I remember therefore I am: Episodic memory retrieval and self-reported trait empathy judgments in young and older adults and individuals with medial temporal lobe excisions.

How do we know what sort of people we are? Do we reflect on specific past instances of our own behaviour, or do we just have a general idea? Previous work has emphasized the role of personal semantic memory (general autobiographical knowledge) in how we assess our own personality traits. Using a standardized trait empathy questionnaire, we show in four experiments that episodic autobiographical memory (memory for specific personal events) is associated with people's judgments of their own trait empathy. Specifically, neurologically healthy young adults rated themselves as more empathic on questionnaire items that cued episodic memories of events in which they behaved empathically. This effect, however, was diminished in people who are known to have poor episodic memory: older adults and individuals who have undergone unilateral excision of medial temporal lobe tissue (as treatment for epilepsy). Further, self-report ratings on individual questionnaire items were generally predicted by subjectively rated phenomenological qualities of the memories cued by those items, such as sensory detail, scene coherence, and overall vividness. We argue that episodic and semantic memory play different roles with respect to self-knowledge depending on life experience, the integrity of the medial temporal lobes, and whether one is assessing general abstract traits versus more concrete behaviours that embody these traits. Future research should examine different types of self-knowledge as well as personality traits other than empathy.

Episodic simulation and empathy in older adults and patients with unilateral medial temporal lobe excisions.

Recent work shows that vividly imagining oneself helping others in situations of need (episodic simulation) increases one's willingness to help. The mechanisms underlying this effect are unclear, though it is known that the medial temporal lobe (MTL) is critical for supporting episodic simulation in general. Therefore, individuals who have compromised MTL functioning, such as older adults and those who have undergone resection of medial temporal lobe tissue as treatment for epilepsy (mTLE patients), may not show the prosocial effects of episodic simulation. Our lab previously found that older adults and mTLE patients are impaired on a problem-solving task that requires the simulation of hypothetical scenarios. Using similar logic in the present study, we predicted that older adults and mTLE patients would show reduced effects of episodic simulation on their empathic concern for, and willingness to help, people in hypothetical situations of need, compared to young adults and age-matched healthy controls, respectively. We also predicted that the subjective vividness and the amount of context-specific detail in imagined helping events would correlate with willingness to help and empathic concern. Participants read brief stories describing individuals in situations of need, and after each story either imagined themselves helping the person or performed a filler task. We analyzed the details in participants' oral descriptions of their imagined helping events and also collected subjective ratings of vividness, willingness to help, and empathic concern. Episodic simulation significantly boosted willingness to help in all groups except for mTLE patients, and it increased empathic concern in young adults and healthy controls but not in older adults or mTLE patients. While the level of context-specific detail in participants' oral descriptions of imaged events was unrelated to willingness to help and empathic concern, the effects of episodic simulation on these measures was completely mediated by subjective vividness, though to a significantly lesser degree among mTLE patients. These results increase our understanding not only of how episodic simulation works in healthy people, but also of the social and emotional consequences of compromised MTL functioning.

Increased Cortical Thickness in Attentional Networks in Parkinson's Disease with Minor Hallucinations.

Hallucinations are common in Parkinson's disease (PD). Based on functional brain MRI data, hallucinations are proposed to result from alterations in the dorsal attention network (DAN), ventral attention network (VAN), and default mode network. Using structural MRI data from Parkinson's Progression Markers Initiative (PPMI), we examined cortical thickness in these networks in PD patients with (n=30) and without (n=30) minor hallucinations who were matched on multiple clinical characteristics (e.g., age, sex, education, cognitive diagnosis, MoCA score, medication, disease duration, and severity) as well as healthy controls (n=30) matched on demographic variables. Multivariate analyses revealed mild hallucinations to be associated with thicker cortex in the DAN and VAN, and these effects were driven by the left superior precentral sulcus and postcentral sulcus for the DAN and by the right insular gyrus for the VAN. While these findings may seem at odds with prior work showing grey matter reductions, our patients are in earlier stages of the disease than those in other studies. This is consistent with an inverted U-shape pattern of cortical thickness alterations in other neurodegenerative diseases and warrants further investigations in longitudinal studies tracking brain correlates of PD psychosis progression.