A PET Study of Persistent Psychogenic Amnesia Covering the Whole Life Span

A patient with ongoing psychogenic amnesia is described. NN lost his personal identity eight months prior to the reported investigation. All physical and neurological examinations, including magnetic resonance imaging, were unremarkable. Neuropsychological testing revealed above-average intelligence and anterograde memory abilities. No retrograde amnesia for factual knowledge was detected. However, severe persistent amnesia was found for personal events prior to the psychogenic fugue (retrograde episodic amnesia). In contrast, personal episodes subsequent to the fugue were well preserved. For NN, a PET activation study was performed during the following phases: Baseline, a rest or control state; Prefugue, during which sentences containing episodic information of NN's past prior to the fugue were presented; and Postfugue, where episodic information concerned with personal experiences following the fugue was presented. The two activation tasks both led to increases in regional cerebral blood flow in memoryassociated areas in the left hemisphere only. A group of control subjects (n ≥ 7), however, tested in a similar paradigm showed activations in associated regions predominantly in the right hemisphere (Baseline; Impersonal, i.e. information about NN's past that had been presented one hour prior to PET scanning; Personal information about one's own autobiographical events). This suggests that normal controls access personal (autobiographical) episodic information using mainly right hemisphere memory-associated brain regions. NN, in contrast, appears to treat personal episodic information in a neutral (semantic, "left hemisphere") way. Taken together, our findings suggest, for the first time, a functional neuronal correlate for psychogenic amnesia.