Assaf Horowitz

PhD student at Prof. Yaniv Assaf’s laboratory

Research title
Axon diameter and conduction velocity changes along Multiple Sclerosis progression.

Research project

The relentless pursuit to understand the relationship between structure and function has always characterized biology in general and neurobiology in particular. One such fundamental relationship is that between axon diameter and the axon’s conduction velocity (ACV). Measurement of these neuronal properties, however, requires invasive procedures that preclude direct elucidation of this relationship in-vivo. Here we demonstrate that diffusion-based MRI is sensitive to the fine microstructural elements of brain wiring and can be used to quantify axon diameter in-vivo. Moreover, we demonstrate the in-vivo correlation between the diameter of an axon and its conduction velocity in the human brain. Using AxCaliber, a novel magnetic resonance imaging technique that enables us to estimate in-vivo axon diameter distribution (ADD) and by measuring the interhemispheric transfer time (IHTT) by electroencephalography, we found significant linear correlation, across a cohort of subjects, between brain microstructure morphology (ADD) and its physiology (ACV) in the tactile and visual sensory domains. The ability to make a quantitative assessment of a fundamental physiological property in the human brain from in-vivo measurements of ADD may shed new light on neurological processes occurring in neuroplasticity as well as in neurological disorders and neurodegenerative diseases.


  • Oral presentation on both ISMRM 2013 and OHBM 2014.


  • Horowitz A. et al, (2014), In vivo correlation between axon diameter and conduction velocity in the human brain. Brain Struct Funct, 1–12.


  • My work on finding the In-vivo correlation between human axon diameter and axon conduction velocity, received the summa cum laude award from the ISMRM committee (2013).


Research Categories: Behavioral Neuroscience, Brain Disorders