Aging and Sustained Attention

This week we look into the effects that age has on mind wandering and sustained attention.

          Lin, Hsiao, & Chen (1999) used the Continuous Performance Test (CPT) to study sustained attention development in primary school aged children.  The CPT measures sustained attention deficits caused by cognitive inhibition and has been used in the past to measure  sustained attention deficits in children with ADHD as well as those at risk for schizophrenia.  The reasoning behind this is that in those at high risk for schizophrenia, there will be certain brain regions that are not being activated during the CPT.   Previous CPT studies have been rather limited in scope and therefore this study was useful as it tested a large sample of children of both genders.  They found that CPT performance improves in children between the ages of 6 and 15, particularly between the ages of 6 and 12.  This finding suggests that the cognitive inhibition aspect of sustained attention develops during this age range.  

      Carriere et al. (2010) studied a larger age span (20-70) to examine sustained attention over age and time.  By looking across decades, they were able to find that both SART errors and response speed decreased with age in an overall linear trend (see Figure 1). More specifically, they found that measures of task disengagement on the SART decreased rapidly in early adulthood (~3^rd decade), following which they remained rather stable despite the increasing of age (See Figure 2).  The differences between that of Figure 1 and Figure 2 suggest that SART error and RT (Figure 1) explain different aspects of performance that that of the task disengagement measured in this study (RTCT, anticipations, & omissions; Fig. 2).  

The findings on task disengagement suggest that sustained ability does not change as a function of aging but rather as a function of maturation early in adulthood but then remains stable with further aging.  The decreased response time of older adults may reflect the use of a more strategic response style that leads to a reduction in SART errors. There are a couple of possibilities for why this might be the case.  According to Jackson & Balota (2011), older adults are higher in conscientiousness compared to younger adults.  This could have an impact this difference of mind-wandering seen in age difference.  Carriere et al. conclude with an important point, which is that had they not chosen such a large age range and looked only at those in the second decade compared to the seventh, for example, it would have looked as if sustained attention continuously improves with age.  However, by looking across each decade, we are able to see that it actually remains generally unchanged following the 3^rd decade. 

       This idea of effect of the design and chosen sample of study is important to note in the work by Lin, Hsiao, & Chen.  Unlike the other articles, where Carriere et al. found no gender effect (while Jackson & Balota (2011) only test female subjects), Lin, Hsiao, & Chen found that sex was also associated with performance on the degraded CPT, with girls performing worse than boys in hit rate and sensitivity.  However they note that this gender effect changes depending on the version of CPT used which also reinforces the importance of comparing findings which have used comparable methods.  

          Using versions of SART followed by a probed reading comprehension task (noting that this was a more realistic measure), Jackson & Balota (2011) found that not only do older adults not mind wander more than younger adults, they actually tend to mind wander less.  When using an easier version of the SART, older adults responded at a slower pace and were more accurate than younger adults.  In addition, older adults had an increase in response time following an error, which indicates that they had an increased difficulty reengaging in the task after making an error. Older adults were higher in conscientiousness while they also rated the tasks as both more difficult and more interesting than younger adults.  Interest in task may be an important predictor of performance. The researchers do comment that for older adults, as opposed to college students, conducting this novel experimental context on a college campus may contribute to their reported decreased mind-wandering.  I found this point interesting as I would expect that this could actually have an opposite effect, in that perhaps bringing these older adults onto a college campus could create a nostalgic effect in which they mind wander more, to their experiences when in college.  This however would have caused an increase in mind-wandering.  Another thought that this point then brought me to is the idea that perhaps the participation itself in a psychological study is a novel experience for older adults, whereas nowadays it is so common to conduct studies using undergraduate students, that these undergraduate participants may participate in many of these experiments and therefore may not find the act of participating as exciting as older adults new to such an experience may find it.  If so, this aspect of participating in an experiment may contribute to why older adults reported the task as more interesting.  If this is the case, it would be expected that older adults would generally rate tasks as more interesting/engaging over a wider variety of tasks compared to younger adults.  However, regardless of what it was that made the experiment more engaging and interesting for older adults, the idea that the extent of task interest may be an important age-related difference in understanding observed effects.

            In comparing their work to that of Carriere et al. (2010) Jackson & Balota note an important point that “…their study used a version of the SART consistent with Robertson et al. (1997), and thus can only be directly compared with Experiment 1 of the present study” (p.116).  I think this is a very important point because it is easy to just compare the findings of different studies on mind wandering, however, it is important to take into account the actual methods used in such studies which could account for any discrepancies between findings. 

