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Engaging Grammar and Visual Networks

Periodic Reporting for period 1 - ENGRAVINg (Engaging Grammar and Visual Networks)

Reporting period: 2019-12-01 to 2021-11-30

Problem: Our understanding of the brain mechanisms is highly constrained by the methodologies we use as neuroscientists (e.g. electrophysiology, neuroimaging). In recent years great technological advances (e.g. software for white matter segmentation of white matter fibers, refined MEG source reconstruction pipelines) enabled researchers to achieve a more precise description of structural and functional properties of the human brain. However, the interaction between research communities using different methodologies (e.g. MRI and MEG) is still limited, which often results in separate publications and scientific events dedicated to different research questions (e.g. where brain structures change with learning vs when brain functions change with learning). We are at a historical stage where advances of our neuroscientific knowledge highly depend on the fruitful interactions between different disciplines, fields and methods. Being able to describe how structural properties of the brain are related to brain functional responses represents a challenge that neuroscientists need to be able to address in the near future. The ENGRAVINg project followed this philosophy and consisted of a cross-disciplinary neuroscience research work where brain mechanisms are described from different methodological perspectives (MEG and diffusion MRI) with the general aim of bridging structural and functional properties of the brain within the context of vision and reading.

Relevance for the society: Reading is an essential human right and a key skill to become a knowledgeable and critical thinking human being. Being able to characterize how the brain enables this unique human ability is essential to ensure to every single individual a successful reading experience. This project provided a multi-level description of the developing reading brain circuitry to maximize our future ability to prevent, detect and treat reading difficulties.

Overall objectives: The aim of the ENGRAVINg project was to uncover how structural properties of white matter brain tracts (e.g. which are related to myelination and fiber spatial organization) are related to the functional brain responses (e.g. electrophysiological responses) within the context of vision and reading. Specifically, Dr Caffarra and collaborators from the Basque Center on Cognition, Brain and Language (BCBL) and Stanford University tried to:
1) characterize structural-functional relationship in healthy individuals within the context of vision and written language processing
2) describe how this structural-functional relationship changes in reading acquisition and reading impairment.

*Part of aim 2) was not carried out due to the early termination of the project. The project had to be termination to start a tenure-track position in Europe.

Conclusions: Dr Caffarra could report a structural-functional relationship within the human vision system (i.e. the development of structural properties of white matter pathways mediates the maturation of electrophysiological responses in the visual cortex). She is now trying to translate these results to higher-level cognitive functions (e.g. language and reading).
1st part
Aim: Describe the relationship between structural and functional properties of the brain within the context of reading and vision. We collected functional (MEG) and structural (diffusion MRI) brain measures of 38 healthy individuals (English native speakers) to test whether white matter properties of the brain can predict electrophysiological measures recorded on the scalp.
Results: Within the context of vision, we could observe a structural-functional relationship of brain properties. Specifically, the structural integrity of visual white matter fibers (fractional anisotropy of the left and right optic radiations) predict the latency of electrophysiological responses measured on the scalp (i.e. M100 half-peak latency). Within the context of language, we could not observe a clear relationship between structural properties of white matter (fractional anisotropy of arcuate fasciculus or inferior longitudinal fasciculus) and language-related evoked responses (i.e. latency or amplitude of the M170/M400 in response to words). This might suggest that the language circuitry involves highly interactive top-down and bottom-up effects that make the detection of structural-functional correspondences more challenging.

2nd part
Aim: Characterize the relationship between structural and functional properties while normal developing children learn to read. We collected behavioural (language and reading skills), functional (MEG and fMRI) and structural (diffusion MRI) brain measures of 48 healthy children (5-6 year old English native speakers) to test whether white matter properties of the brain can predict functional brain responses while children learn to read. The data were collected longitudinally before and after the participants went through an intensive reading program.
Results: We are still analysing the data for this part of the project. Preliminary results of the behavioural and diffusion MRI data showed that (A) children improved their reading skills thanks to the training (B) we could observe some relationship between structural properties of white matter pathways (e.g. mean diffusivity of left uncinate) and children’s linguistic skills (i.e. accuracy at a phoneme matching task). Dr. Caffarra is planning to analyze the corresponding MEG data and try to relate it with diffusion properties of white matter.

General results, exploitation, dissemination: This project led to a new understanding of the coupling between neural anatomy and functional mechanisms of the visual brain network. These findings were presented to events for general and scientific audience; an open web-browser has been published based on the project findings; 6 papers related to this topic have been published (Journal or Neuroscience, Scientific Reports, Brain and Language, Aperture, Human Brain Mapping, Brain Structure and Function). The project spread general knowledge on reading brain mechanisms through multiple outreach activities (general talks, press releases, public posts on social media). The scientific advances achieved with the project resulted in the proposal of a new theoretical model on the reading brain circuitry (see attached figure), which can be the starting point to better understand structural and functional neural basis of reading.
The ENGRAVINg project had an impact on the scientific and general public. It increased the occasions to collaborate among scientists coming from different cultures (European, American, Asian), backgrounds (psychology, software engineer, data science, physics) and professional positions (academia and industry). It increased our understanding of the structural-functional relationship of the visual brain and how it changes during reading development. It provided a theoretical model of reading that describes functional-structural relationships in the brain supporting the transition from vision to language (see attached figure). This novel theoretical contribution can be translated into clinical and educational practice. This knowledge represents an important starting point to uncover the biological bases of children’s reading performance differences, understand what structures and mechanisms are impaired in reading disorders (e.g. dyslexia), and plan evidence-based intervention programs.
Summary of the theoretical model proposed by Caffarra et al. (under review, preprint available here)