Neural Representation of Exogenous and Endogenous Temporal Expectations Based on fMRI

Temporal expectations are considered as implicit timing, which is different from explicit timing. Furthermore, temporal expectations could be divided into exogenous and endogenous temporal expectations. However, it is still unclear about the neural activation under temporal expectations.

In the present study, an experimental paradigm was designed for eliciting the related brain activation under exogenous temporal expectations. Three conditions were used for the exogenous temporal expectations task. In order to compare the exogenous temporal expectations related activations to the endogenous', a proper endogenous temporal expectations task was used. Brain activations were obtained by using functional magnetic resonance imaging (fMRI).

Exogenous temporal perception-related regions, including TPJ, MTG, thalamus, IFG, caudate, cuneus, SOG, calcarine, FEF, and SPL have a good agreement with previous studies. Furthermore, it shows that the precuneus, PCC, Brodmann area 8 (BA8), ACC, and BA10 were also activated, which overlap with regions of the mesial of the so-called "default mode network". Negative correlated activations to exogenous temporal expectations task (use an endogenous temporal expectations task as an analysis baseline) were also evaluated.

We found that the sum of exogenous and endogenous temporal expectations related cerebral regions was almost the same when compared to resting-state networks (RSNs). We propose that the cerebrum could activate in two modes for cognition: one is based on endogenous temporal expectations, and another is based on exogenous temporal expectations.