expressive and receptive language performance was assessed at 12 months. Voxel-based morphometry (VBM) identified brain regions where gray-matter and white-matter concentrations at 7 months correlated significantly with children’s language scores at 12 months. Early gray-matter concentration in the right cerebellum, early white-matter concentration in the right cerebellum, and early white-matter concentration in the left posterior limb of the internal capsule (PLIC)/cerebral peduncle were positively and strongly associated with infants’ receptive language ability at 12 months. Early gray-matter concentration in the right hippocampus was positively and strongly correlated with infants’ expressive language ability at 12 months. Our results suggest that the cerebellum, PLIC/cerebral peduncle, and the hippocampus may be associated with early language development. Potential links between these structural predictors and infants’ linguistic functions are discussed.
PMCID: PMC3551987  PMID: 23274797
Voxel-based morphometry; Infancy; Cerebellum; Hippocampus; Posterior Limb of the Internal Capsule (PLIC); Cerebral Peduncle; Expressive Language; Receptive Language
9.  Reinforcement Learning in Young Adults with Developmental Language Impairment 
Brain and language  2012;123(3):154-163.
The aim of the study was to examine reinforcement learning (RL) in young adults with developmental language impairment (DLI) within the context of a neurocomputational model of the basal ganglia-dopamine system (Frank et al., 2004). Two groups of young adults, one with DLI and the other without, were recruited. A probabilistic selection task was used to assess how participants implicitly extracted reinforcement history from the environment based on probabilistic positive/negative feedback. The findings showed impaired RL in individuals with DLI, indicating an altered gating function of the striatum in testing. However, they exploited similar learning strategies as comparison participants at the beginning of training, reflecting relatively intact functions of the prefrontal cortex to rapidly update reinforcement information. Within the context of Frank’s model, these results can be interpreted as evidence for alterations in the basal ganglia of individuals with DLI.
PMCID: PMC3502713  PMID: 22921956
reinforcement learning; language; developmental language impairment; corticostriatal loops; Procedural Deficit Hypothesis
10.  Intact discourse cohesion and coherence following bilateral ventromedial prefrontal cortex 
Brain and language  2012;123(3):222-227.
Discourse cohesion and coherence give communication its continuity providing the grammatical and lexical links that hold an utterance or text together and give it meaning. Researchers often link cohesion and coherence deficits to the frontal lobes by drawing attention frontal lobe dysfunction in populations where discourse cohesion and coherence deficits are reported and through attribution of these deficits to underlying cognitive impairments putatively associated with the frontal lobes. We examined the distinct contribution of a region of the frontal lobes, the ventromedial prefrontal cortex (vmPFC), to discourse cohesion and coherence across a range of discourse tasks. We found that bilateral vmPFC damage does not impair cohesion and coherence in spoken discourse. This study provides insights into contribution of the major anatomical subdivisions of the frontal lobes to language use and furthers our understanding of the neural and cognitive underpinnings of discourse cohesion and coherence.
PMCID: PMC3541036  PMID: 23102898
cohesion; coherence; referential processing; ventromedial prefrontal cortex; discourse
11.  Elicitation of specific syntactic structures in primary progressive aphasia 
Brain and language  2012;123(3):183-190.
Many patients with primary progressive aphasia (PPA) are impaired in syntactic production. Because most previous studies of expressive syntax in PPA have relied on quantitative analysis of connected speech samples, which is a relatively unconstrained task, it is not well understood which specific syntactic structures are most challenging for these patients. We used an elicited syntactic production task to identify which syntactic structures pose difficulties for 31 patients with three variants of PPA: non-fluent/agrammatic, semantic and logopenic. Neurodegenerative and healthy age-matched participants were included as controls. As expected, non-fluent/agrammatic patients made the most syntactic errors. The structures that resulted in the most errors were constructions involving third person singular present agreement, and constructions involving embedded clauses. Deficits on this elicited production task were associated with atrophy of the left posterior inferior frontal gyrus.
PMCID: PMC3502680  PMID: 23046707
syntax; production; primary progressive aphasia; voxel-based morphometry
12.  Musical training during early childhood enhances the neural encoding of speech in noise 
Brain and language  2012;123(3):191-201.
