Time-to-Onset latency in fMRI: Fast detection of delayed activation

A standard fMRI experiment is structured around the assumption that onset of relevant neural activity occurs almost immediately after external stimulus. Introducing deliberate lengthy delays in cognition, e.g. in problem solving tasks, necessitates adjusting the analysis model to account for any possible temporal latency. This is usually a computationally intensive task. Using Lagrange Multipliers, we develop a fast method to detect such delay in the Time-to-Onset of BOLD signal. This is conceptually different to measuring the Time-to-Peak of the BOLD Hemodynamic Response. Additionally, our method does not require prior knowledge of the length of the delay.