Manipulation of length and lexicality localizes the functional neuroanatomy of phonological processing in adult readers

Neural Correlates of Semantic Interference and Phonological Facilitation in Picture Naming: A Systematic Review and Coordinate-Based Meta-analysis

Semantic interference (SI) and phonological facilitation (PF) effects occur when multiple representations are co-activated simultaneously in complex naming paradigms, manipulating the context in which word production is set. Although the behavioral consequences of these psycholinguistic effects are well-known, the involved brain structures are still controversial. This paper aims to provide a systematic review and a coordinate-based meta-analysis of the available functional neuroimaging studies investigating SI and PF in picture naming paradigms. The included studies were fMRI experiments on healthy subjects, employing paradigms in which co-activations of representations were obtained by manipulating the naming context using semantically or phonologically related items. We examined the principal methodological aspects of the included studies, emphasizing the existing commonalities and discrepancies across single investigations. We then performed an exploratory coordinate-based meta-analysis of the reported activation peaks of neural response related to SI and PF. Our results consolidated previous findings regarding the involvement of the left inferior frontal gyrus and the left middle temporal gyrus in SI and brought out the role of bilateral inferior parietal regions in PF.

High-level language brain regions process sublexical regularities

A network of left frontal and temporal brain regions supports language processing. This "core" language network stores our knowledge of words and constructions as well as constraints on how those combine to form sentences. However, our linguistic knowledge additionally includes information about phonemes and how they combine to form phonemic clusters, syllables, and words. Are phoneme combinatorics also represented in these language regions? Across five functional magnetic resonance imaging experiments, we investigated the sensitivity of high-level language processing brain regions to sublexical linguistic regularities by examining responses to diverse nonwords-sequences of phonemes that do not constitute real words (e.g. punes, silory, flope). We establish robust responses in the language network to visually (experiment 1a, n = 605) and auditorily (experiments 1b, n = 12, and 1c, n = 13) presented nonwords. In experiment 2 (n = 16), we find stronger responses to nonwords that are more well-formed, i.e. obey the phoneme-combinatorial constraints of English. Finally, in experiment 3 (n = 14), we provide suggestive evidence that the responses in experiments 1 and 2 are not due to the activation of real words that share some phonology with the nonwords. The results suggest that sublexical regularities are stored and processed within the same fronto-temporal network that supports lexical and syntactic processes.

The Brain's Control Networks in Reading: Insights From Cross-Task Studies of Youth

Humans engage multiple brain systems to read successfully, including using regions important for vision, language, and control. Control refers to the set of executive processes in the brain that guide moment-to-moment behavior in service of our goals. There is a growing appreciation for the role of the brain's control system in reading comprehension, in reading skill change over time, and in those who have difficulty with the reading process. One way to understand the brain's control engagement in reading may be to study control engagement across multiple tasks in order to study consistencies, or cross-task similarities, relative to reading-specific variations. In this commentary, I briefly summarize some of our recent work studying the brain's control networks across different tasks (e.g., when reading, or doing different executive function tasks). I then review our findings of when control activation does or does not relate to measures of reading ability, and reading growth over time. The utility of cross-task comparisons in neuroimaging is noted, as well as the need to better understand multiple sources of heterogeneity in our developmental samples. I end by discussing a few of the many future directions for further study of the brain with regard to the brain's control processing and academic achievement.

Reading Braille by Touch Recruits Posterior Parietal Cortex

Blind readers use a tactile reading system consisting of raised dot arrays: braille/⠃⠗⠇. How do human brains implement reading by touch? The current study looked for signatures of reading-specific orthographic processes in braille, separate from low-level somatosensory responses and semantic processes. Of specific interest were responses in posterior parietal cortices (PPCs), because of their role in high-level tactile perception. Congenitally blind, proficient braille readers read real words and pseudowords by touch while undergoing fMRI. We leveraged the system of contractions in English braille, where one braille cell can represent multiple English print letters (e.g., "ing" ⠬, "one" ⠐⠕), making it possible to separate physical and orthographic word length. All words in the study consisted of four braille cells, but their corresponding Roman letter spellings varied from four to seven letters (e.g., "con-c-er-t" ⠒⠉⠻⠞. contracted: four cells; uncontracted: seven letters). We found that the bilateral supramarginal gyrus in the PPC increased its activity as the uncontracted word length increased. By contrast, in the hand region of primary somatosensory cortex (S1), activity increased as a function of a low-level somatosensory feature: dot-number per word. The PPC also showed greater response to pseudowords than real words and distinguished between real and pseudowords in multivariate-pattern analysis. Parieto-occipital, early visual and ventral occipito-temporal, as well as prefrontal cortices also showed sensitivity to the real-versus-pseudoword distinction. We conclude that PPC is involved in orthographic processing for braille, that is, braille character and word recognition, possibly because of braille's tactile modality.

