Céline Duval

What happens to personal identity when semantic knowledge degrades? A study of the self and autobiographical memory in semantic dementia

While the self has been extensively explored in amnesic patients with severe episodic but not semantic memory disturbance, little is known about the self in semantic dementia (SD), which generally features the reverse pattern of impairment. In the present study, we investigated the structural (self-representations) and functional (consciousness) dimensions of the self in a group of eight SD patients in the early to moderate stages of the disease. We used two original tasks designed to probe both structural characteristics, namely the strength and the certainty of self-concept and the episodic/semantic nature of self-representations, and functional characteristics, namely autonoetic/noetic level of consciousness, self-evaluation and self-projection into the past, present and future. Results for the structural self showed impairment on the semantic aspects of the self-representations, except for those related to the present. Moreover, SD patients were affected regardless of the episodic or semantic nature of self-representations into the future. As regards the functional self, self-projection and level of consciousness were only impaired for the future. This study confirms the persistence of a feeling of identity in SD over time for the past and present selves. However, it also highlights the loss of the future self in SD patients. These results are discussed in relation to models of long-term memory and future thinking focusing on the interplay of episodic and semantic memory and mental time travel.

Quid du voyage mental dans le temps subjectif et effets de l’âge ?

According to Tulving, episodic memory allows humans to travel mentally through subjective time into either the past or the future, this ability being at the origin of adaptation, organization and planning of future behavior. The main aim of this review is to present a state of art of episodic mental time travel and a lifespan perspective from children to elderly people. We examine the numerous similarities between remembering the past and envisioning the future which have been highlighted in cognitive, neuroimaging, and neuropsychological studies. We also present studies that have given evidence that remembering the past and imagining the future differ somewhat. We focus on demonstrating that hippocampal dysfunction is associated with disturbances in the recall of episodic autobiographical details in past memories, but also in the imagining of episodic detailed future events. More specifically, we discuss that the future seems to involve higher semantic processes mediated by the inferior frontal and lateral temporal gyri. We propose that the study of mental travel in personal time could be undertaken in line with the distinction between the memory of (episodic) experiences and (semantic) personal knowledge of ones life, which constitutes a major part of the self and constraints what we have been, what we are now, and what we might yet become.