Single-trial coupling of the gamma-band response and the corresponding BOLD signal

Reaction times (p < 0.001), error rates (p < 0.05) and self-ratings of task difficulty and effort demands (p < 0.001) were related to the level of difficulty in the task. In addition, we found a significant influence of task difficulty on the amplitude of the GBR at Cz (p < 0.05). Using single-trial coupling of EEG and fMRI GBR-specific activations were found only in the auditory cortex, the thalamus and the anterior cingulate cortex (ACC) in the most difficult run. Single-trial coupling might be a useful method in order to increase our knowledge about the functional neuroanatomy of “neural ensembles” coupled by 40 Hz oscillations.