Mapping cortical activations underlying covert and overt language production using high-density diffuse optical tomography

Gold standard neuroimaging modalities such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and more recently electrocorticography (ECoG) have provided profound insights regarding the neural mechanisms underlying the processing of language, but they are limited in applications involving naturalistic language production especially in developing brains, during face-to-face dialogues, or as a brain-computer interface. High-density diffuse optical tomography (HD-DOT) provides high-fidelity mapping of human brain function with comparable spatial resolution to that of fMRI but in a silent and open scanning environment similar to real-life social scenarios. Therefore, HD-DOT has potential to be used in naturalistic settings where other neuroimaging modalities are limited. While HD-DOT has been previously validated against fMRI for mapping the neural correlates underlying language comprehension and covert (i.e., "silent") language production, HD-DOT has not yet been established for mapping the cortical responses to overt (i.e., "out loud") language production. In this study, we assessed the brain regions supporting a simple hierarchy of language tasks: silent reading of single words, covert production of verbs, and overt production of verbs in normal hearing right-handed native English speakers (n = 33). First, we found that HD-DOT brain mapping is resilient to movement associated with overt speaking. Second, we observed that HD-DOT is sensitive to key activations and deactivations in brain function underlying the perception and naturalistic production of language. Specifically, statistically significant results were observed that show recruitment of regions in occipital, temporal, motor, and prefrontal cortices across all three tasks after performing stringent cluster-extent based thresholding. Our findings lay the foundation for future HD-DOT studies of imaging naturalistic language comprehension and production during real-life social interactions and for broader applications such as presurgical language assessment and brain-machine interfaces.

Lexical and sublexical cortical tuning for print revealed by Steady-State Visual Evoked Potentials (SSVEPs) in early readers

There are multiple levels of processing relevant to reading that vary in their visual, sublexical, and lexical orthographic processing demands. Segregating distinct cortical sources for each of these levels has been challenging in EEG studies of early readers. To address this challenge, we applied recent advances in analyzing high-density EEG using Steady-State Visual Evoked Potentials (SSVEPs) via data-driven Reliable Components Analysis (RCA) in a group of early readers spanning from kindergarten to second grade. Three controlled stimulus contrasts-familiar words versus unfamiliar pseudofonts, familiar words versus pseudowords, and pseudowords versus nonwords-were used to isolate coarse print tuning, lexical processing, and sublexical orthography-related processing, respectively. First, three overlapping yet distinct neural sources-left vOT, dorsal parietal, and primary visual cortex were revealed underlying coarse print tuning. Second, we segregated distinct cortical sources for the other two levels of processing: lexical fine tuning over occipito-temporal/parietal regions; sublexical orthographic fine tuning over left occipital regions. Finally, exploratory group analyses based on children's reading fluency suggested that coarse print tuning emerges early even in children with limited reading knowledge, while sublexical and higher-level lexical processing emerge only in children with sufficient reading knowledge. RESEARCH HIGHLIGHTS: Cognitive processes underlying coarse print tuning, sublexical, and lexical fine tuning were examined in beginning readers. Three overlapping yet distinct neural sources-left ventral occipito-temporal (vOT), left temporo-parietal, and primary visual cortex-were revealed underlying coarse print tuning. Responses to sublexical orthographic fine tuning were found over left occipital regions, while responses to higher-level linguistic fine tuning were found over occipito-temporal/parietal regions. Exploratory group analyses suggested that coarse print tuning emerges in children with limited reading knowledge, while sublexical and higher-level linguistic fine tuning effects emerge in children with sufficient reading knowledge.

Dyslexia: Causes and Concomitant Impairments

In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of letters. When these impairments are compensated by a new reading strategy, reading ability improves immediately.

Interhemispheric functional brain connectivity predicts new language learning success in adults

Investigating interhemispheric interactions between homologous cortical regions during language processing is of interest. Despite prevalent left hemisphere lateralization of language, the right hemisphere also plays an important role and interhemispheric connectivity is influenced by language experience and is implicated in second language (L2) acquisition. Regions involved in language processing have differential connectivity to other cortical regions and to each other, and play specific roles in language. We examined the interhemispheric interactions of subregions of the inferior frontal gyrus (areas 44 and 45), the adjacent area 9/46v in the middle frontal gyrus, the superior temporal gyrus (STG), and the posterior inferior parietal lobule (pIPL) in relation to distinct and specific aspects of L2 learning success. The results indicated that the connectivity between left and right areas 44 and 9/46v predicted improvement in sentence repetition, connectivity between left and right area 45 and mid-STG predicted improvement in auditory comprehension, and connectivity between left and right pIPL predicted improvement in reading speed. We show interhemispheric interactions in the specific context of facilitating performance in adult L2 acquisition that follow an anterior to posterior gradient in the brain, and are consistent with the respective roles of these regions in language processing.

Reinvestigating the Neural Bases Involved in Speech Production of Stutterers: An ALE Meta-Analysis

Background: Stuttering is characterized by dysfluency and difficulty in speech production. Previous research has found abnormalities in the neural function of various brain areas during speech production tasks. However, the cognitive neural mechanism of stuttering has still not been fully determined. Method: Activation likelihood estimation analysis was performed to provide neural imaging evidence on neural bases by reanalyzing published studies. Results: Our analysis revealed overactivation in the bilateral posterior superior temporal gyrus, inferior frontal gyrus, medial frontal gyrus, precentral gyrus, postcentral gyrus, basal ganglia, and cerebellum, and deactivation in the anterior superior temporal gyrus and middle temporal gyrus among the stutterers. The overactivated regions might indicate a greater demand in feedforward planning in speech production, while the deactivated regions might indicate dysfunction in the auditory feedback system among stutterers. Conclusions: Our findings provide updated and direct evidence on the multi-level impairment (feedforward and feedback systems) of stutterers during speech production and show that the corresponding neural bases were differentiated.

