Mechanical properties of gray and white matter brain tissue by indentation

Budday, S., Nay, R., de Rooij, R., Steinmann, P. , Wyrobek, T., Ovaert, T. C. and Kuhl, E. (2015) Mechanical properties of gray and white matter brain tissue by indentation. Journal of the Mechanical Behavior of Biomedical Materials, 46, pp. 318-330. (doi: 10.1016/j.jmbbm.2015.02.024)

Abstract

The mammalian brain is composed of an outer layer of gray matter, consisting of cell bodies, dendrites, and unmyelinated axons, and an inner core of white matter, consisting primarily of myelinated axons. Recent evidence suggests that microstructural differences between gray and white matter play an important role during neurodevelopment. While brain tissue as a whole is rheologically well characterized, the individual features of gray and white matter remain poorly understood. Here we quantify the mechanical properties of gray and white matter using a robust, reliable, and repeatable method, flat-punch indentation. To systematically characterize gray and white matter moduli for varying indenter diameters, loading rates, holding times, post-mortem times, and locations we performed a series of n=. 192 indentation tests. We found that indenting thick, intact coronal slices eliminates the common challenges associated with small specimens: it naturally minimizes boundary effects, dehydration, swelling, and structural degradation. When kept intact and hydrated, brain slices maintained their mechanical characteristics with standard deviations as low as 5% throughout the entire testing period of five days post mortem. White matter, with an average modulus of 1.895. kPa±0.592. kPa, was on average 39% stiffer than gray matter, p<. 0.01, with an average modulus of 1.389. kPa±0.289. kPa, and displayed larger regional variations. It was also more viscous than gray matter and responded less rapidly to mechanical loading. Understanding the rheological differences between gray and white matter may have direct implications on diagnosing and understanding the mechanical environment in neurodevelopment and neurological disorders.

• Item Type: Articles
• Additional Information: This work was supported by the German National Science Foundation Grant STE 544/50-1 to Silvia Budday and Paul Steinmann, by the Stanford Bio-X Interdisciplinary Initiatives Program, by the National Science Foundation CAREER award CMMI 0952021, and by the National Institutes of Health Grant U01 HL119578 to Ellen Kuhl.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Steinmann, Professor Paul
• Authors: Budday, S., Nay, R., de Rooij, R., Steinmann, P., Wyrobek, T., Ovaert, T. C., and Kuhl, E.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment
• Journal Name: Journal of the Mechanical Behavior of Biomedical Materials
• Publisher: Elsevier
• ISSN: 1751-6161
• ISSN (Online): 1878-0180
• Published Online: 02 March 2015

Related URLs

• Other