Brain activation during phonological and semantic processing of Chinese characters in deaf signers

The inter-related effects of alcohol use severity and sleep deficiency on semantic processing in young adults

BACKGROUND

Both alcohol misuse and sleep deficiency are associated with deficits in semantic processing. However, alcohol misuse and sleep deficiency are frequently comorbid and their inter-related effects on semantic processing as well as the underlying neural mechanisms remain to be investigated.

METHODS

We curated the Human Connectome Project data of 973 young adults (508 women) to examine the neural correlates of semantic processing in link with the severity of alcohol use and sleep deficiency. The latter were each evaluated using the first principal component (PC1) of principal component analysis of all drinking metrics and the Pittsburgh Sleep Quality Index (PSQI). We employed path modeling to elucidate the interplay among clinical, behavioral, and neural variables.

RESULTS

Among women, we observed a significant negative correlation between the left precentral gyrus (PCG) and PSQI scores. Mediation analysis revealed that the left PCG activity fully mediated the relationship between PSQI scores and word comprehension in language tasks. In women alone also, the right middle frontal gyrus (MFG) exhibited a significant negative correlation with PC1. The best path model illustrated the associations among PC1, PSQI scores, PCG activity, and MFG activation during semantic processing in women.

CONCLUSIONS

Alcohol misuse may lead to reduced MFG activation while sleep deficiency hinder semantic processing by suppressing PCG activity in women. The pathway model underscores the influence of sleep quality and alcohol consumption severity on semantic processing in women, suggesting that sex differences in these effects need to be further investigated.

Neural underpinnings of sentence reading in deaf, native sign language users

The goal of this study was to investigate sentence-level reading circuits in deaf native signers, a unique group of deaf people who are immersed in a fully accessible linguistic environment from birth, and hearing readers. Task-based fMRI, functional connectivity and lateralization analyses were conducted. Both groups exhibited overlapping brain activity in the left-hemispheric perisylvian regions in response to a semantic sentence task. We found increased activity in left occipitotemporal and right frontal and temporal regions in deaf readers. Lateralization analyses did not confirm more rightward asymmetry in deaf individuals. Deaf readers exhibited weaker functional connectivity between inferior frontal and middle temporal gyri and enhanced coupling between temporal and insular cortex. In conclusion, despite the shared functional activity within the semantic reading network across both groups, our results suggest greater reliance on cognitive control processes for deaf readers, possibly resulting in greater effort required to perform the task in this group.

The puzzle of ideography

An ideography is a general-purpose code made of pictures that do not encode language, which can be used autonomously - not just as a mnemonic prop - to encode information on a broad range of topics. Why are viable ideographies so hard to find? I contend that self-sufficient graphic codes need to be narrowly specialized. Writing systems are only an apparent exception: At their core, they are notations of a spoken language. Even if they also encode nonlinguistic information, they are useless to someone who lacks linguistic competence in the encoded language or a related one. The versatility of writing is thus vicarious: Writing borrows it from spoken language. Why is it so difficult to build a fully generalist graphic code? The most widespread answer points to a learnability problem. We possess specialized cognitive resources for learning spoken language, but lack them for graphic codes. I argue in favor of a different account: What is difficult about graphic codes is not so much learning or teaching them as getting every user to learn and teach the same code. This standardization problem does not affect spoken or signed languages as much. Those are based on cheap and transient signals, allowing for easy online repairing of miscommunication, and require face-to-face interactions where the advantages of common ground are maximized. Graphic codes lack these advantages, which makes them smaller in size and more specialized.

Multisensory temporal processing in early deaf

Navigating the world relies on understanding progressive sequences of multisensory events across time. Early deaf (ED) individuals are more precise in visual detection of space and motion than their normal hearing (NH) counterparts. However, whether ED individuals show altered multisensory temporal processing abilities is less clear. According to the connectome model, brain development depends on experience, and therefore the lack of audition may affect how the brain responds to remaining senses and how they are functionally connected. We used a temporal order judgment (TOJ) task to examine multisensory (visuotactile) temporal processing in ED and NH groups. We quantified BOLD responses and functional connectivity (FC) in both groups. ED and NH groups performed similarly for the visuotactile TOJ task. Bilateral posterior superior temporal sulcus (pSTS) BOLD responses during the TOJ task were significantly larger in the ED group than in NH. Using anatomically defined pSTS seeds, our FC analysis revealed stronger somatomotor and weaker visual regional connections in the ED group than in NH during the TOJ task. These results suggest that a lack of auditory input might alter the balance of tactile and visual area FC with pSTS when a multisensory temporal task is involved.

