The effect and mechanisms of implementation intention in improving prospective memory performance in schizophrenia patients
Introduction
Schizophrenia (SCZ) is a mental illness associated with significant neurocognitive dysfunctions (Heinrichs and Zakzanis, 1998, Roitman et al., 2000), and memory deficit is one of the core impairments (Loughland et al., 2007, Saykin et al., 1994, Weiss and Heckers, 2001). Substantial evidence has been accumulated to suggest that people with SCZ suffer from severe prospective memory (PM) impairments (e.g., Ordemann et al., 2014, Shum et al., 2004, Wang et al., 2008a, Wang et al., 2008b, Wang et al., 2009).
PM refers to forming an intention and then carrying it out after a delay without external reminders (Einstein and McDaniel, 1990). It plays an important role in people’s daily life, such as keeping an appointment, or taking medicine on time. The PM intention needs to be realized at a particular time (time-based PM), when an event appears (event-based PM), or when an activity is completed (activity-based PM) (Einstein and McDaniel, 1990, Kvavilashvili and Ellis, 1996). Impaired PM has been shown to significantly affect quality of daily life (Doyle et al., 2012). Studies have shown that people tend to experience more PM failures than retrospective memory (RM) failures (Crovitz and Daniel, 1984, Terry, 1988).
PM ability has been shown to be related to medication adherence and social functioning in SCZ (Lam et al., 2013, Twamley et al., 2008, Zogg et al., 2012). In addition, previous studies have suggested that the PM deficits in people with SCZ may be related to several processes including slow recognition of cues (Kondel, 2002), inefficient high-level encoding of cues, intentions and the links between them (Twamley et al., 2008), and difficulties in intention encoding and shifting attention between the ongoing and PM tasks (Chen et al., 2016).
Implementation intention is a technique originally proposed by Gollwitzer, 1993, Gollwitzer, 1996, 1999) to help people to achieve their goals. A meta-analysis showed that implementation intention had a positive effect on people's goal attainment (Gollwitzer and Sheeran, 2006). This is also true for people with mental health problems as revealed by a meta-analysis (Toli et al., 2015). More recently, implementation intention has been used as a technique to improve PM performance (e.g., Chasteen et al., 2001, Liu and Park, 2004). Implementation intention is an encoding strategy in the form of “if situation Y is encountered, then I will initiate the goal-directed behavior X” (Gollwitzer, 1999, Gollwitzer and Sheeran, 2006). It contains an “if” part and a “then” part. In a typical PM experiment, participants are engaged in an ongoing task during which PM cues appear. When the PM cues appear, participants need to make PM responses. During a PM task, the “if” part of implementation intention specifies the situation that PM cues appear and when a response is needed. The “then” part identifies the exact response to realize the PM intention. Implementation intention is believed to facilitate the detection of critical cues and the initiation of actions, and it affects both attention and memory processes (Wieber et al., 2015). All these cognitive processes are necessary to PM processing. A number of studies have shown that implementation intention could improve PM performances effectively in various populations, including healthy participants (Chen et al., 2015) and some clinical and sub-clinical populations with PM deficits (Chen et al., 2014, Grilli and McFarland, 2011, Kardiasmenos et al., 2008, Khoyratty et al., 2015, Kretschmer et al., 2014).
The underlying mechanisms of how implementation intention improves PM performance are not clearly understood. To date, three possible mechanisms have been proposed. First, McDaniel et al. (2008) suggested that implementation intention creates a strong link between the PM cues and intentions, and reduces the reliance on cognitive resources in prospective remembering. Therefore, compared with the control PM instruction, implementation intention improves PM performance, but does not reduce ongoing task performance (Breneiser, 2009, Brewer et al., 2011, McDaniel et al., 2008, McFarland and Glisky, 2012). According to this explanation, implementation intention is an automatic process. Second, it has been suggested that implementation intention causes participants to perceive PM tasks as more important (Meeks and Marsh, 2010) such that more cognitive resources are allocated to PM tasks by reducing cognitive resources for the ongoing task (Brewer and Marsh, 2010, Meeks and Marsh, 2010, Smith et al., 2014). According to the explanation, implementation intention is a controlled process. The third proposed mechanism suggests that implementation intention encoding does not automatize PM responses but contains both automatic and controlled processes (McDaniel and Scullin, 2010). Implementation intention can cause people to spontaneously recall the intentions when PM cues appear, but cognitive resources are needed to switch attention from ongoing task to PM task.