            

Lost & Disordered

The articles by Berman et al. (2011), Sayette, Reichle, & Schooler (2009), Manly et al. (2003), and Bonnelle et al. (2011) which will be discussed in this post, examine subjects with disordered attention.  These studies were particularly interesting to me as I have done a lot of work focusing on the study of clinical psychology.  Therefore, as my knowledge in mind wandering has progressed throughout this semester, I have been constantly questioning how this mind wandering research relates to those with certain psychological disorders (refer to the Clinical Corners found in past posts).

The cyclical nature of depression is characterized by one’s increased rumination, thus leading to increased salience of negative information.  It has already been established that the default network is engaged during mind wandering episodes (Mason et al., 2007), however the study by Berman et al. (2011) suggests that this activation is different for those diagnosed with depression compared to healthy subjects.  By studying this effect in those diagnosed with major depressive disorder (MDD) we can better understand basic mind wandering research as it helps us understand the functions of more specific brain regions affected by this disordered attention, such as the subgenual-cingulate cortex, past just noting general engagement of the default network during mind wandering episodes.  While this study examines effects of rumination resulting from MDD, in order to do so, the study must also examine the rumination of HCs as a comparison group, thus offering important information about normal functioning.  This research is also important because most psychological disorders, like depression, involve symptoms that everyone experiences.  Therefore, clinical research  is relevant to normal functioning because it is just looking at the extreme cases of normal behaviors. Therefore, while excessive rumination is a symptom of MDD, HCS ruminate too, but just do so less of the time.  More specifically (see Figure bellow) this study found that HCs’ propensity to ruminate remains constant whether or not they are engaged in a task. MDDs, on the other hand, showed a difference in rumination propensity, with s significant reduction in rumination while engaged in a task (as seen in decreased connectivity) compared to during an off-task condition. 

This is particularly important in general because MDD affects approximately 17% of the U.S. population will suffer from at least one major depressive episode in their lifetime  (Lu, 2000).  Therefore, an understanding of the effects of increased rumination associated with MDD has a much larger impact than just on those currently diagnosed with MDD.  The fact that increased connectivity in the subgenual cingulate was only seen during off-task periods for MDD suggests that task engagement can temporarily relieve rumination and improve mood.  This therefore could also be an important tactic which could be used when HCs find themselves in a slightly depressed mood and task engagement at these times may act as a more permanent way to decrease rumination and improve their decreased mood back to its baseline state.

The work of Bonnelle et al. (2011) further supports the importance of the default mode network  (DMN) connectivity and associated measures of sustained attention.  It has been previously discussed that DMN activation increases when one is mind wandering.  The finding that sustained attention is impaired in those with a traumatic brain injury (TBI) is associated with an increased activation of the DMN follows in line with these past findings.  This research is particularly interesting in that the connectivity within the DMN, specifically that of the precuneus and posterior cingulate cortex, predict which patients will show sustained attention impairments.  By understanding that the impairments of TBIs’ ability to maintain consistent goal-directed behavior has to do with their increased activation of the DMN strengthens the previous findings of the importance of DMN activity regulation of normal brain function.  The changes in DMN connectivity are key to understanding impairment in sustained attention after TBI.  This is also an important finding because even though TBI seems to be able to sustain attention normally following the accident, it is over time in which such impairment occurs.  This is important for those patients as they increasingly may become less able to sustain attention though may not associate the TBI with this if they were originally told that their functioning was not impaired.

Manly et al. (2003) examine children diagnosed with ADHD, finding an associated impairment in their sustained attention. In the first study, they test a normative sample of healthy children in order to test the validity of the rather novel battery adapted from measures used to test adults’ sustained attention.  The second study then applied these measures to children diagnosed with ADHD.  In the first study they mention how they wanted to recreate the conditions in which most clinical tests occur, i.e. in rooms where experimenters can minimize noise and visual distractions.  In the second study, similar procedures were taken, however they mention that testing took place either at the clinic or at home.  I would think that these two environments could create different results as it would be much more difficult to control for distractions in one’s home environment, and I would therefore think that having the testing at home could create more distractions and therefore increase deficits in self-sustained attention of those subjects.  However, I also think that this type of testing in such an isolated environment in general is not useful because in everyday life there are distractions as well as others present, both of which will affect where and how one behaves and directs his or her attention. It is important to note that those diagnosed with ADHD in this study had not yet received any medication for treatment.  This is important to note because after being diagnosed with ADHD, patients most likely will be prescribed medication.  Therefore, it is important to understand the effects of sustained attention when on such medication.

