Examining the Relationship between Autobiographical Episodic Memory and Theory of Mind in Developmental Amnesia and with fMRI: The Role of Personal Familiarity

The purpose of this dissertation was to examine if, and under what conditions, autobiographical memory (AM) supported by the hippocampus benefits theory of mind (ToM). To this end, I attempted to address two main questions: (a) Are AM difficulties caused by early-onset hippocampal damage associated with impaired performance on standard measures of ToM (Experiment 1)? (b) Is AM and the brain regions that support it involved to a greater extent in imagining the experiences of personally known others compared to unknown others (Experiments 2, 3, and 4)? In Experiment 1, ToM abilities were examined in H.C., a young woman with impaired AM development due to early hippocampal damage. H.C. performed at the same level as controls on a wide range of ToM tests. These findings suggest that normal AM development is not critical for the development or expression of ToM, at least as measured by standard tests. In Experiment 2, healthy individuals were scanned with fMRI to test whether different neural and cognitive mechanisms support imagining the experiences of personally known others (pToM) versus unknown others (ToM). There was greater neural overlap between AM and pToM compared to pToM and ToM. Furthermore, a direct comparison between pToM and ToM revealed that midline regions associated with AM predominated during pToM, whereas more lateral regions associated with semantic memory predominated during ToM. These findings suggest that there are multiple routes to ToM and the extent to which AM is recruited depends, at least in part, on whether the target person is personally known. Experiment 3 corroborated the neuroimaging results reported in Experiment 2 by showing that H.C. was impaired at producing detailed descriptions of events relating to her own past as well as events relating to personally known others. In contrast, she was intact at describing events relating to unknown others. Experiment 4 explored the neural basis of H.C.’s performance on AM, pToM, and ToM. fMRI analyses revealed that measures of percent signal change and functional connectivity were equivalent between H.C. and controls across all conditions. These finding suggest that BOLD fMRI cannot necessarily distinguish between preserved and impaired behavioural performance in developmental amnesia. Overall, these results contribute substantially to our current understanding of the functional and neural relationship between AM and ToM, and add to the literature suggesting that the hippocampus plays a broader role in cognition beyond that of recalling past events.