Prospective memory training in healthy older adults : A systematic review and an experiment of mindfulness induction to improve prospective memory

Abstract

Prospective memory (PM) is the ability to execute a future intention, which includes event-based and time-based PM. Event-based PM (EBPM) is activated by an external cue and is further determined by its cue focality. Focal EBPM is cued by the processing features of an ongoing task, whereas non-focal EBPM shares no common features with the ongoing task. Time-based PM (TBPM) is triggered after a certain amount of time. Previous studies have shown an aging decline in PM, but it is vital for older adults to achieve functional independence. Exploring ways to attenuate an aging decline is crucial to a successful aging experience. A systematic review was first performed to synthesize existing PM training for older adults (>55 years). This includes strategy-based, process-based, and combined training. Strategy-based training utilizes mnemonics to compensate a PM decline. Process-based training restores the efficiency of cognitive processes that support PM. Combined training uses both approaches to facilitate PM. Eleven studies were identified, including six studies of strategy-based training, two studies of process-based training, and three studies of combined training. Although strategy-based training can facilitate PM in older adults, it often produces limited transfers. Alternatively, process-based training encourages far transfers by targeting its underlying cognitive processes. Considering a lack of evidence of mindfulness as a process-based PM training, two experiments (Experiment I and II) were conducted to evaluate the potential effects of mindfulness on PM. Mindfulness refers to a state of non-judgmental, present-moment awareness. There are two common styles of mindfulness meditation: focused attention (FA) and open monitoring (OM). Focused attention sustains attention toward an anchor object. Open monitoring involves self-monitoring of present-moment experience using a non-judgmental attitude. To understand how mindfulness facilitates PM, Experiment I and II explore the specific effects of FA and OM on PM. It is hypothesized that FA improves PM by enhancing attentional control while OM facilitates PM by reducing emotional interference. In Experiment I, 127 healthy older adults (Mage = 64.87) were randomized into a FA group or a mind wandering (MW) control group. An experimental paradigm was used to measure PM with commands embedded in an ongoing task. Three types of PM cues were assessed: focal EBPM, non-focal EBPM, and TBPM. Two additional ecological PM tasks (EBPM and TBPM) were included. To explore whether there is a mediation effect of attentional control between FA and PM, two experimental tasks were employed to measure sustained, selective, and executive attention. The results indicated the FA group performed better in experimental focal EBPM (p < 0.05) and ecological focal EBPM (p < 0.05). While FA improved attentional control, there is only a weak, partial meditation of sustained attention (p < 0.05) between FA and experimental focal EBPM. In Experiment II, 157 healthy older adults (Mage = 66.19) were randomized into two between-subject factors: induction types (OM vs. MW) and mood conditions (negative vs. neutral). Three types of PM cue were assessed: focal EBPM, non-focal EBPM, and TBPM. In the negative mood condition, the OM group performed better than the MW group in experimental focal EBPM (p < 0.01). This thesis offers preliminary evidence of mindfulness as a process-based PM training for older adults. Even brief inductions of FA and OM produced measurable benefits in focal EBPM. While FA improved focal EBPM, such improvement was only weakly and partially mediated by better sustained attention. On the other hand, OM primarily facilitated focal EBPM by reducing emotional interference from negative emotions. Therefore, mindfulness may hold the promise to facilitate older adults to achieve functional independence, which ultimately contributes to a successful aging experience.