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Published on: August 11, 2016
Occipital-callosal pathways in children: Validation and atlas development
Robert F Dougherty1, Michal Ben-Shachar, Gayle Deutsch
1Stanford Institute for Reading and Learning, Stanford, CA, USA. bobd@stanford.edu
Insights
This study used diffusion tensor imaging to map brain connections in children. Findings reveal organized pathways in the splenium connecting the occipital lobes, relevant to understanding alexia.
Area of Science:
- Neuroscience
- Neuroimaging
- Human Anatomy
Background:
- The corpus callosum facilitates interhemispheric communication.
- Understanding the precise organization of occipital callosal fibers is crucial for neurological studies, particularly concerning reading disorders like alexia.
Purpose of the Study:
- To investigate and map the fiber bundles connecting the two occipital lobes in children using advanced neuroimaging techniques.
- To create an atlas of these pathways and compare their anatomical properties with known neurological pathways associated with alexia.
Main Methods:
- Diffusion tensor imaging (DTI) and fiber tracking were employed to analyze white matter tracts in 53 children aged 7-12.
- Data from individual hemispheres were combined to generate a comprehensive atlas of occipital-callosal connections.
Main Results:
- Fiber bundles from both hemispheres converge in the splenium of the corpus callosum.
- A regular, topographical organization was observed, with distinct pathways corresponding to dorsal and ventral visual cortex projections.
- These pathways form specific anatomical structures around the lateral ventricle's occipital horn.
Conclusions:
- The study validates DTI methodology for mapping occipital-callosal fibers.
- The observed organization of these pathways aligns with previously hypothesized tracts implicated in alexia.
- The generated atlas provides a valuable resource for understanding brain connectivity and its relation to reading.
Abstract:
Diffusion tensor imaging and fiber tracking were used to measure fiber bundles connecting the two occipital lobes in 53 children of 7-12 years of age. Independent fiber bundle estimates originating from the two hemispheres converge onto the lower half of the splenium. This observation validates the basic methodology and suggests that most occipital-callosal fibers connect the two occipital lobes. Within the splenium, fiber bundles are organized in a regular pattern with respect to their cortical projection zones. Visual cortex dorsal to calcarine projects through a large band that fills much of the inferior half of the splenium, while cortex ventral to calcarine sends projections through a band at the anterior inferior edge of the splenium. Pathways projecting to the occipital pole and lateral-occipital regions overlap the dorsal and ventral groups slightly anterior to the center of the splenium. To visualize these pathways in a typical brain, we combined the data into an atlas. The estimated occipital-callosal fiber paths from the atlas form the walls of the occipital horn of the lateral ventricle, with dorsal paths forming the medial wall and the ventral paths bifurcating into a medial tract to form the inferior-medial wall and a superior tract that joins the lateral-occipital paths to form the superior wall of the ventricle. The properties of these fiber bundles match those of the hypothetical pathways described in the neurological literature on alexia.
