Neural substrates of emotionally valenced episodic memory: A PET study using film stimuli

Abstract  To reveal the pathogenetic mechanism of post-traumatic stress disorder (PTSD), we modeled the ‘re-experience’ symptom of PTSD in healthy subjects, and investigated its neural substrates using PET activation experiments on an emotionally (fear) valenced episodic memory task and several contrast tasks. Ten right-handed healthy male volunteers underwent H215O-PET. Each subject was required to watch a horror film the previous day. During the PET scan, the subject was shown part of the film for 60 s immediately before the terrifying climax scene and told to recall the following scene. The subject did not watch the scene directly, but re-experienced fear induced by the trigger. The rCBF in this task compared with that in control tasks was analyzed with SPM99. The subjective emotional state of the subject in each task was evaluated using an analog scale. The main cerebral areas where rCBF significantly correlated with the task of emotionally valenced episodic memory, compared with the novel emotional task, were the left retrosplenial cortex (Brodmann's area: BA 31), the left visual association cortex (BA 19) and the right prefrontal cortex (BA 10). Although the retrosplenial cortex or the posterior cingulate gyrus has been regarded as engaged in processing either only emotion or only episodic memory, this area is considered to be involved in processing ‘emotionally valenced episodic memory’.