1. Problem Goals Method Conclusions Results
THE RELATION BETWEEN THE METRICS OF THE CORPUS CALLOSUM AND LANGUAGE LATERALIZATION IN THE BRAIN Tatiana Bolgina1, Svetlana Malyutina1, Victoriya Zinchenko1,2, Grigoriy Ignatyev1, Vadim Ushakov2, Yulia Akinina 1, Maria Ivanova1, Olga Dragoy1 1National Search University Higher School of Economics, 2 National Research Center ‘Kurchatov Institute’
Picture 5 The correlation between CC volume and lateralization indices in 50 participants
Picture 1 Presentation of experimental sentences
Problem
The organization of the Corpus Callosum may be related to language lateralization in the brain
few studies considered both anatomy and function to test this hypothesis
the authors of previous study used the indirect metric of the corpus callosum (the measurement of midsagital surface of the corpus callosum using anatomical T1-weighted images)
Goals
to measure the corpus callosum’s size with the use of white matter tractography
to correlate the corpus callosum’s size with lateralization indices in participants with different individual handedness
Picture 6 The correlation between handedness scores and lateralization indices in 50 participants
Picture 2 Presentation of sequences of syllables
Method
fMRI
Siemens Magnetom Verio 3T Scanner
A sparse sampling paradigm, TR=7 sec. Block design.
SPM 8 software; Lateralization Index (LI) toolbox
Reading aloud, two conditions:
Experimental condition
Yesterday the nurse cooked a tasty …
Task: complete with an appropriate word
Baseline condition
Рееееее рееееее рееееее реееееееее ...
Task: complete with the same syllable
2 experimental sessions
In each session:
120 stimuli (60 sentences, 60 sequences of syllables)
sequences of syllables had the same length in letters and syllables as experimental sentences
Both conditions involved:
Reading
Articulation
Choice of an answer
The control condition does not involve:
Grammatical processing
Lexico-semantic processing
DTI
The same scanner
Two sequences (64 directions, b=1500, voxel size 2х2х2 mm)
Preprocessing in FSL and Explore DTI
The tensor model for the corpus callosum’s reconstruction in Track Vis =>
CC metrics: mean MD, mean FA, CC volume and CC track count
Picture 7 The correlation between handedness scores and mean FA in 50 participants
Participants
50 neurologically healthy people
Mean age – 24, 18 males, 32 females
20 right-handers, handedness scores (from 45 to 100), LI (from 0,30 to 0,55)
20 left-handers, handedness scores (from -100 to -45), LI (from -0,44 to 0,53)
10 ambidexters, handedness scores (from -18 to 23), LI (from -0,44 to 0,62)
Handedness degree – the Edinburgh Inventory (handedness scores from +100 (strong right-hander) to -100 (strong left-hander)
Lateralization indices (LI) from -1 (right hemisphere) to 1 (left hemisphere)
Conclusions
the larger in volume the corpus callosum is, the more language-related activation is left-lateralized
strong right-handers have the corpus callosum with the largest fractional anisotropy, compared to strong left-handers with the smallest fractional anisotropy
the increase of the corpus callosum’s size may reflect the possible transfer of information related to language processing from the right hemisphere to the left one or the suppression of excessive activation in the right hemisphere
The result is consistent with previous findings by (Josse et al., 2009), but in the present study for the first time the real tractography data was used to reconstruct the corpus callosum and get its metrics in order to test their correlation with language lateralization indices
Results
Picture 3 The example of a tensor model of a right-handed participant, handedness score + 77
Edinburgh Inventory (Oldfield, 1971)
Picture 4 The reconstructed CC of this participant
Bibliography
Oldfield R.C. The assessment and analysis of handedness: the Edinburgh inventory. // Neuropsychologia Vol. 9. No 1. P
Josse G., Seghier M.L., Kherif F., Price C.J. Explaining function with anatomy: language lateralization and corpus callosum size. // Journal of Neuroscience Vol. 28. No 52. P
The Bonferroni correction of multiple comparisons (α = .0025)
The correlation analysis revealed the positive correlation between:
whole brain lateralization indices and the CC volume in ml (r = 0.384, p = 0.006)
individual handedness scores and whole brain lateralization indices (r = , p = 0.018)
individual handedness scores and fractional anisotropy of CC (r = 0.397, p = 0.007)
None of the variables significantly correlated with age and gender