Abstract
We assessed the effects of forming multiple intentions, task switching, and encoding strategies during intention formation on PM performance in PD. We found that PD participants were preferentially impaired in forming multiple intentions at once and that encoding strategies were particularly effective for addressing this deficit. These findings identify a novel PM deficit in PD and support clinical use of encoding strategies.
Primary Author and Speaker: Elinor Taylor
Contributing Authors: Erin Foster
Prospective memory (PM) is the ability to set intentions for the future then recall and execute them at the appropriate moment. PM impairment is common in individuals with Parkinson’s disease (PD), and can reduce their daily function (Foster et al., 2009). The intention formation stage of PM is when new intentions are formed and encoded, and this stage is particularly problematic for people with PD. Studies have yet to delineate which factors during intention formation may impair PM performance in PD and whether encoding strategies can mitigate these effects. Our study investigated the effects of task switching, multiple intention formation, and the use of encoding strategies during intention formation on PM performance in PD.
This is a secondary analysis of data from two prior experimental studies of PM in PD. Study 1 was a cross-sectional study comparing PD (n=24) and healthy comparison (HC, n=28) participants’ PM performance (Foster et al., 2013), and Study 2 was a randomized controlled trial of encoding strategy training on PM performance in PD (n=70) (Foster et al., 2017). For both studies, PD participants were recruited from the university’s Movements Disorders Clinic with the following inclusion criteria: males and females over age 50 with idiopathic PD, Hoehn and Yahr stage I-III. Exclusion criteria included suspected dementia or global cognitive impairment (as per physician or Mini Mental State Examination score < 27), treatment with medications that impair cognition, significant psychiatric disorder, neurosurgery, other neurological conditions, or any other feature that would interfere with participation. HC participants were recruited from the community with the same eligibility criteria as PD participants (other than those specific to PD), except they could not have PD or a first degree relative with PD.
The Virtual Week (VW), a computerized test that simulates daily life (Rendell & Henry, 2009), was used to assess PM in both studies. Half of the PM tasks in the VW require multiple intentions encoding but not task switching during intention formation (MI condition), whereas the other half require task switching but not multiple intentions encoding during intention formation (TS condition). Mixed ANOVA compared PD and HC participants’ performance on MI and TS tasks (Study 1), and PD participants’ performance on MI and TS tasks before and after encoding strategy training (Study 2).
PD participants were impaired on MI tasks, both in comparison to HC (p = 0.003) and to TS tasks within PD (p = 0.034). Use of an encoding strategy at intention formation improved PD participants’ PM performance for both types of tasks (p < 0.001), but improvement was greater for MI tasks such that the pre strategy training decrement in MI compared to TS performance (p = 0.008) was eliminated post strategy training (p = 0.58).
Our findings indicate that encoding multiple intentions at one time is particularly problematic for PM performance among people with PD. However, the use of encoding strategies such as implementation intentions or even simple verbal rehearsal may ameliorate this deficit. Everyday life, especially for people with chronic health conditions like PD, often involves managing multiple PM intentions (e.g., remembering to take medications, use fall prevention strategies, do home exercises). We identified a novel PM deficit in PD related to how these intentions are formed, but we also found that this negative effect is modifiable. This work can impact occupational therapy practice by providing evidence-based solutions (e.g., encoding strategies, teaching clients to space encoding of intentions) to address PM impairment in PD.
Foster, E. R., McDaniel, M. A., & Rendell, P. G. (2017). Improving prospective memory in persons with Parkinson Disease: A randomized controlled trial. Neurorehabilitation and Neural Repair, 31(5), 451-461. doi:10.1177/1545968317690832
Foster, E. R., Rose, N. S., McDaniel, M. A., & Rendell, P. G. (2013). Prospective memory in Parkinson disease during a virtual week: Effects of both prospective and retrospective demands. Neuropsychology, 27(2), 170-181. doi:10.1037/a0031946
Foster, E. R., McDaniel, M. A., Repovš, G., & Hershey, T. (2009). Prospective memory in Parkinson disease across laboratory and self-reported everyday performance. Neuropsychology, 23(3), 347-358. doi:10.1037/a0014692
Rendell, P., & Henry, J. (2009). A review of Virtual Week for prospective memory assessment: Clinical implications. Brain Impairment, 10(1), 14-22. doi:10.1375/brim.10.1.14