A personalized history of EEG-fMRI integration.

In this personalized review, the history of EEG recorded simultaneously with functional MRI (EEG-fMRI) is summarized. A brief overview is given of the hardware development followed by a discussion of EEG-fMRI applications. The technique's development was clinically motivated in the context of epilepsy. Accordingly, the evolution of studies trying to identify with EEG-fMRI the origin of individual epileptiform discharges up to those revealing general mechanisms of epilepsy syndromes is sketched. In epilepsy centers experienced with the methodology, EEG-fMRI has found its place in the presurgical evaluation of patients. In cognitive neuroscience, the multimodal technique has significantly contributed to the understanding of phenomena of the resting state and neuronal oscillations. While most of the studies discussed relate EEG to fMRI by means of prediction, the development of forward models facilitating the symmetrical 'fusion' of EEG and fMRI data is the subject of current neuro-computational research. Recently, intracranial EEG has been safely recorded during (functional) MRI broadly extending the perspectives for epilepsy and research into neurovascular coupling. EEG-fMRI has evolved into a mature, generally accessible and in principle easily applicable technique, which is a great achievement. Because this at the same time bears the risk of unreflected use, EEG-fMRI safety issues are also highlighted.