Alicia Novick
3.3. El “giro espacial”. Procesos globales y cambios epistemológicos
In Chapter 2 the assumption that there is an association between executive processes and prospective remembering was made. Evidence for this assumption comes from studies demonstrating that PM processes such as dividing attention, monitoring the environment for a cue, associating a cue for intention and interrupting an ongoing activity, may also involve planning and therefore the frontal lobes (Lezak, 1982; Shallice, 1982). Also, Marsh and Hicks (1998) have argued that PM depends on self-initiated and attention demanding resources so
60 PM performance can be correlated with measures of central EF. Both neuropsychological (Martin et al., 2003; Kliegel et al., 2000; Kliegel et al., 2008) and neuroimaging (Burgess et al., 2003; Okuda et al., 2002; Simons et al., 2006;
Okuda et al. 2007) evidence suggest the involvement of executive processes in PM performance since regions of the frontal lobe, such as the rostral prefrontal cortex, are involved in both the performance of PM and EF.
In order to examine the effect of external alerting in complex situations Manly et al. (2002) used a modification of the six elements test (Shallice and Burgess, 1991) called the hotel test. These tests have been demonstrated to be more sensitive to real-life problems with EF than traditional tests such as the WCST.
The six elements test and the hotel test require the participant to carry out simple subtasks in a limited time period. The participant needs to divide the available time evenly across the tasks in order to attempt at least something from each task.
The purpose of these tests is therefore not to successfully complete all tasks but to apply an effective strategy. The authors used the hotel test with Acquired Brain Injury (ABI) patients to test the effect of external alerting in complex situations, thus reflecting, everyday demands. They found that test performance was no different between the ABI patients and the control group in the alerted condition (where participants had prompts) as opposed to the control condition where ABI patients performed worse than controls. These studies on alerting strategies provide evidence that by providing external support (i.e., a cue) for monitoring processes, significant improvements in performance can be seen (Fish et al., 2007).
61 Although these studies use different paradigms they all require goal management with an important PM component. According to Fish et al. (2007), any situation in which an intention is formed in order to successfully carry out a task and which cannot be executed immediately but in the near future, can be considered as requiring PM. This retrieval of the intention and the performance of the intention, as discussed in the previous chapter, can either be time-based (cued by the passage of time) or event- based (cued by an external event). In order to successfully remember to carry out the task in the near future, it is important to retrieve that memory at the appropriate time and according to Norman and Shallice (1986), this is very likely to depend on attentional or executive systems.
Also, in complex tasks/situations in which several activities run simultaneously, additional planning and monitoring processes maybe required (Fish et al., 2007).
Although strategic and automatic processes are involved in PM retrieval (Einstein et al., 2005), it is likely that the extent to which executive processes are involved in PM retrieval is dependent on the specific requirements of the task (Glisky, 1996). For instance, time-based prospective tasks are more likely to rely on EF than event-based tasks as they require a higher degree of self-initiated retrieval (Einstein et al., 1995).
Having evaluated the role of EF in PM retrieval it is then possible that executive dysfunction is correlated with poor PM performance. It is therefore essential when studying PM performance to evaluate the role of executive resources as well. Fish et al. (2007) examined the contribution of executive monitoring towards the completion of a PM task in people with differing brain injuries and PM difficulties. After a period of brief training, the participants were required to make
62 telephone calls to a voicemail service at four set times each day over a period of 10 days. On five randomly selected days, eight text messages with the cue word
“STOP” were sent to the participants’ mobile telephones (but not within an hour of the target time) in order to investigate whether executive monitoring improves PM performance. Remarkable improvements were observed on cued days, hence demonstrating modulation of PM performance using cues, suggesting that such strategies are useful to remediate some negative consequences of executive dysfunctions.
Further evidence supporting the role of EF in PM performance comes from the definition of PM. Einstein and McDaniel (1990) propose that there are two components during a PM task; the retrospective component and the prospective component. The retrospective component is a typical memory function whilst the prospective component relies mainly on executive processes. Furthermore, in a multitask PM paradigm, Kliegel et al. (2000) showed that individual differences in executive functioning (e.g., working memory and inhibition) predicted the successful initiation and execution of a complex PM task while retrospective memory did not. In a later study, Kopp and Thone-otto (2003) tried to separate the cognitive processes involved in PM by testing patients with specific cognitive deficits in an event-based PM task. They found that patients with brain injury and impaired performance on neuropsychological tests of EF performed worse in the PM task than patients with no executive dysfunction thus supporting the role of EF in PM performance.
63 Executive functions are an integral part of PM performance. PM tasks create the need to monitor the environment in order to detect the relevant cue. This means that attention needs to be divided between monitoring and performing the ongoing task. According to Smith and Jonides (1999), such activity relies on executive processes like monitoring and working memory. It is therefore reasonable to assume that impairments on EF such as inhibition and working memory might predict poor PM performance because patients with impaired EF allocate more resources to the ongoing task in order to compensate for their executive deficits thus reducing the available resources for monitoring cues.
Another possible mechanism through which EF plays a role in PM is in maintaining the activation level of the mental representation of the future intention. According to Goschke and Kuhl (1993), delayed intentions are held in a higher activational state than other mental representations so they can be retrieved more easily when the cue occurs. In relation to this, Einstein and McDaniel (1996) maintain that the cue first creates a sense of familiarity (noticing) that is followed by a memory search for the content of the intention. Therefore, noticing depends on how easily the mental representation of the intention comes to mind.
To conclude, there is growing evidence that the successful performance of a PM task is heavily dependent on executive processes and that executive dysfunction predicts poor PM performance. Further research for the exact role and the extent to which executive processes contribute to successful PM performance is essential as both executive processes and PM play a crucial role in our everyday functioning.
64 3.6 Chapter summary
Although the research on EF is plentiful, the term EF still remains somewhat elusive as different definitions have been proposed throughout the years and different theoretical models have been devised to explain this complex term and evaluate whether EF are unitary or fractionated. In this chapter the most influential models that provide evidence for the fractionisation of EF have been discussed as well as the different approaches to measure executive dysfunction in clinical cases. The most widely used laboratory-based measures of assessing EF and the importance of using self-report measures that are able to capture the behavioural manifestations of EF in the everyday environment were also discussed. The biological underpinnings of EF and especially the involvement of the frontal lobes and their crucial role in our everyday environment and in PM performance were also evaluated.
A new line of investigation linking these theoretical constructs is concerned with how the common mechanisms supporting EF and PM operate in recreational drug users. More specifically, existing research suggests that ecstasy/polydrug users perform worse on both PM and EF tasks in comparison to drug naïve persons (Montgomery et al., 2005; Fisk & Montgomery, 2009b). Given that recreational drugs such as ecstasy, cannabis and cocaine are widely used and that both EF and PM play an important role in the everyday functioning, it is crucial to examine the possible effects of recreational drug use on these cognitive processes. The subsequent chapters will therefore evaluate the effect of ecstasy/polydrug use on EF and PM performance and discuss the different approaches of measuring executive dysfunction and prospective remembering among recreational users.
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