For children, learning often occurs in the presence of background noise. As such, there is growing desire to improve a child’s access to a target signal in noise. Given adult musicians’ perceptual and neural speech-in-noise enhancements, we asked whether similar effects are present in musically-trained children. We assessed the perception and subcortical processing of speech in noise and related cognitive abilities in musician and nonmusician children that were matched for a variety of overarching factors. Outcomes reveal that musicians’ advantages for processing speech in noise are present during pivotal developmental years. Supported by correlations between auditory working memory and attention and auditory brainstem response properties, we propose that musicians’ perceptual and neural enhancements are driven in a top-down manner by strengthened cognitive abilities with training. Our results may be considered by professionals involved in the remediation of language-based learning deficits, which are often characterized by poor speech perception in noise.
PMCID: PMC3502676  PMID: 23102977
Auditory; Brainstem; ABR; Speech in Noise; Attention; Memory; Musicians; Children; Development
13.  Hemispheric Differences in the Organization of Memory for Text Ideas 
Brain and language  2012;123(3):145-153.
The goal of this study was to examine hemispheric asymmetries in episodic memory for discourse. Access to previously comprehended information is essential for mapping incoming information to representations of “who did what to whom” in memory. An item-priming-in-recognition paradigm was used to examine differences in how the hemispheres represent discourse. Both hemispheres retained accurate information about concepts from short passages, but the information was organized differently. The left hemisphere was sensitive to the structural relations among concepts in a text, whereas the right hemisphere differentiated information that appeared in one passage from information that appeared in another. Moreover, the right hemisphere, but not the left hemisphere, retained information about the spatial/temporal proximity among concepts in a passage. Implications of these results for the roles of the right and left hemispheres in comprehending connected discourse are discussed.
PMCID: PMC3502672  PMID: 23089586
14.  Children with Specific Language Impairment are not impaired in the acquisition and retention of Pavlovian delay and trace conditioning of the eyeblink response☆ 
Brain and Language  2013;127(3):428-439.
•We tested the integrity of small regions of the cerebellum and hippocampal formation in children with SLI.•Pavlovian delay conditioning engages elements of the procedural memory system.•Pavlovian trace conditioning engages procedural and declarative memory systems.•Children with Specific Language Impairment learned to delay and trace conditioning.•Brain regions engaged in eyeblink conditioning are normal in children with SLI.
Three converging lines of evidence have suggested that cerebellar abnormality is implicated in developmental language and literacy problems. First, some brain imaging studies have linked abnormalities in cerebellar grey matter to dyslexia and specific language impairment (SLI). Second, theoretical accounts of both dyslexia and SLI have postulated impairments of procedural learning and automatisation of skills, functions that are known to be mediated by the cerebellum. Third, motor learning has been shown to be abnormal in some studies of both disorders. We assessed the integrity of face related regions of the cerebellum using Pavlovian eyeblink conditioning in 7–11 year-old children with SLI. We found no relationship between oral language skills or literacy skills with either delay or trace conditioning in the children. We conclude that this elementary form of associative learning is intact in children with impaired language or literacy development.
PMCID: PMC3847270  PMID: 24139661
Specific Language Impairment; SLI; Pavlovian; Classical; Conditioning; Eyeblink; Delay; Trace; Cerebellum; Procedural
15.  Contrast of hemispheric lateralization for oro-facial movements between learned attention-getting sounds and species-typical vocalizations in chimpanzees: Extension in a second colony 
Brain and language  2012;123(1):10.1016/j.bandl.2012.07.002.
Studies involving oro-facial asymmetries in nonhuman primates have largely demonstrated a right hemispheric dominance for communicative signals and conveyance of emotional information. A recent study on chimpanzee reported the first evidence of significant left-hemispheric dominance when using attention-getting sounds and rightward bias for species-typical vocalizations (Losin, Russell, Freeman, Meguerditchian, Hopkins & Fitch, 2008). The current study sought to extend the findings from Losin et al. (2008) with additional oro-facial assessment in a new colony of chimpanzees. When combining the two populations, the results indicated a consistent leftward bias for attention-getting sounds and a right lateralization for species-typical vocalizations. Collectively, the results suggest that both voluntary- controlled oro-facial and gestural communication might share the same left-hemispheric specialization and might have coevolved into a single integrated system present in a common hominid ancestor.
PMCID: PMC3823530  PMID: 22867751
Hemispheric specialization; Oro-facial asymmetry; Communicative behaviors; Gestural communication; Oro-facial communication; Emotions; Primates
16.  Using in vivo probabilistic tractography to reveal two segregated dorsal ‘language-cognitive’ pathways in the human brain☆ 
Brain and Language  2013;127(2):230-240.
•The dorsal stream has been postulated to constitute multiple pathways.•Tractography was used to map the connectivity of regions within the left SMG.•The arcuate fasciculus was subdivided into dorso-dorsal/ventro-dorsal pathways.•The parallel pathways appear to underlie functional heterogeneity within the SMG.