Phonological Working Memory Representations in the Left Inferior Parietal Lobe in the Face of Distraction and Neural Stimulation

The neural basis of phonological working memory (WM) was investigated through an examination of the effects of irrelevant speech distractors and disruptive neural stimulation from transcranial magnetic stimulation (TMS). Embedded processes models argue that the same regions involved in speech perception are used to support phonological WM whereas buffer models assume that a region separate from speech perception regions is used to support WM. Thus, according to the embedded processes approach but not the buffer approach, irrelevant speech and TMS to the speech perception region should disrupt the decoding of phonological WM representations. According to the buffer account, decoding of WM items should be possible in the buffer region despite distraction and should be disrupted with TMS to this region. Experiment 1 used fMRI and representational similarity analyses (RSA) with a delayed recognition memory paradigm using nonword stimuli. Results showed that decoding of memory items in the speech perception regions (superior temporal gyrus, STG) was possible in the absence of distractors. However, the decoding evidence in the left STG was susceptible to interference from distractors presented during the delay period whereas decoding in the proposed buffer region (supramarginal gyrus, SMG) persisted. Experiment 2 examined the causal roles of the speech processing region and the buffer region in phonological WM performance using TMS. TMS to the SMG during the early delay period caused a disruption in recognition performance for the memory nonwords, whereas stimulations at the STG and an occipital control region did not affect WM performance. Taken together, results from the two experiments are consistent with predictions of a buffer model of phonological WM, pointing to a critical role of the left SMG in maintaining phonological representations.

Frontoparietal Anatomical Connectivity Predicts Second Language Learning Success

There is considerable individual variability in second language (L2) learning abilities in adulthood. The inferior parietal lobule, important in L2 learning success, is anatomically connected to language areas in the frontal lobe via the superior longitudinal fasciculus (SLF). The second and third branches of the SLF (SLF II and III) have not been examined separately in the context of language, yet they are known to have dissociable frontoparietal connections. Studying these pathways and their functional contributions to L2 learning is thus of great interest. Using diffusion MRI tractography, we investigated individuals undergoing language training to explore brain structural predictors of L2 learning success. We dissected SLF II and III using gold-standard anatomical definitions and related prelearning white matter integrity to language improvements corresponding with hypothesized tract functions. SLF II properties predicted improvement in lexical retrieval, while SLF III properties predicted improvement in articulation rate. Finer grained separation of these pathways enables better understanding of their distinct roles in language, which is essential for studying how anatomical connectivity relates to L2 learning abilities.

Is Developmental Dyslexia Due to a Visual and Not a Phonological Impairment?

It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which readers have difficulty associating graphemes with their corresponding phonemes. In contrast, the magnocellular theory of dyslexia assumes that DD is a visual disorder caused by dysfunctional magnocellular neural pathways. The review explores arguments for and against these theories. Recent results have shown that DD is caused by (1) a reduced ability to simultaneously recognize sequences of letters that make up words, (2) longer fixation times required to simultaneously recognize strings of letters, and (3) amplitudes of saccades that do not match the number of simultaneously recognized letters. It was shown that pseudowords that could not be recognized simultaneously were recognized almost without errors when the fixation time was extended. However, there is an individual maximum number of letters that each reader with DD can recognize simultaneously. Findings on the neurobiological basis of temporal summation have shown that a necessary prolongation of fixation times is due to impaired processing mechanisms of the visual system, presumably involving magnocells and parvocells. An area in the mid-fusiform gyrus also appears to play a significant role in the ability to simultaneously recognize words and pseudowords. The results also contradict the assumption that DD is due to a lack of eye movement control. The present research does not support the assumption that DD is caused by a phonological disorder but shows that DD is due to a visual processing dysfunction.

Distinct neural sources underlying visual word form processing as revealed by steady state visual evoked potentials (SSVEP)

EEG has been central to investigations of the time course of various neural functions underpinning visual word recognition. Recently the steady-state visual evoked potential (SSVEP) paradigm has been increasingly adopted for word recognition studies due to its high signal-to-noise ratio. Such studies, however, have been typically framed around a single source in the left ventral occipitotemporal cortex (vOT). Here, we combine SSVEP recorded from 16 adult native English speakers with a data-driven spatial filtering approach—Reliable Components Analysis (RCA)—to elucidate distinct functional sources with overlapping yet separable time courses and topographies that emerge when contrasting words with pseudofont visual controls. The first component topography was maximal over left vOT regions with a shorter latency (approximately 180 ms). A second component was maximal over more dorsal parietal regions with a longer latency (approximately 260 ms). Both components consistently emerged across a range of parameter manipulations including changes in the spatial overlap between successive stimuli, and changes in both base and deviation frequency. We then contrasted word-in-nonword and word-in-pseudoword to test the hierarchical processing mechanisms underlying visual word recognition. Results suggest that these hierarchical contrasts fail to evoke a unitary component that might be reasonably associated with lexical access.

How do expectant fathers respond to infant cry? Examining brain and behavioral responses and the moderating role of testosterone

Expectant parents’ responses to infant cry may indicate future risk and resiliency in the parent-child relationship. Most studies of parental reactivity to infant cry have focused on mothers, and few studies have focused on expectant fathers, although fathers make important contributions to parenting. Additionally, although different responses to infant cry (behavioral, psychological and neural) are hypothesized to track together, few studies have analyzed them concurrently. The current investigation aimed to address these gaps by characterizing multimodal responses to infant cry within expectant fathers and testing whether prenatal testosterone moderates these responses. Expectant fathers responded to infant cry vs frequency-matched white noise with increased activation in bilateral areas of the temporal lobe involved in processing speech sounds and social and emotional stimuli. Handgrip force, which has been used to measure parents’ reactivity to cry sounds in previous studies, did not differentiate cry from white noise within this sample. Expectant fathers with higher prenatal testosterone showed greater activation in the supramarginal gyrus, left occipital lobe and precuneus cortex to cry sounds. Expectant fathers appear to interpret and process infant cry as a meaningful speech sound and social cue, and testosterone may play a role in expectant fathers’ response to infant cry.