The neurocognitive basis of skilled reading in prelingually and profoundly deaf adults

Deaf individuals have unique sensory and linguistic experiences that influence how they read and become skilled readers. This review presents our current understanding of the neurocognitive underpinnings of reading skill in deaf adults. Key behavioural and neuroimaging studies are integrated to build a profile of skilled adult deaf readers and to examine how changes in visual attention and reduced access to auditory input and phonology shape how they read both words and sentences. Crucially, the behaviours, processes, and neural circuity of deaf readers are compared to those of hearing readers with similar reading ability to help identify alternative pathways to reading success. Overall, sensitivity to orthographic and semantic information is comparable for skilled deaf and hearing readers, but deaf readers rely less on phonology and show greater engagement of the right hemisphere in visual word processing. During sentence reading, deaf readers process visual word forms more efficiently and may have a greater reliance on and altered connectivity to semantic information compared to their hearing peers. These findings highlight the plasticity of the reading system and point to alternative pathways to reading success.

Sign phonological parameters modulate parafoveal preview effects in deaf readers

Research has found that deaf readers unconsciously activate sign translations of written words while reading. However, the ways in which different sign phonological parameters associated with these sign translations tie into reading processes have received little attention in the literature. In this study on Chinese reading, we used a parafoveal preview paradigm to investigate how four different types of sign phonologically related preview affect reading processes in adult deaf signers of Hong Kong Sign Language (HKSL). The four types of sign phonologically related preview-target pair were: (1) pairs with HKSL translations that overlapped in three parameters-handshape, location, and movement; (2) pairs that overlapped in only handshape and location; (3) pairs that only overlapped in handshape and movement; and (4) pairs that only overlapped in location and movement. Results showed that the handshape parameter was of particular importance as only sign translation pairs that had handshape among their overlapping sign phonological parameters led to early sign activation. Furthermore, we found that, compared to control previews, deaf readers took longer to read targets when the sign translation previews overlapped with targets in either handshape and movement or handshape, movement, and location. In contrast, fixation times on targets were shorter when previews and targets overlapped location and any single additional parameter-either handshape or movement. These results indicate that the phonological parameters of handshape, location, and movement are activated via orthography during Chinese reading and can have different effects on parafoveal processing in deaf signers of HKSL.

Orthographic and phonological selectivity across the reading system in deaf skilled readers

People who are born deaf often have difficulty learning to read. Recently, several studies have examined the neural substrates involved in reading in deaf people and found a left lateralized reading system similar to hearing people involving temporo-parietal, inferior frontal, and ventral occipito-temporal cortices. Previous studies in typical hearing readers show that within this reading network there are separate regions that specialize in processing orthography and phonology. We used fMRI rapid adaptation in deaf adults who were skilled readers to examine neural selectivity in three functional ROIs in the left hemisphere: temporoparietal cortex (TPC), inferior frontal gyrus (IFG), and the visual word form area (VWFA). Results show that in deaf skilled readers, the left VWFA showed selectivity for orthography similar to what has been reported for hearing readers, the TPC showed less sensitivity to phonology than previously reported for hearing readers using the same paradigm, and the IFG showed selectivity to orthography, but not phonology (similar to what has been reported previously for hearing readers). These results provide evidence that while skilled deaf readers demonstrate coarsely tuned phonological representations in the TPC, they develop finely tuned representations for the orthography of written words in the VWFA and IFG. This result suggests that phonological tuning in the TPC may have little impact on the neural network associated with skilled reading for deaf adults.

The neural underpinnings of reading skill in deaf adults

We investigated word-level reading circuits in skilled deaf readers (N=14; mean reading age=19.5years) and less skilled deaf readers (N=14; mean reading age=12years) who were all highly proficient users of American Sign Language. During fMRI scanning, participants performed a semantic decision (concrete concept?), a phonological decision (two syllables?), and a false-font control task (string underlined?). No significant group differences were observed with the full participant set. However, an analysis with the 10 most and 10 least skilled readers revealed that for the semantic task (vs. control task), proficient deaf readers exhibited greater activation in left inferior frontal and middle temporal gyri than less proficient readers. No group differences were observed for the phonological task. Whole-brain correlation analyses (all participants) revealed that for the semantic task, reading ability correlated positively with neural activity in the right inferior frontal gyrus and in a region associated with the orthography-semantics interface, located anterior to the visual word form area. Reading ability did not correlate with neural activity during the phonological task. Accuracy on the semantic task correlated positively with neural activity in left anterior temporal lobe (a region linked to conceptual processing), while accuracy on the phonological task correlated positively with neural activity in left posterior inferior frontal gyrus (a region linked to syllabification processes during speech production). Finally, reading comprehension scores correlated positively with vocabulary and print exposure measures, but not with phonological awareness scores.