A mini-cap for simultaneous EEG and fMRI recording in rodents

Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) is now widely accepted as a prevailing tool to study brain functions. For over a decade, EEG caps with high-dense arrays of electrodes for EEG-fMRI studies in humans have been commercially available. However, simultaneous EEG and fMRI recording in rodents has been limited to only a few electrodes due mainly to two technical reasons, i.e. a small available scalp area and the proximity of the electrodes to the brain tissue. In this paper, we introduce both a new EEG mini-cap and a protocol to obtain whole scalp EEG recordings simultaneously with 7 T fMRI signals in rodents. We provide methodological protocol to evaluate a number of problems emerging from the particulars of using rodents in simultaneous EEG and fMRI recording. The quality and reproducibility of both EEG and fMRI signals were demonstrated using a conventional forepaw stimulation paradigm in Wistar rats. Based on this quantitative analysis, we conclude that simultaneous EEG-fMRI recordings are achievable in rodents without significant signal loss. In light of the contemporary transgenic models and advanced drug administration protocols in rodents, the proposed methodology could be remarkable as a futurist experimental platform.