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A novel approach for investigating the functional segregation of linguistic functions within fronto-parietal networks

Valeria Parlatini1*, Joaquim Radua1, Flavio Dell'Acqua1, Marco Catani1, Declan Murphy1 and Michel Thiebaut De Schotten1
  • 1 Institute of Psychiatry, Psychology and Neuroscience, King's College London, United Kingdom

Introduction: experimental data on monkeys and functional studies in humans support the existence of a complex fronto-parietal system activating for linguistic and non-linguistic functions, which may be anatomically supported by fronto-parietal associative connections, namely by the superior longitudinal fasciculus (SLF) (Petrides & Pandya, 1984; Rottschy et al., 2012). Advanced tractography methods have recently allowed the separation of the three branches of the SLF but are not suitable for their functional investigation (Thiebaut de Schotten et al., 2011). In this study we employed an innovative method, which combined tractography in a large dataset (129 subjects) with 14 meta-analyses of functional magnetic resonance imaging (fMRI) studies, in order to investigate the anatomical and functional segregation of linguistic functions supported by the three branches of the SLF, as compared to that of non-linguistic functions. Methods: we performed bilateral virtual dissections of the three branches of the SLF in a dataset of 129 adult healthy participants and extracted their cortical projections. A comprehensive representation of the fronto-parietal networks was obtained by performing 14 meta-analyses of functions co-activating fronto-parietal regions, using the SDM software (www.sdmproject.com) (Radua & Mataix-Cols, 2012). Linguistic functions included semantic processing, phonological processing and verbal working memory, whereas non-linguistic functions included visuo-spatial and motor functions, emotion and number processing, decision making and mirror neuron related functions. We then quantified the overlap between the projections of the SLF and the meta-analytic maps, and assess the involvement of each branch in each function by using one-sample t-tests in SPSS. Results: we found that linguistic functions were partially segregated although supported by all three branches in the left hemisphere. Indeed, semantic processing relied more on the left SLF 2 than phonological processing, and also demonstrated a greater contribution of the right hemisphere. Further, a ventro-dorsal segregation was observed between verbal and spatial working memory, with the former mainly relying on left ventral regions and the latter on more dorsal regions, fact that reflected on their different involvement of the SLF braches. Notably, this ventro-dorsal segregation was observed more generally between areas (and related tracts) devoted to language and those supporting the processing of motor and spatial stimuli. Conclusion: 10 years of fMRI studies integrated in our 14 meta-analyses and combined with high resolution tractography provided novel findings on the functional organisation of linguistic functions within fronto-parietal networks. These results suggested the existence of both within-domain and between domains functional segregation. In fact, linguistic functions were partially segregated and differently supported by the three branches of the SLF, but also a ventro-dorsal segregation was observed more generally between areas (and related tracts) devoted to language and those supporting the processing of motor and spatial stimuli. In sum, our novel combined approach was successful and may be effectively applied to other brain connections.

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References

Petrides, M., & Pandya, D. N. (1984). Projections to the frontal cortex from the posterior parietal region in the rhesus monkey. J Comp Neurol, 228(1), 105-116. doi: 10.1002/cne.902280110

Radua, J., & Mataix-Cols, D. (2012). Meta-analytic methods for neuroimaging data explained. Biol Mood Anxiety Disord, 2(1), 6. doi: 10.1186/2045-5380-2-6

Rottschy, C., Langner, R., Dogan, I., Reetz, K., Laird, A. R., Schulz, J. B., . . . Eickhoff, S. B. (2012). Modelling neural correlates of working memory: a coordinate-based meta-analysis.Neuroimage, 60(1), 830-846. doi: 10.1016/j.neuroimage.2011.11.050

Thiebaut de Schotten, M., Dell'Acqua, F., Forkel, S. J., Simmons, A., Vergani, F., Murphy, D. G., & Catani, M. (2011). A lateralized brain network for visuospatial attention. Nat Neurosci, 14(10), 1245-1246. doi: 10.1038/nn.2905

Keywords: semantics, phonological processing, Verbal Working Memory, functional magnetic resonance imaging (fMRI), tractography, frontoparietal

Conference: 54th Annual Academy of Aphasia Meeting, Llandudno, United Kingdom, 16 Oct - 18 Oct, 2016.

Presentation Type: Poster Sessions

Topic: Student Submissions

Citation: Parlatini V, Radua J, Dell'Acqua F, Catani M, Murphy D and Thiebaut De Schotten M (2016). A novel approach for investigating the functional segregation of linguistic functions within fronto-parietal networks. Front. Psychol. Conference Abstract: 54th Annual Academy of Aphasia Meeting. doi: 10.3389/conf.fpsyg.2016.68.00105

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Received: 30 Apr 2016; Published Online: 15 Aug 2016.

* Correspondence: Dr. Valeria Parlatini, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom, valeria.parlatini@kcl.ac.uk