The impact of uncertain spike identification in event related EEG-fMRI in epilepsy

In EEG correlated fMRI interictal spikes as identified in the EEG during scanning of an epilepsy patient are used as events in an event related fMRI design. Spike identification, whether automatic or by a human observer, is accompanied by uncertainty and inevitably leads to false detections and missed events. This situation is not common in event related fMRI, where events are usually controlled by the experimental paradigm. In a simulation study based on a well controlled fMRI motor task we evaluated the effect on the significance of the expected fMRI activation of missed and false events. It is found that the impact of missed events is larger, suggesting that uncertain spikes should be included in the analysis.