Development of Print-Speech Integration in the Brain of Beginning Readers With Varying Reading Skills

Learning print-speech sound correspondences is a crucial step at the beginning of reading acquisition and often impaired in children with developmental dyslexia. Despite increasing insight into audiovisual language processing, it remains largely unclear how integration of print and speech develops at the neural level during initial learning in the first years of schooling. To investigate this development, 32 healthy, German-speaking children at varying risk for developmental dyslexia (17 typical readers and 15 poor readers) participated in a longitudinal study including behavioral and fMRI measurements in first (T1) and second (T2) grade. We used an implicit audiovisual (AV) non-word target detection task aimed at characterizing differential activation to congruent (AVc) and incongruent (AVi) audiovisual non-word pairs. While children’s brain activation did not differ between AVc and AVi pairs in first grade, an incongruency effect (AVi > AVc) emerged in bilateral inferior temporal and superior frontal gyri in second grade. Of note, pseudoword reading performance improvements with time were associated with the development of the congruency effect (AVc > AVi) in the left posterior superior temporal gyrus (STG) from first to second grade. Finally, functional connectivity analyses indicated divergent development and reading expertise dependent coupling from the left occipito-temporal and superior temporal cortex to regions of the default mode (precuneus) and fronto-temporal language networks. Our results suggest that audiovisual integration areas as well as their functional coupling to other language areas and areas of the default mode network show a different development in poor vs. typical readers at varying familial risk for dyslexia.

NDRA: A single route model of response times in the reading aloud task based on discriminative learning

We present the Naive Discriminative Reading Aloud (ndra) model. The ndra differs from existing models of response times in the reading aloud task in two ways. First, a single lexical architecture is responsible for both word and non-word naming. As such, the model differs from dual-route models, which consist of both a lexical route and a sub-lexical route that directly maps orthographic units onto phonological units. Second, the linguistic core of the ndra exclusively operates on the basis of the equilibrium equations for the well-established general human learning algorithm provided by the Rescorla-Wagner model. The model therefore does not posit language-specific processing mechanisms and avoids the problems of psychological and neurobiological implausibility associated with alternative computational implementations. We demonstrate that the single-route discriminative learning architecture of the ndra captures a wide range of effects documented in the experimental reading aloud literature and that the overall fit of the model is at least as good as that of state-of-the-art dual-route models.

Prospective relations between resting-state connectivity of parietal subdivisions and arithmetic competence

The present study investigates the relation between resting-state functional connectivity (rsFC) of cytoarchitectonically defined subdivisions of the parietal cortex at the end of 1st grade and arithmetic performance at the end of 2nd grade. Results revealed a dissociable pattern of relations between rsFC and arithmetic competence among subdivisions of intraparietal sulcus (IPS) and angular gyrus (AG). rsFC between right hemisphere IPS subdivisions and contralateral IPS subdivisions positively correlated with arithmetic competence. In contrast, rsFC between the left hIP1 and the right medial temporal lobe, and rsFC between the left AG and left superior frontal gyrus, were negatively correlated with arithmetic competence. These results suggest that strong inter-hemispheric IPS connectivity is important for math development, reflecting either neurocognitive mechanisms specific to arithmetic processing, domain-general mechanisms that are particularly relevant to arithmetic competence, or structural 'cortical maturity'. Stronger connectivity between IPS, and AG, subdivisions and frontal and temporal cortices, however, appears to be negatively associated with math development, possibly reflecting the ability to disengage suboptimal problem-solving strategies during mathematical processing, or to flexibly reorient task-based networks. Importantly, the reported results pertain even when controlling for reading, spatial attention, and working memory, suggesting that the observed rsFC-behavior relations are specific to arithmetic competence.

The consonant/vowel pattern determines the structure of orthographic representations in the left fusiform gyrus

Recent findings demonstrated readers' sensitivity to the distinction between consonant and vowel letters. Especially, the way consonants and vowels are organised within written words determines their perceptual structure. The present work attempted to overcome two limitations of previous studies by examining the neurophysiological correlates of this perceptual structure through magnetoencephalography (MEG). One aim was to establish that the extraction of vowel-centred units takes place during early stages of processing. The second objective was to confirm that the vowel-centred structure pertains to the word recognition system and may constitute one level in a hierarchy of neural detectors coding orthographic strings. Participants performed a cross-case matching task in which they had to judge pairs of stimuli as identical or different. The critical manipulation concerned pairs obtained by transposing two letters, so that the vowel-centred structure was either preserved (FOUVERT-fovuert, two vowel letter clusters) or modified (BOUVRET-bovuret). Mismatches were detected faster when the structure was modified. This effect was associated with a significant difference in evoked neuromagnetic fields extending from 129 to 239 msec after the stimulation. Source localization indicated a significant effect in the visual word form area around 200 msec. The results confirm the hypothesis that the vowel-centred structure is extracted during the early phases of letter string processing and that it is encoded in left fusiform regions devoted to visual word recognition.

