One of the key questions in the study of human language acquisition is the extent to which the development of neural processing networks for different components of language are modulated by exposure to linguistic stimuli. Sign languages offer a unique perspective on this issue, because prelingually Deaf children who receive access to complex linguistic input later in life provide a window into brain maturation in the absence of language, and subsequent neuroplasticity of neurolinguistic networks during late language learning. While the duration of sensitive periods of acquisition of linguistic subsystems (sound, vocabulary, and syntactic structure) is well established on the basis of L2 acquisition in spoken language, for sign languages, the relative timelines for development of neural processing networks for linguistic sub-domains are unknown. We examined neural responses of a group of Deaf signers who received access to signed input at varying ages to three linguistic phenomena at the levels of classifier signs, syntactic structure, and information structure. The amplitude of the N400 response to the marked word order condition negatively correlated with the age of acquisition for syntax and information structure, indicating increased cognitive load in these conditions. Additionally, the combination of behavioral and neural data suggested that late learners preferentially relied on classifiers over word order for meaning extraction. This suggests that late acquisition of sign language significantly increases cognitive load during analysis of syntax and information structure, but not word-level meaning.

Previous studies investigating the processing of complex sentences have demonstrated the involvement of the left inferior frontal gyrus (LIFG) and left superior temporal gyrus (LSTG), which might subserve ordering and storage of linguistic components, respectively, for sentence comprehension. However, how these brain regions are interconnected, especially during the processing of Chinese sentences, need to be further explored. In this study, the neural network supporting the comprehension of Chinese relative clause was identified. Both the LIFG and LSTG exhibited higher activation in processing subject-extracted relative clauses (SRCs) than object-extracted relative clauses (ORCs). Moreover, a Granger causality analysis revealed that the effective connectivity from the LIFG to LSTG was significant only when participants read Chinese SRCs, which were argued to be more difficult than ORCs. Contrary to the observations of an SRC advantage in most other languages, the present results provide clear neuroimaging evidence for an ORC advantage in Chinese.

This study used voxel-based lesion-symptom mapping to examine the cortical and white matter regions associated with language production impairments in a sample of 63 preoperative tumour patients. We identified four cognitive functions considered crucial for spoken language production: semantic-to-lexical mapping (selecting the appropriate lexical label for the intended concept); phonological encoding (retrieving the word’s phonological form); articulatory-motor planning (programming the articulatory motor movements); and goal-driven language selection (exerting top-down control over the words selected for production). Each participant received a score estimating their competence on each function. We then mapped the region(s) where pathology was significantly associated with low scores. For semantic-to-lexical mapping, the critical map encompassed portions of the left posterior middle and inferior temporal gyri, extending into posterior fusiform gyrus, overlapping substantially with the territory of the inferior longitudinal fasciculus. For phonological encoding, the map encompassed the left inferior parietal lobe and posterior middle temporal gyrus, overlapping with the territory of the inferior longitudinal and posterior arcuate fasciculi. For articulatory-motor planning, the map encompassed parts of the left frontal pole, frontal operculum, and inferior frontal gyrus, and overlapped with the territory of the frontal aslant tract. Finally, the map for goal-driven language selection encompassed the left frontal pole and the anterior cingulate cortex. We compare our findings with those from other neuropsychological samples, and conclude that the study of tumour patients offers evidence that complements that available from other populations.

Deviations of attention from the task at hand are often associated with worse reading performance (Schooler, Reichle, & Halpern, 2004). Ironically, current methods for detecting these shifts of attention typically generate task interruptions and further disrupt performance. In the current study, we developed a method to (1) track shifts of attention away from the reading task by examining the similarity between 5 min of eyes-closed-resting-state EEG and 5 min reading EEG; and (2) investigate, during reading, how the ratio between attention shifts and focused reading relates to readers’ comprehension. We performed a Spectral Similarity Analysis (SSA) that examined the spectral similarity between EEG recorded during reading and at rest on a moment-by-moment basis. We then recursively applied the algorithm to the resting-state data itself to obtain an individual baseline of the stability of brain activation recorded during rest. We defined any moment in which SSA during reading was greater than the mean correlation between resting-state EEG and itself as an “attentional shift.” The results showed that the proportion of such attentional shifts recorded over the left visual region (O1) significantly predicted reading comprehension, with higher ratios (indicative of more frequent attentional shifts) relating to worse comprehension scores on the reading test. As a proof of its validity, the same measure collected during the reading comprehension test also predicted participants’ Simon effect (incongruent - congruent response times) which is a common index of selective attention. This novel method allows researchers to detect attention shifts moments during reading without interrupting natural reading process.

The current study aims to determine the brain areas critical for response to anodal transcranial direct current stimulation (tDCS) in PPA. Anodal tDCS and sham were administered over the left inferior frontal gyrus (IFG), combined with written naming/spelling therapy. Thirty people with PPA were included in this study, and assessed immediately, 2 weeks, and 2 months post-therapy. We identified anatomical areas whose volumes significantly predicted the additional tDCS effects. For trained words, the volumes of the left Angular Gyrus and left Posterior Cingulate Cortex predicted the additional tDCS gain. For untrained words, the volumes of the left Middle Frontal Gyrus, left Supramarginal Gyrus, and right Posterior Cingulate Cortex predicted the additional tDCS gain. These findings show that areas involved in language, attention and working memory contribute to the maintenance and generalization of stimulation effects. The findings highlight that tDCS possibly affects areas anatomically or functionally connected to stimulation targets.