Primate studies have recently identified the dorsal stream as constituting multiple dissociable pathways associated with a range of specialized cognitive functions. To elucidate the nature and number of dorsal pathways in the human brain, the current study utilized in vivo probabilistic tractography to map the structural connectivity associated with subdivisions of the left supramarginal gyrus (SMG). The left SMG is a prominent region within the dorsal stream, which has recently been parcellated into five structurally-distinct regions which possess a dorsal–ventral (and rostral-caudal) organisation, postulated to reflect areas of functional specialisation. The connectivity patterns reveal a dissociation of the arcuate fasciculus into at least two segregated pathways connecting frontal-parietal-temporal regions. Specifically, the connectivity of the inferior SMG, implicated as an acoustic-motor speech interface, is carried by an inner/ventro-dorsal arc of fibres, whilst the pathways of the posterior superior SMG, implicated in object use and cognitive control, forms a parallel outer/dorso-dorsal crescent.
PMCID: PMC3842500  PMID: 23937853
Arcuate fasciculus; Connectivity; Dual stream model; Functional specialization; Language production; Performance feedback; Repetition; Sensory-motor integration; Supramarginal gyrus; Tool use
17.  Patterns of longitudinal brain atrophy in the logopenic variant of primary progressive aphasia 
Brain and Language  2013;127(2):121-126.
► Patterns of cell loss in lvPPA remain asymmetrical over time. ► More anterior left hemisphere areas become involved over time. ► Right hemisphere regions become affected that mirror early left hemisphere change. ► Left hemisphere atrophy rates are greater than right hemisphere. ► Over time patients with lvPPA develop single word level processing deficits.
The logopenic variant of primary progressive aphasia (PPA) is characterised by impaired sentence repetition and word retrieval difficulties. Post mortem studies, amyloid imaging and CSF tau/Aβ measurements suggest Alzheimer’s disease (AD) pathology as the underlying cause. Relatively little is known about patterns of progression in patients with the logopenic variant of PPA. 21 patients (3 with post mortem confirmation of AD and 5 with positive amyloid PIB-PET scans) were studied with longitudinal T1-weighted MR imaging (mean interscan interval 1.2 years) using volumetric analysis and voxel-based morphometry (VBM). Baseline imaging showed asymmetrical (left greater than right) involvement of the posterior superior temporal and inferior parietal lobes as well as posterior cingulate and medial temporal lobes. The whole brain rate of volume loss was 2.0% per year with a greater rate of left hemisphere atrophy (2.3%/year) than right hemisphere (1.6%/year). Longitudinal VBM analysis showed increasing involvement of other areas in the left hemisphere (temporal, parietal, frontal and caudate) and atrophy of areas in the right hemisphere that had been involved earlier in the disease in the left hemisphere, particularly posterior cingulate/precuneus. With disease progression there was worsening of anomia, sentence repetition and sentence comprehension but consistent with the spread of imaging changes also deficits in single word comprehension, single word repetition and verbal memory. This study shows that the logopenic variant of PPA remains an asymmetrical disease, with spread through the left hemisphere language network but also involvement to a lesser degree of regions in the right hemisphere that mirror the earlier left hemisphere changes.
PMCID: PMC3880853  PMID: 23395096
Primary progressive aphasia; Logopenic aphasia
18.  Homotopic Language Reorganization in the Right Hemisphere after Early Left Hemisphere Injury 
Brain and language  2012;123(1):1-10.
To determine the areas involved in reorganization of language to the right hemisphere after early left hemisphere injury, we compared fMRI activation patterns during four production and comprehension tasks in post-surgical epilepsy patients with either left (LH) or right hemisphere (RH) speech dominance (determined by Wada testing) and healthy controls. Patient groups were carefully matched for IQ, lesion location and size. RH patients’ activation across all tasks was greatest in right hemisphere areas homotopic to areas activated by LH and control participants. Differences in right vs. left dominant hemisphere activation were limited to homologous areas typically activated by language tasks, supporting the hypothesis that language localization following transfer to the RH is the mirror-image of localization in the absence of transfer. The similarity of these findings to those in patients with larger, peri-sylvian lesions suggests that these areas in both hemispheres may be uniquely predisposed to subserve various language functions.
PMCID: PMC3443966  PMID: 22835489
language reorganization; fMRI; epilepsy; Wada test; temporal lobectomy
19.  The phonotactic influence on the perception of a consonant cluster /pt/ by native English and native Polish listeners: A behavioral and event related potential (ERP) study 
Brain and language  2012;123(1):30-41.