To date, there were only a few studies applied implementation intention in SCZ. For example, Brandstätter et al. (2001) suggested that implementation intention can help schizophrenia patients with action initiation. Sailer et al. (2015) showed that implementation intention can help inpatients with schizophrenia to achieve the goal of doing physical exercise. These results indicated that implementation intention may benefit SCZ’s cognitive function and goal achievement. Although no study has investigated the effect and mechanisms of implementation intention on PM in people with SCZ directly, implementation intention has been shown to benefit PM performance in some other clinical populations, including early psychosis (Khoyratty et al., 2015), multiple sclerosis (Kardiasmenos et al., 2008), brain injury (Grilli and McFarland, 2011), and autism spectrum disorders (Kretschmer et al., 2014). Khoyratty et al. (2015) recently found that implementation intention improved PM performance in people with early psychosis by making PM responses more automatic (without ongoing task cost). Moreover, Chen et al. (2014) found that implementation intention improved PM performance in individuals with schizotypal personality features. More importantly, they found that implementation intention improved PM performance without ongoing task cost in low ongoing task cognitive load conditions, and with ongoing task cost in high ongoing task cognitive load conditions. These findings suggest that implementation intention may change cognitive resources allocation. In other words, in the high ongoing task cognitive load conditions, schizotypal participants paid more attention to PM tasks while reducing the cognitive resources allocated to the ongoing task (Chen et al., 2014). Based on these findings, implementation intention may help SCZ to improve their PM performances.
In the present study, we aimed to explore the effect and mechanisms of implementation intention on PM in people with SCZ. We manipulated the cognitive load of the ongoing task as in our previous study (Chen et al., 2014). We hypothesized that the PM performance of individuals with SCZ would benefit from implementation intention. We further hypothesized that implementation intention would work differently in individuals with SCZ and HC. Previous studies suggested that people with PM impairment such as individuals with early psychosis and older adults, implementation intention can improve their PM performance without ongoing task cost (Khoyratty et al., 2015, Zimmermann and Meier, 2010). Therefore, for individuals with SCZ, we hypothesized that implementation intention would work in an automatic way (similar to people with PM impairment like early psychosis and older adults). For HC, we hypothesized that implementation intention would improve PM performance in the low ongoing task cognitive load condition automatically but would not improve PM performance in the high ongoing task cognitive load condition based on the results of HC in a previous study (Chen et al., 2014).
Section snippets
Participants
Fifty individuals with SCZ were recruited from the Beijing Huilonguan Hospital. All patients met diagnostic criteria for SCZ according to the Diagnostic and Statistical Manual of Mental Disorders 4th Edition (American Psychiatric Association, 1994), ascertained using the Structured Clinical Interview for DSM-IV (First et al., 1995). Participants were excluded if they had a history of neurological disorders, alcohol/drug dependence, or had received electroconvulsive therapy in the past three
Results
The proportion of correct PM and ongoing task responses and the reaction times on correct trials in each experimental condition were calculated and are displayed in Table 2.
For the baseline task (the N-back task without PM cues), the main effect of PM instruction was not significant (accuracy: F(1,96)<1, p=0.92, MII=0.87, M control=0.87; reaction time: F(1,96)<1, p=0.88, MII=982 ms, Mcontrol=974 ms), indicating that for the baseline condition, the participants in the two instruction conditions
Discussion
To our knowledge, this is the first study that has examined the effect of implementation intention on PM performance in people with SCZ. We found that implementation intention could enable people with SCZ and HC to improve their PM performance. Based on the pattern of results for the low and high ongoing task cognitive load conditions, the underlying mechanisms of implementation intention in improving PM performance in SCZ participants appears to be an automatic process.
