Older age, traumatic brain injury, and naturalistic assessment of prospective memory

Submission note: A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Clinical Neuropsychology to the School of Psychological Science, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.

Prospective memory (ProM), the realization of delayed intentions, is a pervasive aspect of real-life memory processes due to its practical applications. ProM is considered a complex process, comprising several interrelated components. Given the central importance of ProM, surprisingly little experimental and theoretical investigations on the topic have been conducted particularly in older adult and neuropsychological patients. This study investigated whether commonly reported impairments in ProM after Traumatic Brain Injury (TBI) in older age, are related to discreet difficulties at selected stages of prospective remembering (i.e. planning, timely execution, accuracy in execution, and retention) of a complex naturalistic intention. The study also examined the ability of acute injury variables and commonly used neuropsychological measures to predict prospective memory performance at six months post-injury. 31 older adults (≥65 years old) six months post mild-moderateTBI and 31 healthy older adults completed a naturalistic complex prospective memory task (the Picnic Task) that allowed for the separate assessment of the four components of ProM. Furthermore, cognitive functioning was assessed using standard neuropsychological tests of executive functioning and retrospective memory. There were no differences between groups in the planning or retention components of ProM. In contrast, the participants with a TBI performed worse than the healthy control group in timely execution, and accuracy of execution. Results revealed the componentspecific influence of executive functions on the process of naturalistic ProM and showed that ProM performance can be predicted by early neuropsychological assessment. The implications of groups difference in performance and the importance of executive functioning for ProM in TBI is discussed.