Isaac Lebogang Khobo1,2, Ernesta Meintjes1,2, Barbara Laughton3, Kaylee van Wyhe3,4, Andre van der Kouwe1,5,6, and Frances Robertson1,2
1Human Biology, University of Cape Town, Cape Town, South Africa, 2Neuroscience Institute UCT, Cape Town, South Africa, 3Paediatrics and Child Health, Stellenbosch University, Family Centre for Research with Ubuntu, Cape Town, South Africa, 4Psychology, Acsent Lab, University of Cape Town, Cape Town, South Africa, 5A.A. Martinos Centre for Biomedical Imaging, Boston, MA, United States, 6Radiology, Harvard Medical School, Boston, MA, United States
Synopsis
Keywords: Diagnosis/Prediction, Multimodal
Motivation: The relationship between multimodal MRI neuroimaging and future cognitive performance of children from low-socioeconomic status backgrounds remains incompletely understood.
Goal(s): We aimed to predict cognitive performance at age 9 using multimodal MRI data of the same children at age 7.
Approach: We implemented 10-fold cross validated support vector machines and regression modelling on a combination of structural, diffusion, and spectroscopic MRI to predict continuous scores and categories of cognitive performance.
Results: We could predict whether children would fall into a poorer or better scoring category at age 9 with 76% accuracy, 81% specificity, and 72% sensitivity.
Impact: We demonstrate the ability to predict overall cognitive
performance at age 9 from neuroimaging 2 years earlier. This could facilitate
identification of at-risk children who may benefit the most from earlier
targeted interventions.
Introduction
Children from low socio-economic status (SES)
households and communities are at a risk of developmental delays1
and cognitive deficits which lead to high rates of school dropouts2.
Therefore, the ability to predict future cognitive outcomes from neuroimaging
or other methods could make it easier to identity at-risk children who may
benefit the most from early targeted interventions.
In
this work, we aimed to predict cognitive performance of children from low-SES
backgrounds at age 9 using cross-validated support vector machines and
regression (SVMs and SVR) on a multimodal MRI dataset at age 7.Methods
Our study population comprised 127 children (64 female, 63 male) from
low-SES backgrounds in Cape Town, South Africa. At age 7, we acquired
structural MRI (sMRI; 1.3x1.0x1.0 mm3), diffusion tensor imaging
(DTI; 2x2x2 m3), and single-voxel spectroscopy (1H-MRS; 1.5x1.5x1.5
cm3) in the midfrontal grey matter (MFGM) on a 3T Allegra scanner
(Siemens, Erlangen) using acquisition parameters specified
previously3-5.
Automated cortical reconstruction and volumetric segmentation were
performed on the structural T1-weighted dataset with FreeSurfer version 6.06.
We computed sMRI cortical measures—thickness, area, mean
curvature, volumes, and local gyrification index for each of the 68 regions of
the Desikan-Kalliany atlas7. Additionally, 47 sMRI subcortical and
other non-cortical regional and total volumes were included in the analyses. Motion and eddy current
distortion corrections on the DTI dataset were done in Tortoise v.2.5.28.
Voxel-wise diffusivity measures were calculated in AFNI9. We calculated average values of fractional anisotropy (FA)
as well as mean, radial, and axial diffusivities (MD, RD, AD) for each of the
20 white matter tracts in the Johns Hopkins
University (JHU) atlas10. The processing of MFGM 1H-MRS
data was performed using LCModel version 6.111. We
calculated the absolute concentrations of 11 metabolites and their
ratios to total creatine (CrPCr): creatine (Cr), phosphocreatine (PCr),
glutamate (Glu), myo-inositol (Ins), N-acetylaspartate (NAA), choline (Cho),
phosphocholine, total choline, glutamate plus glutamine,
N-acetylaspartylglutamate plus N-acetylaspartate, and CrPCr. In total, 489
imaging features were included as predictors in the models.
At age 9, all participants were administered a battery of standardised
cognitive tests, including the Kauffman battery for children, Purdue pegboard
test, Peabody picture vocabulary test, semantic fluency test, test of variables
of attention, and Beery-Buktenica developmental test of visual-motor
integration. These tests assessed 7 domains of learning, namely auditory working
memory, short-term memory (attention), psychomotor integration, working memory
(executive function), language, and motor control, which have been shown to
share a bidirectional link with children’s academic skills12.
We
used 10-fold cross-validated (CV) support vector regression (SVR) modelling to
predict the 7 individual cognitive domain scores. Regression performance was
assessed via 10-fold CV SVR errors, coefficient of determination, and Pearson’s
r between predicted and actual values. We further used hierarchical clustering algorithm to group the children into performance categories based on overall cognitive performance, represented by a 7-element vector corresponding to each domain. We identified 2 main clusters of poorer and better scoring children, which were used for classification. Sensitivity, specificity, and area under the receiver
operating characteristic curve (AUC) were obtained for the 10-fold CV SVM classification models. Relevant features in the models were identified with SVM
recursive feature elimination (SVM-RFE).Results
Prediction of the individual cognitive domain
scores resulted in poor regression performance, characterised by high
generalised errors and weak Pearson’s correlation between actual and predicted
values. However, using multimodal MRI at age 7 we could predict whether the
children would be in the poorer or better performance category at age 9 with 81%
specificity, 72% sensitivity, 76% accuracy, and 0.80 AUC (Figure 1).
Using
SVM-RFE, we identified 27 relevant features out of 489 imaging
predictors. Fourteen cortical measures (Figure 2), 4 diffusivity
measures (Figure 3), 4 subcortical volumes (Figure 4), and concentrations
of Cr, PCr, Glu, Cho, and NAA in midfrontal GM contributed to the prediction of
categories of overall cognitive performance.Discussion
Consistent with previous studies that have predicted
cognition from cortical measures13,14,15, we identified many
cortical morphology related biomarkers of future cognitive performance. It is
well known that higher level processes such as thought, reasoning,
language, and memory are associated with cortical measures. However, predictors
from diffusion MRI and MR spectroscopy were also present in our models. These
modalities are rarely studied for predicting paediatric cognitive performance16,17.Conclusion
Notwithstanding the small sample size, this
study suggests multimodal MRI can be a useful technique to predict future
cognitive performance. Using more
training data, adding more time-points, adding functional MRI to the current
multimodal MR imaging, and exploring different ways of feature construction and
implementing deep learning models all have potential to further improve
performance accuracy.Acknowledgements
We would like to acknowledge the MRI Research team, CUBIC staff, participants and their parents/caregivers. The project was funded via the
UCT
Accelerated Transformation of the Academic Program Scholarship,
NRF/DST
South African Research Chairs Initiative (UID
48337, 120140),
NIH
grants R01HD099846, R01DC015984, R21MH108346, R01HD071664, R21MH096559, U19 AI53217, R01MH105134,
NRF
grant CPR20110614000019421 (UID 99069, 78737), South
African Medical Research Council (SAMRC), and UCT
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