Functional and structural neural contributions to skilled word reading

Reading is an essential skill in our everyday lives and individuals are required to process, understand, and respond to textual information at an increasingly rapid rate in order to be active participants in society. The role of spatial attention in reading has recently been emphasized, whereby better spatial attentional skills are associated with stronger reading skills, and spatial attentional training has a large impact on improving reading ability. However, the neuroanatomical correlates of reading and attention have primarily been studied in isolation. Further, there has recently been a shift to understanding how underlying white matter connectivity networks contribute to cognitive processes. However, much of the research focusing on the intersection of reading and spatial attention, as well as underlying white matter connectivity, has focused primarily on individuals with reading impairments. This thesis will focus on unraveling the neural relationship between spatial attention and reading, and how structural connectivity accounts for functional activation in reading tasks. In Chapter 2, we examine the neural relationship between lexical and sublexical reading with voluntary and reflexive spatial attention. In Experiments 1 and 2, participants performed overt reading of both lexical exception word (EW; words with inconsistent spelling-to-sound correspondences, e.g., ‘pint’) and sublexical pseudohomophone (PH; non-words that when decoded phonetically sound like real words, e.g., ‘pynt’) reading tasks, as well as tasks involving either voluntary attention (Experiment 1) or reflexive attention (Experiment 2) during functional magnetic resonance imaging (fMRI). Experiment 3 used hybrid combined reading attention tasks during fMRI, whereby the spatial attentional cue preceded presentation of the EW or PH stimulus. Overall, the results from these experiments showed that sublexical reading was more strongly associated with brain regions involved in voluntary attention, whereas lexical reading was more strongly associated with brain regions involved in reflexive attention. Thus, Experiments 1, 2 and 3 lend support to the idea that lexical and sublexical reading strategies are differentially associated with these two types of attention. In Chapter 3, we examined the extent to which fine-grained underlying white matter connectivity is able to predict fMRI activation during both lexical reading and phonetic decoding in skilled readers. Experiment 4 employed EW and PH reading and a computational modeling technique to model the relationship between whole-brain structural DTI connectivity and task-based fMRI activation during lexical and sublexical reading. Results from this study showed that brain activation during both lexical and sublexical reading in skilled readers can be accurately predicted using DTI connectivity, specifically in known reading and language areas, as well as important spatial attentional areas. Thus, this research suggests that there is a fine-grained relationship between skilled reading and extrinsic brain connectivity, showing that functional organization of reading and language can be determined (at least in part) by structural connectivity patterns. Together, the studies presented in this thesis provide valuable insight into functional and structural contributions to word reading that may serve as biomarkers of skilled reading, which in turn may have important implications for understanding and remediating reading impairments

Somatosensory Involvement in the Conceptual Representation of Objects

The involvement of the sensorimotor system in visual object processing is at the forefront of cognitive neuroscience research. Since the discovery of the mirror neuron system, a plethora of research has been dedicated to understanding how action influences cognition. Of particular interest to the current work is the way in which two-dimensional objects are represented in the human brain. Embodied cognition theories assert that the sensorimotor system plays a large (if not entire) role in the conceptual representation of objects. Interestingly, however, although somatosensation provides the first means of acquiring information from our environments and thus is integral to the development of conceptual representation, research has generally focused on motor system contributions to object processing. Therefore, this series of experiments will focus on unravelling the relationship between the somatosensory system and object processing. To do this, we employed two different priming paradigms, one in which vibratory stimulation served as a prime and an object picture as the target (Experiments 1 to 4), and the other where the object was the prime and the vibration the target (reverse priming task; Experiments 5 and 6). In Experiments 1 to 3, the participant was required to indicate how they would interact with the presented object (i.e., a semantic generation task). Results from Experiments 1 and 2 showed that object processing of graspable objects could be facilitated by a vibratory hand prime, compared to non-graspable objects (Experiment 1) and objects with foot related action affordances (Experiment 2), both of which showed no priming effects. Experiment 3 used a vibratory foot prime to investigate whether the priming effects in Experiments 1 and 2 were due semantic matching effects, such that drawing attention to a modality serves to enhance processing of objects related to that modality, and found no evidence to support this account. Experiment 4 assessed the degree to which sensorimotor representations are automatically activated using an object-naming paradigm, which showed no somatosensory priming effects, and thus no evidence for automatic somatosensory involvement. Experiment 5 utilized the reverse priming task (described above), and found evidence for faster somatosensory detection when primed with a hand object, providing converging evidence of a reciprocal relationship between the somatosensory system and object processing. Finally, Experiment 6 examined whether the results from Experiment 5 were due to matching effects (similar to Experiment 3), and found no evidence for this account. Taken together, our research provides corroborative, converging evidence that semantic knowledge about how one interacts with manipulable objects involves sensorimotor representations in the somatosensory system. This supports theories of embodied cognition and the mirror neuron system, and extends them from the motor domain to accommodate somatosensory influences, opening a new window into exploration of how touch may be incorporated into these theories. Implications for models of the mirror neuron system, and future directions for localizing these effects using neuroimaging are discussed

