Autobiographical age awareness disturbance syndrome in autoimmune limbic encephalitis: Two case reports

Abstract

Background: Autobiographical memory is a form of episodic memory characterized by a sense of time and consciousness that enables an individual to subjectively re-experience his or her past. As part of this mental re-enactment, the past is recognized relative to the present. Dysfunction of this memory system may lead to confusion regarding the present perception of time. Case presentation: Two Japanese women (42 and 55 years old) temporarily believed they were living in their past during a course of autoimmune limbic encephalitis. Their autobiographical memories and behaviour reflected their self-estimated age, and they could not recall memories experienced beyond that age. More surprisingly, their subjective age estimations and autobiographical memories were transiently corrected when they were made aware of their true age. Disorientation, anterograde amnesia, and retrograde amnesia were common additional symptoms. Neuroimaging suggested disturbances in medial temporal and orbitofrontal brain regions in both cases. Conclusions: This syndrome is characterized by three elements: 1) failure to subjectively recognize the present; 2) inability to suppress irrelevant past memories; and 3) transient restitution of awareness of the present through realization of the individual's true age. We defined this syndrome as 'autobiographical age awareness disturbance', and focused our investigation on the role of age self-awareness. If recall of relevant and suppression of irrelevant past memories are both necessary to subjectively recognize the present relative to the past, dysfunction of medial temporal and orbitofrontal brain regions is predicted to lead to abnormal subjective placement in time. However, the subjective experience of age tends to be an important informational component for retrieving remote autobiographical memories. This suggests that correct age awareness is essential for the proper recognition of the remote past in relation to the present. This is the first report to focus on the relationship between subjective temporal orientation and age self-awareness. While the role of age awareness in this process is still unclear, investigating autobiographical age awareness disturbance as a part of subjective temporal awareness dysfunction can be useful in understanding the processes underlying human time recognition.