Posted comment on ´Benefits of a Working Memory Training Program for Inattention in Daily Life: A Systematic Review and Meta-Analysis` by M. Spencer-Smith and T. Klingberg published in PLoS One, DOI: 10.1371/journal.pone.01195522 March 2015
The authors, Spencer-Smith and Klingberg, carried out a meta-analysis of the results of training using the Cogmed program on inattention in daily life. Their meta-analysis included 11 studies with 12 group comparisons who met their inclusion criteria of using the full Cogmed program from a total of 622 studies identified between 2005 and 2013 using the Medline and PsychINFO journals as source. The measures used to estimate inattention in daily life were general and specific to take into account complex behavior and were coded independently by the authors themselves. Working memory performance was estimated and coded by investigating visuospatial working memory and verbal working memory and the results were given as pooled standardized difference in means (SMD) between intervention and control groups. The study was brought about by a dispute that training can increase working memory, but since most studies are based on a small sample size, the authors believe a meta-analysis would be advantageous.
The results of Spencer-Smith and Kingberg`s meta-analysis showed the effect of Cogmed training to be moderate and significant, and hence concluded that there was a significant training effect on inattention in daily life. This conclusion was based on pooled sample groups. They also performed the analysis on sub-groups. Participants were grouped according to age (coded as children and adolescents or adults) or status (coded as healthy, diagnosed with ADHD or at-risk for WM impairment). For studies using an active and non-adaptive control group or a waitlist control group the pooled subgroup effect size was small to moderate and significant. Studies using a specific measure as well as studies using a general measure to estimate inattention in daily life showed subgroup effect sizes that were moderate and significant, with no significant difference between the subgroups.
The investigation of the effect following a delay after the Cogmed program had finished showed that the training effect remained significant 2 to 8 months after training with the pooled effect size small to moderate and significant with heterogeneity between studies low and non-significant. The authors concluded that the results indicate persistent training benefits for inattention in daily life, although they did report a need for more long-term studies and bigger sample sizes.
Since other researchers have reported significant and large training effects for verbal working memory and significant and moderate training effects for visuospatial working memory, a meta-analyses on these were also performed. Spencer-Smith and Klingberg showed an improved visuo-spatial working memory with large and significant pooled effect size and with heterogeneity between the studies moderate and significant. In the case of verbal memory, the pooled effect size was moderate and significant, with heterogeneity between studies low and non-significant. Cogmed better than other training programs
Therefore, Spencer-Smith and Klingberg concluded that the working memory training program Cogmed elicits improvements in everyday functioning and significant benefits for inattention in daily life.
From their meta-analysis of study results, the authors, Spencer-Smith and Klingberg (the developer of the Cogmed training program) claim moderate and significant improvement of inattention in daily life. For their analysis they pooled the effects and defined the results using standardized difference in means. By returning to the actual results used in the meta-analysis and looking at the actual mean values given, it can be seen that if the results are grouped in 10% increments then most groups fall within the 11-20% improvement category (6 from 12). The average improvement from the Cogmed training program is 16.5% and covers 69% of all the subjects and includes Klingberg`s own published results at 16%. This improvement although it may be significant could be considered low especially if the expectation of the improvement is high after such considerable effort and commitment to carry out such a training program.
However, since any improvement should be considered beneficial the question has to be asked what actually is the training program improving? We could suggest that since the effect is independent of the status of the subjects (eg whether they suffer from ADHD or any other condition linked with working memory impairment) that the effect of the training could be general. (However, it cannot be ruled out that the improvement lies in one area for one condition and somewhere else for another.) A general advantageous effect of the training program is its repetitive nature, the routine, the familiarity with sitting and performing the training program, the skills involved all leading to the improvement observed being linked to expertise achieved from practice. This could mean that the improvement comes from each participant dividing up the training units into chunks or templates, meaningful encoding them and setting up appropriate retrieval structures as well as factors linked to the general theory of expertise (Ericsson and Lehmann – eg having the task at the appropriate level of difficulty, the training program participant being provided with feedback, or having the opportunity for repetition, or correct errors) so that with practice efficiency at performing the tasks increases.
This view could be supported by the results achieved from the delay after the training program. In each case a decrease in performance advantage was observed with the exception of one study. There was however a discrepancy with the amount of decrease observed. With groups where there was no big difference in the number of participants then 2 groups demonstrated a decrease of 16%, and one 62%, but a further examination of the delay controls could mean that the latter is disregarded so that a 16% decrease is average. This indicates that the training program although eliciting a low level of improvement it is sustained even after the program has been stopped.
The authors, Spencer-Smith and Klingberg also showed in their meta-analysis study that there was a greater effect on visuo-spatial memory than verbal memory. When the mean values were examined then it can be seen that the visuo-spatial memory improvement is greater than the normal improvement in half of studies, but same as normal in 3 from the 8. A higher frequency of improvement would be expected if visuo-spatial cognitive abilities are being trained by the program and these capabilities are being specifically tested for. (One study showed less than normal improvement, in fact Klingsberg own study, but here 4 subjects did not take part hence biasing the overall effect). An examination of the mean values for verbal memory studies showed that the training program brought about an increase in verbal memory performance and in 5 out of 8 studies this was greater than normal with 2 cases being extreme (94%) and 2 less. Therefore, in both cases the Cogmed program has an effect.
