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Front Neurosci. 2019 Aug 23;13:875. doi: 10.3389/fnins.2019.00875. eCollection 2019.

Inferior Longitudinal Fasciculus' Role in Visual Processing and Language Comprehension: A Combined MEG-DTI Study.

Author information

1
Montreal Neurological Institute and Hospital, McGill University, Montreal, QC, Canada.
2
Translational Neuroimaging Laboratory, McGill University Research Centre for Studies in Aging, McGill University, Montreal, QC, Canada.
3
Multimodal Functional Imaging Lab, Department of Biomedical Engineering, McGill University, Montreal, QC, Canada.
4
Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Département de Psychologie, Université de Montréal, Montreal, QC, Canada.
5
Cognitive Neuroscience Unit, Montreal Neurological Institute, Neurology and Neurosurgery, McGill University, Montreal, QC, Canada.
6
Multimodal Functional Imaging Lab, PERFORM Centre, Department of Physics, Concordia University, Montreal, QC, Canada.

Abstract

The inferior longitudinal fasciculus (ILF) is a white matter tract that connects the occipital and the temporal lobes. ILF abnormalities have been associated with deficits in visual processing and language comprehension in dementia patients, thus suggesting that its integrity is important for semantic processing. However, it remains elusive whether ILF microstructural organization per se impacts the visual semantic processing efficiency in the healthy brain. The present study aims to investigate whether there is an association between ILF's microstructural organization and visual semantic processing at the individual level. We hypothesized that the efficiency of visual semantic processing positively correlates with the degree of anisotropy of the ILF. We studied 10 healthy right-handed subjects. We determined fractional anisotropy (FA) of the ILF using diffusion tensor imaging (DTI). We extracted N400m latency and amplitude from magnetoencephalography (MEG) signals during a visual semantic decision task. N400m and mean FA of the ILF were left lateralized with the higher FA value in the left hemisphere. Inter-individual analysis showed that FA of the ILF negatively correlated with the N400m latency and amplitude, which suggests that high ILF anisotropy is associated with more efficient semantic processing. In summary, our findings provide supporting evidence for a role of the ILF in language comprehension.

KEYWORDS:

diffusion tensor imaging; language comprehension; magnetoencephalography; ventral language pathway; white matter

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