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The anatomy of the posterior segment of the arcuate fasciculus correlates with reading and vocabulary comprehension performance

Naianna Robertsson1*, Stephanie Forkel1, Flavio Dell'Acqua2 and Marco Catani2
  • 1 King's College London, Centre for Neuroimaging Sciences, United Kingdom
  • 2 King's College London, Department of Forensics and Neurodevelopmental Science, United Kingdom

The inferior parietal lobule (Geschwind’s territory) is a multimodal integration hub directly linked to Wernicke’s and Broca’s territories via the arcuate fasciculus (AF) (Catani et al., 2005; Lopez-Barroso et al., 2013). Recent studies suggest that connections between Geschwind’s and Wernicke’s territory, mediated by the posterior segment of the AF, are specifically important for reading (Thiebaut de Schotten et al., 2012). However, it is not clear whether the role of the posterior segment is linked only to orthographic-to-phonological coding or whether it also involves semantic aspects of reading. In this study, we performed tractography in-vivo dissections of the posterior segment of the AF in healthy subjects and explored the correlation between its anatomical variability and performances in reading and vocabulary comprehension tasks. METHODS Thirty-eight right-handed healthy participants, 20 females, aged 23-35 from the Human Connectome Project (Van Essen et al., 2013) were scanned on a 3T Siemens MRI scanner (voxel size 1.25mm3, 210x210 matrix, 111 slices, b-value 2000s/mm2, 90 diffusion-weighted volumes and 18 non-diffusion weighted volumes. Diffusion data was collected using a HARDI sequence and processed for deterministic spherical deconvolution tractography (Dell’Acqua et al., 2013, www.natbrainlab.com). Virtual dissections were manually performed on TrackVis using anatomically defined regions of interest. The long segment (from Broca’s to Wernicke’s territories) of AF, considered to be a multifunctional language pathway involved in production of meaningful language and speech, was chosen as a control tract. Behavioural tasks were obtaimed from the NIH Toolbox 1.0 (www.nihtoolbox.com). Oral Reading task: participants were asked to read and pronounce words as accurately as possible. Higher scores indicate more accurate and faster pronunciation of increasingly difficult words. Picture vocabulary comprehension: Participants were presented with an audio-recording of a word and four photographic images on a computer screen and asked to select the picture that most closely matches the meaning of the word. Higher scores reflected wider vocabulary knowledge and faster comprehension. RESULTS Correlation analyses were used to investigate the relationship between tract properties of the posterior segment of AF and language skills. Results showed that reading performance scores correlated significantly with the volume of the left hemisphere posterior segment (r=0.6; p=0.02). Similarly, vocabulary comprehension scores correlated with volume of the left hemisphere posterior segment (r=0.5, p=0.04). There was no association between oral reading and the long segment of AF (r=0.2, p=0.2), nor between vocabulary comprehension and the long segment (r=0.2, p=0.2). No correlation with the posterior segment of the AF in the right hemisphere. CONCLUSION Performances in oral reading and vocabulary comprehension were associated with increased volume of the left posterior segment of the AF. By mediating connections between the visual word form area (temporal-occipital region) (Braet et al., 2012) and inferior parietal areas, the posterior segment is likely involved in encoding an orthographic-to-phonological route as well as visual representations of words (Ben-Shachar et al., 2007). Moreover, the posterior segment might also be involved in enforcing a semantic route that is dependent on auditory and temporal connections related to word comprehension (Carreiras et al., 2009). As the inferior parietal region is amongst the latest regions to evolve and develop, this might explain why general semantic knowledge progressively increases throughout life.

Acknowledgements

Data collection and sharing for this project was provided by the Human Connectome Project (HCP; Principal Investigators: Bruce Rosen, M.D., Ph.D., Arthur W. Toga, Ph.D., Van J. Weeden, MD). HCP funding was provided by the National Institute of Dental and Craniofacial Research (NIDCR), the National Institute of Mental Health (NIMH), and the National Institute of Neurological Disorders and Stroke (NINDS). HCP data are disseminated by the Laboratory of Neuro Imaging at the University of Southern CA

References

Catani, M., & Jones, D. K. (2005). Perisylvian language networks of the human brain. Annals of neurology, 57(1), 8-16.

López-Barroso, D., Catani, M., Ripollés, P., Dell'Acqua, F., Rodríguez-Fornells, A., & de Diego-Balaguer, R. (2013). Word learning is mediated by the left arcuate fasciculus. Proceedings of the National Academy of Sciences, 110(32), 13168-13173.

De Schotten, M. T., Cohen, L., Amemiya, E., Braga, L. W., & Dehaene, S. (2012). Learning to read improves the structure of the arcuate fasciculus. Cerebral Cortex, bhs383.

Van Essen, D. C., Smith, S. M., Barch, D. M., Behrens, T. E., Yacoub, E., Ugurbil, K., & WU-Minn HCP Consortium. (2013). The WU-Minn human connectome project: an overview. Neuroimage, 80, 62-79.

Dell'Acqua, F., Simmons, A., Williams, S. C., & Catani, M. (2013). Can spherical deconvolution provide more information than fiber orientations? Hindrance modulated orientational anisotropy, a true‐tract specific index to characterize white matter diffusion. Human brain mapping, 34(10), 2464-2483.

Braet, W., Wagemans, J., & de Beeck, H. P. O. (2012). RETRACTED: The visual word form area is organized according to orthography. Neuroimage, 59(3), 2751-2759.

Ben-Shachar, M., Dougherty, R. F., & Wandell, B. A. (2007). White matter pathways in reading. Current opinion in neurobiology, 17(2), 258-270.

Carreiras, M., Seghier, M. L., Baquero, S., Estévez, A., Lozano, A., Devlin, J. T., & Price, C. J. (2009). An anatomical signature for literacy. Nature, 461(7266), 983-986.

Keywords: Neuroanatomy, tractography, reading, vocabulary knowledge, healthy controls, Language, Arcuate Fasciculus, Neuroimaging, Diffusion Tensor Imaging

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

Presentation Type: Poster Sessions

Topic: Student Submissions

Citation: Robertsson N, Forkel S, Dell'Acqua F and Catani M (2016). The anatomy of the posterior segment of the arcuate fasciculus correlates with reading and vocabulary comprehension performance. Front. Psychol. Conference Abstract: 54th Annual Academy of Aphasia Meeting. doi: 10.3389/conf.fpsyg.2016.68.00110

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

* Correspondence: Ms. Naianna Robertsson, King's College London, Centre for Neuroimaging Sciences, London, United Kingdom, naianna@gmail.com