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Working Memory in Attention Deficit and Hyperactivity Disorder (ADHD) Research Paper


Abstract

Impaired working memory is one of the factors associated with symptoms of ADHD. Recent studies have aimed at testing whether repeated training of the working memory (WM) and its improvement can ameliorate the symptoms of ADHD.

Whereas many studies have indicated the possibility of the beneficial effects of WM training on people with ADHD, critics have dismissed them on the basis of flawed research design and interpretation. Given the lack of consensus on this issue, cognitive approaches such as WM training are unlikely to replace traditional interventions for ADHD such as medical stimulants any time soon.

Working Memory in Attention Deficit and Hyperactivity Disorder (ADHD)

ADHD is common in school-age children and has been associated with negative development in social, emotional, academics as well as anti-social behaviors in adult life (Johnstone, Roodenrys, Phillips, Watt, & Mantz, 2010). Recent data indicate that ADHD prevalence rate has increased from the long held figure of 3 to 5% of school-age children but remains at 4 to 5% in adults (Antshel, Hargrave, Simonescu, Kaul, Hendricks, & Faraone, 2011).

Three subtypes of ADHD are recognized namely: hyperactive/impulsive subtype, inattentive subtype and the combined subtype (Toplak, Connors, Shuster, Knezevic, & Parks, 2008). Risk factors associated with variations in prevalence include age, male gender, chronic health problems , low socio-economic status as well as urban living (Antshel et al., 2011). This paper is an attempt to examine new congnitve approaches relating to working memory that empirical studies have proposed as potential intervention strategy for ADHD.

The view supported here is that even with improved working memory deficit ,cognitive approaches that result in such improvement are unlikely become stand-alone interventions but may serve to supplement traditional measures such as pharmacological interventions.

Working Memory in ADHD

The most widely accepted models explaining the cause of ADHD are those that attribute it to deficits in overall executive functions or various aspects related to these functions such as impaired working memory (Bidwell, McClernon, & Kollins, 2011).

This view is supported by high number of studies over the last two decades that have emphasised on impairement of executive functions such as inhibitory control and working memory (Toplak et al., 2008). By definition, working memory is the short-lived ability of the brain to retain information necessary to guide present and future behaviors (Mezzacappa & Bukner, 2010).

It is believed to be made up of three components : a visuo-spatial part for storing visual information, a speech component that handles verbal content and an executive section that directs attention and control of processes (Klingberg, 2007). Later, an additional component, an episodic zone was included. This new inclusion is thought to be a complex system that records serialized contents from visual , spatial and verbal domains of the greater working memory (Rasmussen, Treit & Pei 2012).

MRI investigations have revealed that persons with ADHD have atypical development in the brain’s prefrontal cortex, a region believed to be the nerve centre of executive functions considered critical in developing problems solving skills necesssary for attainment of future personal goals (Bidwell et al., 2011).

Working memory training and ADHD

The primary intervention measure for ADHD has been administration of medical stimulants such as methylphenidate and amphetamine. These have proved effective in arresting inattention, hyperactivity and impulsive behaviours, the major manifestations of ADHD.

However, due to unwanted side effects of these medications such as growth impairment, heart arythmia,and insomnia alternative treatments became desirable for parents and medical caregivers (Johnstone et al., 2010). Behaviour modification, operant conditioning and increasingly computer-based working memory training have emerged as possible alternatives to traditional drug-based interventions (Johnstone et al., 2010).

Working memory training is normally conducted by administration of working memory tasks involving verbal and non-verbal materials (Melby-Lervag & Hulme, 2012). These tasks are designed to evaluate how an individual retains information in active memory while distracted by external happenings in the surroundings (Melby-Lervag & Hulme, 2012).Verbal working memory task may involve requiring individuals to repeatedly process, retain and reproduce a much information as possible until a recall mistake is made.

In contrast, visual spatial working memory tasks may be simple in the sense of rotating pictures and the recalling of their positions. In my own perspective, am persuaded working memory training could emerge as a viable treatment option for developmental disorders. I find it a cheap and potentially side-effect free alternative that may gain widespread acceptance if its efficacy is established.

Empirical evidence for working memory training

Attention towards working memory grew out of the substantial empirical evidence showing that individuals with ADHD have marked impairment in working memory. It is imagined that getting to improve this memory might produce concomitant cognitive improvement in ADHD-related impairments (Melby-Lervag & Hulme, 2012).

Thus it was hypothesized that improved working memory would lead to beneficial effects in affected subjects that should be evident in terms of better language processing, faster speech co-ordination, reduced inattention, better long term memory and possibly improved academic performance.