The effect of exposure to the contextual features of the /pt/ cluster was investigated in native-English and native-Polish listeners using behavioral and event-related potential (ERP) methodology. Both groups experience the /pt/ cluster in their languages, but only the Polish group experiences the cluster in the context of word onset examined in the current experiment. The /st/ cluster was used as an experimental control. ERPs were recorded while participants identified the number of syllables in the second word of nonsense word pairs. The results found that only Polish listeners accurately perceived the /pt/ cluster and perception was reflected within a late positive component of the ERP waveform. Furthermore, evidence of discrimination of /pt/ and /pǝt/ onsets in the neural signal was found even for non-native listeners who could not perceive the difference. These findings suggest that exposure to phoneme sequences in highly specific contexts may be necessary for accurate perception.
PMCID: PMC3645296  PMID: 22867752
Speech perception; Native-language; Phonotactics; Event-related potentials; Late positive component; P3a and P3b; English–Polish; Consonant clusters; /pt/ Cluster; /st/ Cluster
20.  Neuronal correlates of decisions to speak and act: Spontaneous emergence and dynamic topographies in a computational model of frontal and temporal areas 
Brain and Language  2013;127(1):75-85.
► We simulate emergence of decisions to speak and act in a model of the human brain. ► Action intentions spontaneously emerge due to the reverberation of neuronal noise. ► Spontaneous ignition preferentially occurs in higher-association, multimodal areas. ► Connectivity and learning explain cortical dynamics underlying action decisions. ► Connectivity and learning explain natural emergence of cortical specialisation.
The neural mechanisms underlying the spontaneous, stimulus-independent emergence of intentions and decisions to act are poorly understood. Using a neurobiologically realistic model of frontal and temporal areas of the brain, we simulated the learning of perception–action circuits for speech and hand-related actions and subsequently observed their spontaneous behaviour. Noise-driven accumulation of reverberant activity in these circuits leads to their spontaneous ignition and partial-to-full activation, which we interpret, respectively, as model correlates of action intention emergence and action decision-and-execution. Importantly, activity emerged first in higher-association prefrontal and temporal cortices, subsequently spreading to secondary and finally primary sensorimotor model-areas, hence reproducing the dynamics of cortical correlates of voluntary action revealed by readiness-potential and verb-generation experiments. This model for the first time explains the cortical origins and topography of endogenous action decisions, and the natural emergence of functional specialisation in the cortex, as mechanistic consequences of neurobiological principles, anatomical structure and sensorimotor experience.
PMCID: PMC3888926  PMID: 23489583
Voluntary action; Functional specialisation; Free will; Language; Speech; Prefrontal cortex; Neural network; Hebbian learning; Connectivity; Readiness potential
21.  Temporal Context in Speech Processing and Attentional Stream Selection: A Behavioral and Neural perspective 
Brain and language  2012;122(3):151-161.
The human capacity for processing speech is remarkable, especially given that information in speech unfolds over multiple time scales concurrently. Similarly notable is our ability to filter out of extraneous sounds and focus our attention on one conversation, epitomized by the ‘Cocktail Party’ effect. Yet, the neural mechanisms underlying on-line speech decoding and attentional stream selection are not well understood. We review findings from behavioral and neurophysiological investigations that underscore the importance of the temporal structure of speech for achieving these perceptual feats. We discuss the hypothesis that entrainment of ambient neuronal oscillations to speech’s temporal structure, across multiple time-scales, serves to facilitate its decoding and underlies the selection of an attended speech stream over other competing input. In this regard, speech decoding and attentional stream selection are examples of ‘active sensing’, emphasizing an interaction between proactive and predictive top-down modulation of neuronal dynamics and bottom-up sensory input.
PMCID: PMC3340429  PMID: 22285024
22.  The neural basis of syntactic deficits in primary progressive aphasia 
Brain and language  2012;122(3):190-198.
Patients with primary progressive aphasia (PPA) vary considerably in terms of which brain regions are impacted, as well as in the extent to which syntactic processing is impaired. Here we review the literature on the neural basis of syntactic deficits in PPA. Structural and functional imaging studies have most consistently associated syntactic deficits with damage to left inferior frontal cortex. Posterior perisylvian regions have been implicated in some studies. Damage to the superior longitudinal fasciculus, including its arcuate component, has been linked with syntactic deficits, even after gray matter atrophy is taken into account. These findings suggest that syntactic processing depends on left frontal and posterior perisylvian regions, as well as intact connectivity between them. In contrast, anterior temporal regions, and the ventral tracts that link frontal and temporal language regions, appear to be less important for syntax, since they are damaged in many PPA patients with spared syntactic processing.