Sayette, Reichle, & Schooler (2009) use both a self-caught and probe-caught method to understand the effects of alcohol on both mind wandering frequency and meta-awareness (i.e. propensity to catch oneself mind wandering).  This study, while comparing those given alcohol to those given a placebo, applies to all individuals that ever have had a drink, as it is analyzes individuals after consuming a very moderate amount of alcohol as opposed to studies on those with an alcohol addition.  In order to control for the many variables that affect alcohol intake, the researchers control for gender, age, body weight, height, and food intake.  However, I am a little skeptical about the chosen age range (21-35 years old), as I believe that those on the younger side of this group (who fall into the category of college students) probably drink more frequently and in a different manner (more binge drinking) compared to those towards the middle and end of this age group who tend to not drink as recklessly.  If so, both frequency and amount of alcohol intake would affect one’s alcohol tolerance and therefore could affect the results that the one drink in the study has on their sustained attention abilities.  Nevertheless, the study found that the alcohol group mind wandered about 25% more of the time than the placebo group during the reading task. 

Stop and just breathe

        In order to better understand the potential benefits of meditation, I attended an instructional class for beginners in the practice of Zen mediation at Village Zendo.  I entered the session a bit skeptical to be completely honest.  While the idea of sitting still for a 2-hour meditation session may be calming for some, for me it actually really stressed me out. However, while still a little unsure about my feelings towards meditation, looking back on my experience, it really was a surprisingly pleasant experience, and I did feel that it reduced my stress level as it gave me the needed chance to drown out the hustle and bustle of the city and reflect on my feelings, at least for that moment.

      Coming from no previous experience in or understanding of the practice of meditation, the articles by Lutz et al. (2008), Jensen et al. (2013), MacLean et al. (2010), and Baer et al. (2006) helped me better understand the purpose of meditation. Lutz et al. (2008) identifies an important problem in studying meditation, mainly that meditation itself is a very broad term that must be differentiated by type of meditation practice: “Failure to make such distinctions would be akin to the use of the word ‘sport’ to refer to all sports as if they were essentially the same” (163).  In their paper, they examine two Buddhist styles of meditation—Focused attention meditation (FA) in which focus is voluntarily directed to an intended object and open monitoring meditation (OM) in which instead of having an explicit attentional focus, content of one’s experience is monitored in the moment.  In relation to my experience, after spending time learning about the appropriate posture (of which I took the Quarter Lotus position)  

the instructor spoke, having us meditate in a way that seems more consistent with OM as she emphasized focusing on the present moment. She mentioned how we are constantly lost in our thoughts and spend most of our lives worrying about things and end up years later not really knowing where our lives went.

During this time the instructor stressed the importance of not letting our thoughts overpower us but rather to observe them nonjudgmentally, similar to the sitting meditation exercise in the mindfulness-based stress reduction (MBSR) method described by Jensen et al. (2013).  This method, as both Jensen et al. and my instructor noted is used as a means to “let go” and instead focus on the present moment in a non-judgmental way.  
      However, while this OM-based method was used in the beginning to set us in a certain mindset, I feel that the majority of the session I attended was really spent using a more focused attention (FA)-based method, as awareness was directed specifically towards counting our breathing from one to ten, starting over when our minds wandering from our breathing.  We were told that the purpose of doing so was to bring our focus to the present and regulate the mind. Though this may seem like such a simple task, I found myself constantly back at one, as my mind continuously drifted from the counting thus forcing me to start over.  We also did some walking meditation in which we took steps with the rhythm of our breathing.  This was an interesting approach and a more relieving method for me as I can have trouble sitting still for meditation, but at the same time, it was much harder to focus on my breathing with so much else going on, as compared to the sitting meditation.  I think that the walking meditation, at least for me, put into perspective just how difficult it can be to separate yourself with everything going on around you (especially in a crowded, loud city like New York).  In this walking meditation I became much more aware of my surroundings and others present in the class, thus making it even more difficult to focus on my breathing.
      While I am clearly a novice in the practice of meditation, reading a paper like that of MacLean et al. (2010) helps me understand how continuing the practice of such meditation can have future benefits.  Like the meditation class that I participated in, in their paper they use a FA-based model of meditation, in which participants practice sustained attention to a non-visual “chosen stimulus” (e.g. sensations of breathing). In this study, participants are trained for 5hr/day for 3 months in order to examine the effects of such training on sustained selective attention.  Their findings indicated that training lead to visual discrimination improvements resulting from the reduced resources needed to discriminate an unchanging target (the target length was held constant in Retreat 2, see Figure 3).  These improvements were associated with increased perceptual sensitivity as well as improvements in visual attention during sustained visual attention tasks.  Therefore, this study offers support for the long-term continuation of meditation practice.

Figure 3

Overall my time at Village Zendo was a great learning experience, one that provided a short respite of calm from the stressful life of a student in the midst of exams.