Neurobiological Bases of Reading Disorder Part II: The Importance of Developmental Considerations in Typical and Atypical Reading

Decoding-based reading disorder (RD; aka developmental dyslexia) is one of the most common neurodevelopmental disorders, affecting approximately 5-10% of school-aged children across languages. Even though neuroimaging studies suggest an impairment of the left reading network in RD, the onset of this deficit and its developmental course, which may include constancy and change, is largely unknown. There is now growing evidence that the recruitment of brain networks underlying perceptual, cognitive and linguistic processes relevant to reading acquisition varies with age. These age-dependent changes may in turn impact the neurocognitive characteristics of RD observed at specific developmental stages. Here we synthesize findings from functional and structural magnetic resonance imaging (MRI) studies to increase our understanding of the developmental time course of the neural bases underlying (a)typical reading. We first provide an overview of the brain bases of typical and atypical (impaired) reading. Next we describe how the understanding of RD can be deepened through scientific attention to age effects, for example, by integrating findings from cross-sectional studies of RD at various ages. Finally, we accent findings from extant longitudinal studies that directly examine developmental reading trajectories beginning in the preliterate stage at both group and individual levels. Although science is at the very early stage of understanding developmental aspects of neural deficits in RD, evidence to date characterizes RD by atypical brain maturation. We know that reading impairment may adversely impact multiple life domains such as academic achievement and social relationships, and unfortunately, that these negative outcomes can persist and compound into adulthood. We contend that exploring the developmental trajectories of RD will contribute to a greater understanding of how neural systems support reading acquisition. Further, we propose and cite evidence that the etiology of RD can be better investigated by distinguishing primary deficits from secondary impairments unfolding along development. These exciting and modern investigatory efforts can also indirectly contribute to a centered practice of early and accurate identification and optimal intervention to support the development of foundational pre-literacy skills and fluent reading. In sum, integrating a developmental understanding into the science and practice of reading acquisition and intervention is both possible and necessary.

Neural evidence for phonologically based language production deficits in older adults: An fMRI investigation of age-related differences in picture-word interference

INTRODUCTION

Older adults often show declines in phonological aspects of language production, particularly for low-frequency words, but maintain strong semantic systems. However, there are different theories about the mechanism that may underlie such age-related differences in language (e.g., age-related declines in transmission of activation or inhibition).

METHODS

This study used fMRI to investigate whether age-related differences in language production are associated with transmission deficits or inhibition deficits. We used the picture-word interference paradigm to examine age-related differences in picture naming as a function of both target frequency and the relationship between the target picture and distractor word.

RESULTS

We found that the presence of a categorically related distractor led to greater semantic elaboration by older adults compared to younger adults, as evidenced by older adults' increased recruitment of regions including the left middle frontal gyrus and bilateral precuneus. When presented with a phonologically related distractor, patterns of neural activation are consistent with previously observed age deficits in phonological processing, including age-related reductions in the recruitment of regions such as the left middle temporal gyrus and right supramarginal gyrus. Lastly, older, but not younger, adults show increased brain activation of the pre- and postcentral gyri as a function of decreasing target frequency when target pictures are paired with a phonological distractor, suggesting that cuing the phonology of the target disproportionately aids production of low-frequency items.

CONCLUSIONS

Overall, this pattern of results is generally consistent with the transmission deficit hypothesis, illustrating that links within the phonological system, but not the semantic system, are weakened with age.

Moral foundations vignettes: a standardized stimulus database of scenarios based on moral foundations theory

Research on the emotional, cognitive, and social determinants of moral judgment has surged in recent years. The development of moral foundations theory (MFT) has played an important role, demonstrating the breadth of morality. Moral psychology has responded by investigating how different domains of moral judgment are shaped by a variety of psychological factors. Yet, the discipline lacks a validated set of moral violations that span the moral domain, creating a barrier to investigating influences on judgment and how their neural bases might vary across the moral domain. In this paper, we aim to fill this gap by developing and validating a large set of moral foundations vignettes (MFVs). Each vignette depicts a behavior violating a particular moral foundation and not others. The vignettes are controlled on many dimensions including syntactic structure and complexity making them suitable for neuroimaging research. We demonstrate the validity of our vignettes by examining respondents' classifications of moral violations, conducting exploratory and confirmatory factor analysis, and demonstrating the correspondence between the extracted factors and existing measures of the moral foundations. We expect that the MFVs will be beneficial for a wide variety of behavioral and neuroimaging investigations of moral cognition.

The Structural Correlates of Statistical Information Processing during Speech Perception

The processing of continuous and complex auditory signals such as speech relies on the ability to use statistical cues (e.g. transitional probabilities). In this study, participants heard short auditory sequences composed either of Italian syllables or bird songs and completed a regularity-rating task. Behaviorally, participants were better at differentiating between levels of regularity in the syllable sequences than in the bird song sequences. Inter-individual differences in sensitivity to regularity for speech stimuli were correlated with variations in surface-based cortical thickness (CT). These correlations were found in several cortical areas including regions previously associated with statistical structure processing (e.g. bilateral superior temporal sulcus, left precentral sulcus and inferior frontal gyrus), as well other regions (e.g. left insula, bilateral superior frontal gyrus/sulcus and supramarginal gyrus). In all regions, this correlation was positive suggesting that thicker cortex is related to higher sensitivity to variations in the statistical structure of auditory sequences. Overall, these results suggest that inter-individual differences in CT within a distributed network of cortical regions involved in statistical structure processing, attention and memory is predictive of the ability to detect structural structure in auditory speech sequences.

