Repetition of letter strings leads to activation of and connectivity with word-related regions

Arcuate Fasciculus Subsegment Impairments Distinctly Associated with Memory and Language Deficits in Acute Mild Traumatic Brain Injury Patients

In acute mild traumatic brain injury (mTBI), the injury-related axonal swelling leads to white matter fiber bundle impairments, closely related to the memory and language deficits commonly shown in the patients. The arcuate fasciculus (AF) plays a central role in verbal learning and language function but could be functionally heterogeneous along the fiber tract. In this study, 25 patients with acute mTBI (<48 h after trauma) and 33 age- and sex-matched healthy controls (HCs) were included. Impaired verbal memory and language functions were shown in the patient group compared with the HCs. Combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) were applied to investigate the altered diffusion measure profiles of the AF tracts and the associated functional features. The fractional anisotropy (FA) in the right AF temporal subsegment of the mTBI group was negatively associated with the patient verbal memory function, whereas a positive correlation was found in the HC group. On the other hand, the correlation between the FA in the right AF frontal subsegment and the language function in HCs diminished in the patient group. Moreover, the functional connectivity between the inferior frontal gyrus and the middle occipital gyrus decreased, and its correlation with language function in HCs was absent in the patients with mTBI. Our work provides new insights into the understanding of the structural and functional heterogeneity of the AF tracts as well as the distinct associations of its subsegment impairments with verbal memory and language function deficits in patients with acute mTBI.

A neurocognitive model of perceptual decision-making on emotional signals

Humans make various kinds of decisions about which emotions they perceive from others. Although it might seem like a split-second phenomenon, deliberating over which emotions we perceive unfolds across several stages of decisional processing. Neurocognitive models of general perception postulate that our brain first extracts sensory information about the world then integrates these data into a percept and lastly interprets it. The aim of the present study was to build an evidence-based neurocognitive model of perceptual decision-making on others' emotions. We conducted a series of meta-analyses of neuroimaging data spanning 30 years on the explicit evaluations of others' emotional expressions. We find that emotion perception is rather an umbrella term for various perception paradigms, each with distinct neural structures that underline task-related cognitive demands. Furthermore, the left amygdala was responsive across all classes of decisional paradigms, regardless of task-related demands. Based on these observations, we propose a neurocognitive model that outlines the information flow in the brain needed for a successful evaluation of and decisions on other individuals' emotions. HIGHLIGHTS: Emotion classification involves heterogeneous perception and decision-making tasks Decision-making processes on emotions rarely covered by existing emotions theories We propose an evidence-based neuro-cognitive model of decision-making on emotions Bilateral brain processes for nonverbal decisions, left brain processes for verbal decisions Left amygdala involved in any kind of decision on emotions.

Brain Functional Connectivity in Patients With Somatic Symptom Disorder

OBJECTIVE

The aim of the study was to evaluate whether individuals with somatic symptom disorder (SSD) display increased resting-state functional connectivity (FC) within and between the sensorimotor network (SMN), default mode network (DMN), salience network, and dorsal attention network (DAN).

METHODS

Eighteen patients with SSD and 20 age- and sex-matched healthy control participants underwent resting-state functional magnetic resonance imaging. We used a seed-based correlation approach for the four brain networks.

RESULTS

Patients with SSD had higher scores on the Somato-Sensory Amplification Scale (z = 5.22, p < .001) and Symptom Checklist-90-Revised-Somatization (z = 4.94, p < .001) and greater FC within the SMN, DMN, and salience network than healthy control participants. Patients with SSD also had increased FC between the SMN and DMN, SMN and salience network, SMN and DAN, and salience network and DAN (t = 5.10-7.47, all false discovery rate q < .05). The Somato-Sensory Amplification Scale scores correlated with FC between the SMN and salience network and between the SMN and DAN (r = .61-.82, all p < .003).

CONCLUSIONS

Based on the results of the FC analysis between the SMN and salience network, we suggest that SSD may be associated with alterations of sensory-discriminative processing of pain and other somatic symptoms, which is influenced by affective processing. Based on the results of the FC analysis of the SMN and DAN, we suggest that patients with SSD have a deficit in attention, leading to misperception of external stimuli and failure to regulate bodily functions aimed at interactions with external stimuli.

Global gray matter morphometry differences between children with reading disability, ADHD, and comorbid reading disability/ADHD

Extensive, yet disparate, research exists elucidating structural anomalies in individuals with Reading Disability (RD) or ADHD. Despite ADHD and RD being highly comorbid, minimal research has attempted to determine shared patterns of morphometry between these disorders. In addition, there is no published research examining the morphometry of comorbid RD and ADHD (RD/ADHD). Hence, we conducted voxel-based morphometry on the MRI scans of 106 children, ages 8-12 years, with RD, ADHD, or RD/ADHD, and typically developing controls. We found right caudate and superior frontal regions in both RD and ADHD, along with areas specific to RD and to ADHD that are consistent with current theories on these disorders. Perhaps most importantly, we found a potential neurobiological substrate for RD/ADHD. Further, our findings illustrate both shared and specific contributors to RD/ADHD, supporting two current theories on the comorbidity of RD and ADHD, thereby facilitating future work on potential etiologies of RD/ADHD.