These ideas are supported by various investigations showing that training the working memory can lead to enhanced cognitive deficits accompanied by a reduction in the primary symptoms of ADHD (Bidwel et al., 2011;Holmes et al., 2010; Mezzacappa & Bukner, 2010; Klingberg, 2007).

In a school based pilot study, Mezzacappa and Bukner (2010) employed a computer program to train the working memory of children with attention or hypersensitivity problems from economically challenged backgrounds. They were particularly concerned with teacher’s ratings of total ADHD symptoms during the study period.

Overall, there was improved teachers’ rating of total ADHD symptoms in participants taking the program compared to the control group and baseline values. The findings of this study are consistent with effects of cognitive training on working memory reported by other investigators.

Green and fellow researchers (2012) studied the extent to which WM training in ADHD would ameliorate a core dyfunctional behaviour associated with the disorder. In a randomized ,double blind ,placebo-controlled study, the effect of WM training using CogMed training program was compared to healthy control subjects in 26 children(aged 7 to 14 years old) diagnosed with ADHD (Green, et al., 2012). The active training group had 12 children while the placebo had 14.

The study involved intensive 25 sessions and Restricted Academic Situation Task (RAST) observation system was used to assess responses of participants upon completion completion of daily tasks (Green et al., 2012) . Alongside RAST, Conners Parent Rating Scale and standardized WM tests were used to measure improvement in the active training group (Green, et al., 2012).

Result showed significant differences between the placebo and the active participating group. There was also significant improment in WISC-IV WMI, a widely used WM measure in the active group than in the placebo. They concluded that WM training could be generalized to improve non-trained related impairment but called for specific trainings designed for additional impairements in larger samples in future (Green et al., 2012).

In similar vein, a combination of WM training and stimulant medication has been found to produce differential enhancement on WM impairments in children with ADHD (Holmes et al., 2010). Holmes et al.(2010) investigated the changes in WM of children with ADHD as a result of pharmacological intervention and WM training.

The study participants totalled 25 aged between 8 and 11 years old. Assessment was done in four phases within selected weeks for WM training using Cogmed Working Memory Training Program while medication was maintained throughout the study period (Holmes et al., 2010). Each child completed an average of 22 training sessions. Post study assessment was done 6 months after training. Consistent with previous investigations stimulant medications only significantly enhanced visuo-spatial WM performance.

On the other hand, training produced greater improvement in visuo-spatial and verbal components of WM as evident in reduced inattention and behavioural control (Holmes et al., 2010). Notably, from the follow up analysis, the training gains(visual spatial short –term memory, verbal WM and visuo-spatial WM) persisted over a 6-month period but their was no improvement in IQ score during and after the study period (Holmes et al., 2010).

Johnstone and fellow researchers (2010) examined the behavioural and psychological effects of concurrent computer-based WM and inhibition training for children with ADHD. In a pilot double-blind active-control design, 29 ADHD diagnosed children completed a 5-week home training program and a post-study session that involved assessment of overt behaviour, resting EEG, task performances, skin-tests and event related potentials during a go/no-go task.

Final results indicated improved attention and reduced hyperactivity in the active group (Johnstone et al., 2010). In conclusion, the researchers acknowledged the nascent nature of such outcomes and pointed out that although cognitive training indicated potential in treatment of WM impairment for ADHD, further research focussing on extensive training and response inhibition function are needed in the quest for affirming WR training as a viable treatment option for ADHD (Johnstone et al., 2010).

Klingberg and team (2002) used a double blind, placebo controlled design in evaluating the effect of intensive and adaptive training of working memory tasks on children with ADHD. The training lasted 24 days and each day the active group performed 25 minutes of training that involved visuo-spatial, backward digit span, letter span and go/no-go reaction tasks (Klingberg, Forssberg, & Westerberg, 2002).

They found that the training produced marked improvement in trained WM task and interestingly, non-trained visuo-spatial WM tasks (Klingberg et al., 2002). The study also atttributed a reduced motor activity realized in participants to the trainings.

These studies and numerous others indicate the great interest cognitive training in ADHD has generated. Even though not conclusive, I find them useful in providing explanatory knowledge about the diseases. They indicate the possibility that the workng memory can be manipulated.

Pharmacological intervention and cognitive training

There is also evidence indicating that the combination of medical stimulants and cognitive training produces more pronounced desirable cognitive outcomes in ADHD than either stimulant or cognitive training alone. This can inspire the imagination that future therapies against ADHD and related disorders could be made up of the two.

However, questions abound as to the change in medical stimulant to be implemented at such a time in relation to the present given that cognitive training do not form part of current treatments. Despite this uncertainty, it can be suggested that future better cognitive trainings on ADHD and related disorders producing far greater improvement in working memory could have far reaching implications on the kind of medical stimulant therapy that will be administered.

