The efficacy of prospective memory rehabilitation plus metacognitive skills training for adults with traumatic brain injury: study protocol for a randomized controlled trial

Memory problems are the most common cognitive complaint in people with traumatic brain injury (TBI) [1, 2]. Prospective memory (PM) refers to the ability to remember to carry out a planned action or intention at a future point in time [3]. Examples of PM are remembering to pay a bill by the due date, remembering to take medication each morning, or remembering to pass on a message the next time you see a particular person. Successfully remembering to perform an intended action is a critical cognitive skill in daily life. We are constantly making mental notes of tasks that we need to complete in the future, and failures of PM are associated with feelings of having let oneself or others down. Despite its relevance to daily life, PM is a relatively new construct in the scientific literature compared to retrospective memory (RM), which involves the recall or recognition of previously learnt information and past events. However, over the past 10 years research on PM has grown rapidly. Research has shown that people with TBI experience debilitating PM deficits [4‐6] which impact on independent living (e.g., requiring a carer at home), social participation (e.g., failure to keep engagements), and employability (e.g., workers are seen as unreliable) [7]. Therefore, PM impairment is a target for rehabilitation efforts which often focus on the use of compensatory strategies to minimize the impact of PM impairment in everyday life [8, 9].

PM is a complex ability that involves multiple processes and components. According to Ellis [10], there are five stages of PM: (1) formation and encoding of intention and action, (2) retention interval, (3) performance interval, (4) initiation and execution of intended action, and (5) evaluation of the outcomes. The first stage involves realizing that an action needs to be carried out in the future and encoding what the action is and when to execute it. In the second stage, the person stores the intended action and engages in one or more other activities. The action is initiated and executed in the third and fourth stages. During the last stage, the person records and evaluates the outcome of the intended action. Therefore, PM involves a combination of RM (to encode and recall the action), executive function (to plan and initiate the action at the correct time), and metacognitive function (to monitor performance and evaluate the outcome). These functions are commonly impaired after TBI; the prefrontal lobes which are vulnerable to trauma are implicated in executive and metacognitive functions and are also considered the neural basis of PM [11].

Three subtypes of PM have been identified in the scientific literature, according to task characteristics and the type of cue for recalling the intention [12]. These include: time-based PM activities when an action needs to be initiated at a particular time or window of time (e.g., in 10 min or before the close of business on Friday); event-based PM activities where an action is performed in response to an external cue (e.g., turn off the stove when the timer rings or ring a friend for their birthday when a reminder appears on your phone); and activity-based PM activities where an action is performed as part of or at the end of a sequence of actions or behaviors (e.g., put on your seatbelt after you get in the car or add sugar to your coffee after the milk). A study of the subtypes of PM using a computerized task showed that people with TBI performed significantly worse than controls on all subtypes [12]. In another study, patients with TBI had more difficulties compared to controls when the cognitive demand of the ongoing task was high, indicating their PM failures could be attributed to reduced processing capacity and problems allocating cognitive resources [4]. In previous research, significant others of patients with TBI reported that patients had significantly more instances of forgetting daily activities compared to non-injured controls [5]. In contrast, patients with TBI rated their own frequency of forgetting as similar to controls and reported fewer PM failures than their significant others, thus indicating a lack of self-awareness of their PM problems [5].

Like traditional RM rehabilitation, approaches to PM rehabilitation can be categorized as remedial or compensatory [13]. Remedial training approaches aim to restore or ameliorate the underlying impairment through repetitive practice of PM activities; for example, remembering to perform time- and event-based PM tasks embedded within a filler activity that may be pen-and-paper- or computer-based. In contrast, compensatory approaches focus on teaching the patient to use strategies to minimize the impact of PM impairment in everyday life; for example, training in diary or calendar use [13]. Case studies have found positive effects of remedial PM training [14, 15]; however, the training programs involved in these studies required substantial commitments of time and effort; for example, 4–6 h per week over several months. It is also not clear to what extent gains generalized beyond the ability to perform the simple, non-goal directed remedial activities used in training. Compensatory approaches to PM rehabilitation have been less investigated and overall the evidence is weak [16]. This is despite the common prescription of compensatory memory strategies in brain injury rehabilitation settings and the recommendation that training in external memory compensations should be standard practice [17]. Such strategies include the use of a diary, note-taking, routines, checklists, alarms, and paging systems, and are more relevant to everyday functioning, and may be more easily generalized to naturalistic settings compared to remedial activities. Furthermore, compensatory approaches to PM rehabilitation can assist patients with reduced cognitive capacity [18].