Semantic variability predicts neural variability of object concepts

The prevailing approach to the neuroscientific study of concepts is to characterize the neural pattern evoked by a given concept, averaging over any variation that might occur upon multiple retrieval attempts (e.g., across time, tasks, or people). This approach-which diverges substantially from approaches to studying conceptual processing with other methods-treats all variation as noise. Here, our goal is to determine whether variation in neural patterns evoked by semantic retrieval of a given concept is more than just measurement error, and instead reflects variation arising from contextual variability. We measured each concept's diversity of semantic contexts ("SV") by analyzing its word frequency and co-occurrence statistics in large text corpora. To measure neural variability, we conducted an fMRI study and sampled neural activity associated with each concept when it appeared in three separate, randomized contexts. We predicted that concepts with low SV would exhibit uniform activation patterns across stimulus presentations, whereas concepts with high SV would exhibit more dynamic representations over time. We observed that a concept's SV score predicted its corresponding neural variability. This finding supports a flexible, distributed organization of semantic memory, where a concept's meaning and its neural activity patterns both continuously vary across contexts.

Written distractor words influence brain activity during overt picture naming

Language production requires multiple stages of processing (e.g., semantic retrieval, lexical selection), each of which may involve distinct brain regions. Distractor words can be combined with picture naming to examine factors that influence language production. Phonologically-related distractors have been found to speed picture naming (facilitation), while slower response times and decreased accuracy (interference) generally occur when a distractor is categorically related to the target image. However, other types of semantically-related distractors have been reported to produce a facilitative effect (e.g., associative, part-whole). The different pattern of results for different types of semantically-related distractors raises the question about how the nature of the semantic relation influences the effect of the distractor. To explore the nature of these semantic effects further, we used functional MRI to examine the influence of four types of written distractors on brain activation during overt picture naming. Distractors began with the same sound, were categorically-related, part of the object to be named, or were unrelated to the picture. Phonologically-related trials elicited greater activation than both semantic conditions (categorically-related and part-whole) in left insula and bilateral parietal cortex, regions that have been attributed to phonological aspects of production and encoding, respectively. Semantic conditions elicited greater activation than phonological trials in left posterior MTG, a region that has been linked to concept retrieval and semantic integration. Overall, the two semantic conditions did not differ substantially in their functional activation which suggests a similarity in the semantic demands and lexical competition across these two conditions.

The VWFA: it's not just for words anymore

Reading is an important but phylogenetically new skill. While neuroimaging studies have identified brain regions used in reading, it is unclear to what extent these regions become specialized for use predominantly in reading vs. other tasks. Over the past several years, our group has published three studies addressing this question, particularly focusing on whether the putative visual word form area (VWFA) is used predominantly in reading, or whether it is used more generally in a number of tasks. Our three studies utilize a range of neuroimaging techniques, including task based fMRI experiments, a seed based resting state functional connectivity (RSFC) experiment, and a network based RSFC experiment. Overall, our studies indicate that the VWFA is not used specifically or even predominantly for reading. Rather the VWFA is a general use region that has processing properties making it particularly useful for reading, though it continues to be used in any task that requires its general processing properties. Our network based RSFC analysis extends this finding to other regions typically thought to be used predominantly for reading. Here, we review these findings and describe how the three studies complement each other. Then, we argue that conceptualizing the VWFA as a brain region with specific processing characteristics rather than a brain region devoted to a specific stimulus class, allows us to better explain the activity seen in this region during a variety of tasks. Having this type of conceptualization not only provides a better understanding of the VWFA but also provides a framework for understanding other brain regions, as it affords an explanation of function that is in keeping with the long history of studying the brain in terms of the type of information processing performed (Posner, 1978).

Distinct parietal and temporal connectivity profiles of ventrolateral frontal areas involved in language production

Broca's region, which in the language-dominant hemisphere of the human brain plays a major role in language production, includes two distinct cytoarchitectonic areas: 44 and 45. The unique connectivity patterns of these two areas have not been well established. In a resting-state functional connectivity study, we tested predictions about these areas from invasive tract-tracing studies of the connectivity of their homologs in the macaque monkey. We demonstrated their distinct connectivity profiles as well as their differences from the caudally adjacent ventral parts of the premotor cortex and the primary motor cortical region that represent the orofacial musculature. Area 45 is strongly connected with the superior temporal sulcus and the cortex on the adjacent superior and middle temporal gyri. In the parietal region, area 45 is connected with the angular gyrus, whereas area 44 is connected with the supramarginal gyrus. The primary motor cortical region in the caudal precentral gyrus is not connected with the posterior parietal region, which lies outside the confines of the postcentral gyrus, whereas the ventrorostral premotor cortical area 6VR, in the most anterior part of the precentral gyrus, has strong connections with the rostral supramarginal gyrus. Thus, area 44, which has stronger connections to the posterior supramarginal gyrus, can be distinguished from both the adjacent area 6VR and area 45. These findings provide a major improvement in understanding the connectivity of the areas in the ventrolateral frontal region that are involved in language production.