PMCID: PMC3418470  PMID: 22546214
syntax; primary progressive aphasia; voxel-based morphometry; functional MRI; diffusion tensor imaging
23.  A sensitive period for language in the visual cortex: Distinct patterns of plasticity in congenitally versus late blind adults 
Brain and language  2011;122(3):162-170.
Recent evidence suggests that blindness enables visual circuits to contribute to language processing. We examined whether this dramatic functional plasticity has a sensitive period. BOLD fMRI signal was measured in congenitally blind, late blind (blindness onset 9-years-old or later) and sighted participants while they performed a sentence comprehension task. In a control condition, participants listened to backwards speech and made match/non-match to sample judgments. In both, congenitally and late blind participants BOLD signal increased in bilateral foveal-pericalcarine cortex during response preparation, irrespective of whether the stimulus was a sentence or backwards speech. However, only in congenitally blind people left occipital areas (pericalcarine, extrastriate, fusiform and lateral) responded more to sentences than backwards speech. We conclude that age of blindness onset constrains the non-visual functions of occipital cortex: while plasticity is present in both congenitally and late blind individuals, recruitment of visual circuits for language depends on blindness during childhood.
PMCID: PMC3536016  PMID: 22154509
plasticity; development; sensitive-period; critical-period; language evolution; visual cortex; blind; sentence comprehension; foveal; pericalcarine
24.  Dissociating frontal regions that co-lateralize with different ventral occipitotemporal regions during word processing☆ 
Brain and Language  2013;126(2):133-140.
•Co-variation in lateralization during word reading dissociated three subsystems.•Posterior ventral occipito-temporal cortex (vOT) with precentral gyrus.•Middle vOT with pars opercularis, pars triangularis and supramarginal gyrus.•Anterior vOT with pars orbitalis, middle frontal gyrus and thalamus.
The ventral occipitotemporal sulcus (vOT) sustains strong interactions with the inferior frontal cortex during word processing. Consequently, activation in both regions co-lateralize towards the same hemisphere in healthy subjects. Because the determinants of lateralisation differ across posterior, middle and anterior vOT subregions, we investigated whether lateralisation in different inferior frontal regions would co-vary with lateralisation in the three different vOT subregions. A whole brain analysis found that, during semantic decisions on written words, laterality covaried in (1) posterior vOT and the precentral gyrus; (2) middle vOT and the pars opercularis, pars triangularis, and supramarginal gyrus; and (3) anterior vOT and the pars orbitalis, middle frontal gyrus and thalamus. These findings increase the spatial resolution of our understanding of how vOT interacts with other brain areas during semantic categorisation on words.
PMCID: PMC3730055  PMID: 23728081
Functional MRI; Language; Word processing; Semantic matching; Laterality index; Left lateralization; Inter-subject variability; Language subsystems
25.  Multiple routes for compound word processing in the brain: Evidence from EEG☆ 
Brain and Language  2013;126(2):217-229.
•MMN response dissociates lexical access and combinatorial processing of compounds.•Compound lexical frequency and meaning transparency affect the MMN.•Larger MMN for high vs. low-frequency opaque compounds.•No MMN frequency effects for transparent compounds or differences to pseudo-compounds.•Results support a parallel dual-route account of compound word processing.
Are compound words represented as unitary lexical units, or as individual constituents that are processed combinatorially? We investigated the neuro-cognitive processing of compounds using EEG and a passive-listening oddball design in which lexical access and combinatorial processing elicit dissociating Mismatch Negativity (MMN) brain-response patterns. MMN amplitude varied with compound frequency and semantic transparency (the clarity of the relationship between compound and constituent meanings). Opaque compounds elicited an enhanced ‘lexical’ MMN, reflecting stronger lexical representations, to high- vs. low-frequency compounds. Transparent compounds showed no frequency effect, nor differed to pseudo-compounds, reflecting the combination of a reduced ‘syntactic’ MMN indexing combinatorial links, and an enhanced ‘lexical’ MMN for real-word compounds compared to pseudo-compounds. We argue that transparent compounds are processed combinatorially alongside parallel lexical access of the whole-form representation, but whole-form access is the dominant mechanism for opaque compounds, particularly those of high-frequency. Results support a flexible dual-route account of compound processing.
PMCID: PMC3730057  PMID: 23800711
Compounds; Dual-route; Speech; Language; ERPs; MMN

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