Language communication is crucial throughout the lifespan. The current study investigated how aging affects the brain network subserving intelligible speech. Using functional magnetic resonance imaging, we compared brain responses to intelligible and unintelligible speech between older and young adults. Univariate and multivariate analyses revealed reduced brain activation and lower regional pattern distinctions in response to intelligible versus unintelligible speech in the left anterior superior temporal gyrus (aSTG) and the left inferior frontal gyrus (IFG) in the older compared with young adults. Notably, the functional connectivity between the left IFG and the left angular gyrus (AG) was increased and a significantly enhanced bidirectional effective connectivity between the left aSTG and the left AG was observed in the older adults for processing speech intelligibility. Our study revealed aging-related differences in the cortical activity for intelligible speech and suggested that increased frontal-temporal-parietal functional integration may help facilitate spoken language processing in older adults.

The framework of embodied cognition has challenged the modular view of a language-cognition divide by suggesting that meaning-retrieval critically involves the sensory-motor system. Despite extensive research into the neural mechanisms underlying language-motor coupling, it remains unclear how the motor system might be differentially engaged by different levels of linguistic abstraction and language proficiency. To address this issue, we used fMRI to quantify neural activations in brain regions underlying motor and language processing in Chinese-English speakers’ processing of literal, metaphorical, and abstract language in their L1 and L2. Results overall revealed a response in motor ROIs gradually attenuating in intensity from literal to abstract via metaphorical language in both L1 and L2. Furthermore, contrast analyses between L1 and L2 showed overall greater activations of motor ROIs in the L2. We conclude that motor involvement in language processing is graded rather than all-or-none and that the motor system has a dual-functional role.

Adjusting to the vocal characteristics of a new talker is important for speech recognition. Previous research has indicated that adjusting to talker differences is an active cognitive process that depends on attention and working memory (WM). These studies have not examined how talker variability affects perception and neural responses in fluent speech. Here we use source analysis from high-density EEG to show that perceiving fluent speech in which the talker changes recruits early involvement of parietal and temporal cortical areas, suggesting functional involvement of WM and attention in talker normalization. We extend these findings to acoustic source change in general by examining understanding environmental sounds in spoken sentence context. Though there may be differences in cortical recruitment to processing demands for non-speech sounds versus a changing talker, the underlying mechanisms are similar, supporting the view that shared cognitive-general mechanisms assist both talker normalization and speech-to-nonspeech transitions.

Orthographic processing is a critical stage in visual word recognition. However, the white-matter pathways that support this processing are unclear, as prior findings might have been confounded by impure behavioral measures, potential structural reorganization of the brain, and limited sample sizes. To address this issue, we investigated the correlations between the integrity of 20 major tracts in the whole brain and the pure orthographic index across 67 patients with short-term brain damage. The integrity of the tracts was measured by the lesion volume percentage and the mean fractional anisotropy value. The orthographic index was calculated as the residual of the orthographic tasks after regressing out corresponding nonorthographic tasks and the orthographic factor from the principal component analysis (PCA) on the basis of four orthographic tasks. We found significant correlations associated with the left inferior longitudinal fasciculus (ILF), even after controlling for the influence of potential confounding variables. These observations strengthen evidence for the vital role of the left ILF in orthographic processing.

We previously reported impoverished semantic memory in patients with hippocampal amnesia (Klooster & Duff, 2015). Here, we test whether this disruption results from the patients not updating semantic representations since the onset of their amnesia. We extend previous work by comparing performance of hippocampal patients and their current age (CA) comparisons (M = 58.5 years) to a new comparison group matched to the patients’ age of onset (AoO) of hippocampal damage (M = 36.8). Participants completed feature and senses-listing tasks and the Word Associates Test. Both comparison groups performed significantly better than the patients with amnesia. A key new finding was that the older CA group performed significantly better than the younger AoO group. Semantic memory may become richer over time as additional information is added to existing representations. We conclude that a failure to update semantic memory may explain (at least some of) the previously observed deficits in amnesia and that the hippocampus may support semantic memory across the lifespan. Longitudinal data from patients with hippocampal pathology would provide a critical test of our conclusion.

Advanced imaging studies in neurodegenerative disease have yielded new insights into subtypes of disease, progression of disease in various brain regions, and changes in structural and functional connectivity between brain regions related to symptom progression. However, few studies have revealed imaging markers at baseline that correlate with rate or degree of decline in function. Here we tested the hypothesis that imaging features at baseline correlate with outcome of naming in primary progressive aphasia. We obtained longitudinal multimodal imaging in 15 individuals with primary progressive aphasia at the same time points as assessment of naming. We found that functional connectivity between particular brain regions (measured with resting state functional connectivity magnetic resonance imaging) is strongly associated with accuracy of naming 21 months later, independently of baseline severity of naming impairment. These data indicate that functional connectivity may carry information about later performance in naming, and is potentially useful for refining prognosis.