Chapter 9 - The brain's inner time—intrinsic neural timescales

Abstract

The brain exhibits its own inner time as distinguished from the world's outer time. Understanding the dynamics of the brain's own inner time is the goal of this chapter. The brain's neural activity exhibits a variety of different timescales with short and longer durations, the so-called intrinsic neural timescales (INTs) (second part). The INT can be measured by correlating the neural signals with themselves over time, i.e., autocorrelation function, from which the autocorrelation window can be extracted. The findings show a hierarchy of INT in the brain with long INT in transmodal regions (like the prefrontal cortex) and short INT in unimodal regions (like primary sensory regions). Such unitransmodal hierarchy of INT can be observed during both rest and task states with both task-specific and task-unspecific modulation of INT. We conclude that the brain's inner time is characterized by a multitude of timescales as manifest in the unitransmodal hierarchy of INT. This leaves open the role or function of the INT which will be the focus in the next chapter.