SCZ participants had
Conflict of interest
None.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (31571130 and 81571317); Youth Innovation Promotion Association Funding of Chinese Academy of Sciences (Y1CX131003); Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences (113000C136); and the CAS/SAFEA International Partnership Programme for Creative Research Teams (Y2CX131003).
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Cited by (13)
Prospective memory performance and its improvement in individuals with high schizotypal traits: Evidence from eye-tracking studies
2022, Clinical NeurophysiologyCitation Excerpt :The former considers the role of implementation intention to be mainly reflected in the stages of intention retrieval and execution after the appearance of PM cues, while the latter holds that implementation intention plays a role in the stage of intention maintenance before the appearance of PM cues. As mentioned above, implementation intention has been shown to improve PM performance in patients with schizophrenia and individuals with HSTs (Chen et al., 2014, 2016; Liu et al., 2018, 2020). However, it is not clear which processing stages of PM were affected by implementation intention.
Prospective memory in schizophrenia: A meta-analysis of comparative studies
2019, Schizophrenia ResearchCitation Excerpt :However, due to the relatively small number of included studies, these two reviews could not explore the impact of measurement (eco-valid vs. dual-task laboratory) and the stages of illness (first-episode vs. chronic) on PM impairment in schizophrenia. Recent findings on PM in schizophrenia (Au et al., 2014; Cao and Song, 2016; Chan et al., 2013; Chen et al., 2015; Chen et al., 2016; Cheung et al., 2015; Lian et al., 2015; Lu et al., 2016; Lui et al., 2011; Lui et al., 2015; Man et al., 2016; Raskin et al., 2014; Wang et al., 2008a; Wang et al., 2010a; Wang et al., 2012; Xie et al., 2014; Yang, 2016; Zhou et al., 2012; Zhuo et al., 2011; Zou, 2012), have been inconsistent. In addition, many studies had been published in Chinese-language journals (Cao and Song, 2016; Chen et al., 2015; Lian et al., 2015; Wang et al., 2012, 2013; Xie et al., 2014; Yang, 2016; Zou, 2012), which were not included in the previous meta-analysis.
A comparison of different types of prospective memory reminders in schizophrenia
2019, Schizophrenia ResearchCitation Excerpt :However, although several programs are currently available which involve teaching compensatory strategies, such as the Thinking Skills for Work Program (which incorporates the use of practical prospective memory compensatory strategies to aid daily living, McGurk et al., 2015), these also use other approaches to enhance cognitive function, making it difficult to isolate the most effective aspects of the intervention. Analogously, although several studies have shown that compensatory reminder strategies specifically are effective at improving prospective remembering, they have not compared the relative efficacy of different types of reminders (see e.g., Pijnenborg et al., 2010; Velligan et al., 2008; Chen et al., 2016). At present, it therefore remains unclear whether specific types of compensatory strategies are more effective than others for people with schizophrenia, and consequently how best to compensate for schizophrenia-related PM difficulties.
Implementation intention training for prospective memory in schizophrenia: A 3-month follow-up study
2019, Schizophrenia ResearchCitation Excerpt :Implementation intention (II) training uses an internal encoding method in the form of “if I encounter X, then I will do Y” (Gollwitzer, 1999). II has shown robust beneficial effects for PM in various populations (Chen et al., 2015), including individuals with schizophrenia spectrum disorders (Chen et al., 2016; Chen et al., 2014; Khoyratty et al., 2015). In particular, II strategies that combine verbal rehearsal and imagery (e.g., verbal rehearsal of the instruction in the “if… then…” format for three times and imagine performing the PM task for 30 s) has shown robust effect in improving PM performance (Chen et al., 2015).