Suicidal behavior and loss of the future self in semantic dementia.

Semantic dementia impairs semantic autobiographical memory, but tends to spare its episodic components that are critical for the sense of self. Investigators have recently discovered disturbances in the "future self" in semantic dementia. We report a 63-year-old man with semantic dementia who was hospitalized after suicide attempts that he attributed to his loss of a sense of future self. He complained of a decreased sense of being human, because he could not imagine doing things in the future that he had done in the past. Suicidal thinking and inability to place himself in future tasks persisted despite resolution of depression. Clinical assessment revealed a crossmodal loss of semantic knowledge, and neuroimaging showed bilateral anterior temporal atrophy and hypometabolism. On specific tests of autobiographical memory, identity, attribute knowledge, and future projection, the patient could return to the past and visualize himself in familiar scenarios, but he could not visualize himself even passively in these scenarios in the future. His future self was impaired not from seeing himself disabled; it was from an absence of semantic details of potential experiences, associated with impaired semantic autobiographical memory. His self-representations were concrete and specific rather than abstract and generalizable. This patient and recent publications indicate that semantic dementia impairs the ability to imagine oneself as capable in the future, leading some patients to suicidal behavior. We discuss possible mechanisms for these findings, including the potential role of abstract construals for future thinking.