From the mid 20th century, two stimulant formulations; amphetamine and methylphenidate have been associated with reduction in core symptoms of ADHD in majority of children making them the primary intervention approach (Bidwell et al., 2011; Johnstone et al., 2010). However, their efficacy has not been consistent in adults with ADHD although they still form an important part of therapeutic prescriptions for this group (Bidwell et al., 2011).

Despite mixed consensus, bias towards stimulant management of ADHD exits. This is attributed to the findings of the 1999 “Multimodal Treatment Study” of children with ADHD , considered by many to the most influential ADHD treatment study to date (Toplak et al., 2008, p. 803).

The study, which involved 579 children aged 7 to 10 years diagnosed with combined subtype ADHD and a follow up period of 14months found that medication management alone was significantly better than behavioural strategies or the combination of the two (Toplak et al., 2008). Although there was no consensus in the interpretation of the study’s data, it led many to favour stimulant medication intervention (Toplak et al., 2008)

Specifically some studies have also found that stimulants are more effective on non-executive functions tasks such as sustained attention than on tasks related to executive function such as inhibition, working memory and planning (Bidwell et al., 2011; Toplak et al., 2008 ;Klingberg et al., 2002 ).

Additionally, dose-response studies have shown that high doses of stimulants are needed to produce appreciable enhancements in domains such as attention, vigilance and working memory but the same is not the case in areas such as planning, cognitive flexibility, inhibitory control and motor speed (Bidwell et al., 2011).

Although there is no general consensus ,stimulants just like cognitive improvement therapies such as working memory training, have also been found to produce only short-term benefits in academic peformance. This calls for more research in this areas as academic performance is a serious challenge in majority of ADHD individuals.

In summary the above findings suggest that stimulants alone are not completely efficacious in ameliorating ADHD deficits. Given the beneficial effects (albeit preliminary) of WM training on cognitive development ,a combination of medical stimulants and cognitive trainings such as WM training perhaps represents a better treatment approach for ADHD. A possible predilection factor for cognitive trainings such as those targeting working memory is the high dose required for medical stimulants.

Given that such doses are likely to lead to new or much pronounced side effects in users, alternative treatments such as cognitive training could become more attractive. Furthermore, other pharmacological intervention drugs such as Atomoxetine and α 2 agonists have not yet yielded consistent cognitve improvement results in human population although they have already been approved by the FDA (Bidwell et al., 2011; Mezzacappa & Bukner, 2010; Klingberg et al., 2002).

Evidence against working memory training

The plethora of study evidence purporting the ameliorating effects of working memory training on ADHD has led to greater scrutiny of the design and findings of these studies. One such scrutiny published in the American Physiological Association website mid this year involved a meta-analysis of 23 peer reviewed studies that sought to evaluate the effects of memory training programs on general cognitive performance.

The researchers studied among other aspects, the study design ,measures and participants who ranged from healthy children, adults and ADHD children in the studies most of which were published within the last 10 years. In refuting the claims of these studies they cited small sample size, lack of control in some studies and limited generality of the benefits reported.

They concluded that the effects of memory training on cognitive development were only effective on tasks conducted during the training but did not produce any appreciable long term effect on general cognitive performance such as verbal, attention and scholastic improvement (American Physocological Association, 2012).

The above findings are also consistent with those of Shipstead and fellow authors (2012) who in a similar analysis found little evidence from similar studies for the association of WM training with better attention control, reduction in symptoms of ADHD and general fluid intelligence (Shipstead, Redick, & Engle, 2012). The authors offered that, for credibility, future related studies need to demonstrate that WM training and improvement transfer increases WM capacity.

A further related finding is from the analysis of 26 studies (6 cognitive-behavioral, 6 cognitive and 14 neural-based) that found the evidence of these approaches in ameliorating symptoms in ADHD insufficient (Toplak et al. 2008). The authors concluded that further investigations are necessary to determine the efficacy of these approaches on both cognitive and behavioural outcome measures (Toplak et al. 2008).

In my view, I find the analyses in the preceding paragraph uninformative as even authors of the studies analysed have themselves highlighted the inconclusive nature of their findings. However, these developments serve to cast doubts on the supposed benefits of WM training on cognitive development and by extension their theoretical and practical importance.

It also reveals that there is no general consensus among scientist on the effects of memory training on cognitive development in persons with attention disorders such as ADHD. Another challenge for ADHD remediation arises from the fact that ADHD has large comorbidity with other disorders.

This means that intervention strategies need to differentiate the underlying conditions and their related features. However, current literatures is lacking in explaining how different comorbidities influence traditional interventions or those with promising results but still under research. As researchers in this field have suggested, more rigorous study are needed before working memory training is considered a viable treatment alternative for ADHD.