Separable roles for attentional control sub-systems in reading tasks: a combined behavioral and fMRI study

Attentional control is important both for learning to read and for performing difficult reading tasks. A previous study invoked 2 mechanisms to explain reaction time (RT) differences between reading tasks with variable attentional demands. The present study combined behavioral and neuroimaging measures to test the hypotheses that there are 2 mechanisms of interaction between attentional control and reading; that these mechanisms are dissociable both behaviorally and neuro-anatomically; and that the 2 mechanisms involve functionally separable control systems. First, RT evidence was found in support of the 2-mechanism model, corroborating the previous study. Next, 2 sets of brain regions were identified as showing functional magnetic resonance imaging blood oxygen level-dependent activity that maps onto the 2-mechanism distinction. One set included bilateral Cingulo-opercular regions and mostly right-lateralized Dorsal Attention regions (CO/DA+). This CO/DA+ region set showed response properties consistent with a role in reporting which processing pathway (phonological or lexical) was biased for a particular trial. A second set was composed primarily of left-lateralized Frontal-parietal (FP) regions. Its signal properties were consistent with a role in response checking. These results demonstrate how the subcomponents of attentional control interact with subcomponents of reading processes in healthy young adults.

Dissociating frontal regions that co-lateralize with different ventral occipitotemporal regions during word processing

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.

Good, bad and ugly word stress--fMRI evidence for foot structure driven processing of prosodic violations

Using a stress violation paradigm, we investigated whether metrical feet constrain the way prosodic patterns are processed and evaluated. Processing of correctly versus incorrectly stressed words was associated with activation in left posterior angular and retrosplenial cortex, indicating the recognition of an expected and familiar pattern, whereas the inverse contrast yielded enhanced bilateral activation in the superior temporal gyrus, reflecting higher costs in auditory (re-)analysis. More fine-grained analyses of severe versus mild stress violations revealed activations of the left superior temporal and left anterior angular gyrus whereas the opposite contrast led to frontal activations including Broca's area and its right-hemisphere homologue, suggesting that detection of mild violations lead to increased effort in working memory and deeper phonological processing. Our results provide first evidence that different incorrect stress patterns are processed in a qualitatively different way and that the underlying foot structure seems to determine potential stress positions in German words.

Functional network architecture of reading-related regions across development

Reading requires coordinated neural processing across a large number of brain regions. Studying relationships between reading-related regions informs the specificity of information processing performed in each region. Here, regions of interest were defined from a meta-analysis of reading studies, including a developmental study. Relationships between regions were defined as temporal correlations in spontaneous fMRI signal; i.e., resting state functional connectivity MRI (RSFC). Graph theory based network analysis defined the community structure of the "reading-related" regions. Regions sorted into previously defined communities, such as the fronto-parietal and cingulo-opercular control networks, and the default mode network. This structure was similar in children, and no apparent "reading" community was defined in any age group. These results argue against regions, or sets of regions, being specific or preferential for reading, instead indicating that regions used in reading are also used in a number of other tasks.

Why mental arithmetic counts: brain activation during single digit arithmetic predicts high school math scores

Do individual differences in the brain mechanisms for arithmetic underlie variability in high school mathematical competence? Using functional magnetic resonance imaging, we correlated brain responses to single digit calculation with standard scores on the Preliminary Scholastic Aptitude Test (PSAT) math subtest in high school seniors. PSAT math scores, while controlling for PSAT Critical Reading scores, correlated positively with calculation activation in the left supramarginal gyrus and bilateral anterior cingulate cortex, brain regions known to be engaged during arithmetic fact retrieval. At the same time, greater activation in the right intraparietal sulcus during calculation, a region established to be involved in numerical quantity processing, was related to lower PSAT math scores. These data reveal that the relative engagement of brain mechanisms associated with procedural versus memory-based calculation of single-digit arithmetic problems is related to high school level mathematical competence, highlighting the fundamental role that mental arithmetic fluency plays in the acquisition of higher-level mathematical competence.

Understanding white matter integrity stability for bilinguals on language status and reading performance

Recent studies using diffusion tensor imaging (DTI) have described overall white matter integrity in bilinguals but have not related structural neural pathways to language functions. The current study examined white matter integrity and its relationship to reading skill in monolingual English and bilingual Chinese-English speakers. Eleven monolingual speakers (mean age 28.5 years) and 13 bilingual speakers (mean age 24.2 years; English as a second language was acquired post 5 years of age) participated. Behavioural response times and accuracy rates to name regular and exception words were recorded. Participants were then scanned using a standardized DTI protocol. Fractional anisotropy (FA) and mean diffusivity values were derived from a voxelwise statistical analysis for comparisons between participant groups. Tests for relationships between response time and FA were also conducted. Our results show minimal regions of higher FA for monolinguals when compared to bilinguals and no regions of higher FA for bilinguals when compared to monolinguals, which indicates that white matter integrity may not stabilize in bilinguals until late adulthood. We do show several regions where an increase in FA is associated with faster response times. Interestingly, the FA-response time relationship varies between groups and between word types, which may reflect an increased processing demand for retrieval of difficult words (e.g., exception words). These results provide some support for the interference control and reduced frequency hypotheses outlined by Jones et al. (Cerebr Cortex 22:892-902, 2012). The current findings advance our understanding of the underlying cortical networks associated with language status and reading skill in monolingual and bilingual adults.