High Force Unimanual Handgrip Contractions Increase Ipsilateral Sensorimotor Activation and Functional Connectivity

Imaging and brain stimulation studies seem to correct the classical understanding of how brain networks, rather than contralateral focal areas, control the generation of unimanual voluntary force. However, the scaling and hemispheric-specificity of network activation remain less understood. Using fMRI, we examined the effects of parametrically increasing right-handgrip force on activation and functional connectivity among the sensorimotor network bilaterally with 25%, 50%, and 75% maximal voluntary contractions (MVC). High force (75% MVC) unimanual handgrip contractions resulted in greater ipsilateral motor activation and functional connectivity with the contralateral hemisphere compared to a low force 25% MVC condition. The ipsilateral motor cortex activation and network strength correlated with relative handgrip force (% MVC). Increases in unimanual handgrip force resulted in greater ipsilateral sensorimotor activation and greater functional connectivity between hemispheres within the sensorimotor network. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Females exhibit smaller volumes of brain activation and lower inter-subject variability during motor tasks

Abstract Past work has shown that brain structure and function differ between females and males. Males have larger cortical and sub-cortical volume and surface area (both total and subregional), while females have greater cortical thickness in most brain regions. Functional differences are also reported in the literature, yet to date little work has systematically considered whether patterns of brain activity indexed with functional magnetic resonance imaging (fMRI) differ between females and males. The current study sought to remediate this issue by employing task-based whole brain motor mapping analyses using an openly available dataset. We tested differences in patterns of functional brain activity associated with 12 voluntary movement patterns in females versus males. Results suggest that females exhibited smaller volumes of brain activation across all 12 movement tasks, and lower patterns of variability in 10 of the 12 movements. We also observed that females had greater cortical thickness, which is in alignment with previous analyses of structural differences. Overall, these findings provide a basis for considering biological sex in future fMRI research and provide a foundation of understanding differences in how neurological pathologies present in females vs males

Examining the neuroanatomical and the behavioural basis of the effect of basic rhythm on reading aloud

<p>We used functional magnetic resonance imaging (fMRI) to examine the brain regions associated with the effect of congruency between rhythmic stress and syllabic stress on reading aloud (Gould et al., 2016). The region of particular interest was the putamen, which has been shown to be involved in speech processing, rhythm processing, and predicting upcoming events. The task involved naming words that placed the stress on either the first or second syllable (practice versus police), as well as their corresponding pseudohomophones (praktis versus poleese) that were preceded by either a congruent or incongruent rhythmic prime. The fMRI results revealed that a network involving the putamen is involved, and the behavioural results demonstrated that a rhythmic prime matched to the syllabic stress aids reading processes of both words and PHs. Implications for neurobiological models of reading, as well as clinical applications (e.g. speech rehabilitation in Parkinson’s disease) are discussed.</p

Presurgical language mapping in epilepsy: Using fMRI of reading to identify functional reorganization in a patient with long-standing temporal lobe epilepsy

We report a 55-year-old, right-handed patient with intractable left temporal lobe epilepsy, who previously had a partial left temporal lobectomy. The patient could talk during seizures, suggesting that he might have language dominance in the right hemisphere. Presurgical fMRI localization of language processing including reading of exception and regular words, pseudohomophones, and dual meaning words confirmed the clinical hypothesis of right language dominance, with only small amounts of activation near the planned surgical resection and, thus, minimal eloquent cortex to avoid during surgery. Postoperatively, the patient was rendered seizure-free without speech deficits