Recent studies have demonstrated that the P300 Speller can be used to reliably control a brain-computer interface via stereotactic depth electrodes (SDEs) implanted in and adjacent to the hippocampus. The superior bandwidth and spatial resolution of intracranial signals compared to scalp electroencephalography (EEG) may provide better insight into the nature of the responses evoked by the P300 Speller. Furthermore, the signals acquired by SDEs provide a new glimpse at activity from deeper brain structures, with respect to well-established scalp-EEG characterization of the P300 Speller responses. This study examines the spatio-temporal progression of the P300 Speller response from SDEs in and adjacent to the hippocampus for six conventional frequency bands.