Performance of Schizophrenia Patients on Time-, Event-, and Activity-Based Prospective Memory Tasks

Abstract

The present study aimed to determine whether individuals with long-term schizophrenia have impaired prospective memory (PM), the ability to remember to perform intended actions in the future. Three PM tasks (time-, event-, and activity-based) were administered to 60 schizophrenia patients and 60 matched controls. Patients performed significantly more poorly than controls on all three tasks. The between-group difference was disproportionately larger on the time-based task, a task that required a prefrontal lobe process called self-initiated retrieval. To examine the relationship between PM and prefrontal lobe functions, subjects were also administered the Design Fluency Test (DFT), the Tower of London (TOL), and the Wisconsin Card Sorting Test (WCST). For patients, performance on the event-based task was found to correlate significantly with performance on the DFT, and performance on the time-based task was found to correlate significantly with performance on the TOL. Results of this study support the importance and contribution of prefrontal lobe processes in prospective remembering and have implications for the assessment and treatment of individuals with schizophrenia.

Neuropsychological substrates and everyday functioning implications of prospective memory impairment in schizophrenia

“…Extending these results, the present study was undertaken to examine the neuropsychological substrates and functional implications of ProM impairment in schizophrenia. Consistent with the findings of Shum et al (2004), our results showed a modest correlation between ProM and executive functions; however, ProM performance was also associated with performance in several neuropsychological domains, including attention, working memory, processing speed, and learning. Such associations are commensurate with conceptual models suggesting that optimal ProM functioning relies on multiple cognitive substrates (e.g., Carey et al, 2006).…”

“…The literature on ProM in schizophrenia suggests that affected individuals are slow in recognizing the content of intended actions (Kondel, 2002) and are impaired on event-based ProM tasks (Elvevag et al, 2003;Kumar et al, 2005;Shum et al, 2004). Although Shum and colleagues (2004) found disproportionate impairment on time-based versus event-based ProM tasks, our group (Woods et al, 2007b) observed no such discrepancy using a pair of psychometrically balanced tasks.…”

Deficits in cue detection and intention retrieval underlie prospective memory impairment in schizophrenia

“…The increased rate of No Response and Loss of Time errors in this study, the latter of which were exclusive to time-based trials, further supports this contention. Moreover, Shum et al (2004) found a positive correlation between overt time monitoring and time-based ProM performance in SCZ. Time estimation abilities are reduced in SCZ, and may be associated with fronto-striato-thalamo-cortical dysfunction (Volz et al, 2001).…”

“…Kondel (2002) reported that individuals with SCZ-associated executive dysfunction were slowed in recognizing the content of intended actions. More recent SCZ studies revealed evidence of impairment on simple measures of event-based ProM in which an external stimulus (e.g., a target word imbedded in a general knowledge test) served as the cue for performing the intention (Elvevåg et al, 2003;Kumar et al, 2005;Shum et al, 2004). Shum et al (2004) went on to demonstrate a disproportionate deficit in time-based ProM in SCZ, perhaps indicating a particular impairment in the executive aspects of ProM (Shum et al, 2004).…”

“…Considering the findings of Shum et al (2004), we also hypothesized that individuals with SCZ would demonstrate a greater deficit in time-based than event-based ProM. Finally, the severity of the global ProM impairment was expected to correlate with SCZ disease burden variables (e.g., negative symptoms).…”