Reading without the left ventral occipito-temporal cortex

The left ventral occipito-temporal cortex (LvOT) is thought to be essential for the rapid parallel letter processing that is required for skilled reading. Here we investigate whether rapid written word identification in skilled readers can be supported by neural pathways that do not involve LvOT. Hypotheses were derived from a stroke patient who acquired dyslexia following extensive LvOT damage. The patient followed a reading trajectory typical of that associated with pure alexia, re-gaining the ability to read aloud many words with declining performance as the length of words increased. Using functional MRI and dynamic causal modelling (DCM), we found that, when short (three to five letter) familiar words were read successfully, visual inputs to the patient’s occipital cortex were connected to left motor and premotor regions via activity in a central part of the left superior temporal sulcus (STS). The patient analysis therefore implied a left hemisphere “reading-without-LvOT” pathway that involved STS. We then investigated whether the same reading-without-LvOT pathway could be identified in 29 skilled readers and whether there was inter-subject variability in the degree to which skilled reading engaged LvOT. We found that functional connectivity in the reading-without-LvOT pathway was strongest in individuals who had the weakest functional connectivity in the LvOT pathway. This observation validates the findings of our patient’s case study. Our findings highlight the contribution of a left hemisphere reading pathway that is activated during the rapid identification of short familiar written words, particularly when LvOT is not involved. Preservation and use of this pathway may explain how patients are still able to read short words accurately when LvOT has been damaged.

The hemodynamic response in children with Simplex Autism

BACKGROUND

Numerous functional magnetic resonance imaging (fMRI) studies of the brain-bases of autism have demonstrated altered cortical responses in subjects with autism, relative to typical subjects, during a variety of tasks. These differences may reflect altered neuronal responses or altered hemodynamic response. This study searches for evidence of hemodynamic response differences by using a simple visual stimulus and elementary motor actions, which should elicit similar neuronal responses in patients and controls.

METHODS

We acquired fMRI data from two groups of 16 children, a typical group and a group with Simplex Autism, during a simple visuomotor paradigm previously used to assess this question in other cross-group comparisons. A general linear model estimated the blood-oxygen-level-dependent (BOLD) signal time course, and repeated-measures analysis of variance tested for potential cross-group differences in the BOLD signal.

RESULTS

The hemodynamic response in Simplex Autism is similar to that found in typical children. Although the sample size was small for a secondary analysis, medication appeared to have no effect on the hemodynamic response within the Simplex Autism group.

CONCLUSIONS

When fMRI studies show BOLD response differences between autistic and typical subjects, these results likely reflect between-group differences in neural activity and not an altered hemodynamic response.

Matching is not naming: a direct comparison of lexical manipulations in explicit and implicit reading tasks

The neurobiological basis of reading is of considerable interest, yet analyzing data from subjects reading words aloud during functional MRI data collection can be difficult. Therefore, many investigators use surrogate tasks such as visual matching or rhyme matching to eliminate the need for spoken output. Use of these tasks has been justified by the presumption of "automatic activation" of reading-related neural processing when a word is viewed. We have tested the efficacy of using a nonreading task for studying "reading effects" by directly comparing blood oxygen level dependent (BOLD) activity in subjects performing a visual matching task and an item naming task on words, pseudowords (meaningless but legal letter combinations), and nonwords (meaningless and illegal letter combinations). When compared directly, there is significantly more activity during the naming task in "reading-related" regions such as the inferior frontal gyrus (IFG) and supramarginal gyrus. More importantly, there are differing effects of lexicality in the tasks. A whole-brain task (matching vs. naming) by string type (word vs. pseudoword vs. nonword) by BOLD timecourse analysis identifies regions showing this three-way interaction, including the left IFG and left angular gyrus (AG). In the majority of the identified regions (including the left IFG and left AG), there is a string type × timecourse interaction in the naming but not the matching task. These results argue that the processing performed in specific regions is contingent on task, even in reading-related regions and is thus nonautomatic. Such differences should be taken into consideration when designing studies intended to investigate reading.

The left occipitotemporal cortex does not show preferential activity for words

Regions in left occipitotemporal (OT) cortex, including the putative visual word form area, are among the most commonly activated in imaging studies of single-word reading. It remains unclear whether this part of the brain is more precisely characterized as specialized for words and/or letters or contains more general-use visual regions having properties useful for processing word stimuli, among others. In Analysis 1, we found no evidence of greater activity in left OT regions for words or letter strings relative to other high-spatial frequency high-contrast stimuli, including line drawings and Amharic strings (which constitute the Ethiopian writing system). In Analysis 2, we further investigated processing characteristics of OT cortex potentially useful in reading. Analysis 2 showed that a specific part of OT cortex 1) is responsive to visual feature complexity, measured by the number of strokes forming groups of letters or Amharic strings and 2) processes learned combinations of characters, such as those in words and pseudowords, as groups but does not do so in consonant and Amharic strings. Together, these results indicate that while regions of left OT cortex are not specialized for words, at least part of OT cortex has properties particularly useful for processing words and letters.

The putative visual word form area is functionally connected to the dorsal attention network

The putative visual word form area (pVWFA) is the most consistently activated region in single word reading studies (i.e., Vigneau et al. 2006), yet its function remains a matter of debate. The pVWFA may be predominantly used in reading or it could be a more general visual processor used in reading but also in other visual tasks. Here, resting-state functional connectivity magnetic resonance imaging (rs-fcMRI) is used to characterize the functional relationships of the pVWFA to help adjudicate between these possibilities. rs-fcMRI defines relationships based on correlations in slow fluctuations of blood oxygen level-dependent activity occurring at rest. In this study, rs-fcMRI correlations show little relationship between the pVWFA and reading-related regions but a strong relationship between the pVWFA and dorsal attention regions thought to be related to spatial and feature attention. The rs-fcMRI correlations between the pVWFA and regions of the dorsal attention network increase with age and reading skill, while the correlations between the pVWFA and reading-related regions do not. These results argue the pVWFA is not used predominantly in reading but is a more general visual processor used in other visual tasks, as well as reading.