Trials with small TBI samples and case studies have described the use of electronic devices (e.g., palmtop computer, television-assisted prompting, Voice Organizer, and the NeuroPage paging system) as effective to compensate for PM deficits [19‐24]. For an overview of these studies see the systematic review by de Joode et al. [25]. Fish et al. [26] evaluated the use of a “content-free” cue in the form of a text message, to remind 20 people with brain injury to monitor behavior, and found a greater improvement in performance on cued days compared to non-cued days. Ownsworth and McFarland [27] demonstrated that a metacognitive approach was more effective in training people with TBI to regularly use a memory notebook (n = 10) than a procedural learning approach (n = 10). Das Nair and Lincoln [28] compared the effectiveness of compensatory training, remedial training, and a self-help group in a group of 72 adults with memory problems (16 with TBI). They found that greater use of internal memory aids was reported post test by individuals in the two training groups compared to the self-help group, and that significantly better emotional status was reported by those in the compensation group.

In previous research, we developed an 8-week intervention program (consisting of two self-awareness training sessions and six compensatory training sessions) with the aim of rehabilitating the PM of three patients with TBI [8]. The promising findings of this pilot led to a larger-scale randomized controlled trial (RCT) of PM rehabilitation strategies [9], which demonstrated that the six-session compensatory rehabilitation program was more effective than a control intervention in improving PM in people with TBI, as measured by the Cambridge Prospective Memory Test (CAMPROMPT). The control intervention involved a remedial approach of repetitive practice of PM activities over six weekly sessions. The compensatory intervention involved the use of external strategies to both trigger the intention (prospective component) and support retrieval of content salient to the task (retrospective component) over the same time period. Event-based tasks (i.e., taking a cake out of the oven when a timer goes off) are easier than self-initiated or time-based tasks (i.e., remembering to take the cake out of the oven in 40 min) [12]. Therefore, this approach uses compensatory strategies that convert time-based tasks into event-based tasks which provide a cue to initiate performance of the action. Examples are use of an alarm, or linking the task to an event (e.g., taking medication at mealtimes). The significantly greater improvement in PM performance for the compensatory intervention group was attributed to the use of strategies during the PM task. However, these gains did not extend to significantly greater improvements in everyday PM performance or psychosocial function as anticipated. Further research is needed to specifically investigate the generalization of PM compensatory strategies to occupational performance in daily life [29].

One of the difficulties with generalization in TBI rehabilitation is the problem of impaired self-awareness. Estimates of the rates of impaired self-awareness in people with severe TBI are as high as 97% [30]. Impaired self-awareness refers to an inability to recognize limitations due to brain injury and to understand the functional implications of these [31]. It poses significant obstacles to rehabilitation engagement and outcomes in the TBI population and, therefore, is the target of rehabilitation efforts [32]. For example, individuals with poor self-awareness of their impairments post TBI do not see the need to apply strategies learnt in rehabilitation in everyday life to improve their performance. A fundamental principle of cognitive rehabilitation is that individuals need to recognize their impairments before being able to independently employ a strategy to compensate for these problems in daily living [33]. Therefore, to enhance the rehabilitation of PM, it is important that impairments of self-awareness are addressed to maximize engagement and use of strategies in everyday life.

Metacognitive skills training (MST) is a cognitive rehabilitation approach which facilitates the development of self-awareness in patients with TBI [33‐35]. The objective of MST is to teach individuals how to self-monitor their performance, identify and self-correct errors, and generate strategies for future use. A metacognitive approach targets both on-line awareness (i.e., recognition and self-correction of errors in task performance) and intellectual awareness (i.e., self-knowledge of strengths and limitations). This approach incorporates elements of self-awareness training, such as psychoeducation and role modeling of strategy use, and also uses timely verbal, video, and experiential feedback and self-prediction and self-evaluation of performance in therapy activities and everyday life [35]. A MST approach has potential to enhance the outcomes of compensatory PM rehabilitation and lead to better generalization of strategy use beyond the therapy environment.

This paper outlines the protocol for a RCT comparing the efficacy of compensatory (COMP) and COMP-MST training for improving everyday PM performance, psychosocial function, strategy use, self-awareness, and level of care in a sample of adults with TBI.