Functional and developmental significance of amplitude variance asymmetry in the BOLD resting state signal.
It is known that the brain's resting state activity (RSA) is organized in low frequency
oscillations that drive network connectivity. Recent research has also shown that
elements of RSA described by high-frequency and non-oscillatory properties are non-random
and functionally relevant. Motivated by this research, we investigated non-oscillatory
aspects of the BOLD RSA using a novel method for characterizing subtle fluctuation
dynamics. The metric we develop quantifies the relative variance of the amplitude of
local maxima and local minima in a BOLD time course (amplitude variance asymmetry; AVA).
This metric reveals new properties of RSA activity, without relying on connectivity as a
descriptive tool. We applied the AVA analysis to data from 3 different participant groups
(2 adults, 1 children) collected in three different centers. The analyses show that AVA
patterns (a) identify 3 types of RSA profiles in adults’ sensory systems (b) differ in
topology and pattern of dynamics in adults and children, and (c) are stable across MR
scanners. Furthermore, children with higher IQ demonstrated more adult-like AVA patterns.
These findings indicate that AVA reflects important and novel dimensions of brain
development and RSA.