The studies in Kristiina Kompus’s dissertation show that these two different ways of remembering things are initiated by entirely different signal paths in the brain. Efforts to retrieve a specific memory are dealt with by the upper part of the frontal lobe. This area of the brain is activated not only in connection with memory-related efforts but also in all types of mental efforts and intentions, according to the dissertation. This part of the brain is not involved in the beginning of the process of unintentionally remembering something as a response to external stimuli. Instead, such memories are activated by specific signals from other parts of the brain, namely those that deal with perceived stimuli like smells, pictures, and words. Sometimes such memories are thought to be more vivid and emotional; otherwise they would not be activated in this way. But Kristiina Kompus’s dissertation shows that this is not the case — memories do not need to be emotionally charged to be revived spontaneously, unintentionally. Nor do memories that are revived spontaneously activate the brain more than other memories.