Conclusion

Many studies have focused on working memory because it one of the central executive functions impaired in many developmental disorders such as ADHD. This approach is based on the idea that enhanced knowledge on the aspects of working memory in people with ADHD could be beneficial in the development of better intervention measures.

Similarly, many investigations have shown that working memory training can lead to short-lasting and durable reduction in symptoms of ADHD. On the other hand, scrutiny of these studies has led to their dismissal as inadequate and inexact.

The analysts contend these investigations are lacking in various critical aspects such as methodological design, sample size, and interpretation of data to mention just a few. Taken together, this mixed consensus can mean two things. One is that at least some form of artificial WM improvement is possible. The other is that more research is still needed to determine the efficacy of WM training and other cognitive strategies.

Although working memory impairment is a distinguishing feature in developmental disorders and conditions, the exact profile of the deficit in different affected individuals is still unclear. Available literature shows that this is one area many studies have failed to address. If the nature of the impairment is clearly understood, better interventions could be developed.

Lastly, due to the changing etiology and large comorbidity of ADHD with other disorders, its management is likely to remain as complex as it is today. Even with better correction of working memory deficit, stimulant medication and other interventions will likely still form part of treatment for the disorder.

References

American Physocological Association. (2012, May 31). . Web.

Antshel, K. M., Hargrave, T. M., Simonescu, M., Kaul, P., Hendricks, K., & Faraone, S. V. (2011). Advances in understanding and treating ADHD. BMC Medicine, 9, 72.

Bidwell, L. C., McClernon, F. J., & Kollins, S. H. (2011). Cognitive enhancers for the treatment of ADHD. Pharmacology, Biochemistry & Behaviour, 99, 262-274.

Green, C. T., Long, D. L., Green, D., Losif, A.-M., Dixon, F. J., Miller, M. R., et al. (2012). Will working memory training generalize to improve off-task behaviour in children with attention-deficit/hyperactivity disorder? Neurotherapeutics, 12(4), 120-124. doi: 10.1007/s13311-012-0124-y.

Holmes, J., Gathercole, S. E., Place, M., Dunning, D. L., Hilton, K. A., & Elliot, J. G. (2010). Working memory deficit can be overcome: Impacts of training and medication on working memory in children with ADHD. Applied cognitive psychology, 24, 827-836. doi: 10.1002/acp.1589.

Johnstone, S. J., Roodenrys, S., Phillips, E., Watt, A. J., & Mantz, S. (2010). Pilot study of combined working memory and inhibition training for children with AD/HD. Atten Def Hyp Disord, 2, 31- 42. doi: 10.1007/s12402-009-0017-z.

Klingberg, T. (2007). The concept of working memory. Web.

Klingberg, T., Forssberg, H., & Westerberg, H. (2002). Training of working memory in children with ADHD. J of Clinical and Exp Neuropsychology, 24(6), 781-791.

Melby-Lervag, M., & Hulme, C. (2012, May 21). Is working memory training effective? A meta-analytic review. Development Psychology, 28(2), 282-299. doi:10.1037/a0028228.

Mezzacappa, E., & Bukner, J. C. (2010). Working memory training for children with attention problems or hyperactivity: A school-based pilot study. School Mental Health, 12(3), 109- 127. doi:10.1007/s12310-010-9030-9.

Rasmussen C, Treit S, Pei J. (2012). Memory interventions for children with memory deficits. In J. Stone & M. Blouin (Eds.), International Encyclopedia of Rehabilitation (pp. 34-36). New York, US: . Web.

Shipstead, Z., Redick, T. S., & Engle, R. W. (2012). Is working memory training effective. Psychological Bulletin, 26(2), 122-133. doi: 10.1037/a0027473.

Toplak, M. E., Connors, L., Shuster, J., Knezevic, B., & Parks, S. (2008). Review of cognitive , cognitive-behavioural, and neural-based interventions for ADHD. Clinical Psychology Review, 28, 801-823.

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IvyPanda. "Working Memory in Attention Deficit and Hyperactivity Disorder (ADHD)." May 6, 2020. https://ivypanda.com/essays/working-memory-in-attention-deficit-and-hyperactivity-disorder-adhd/.

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IvyPanda. 2020. "Working Memory in Attention Deficit and Hyperactivity Disorder (ADHD)." May 6, 2020. https://ivypanda.com/essays/working-memory-in-attention-deficit-and-hyperactivity-disorder-adhd/.

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IvyPanda. (2020) 'Working Memory in Attention Deficit and Hyperactivity Disorder (ADHD)'. 6 May.

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