The Impact of Language Opacity and Proficiency on Reading Strategies in Bilinguals: An Eye Movement Study

Reading strategies vary across languages according to orthographic depth – the complexity of the grapheme in relation to phoneme conversion rules – notably at the level of eye movement patterns. We recently demonstrated that a group of early bilinguals, who learned both languages equally under the age of seven, presented a first fixation location (FFL) closer to the beginning of words when reading in German as compared with French. Since German is known to be orthographically more transparent than French, this suggested that different strategies were being engaged depending on the orthographic depth of the used language. Opaque languages induce a global reading strategy, and transparent languages force a local/serial strategy. Thus, pseudo-words were processed using a local strategy in both languages, suggesting that the link between word forms and their lexical representation may also play a role in selecting a specific strategy. In order to test whether corresponding effects appear in late bilinguals with low proficiency in their second language (L2), we present a new study in which we recorded eye movements while two groups of late German–French and French–German bilinguals read aloud isolated French and German words and pseudo-words. Since, a transparent reading strategy is local and serial, with a high number of fixations per stimuli, and the level of the bilingual participants’ L2 is low, the impact of language opacity should be observed in L1. We therefore predicted a global reading strategy if the bilinguals’ L1 was French (FFL close to the middle of the stimuli with fewer fixations per stimuli) and a local and serial reading strategy if it was German. Thus, the L2 of each group, as well as pseudo-words, should also require a local and serial reading strategy. Our results confirmed these hypotheses, suggesting that global word processing is only achieved by bilinguals with an opaque L1 when reading in an opaque language; the low level in the L2 gives way to a local and serial reading strategy. These findings stress the fact that reading behavior is influenced not only by the linguistic mode but also by top–down factors, such as readers’ proficiency.

Adding words to the brain's visual dictionary: novel word learning selectively sharpens orthographic representations in the VWFA

The nature of orthographic representations in the human brain is still subject of much debate. Recent reports have claimed that the visual word form area (VWFA) in left occipitotemporal cortex contains an orthographic lexicon based on neuronal representations highly selective for individual written real words (RWs). This theory predicts that learning novel words should selectively increase neural specificity for these words in the VWFA. We trained subjects to recognize novel pseudowords (PWs) and used fMRI rapid adaptation to compare neural selectivity with RWs, untrained PWs (UTPWs), and trained PWs (TPWs). Before training, PWs elicited broadly tuned responses, whereas responses to RWs indicated tight tuning. After training, TPW responses resembled those of RWs, whereas UTPWs continued to show broad tuning. This change in selectivity was specific to the VWFA. Therefore, word learning appears to selectively increase neuronal specificity for the new words in the VWFA, thereby adding these words to the brain's visual dictionary.

Language context modulates reading route: an electrical neuroimaging study

Introduction: The orthographic depth hypothesis (Katz and Feldman, 1983) posits that different reading routes are engaged depending on the type of grapheme/phoneme correspondence of the language being read. Shallow orthographies with consistent grapheme/phoneme correspondences favor encoding via non-lexical pathways, where each grapheme is sequentially mapped to its corresponding phoneme. In contrast, deep orthographies with inconsistent grapheme/phoneme correspondences favor lexical pathways, where phonemes are retrieved from specialized memory structures. This hypothesis, however, lacks compelling empirical support. The aim of the present study was to investigate the impact of orthographic depth on reading route selection using a within-subject design.

Method: We presented the same pseudowords (PWs) to highly proficient bilinguals and manipulated the orthographic depth of PW reading by embedding them among two separated German or French language contexts, implicating respectively, shallow or deep orthography. High density electroencephalography was recorded during the task.

Results: The topography of the ERPs to identical PWs differed 300–360 ms post-stimulus onset when the PWs were read in different orthographic depth context, indicating distinct brain networks engaged in reading during this time window. The brain sources underlying these topographic effects were located within left inferior frontal (German > French), parietal (French > German) and cingular areas (German > French).

Conclusion: Reading in a shallow context favors non-lexical pathways, reflected in a stronger engagement of frontal phonological areas in the shallow versus the deep orthographic context. In contrast, reading PW in a deep orthographic context recruits less routine non-lexical pathways, reflected in a stronger engagement of visuo-attentional parietal areas in the deep versus shallow orthographic context. These collective results support a modulation of reading route by orthographic depth.

Neural correlates of the relationship between discourse coherence and sensory monitoring in schizophrenia

Unusual language use is a core feature of psychosis, but the nature and significance of this are not understood. In particular, thought disorder in schizophrenia (SZ) is characterized by markedly bizarre speech, but the cognitive components that contribute to this and the brain correlates of these components are unknown. A number of studies have demonstrated language abnormalities in single word processing, but few have examined speech in SZ at the discourse level. This has been at least partly due to the difficulty in quantifying content of discourse. Recently, methods in computational linguistics have been found to be useful for detecting differences in semantic coherence during discourse between different clinical groups. We build on this work by demonstrating how these methods can be combined with funtional magnetic resonance imaging (fMRI) in order to tease apart factors that underlie free discourse and its deviations, and how they relate to brain activity. Eleven volunteers with SZ and eleven controls participated in an interview during which they were asked to talk as much as they could about 'religious belief'. These same participants underwent fMRI during a word monitoring task, during which modality of monitoring was manipulated by varying the congruence of auditory and visual stimuli. Semantic coherence scores, measured from free discourse, were examined for their relationship to brain activations during fMRI. In healthy controls, regions associated with executive function were related to coherence. In persons with SZ, coherence was mainly related to auditory and visual regions, depending on the modality of monitoring, but superior/middle temporal cortex related to coherence regardless of task. These findings are consistent with existing evidence for a role of superior temporal cortex in thought disorder, and demonstrate that computational measures of semantic content capture objective measures of coherence in speech that can be usefully related to underlying neurophysiological processes.