The authors claim that the training effects are the result of increased working memory and it has been shown by others that training demonstrates this type of improvement. If we look at working memory perhaps it is possible to see exactly what part of the mechanism is improved by this type of training program. It is known that working memory requires acetylcholine and glutamate and that neurons in the prefrontal cortex are multi-tasking being involved with both attention and working memory (Messinger). It is also known that working memory requires activity in certain brain areas (visual working memory – inferotemporal cortex, V4, medial temporal cortex (Pasternak), prefrontal cortex and globus pallidus (Klingberg), lateral inferoparietal cortex (guided eye movements in attention), post parietal cortex (Koenigs – manipulation of information in working memory). It also requires fronto-hippocampal connectivity (Cordesa-Cruiz) and changes in prefrontal oscillations have been shown (prefrontal theta oscillations increase during temporal order maintenance and alpha oscillations over posterior parietal and lateral occipital for item maintenance (Hsieh) with these alpha oscillations being used to maintain the relevant memory contents rather than suppressing unwanted or no longer relevant memory traces (Manza). In spatial working memory, theta oscillations occur in the medial prefrontal cortex with the ventral hippocampus playing a role in synchronization (O`Neill). So, could the Cogmed training bring about physiological changes that result in an improvement in task performance? In Cogmed, just like in the case of conditioning, the same routines are performed with only the words differing, hence there is better interconnectivity between the relevant brain areas and greater focus and alpha brain waves indicate thinking. Studies have shown that training increases connectivity in frontoparietal and parietal occipital networks (Kunden) and working memory training is associated with variability in white matter (Golestani) and more specifically, increased myelation in white matter neurons in the intraparietal sulcus and anterior body of corpus callosum (Takeichi). Hence, the improvement in working memory performance brought about by the Cogmed training program could be attributed to physiological changes in the relevant brain areas.
Spencer-Smith and Klingberg`s meta-analysis showed that there was improvement in attention in daily life after participating in the Cogmed training program. This indicates that the increase in performance is linked to increases in efficiency of the attention mechanism and it is known that training can bring this about. In fact others have reported that Cogmed decreases inattention and increases how much verbal and visuospatial information a subject can temporarily work with (Slezak). If the Cogmed training program has an effect on attention and inattention, the question has to be asked what part of the attentional mechanism is affected. It could be an increase in efficiency of Posner`s control networks of alerting, orienting or central executive or to the parts of orienting (Posner and Petersen) with disengagement (responsibility of the parietal area), shifting and reengagement of focus (responsibility of the What-Where pathway, cortical medial temporal cortex or pulvinar nuclei of thalamus). Another area that exhibit higher efficiency after training is the selection process that retrieves the relevant items from memory (activation in rostral superior frontal sulcus and posterior cingulate cortex) or the updating process that changes the focus of attention on it (caudal superior frontal sulcus and post parietal cortex). Training could also shift the top-down, bottom-up balance of the control systems (control – stimulus driven and goal directed – Asphland, or top-down and bottom up system – Corbetta and Shulman) with training leading to better control of the top-down attention or by improving working memory biases of attention by initiating the novel pareo-medial-temporal pathway proposed by Soto.
It is possible that training changes the balance of task relevant to task irrelevant (or attended to unattended) information, hence improving overall performance. It is known that working memory performance is dependent on effectively filtering out irrelevant information through neural suppression (Zonto). The dorsal parietal cortex exhibits influence on top-down attention and ventral parietal cortex on bottom up (Curicella) with prefrontal cortex playing a role (Nieuwenhaus – 5HT, DA amplify task relevant information rather than inhibiting distraction), and cingulate cortex (Egner – increase task relevant rather than inhibiting task irrelevant). This balance in task relevant information and task irrelevant can be affected by various factors. There appears to be a decreased inhibition of task irrelevant information with age (Blair; Heshier; Redrick): effects that can be mitigated by training (Matzell). Anxiety also appears to have an effect with a decrease in information with relevance (Weltman), but on the positive note training and computer games can have an advantageous effect (Gofper; Green).
Therefore, if attentional efficiency is the reason for the success of Cogmed training then there are many areas where it could be having an effect. Also linked to attention, is emotional status and it could be said that the practice associated with the training program can also have a positive effect on emotional state. Working memory training has been found to lead to emotional regulation (Schweizer) and a general improved functioning of the frontoparietal network, hence leading to improved efficiency in cognitive capability. The possible fear associated with performing the training at the beginning could attenuate the inefficiency observed since fear attentional state leads to increased perceptual load capacity with increased levels of task relevant and task irrelevant information (Niewenhaus; Egner; Stoets) and increased gist memory (Adolphs). Activation of the prefrontal cortex, amygdala, thalamus and cingulate cortex areas is involved. Practice with training program during its duration is likely to remove the fear element if existing at all and continual feedback and reward shift the balance to positive emotional state. This shift will have an effect on the performance.
What the above comment shows is that although the Cogmed training program may have a positive effect on inattention in daily life and this effect appears to be independent on the status of the participant, there are many areas by which the improvement may occur. Hence, methods more specific for particular areas or a combination of methods may lead to a higher improvement level.
Since we`re talking about the topic ……..
….can it be assumed that caffeine which increases alertness and consolidation of memory, or other stimulants if administered shortly before each participation in the training program would have a noticeable effect on performance?
…..would an administration of the NMDA antagonist, ketamine, known to impair ability to ignore task irrelevant information in a task switch (Stoets) remove all performance improvement? Similarly, would the administration of the NMDA antagonist, dizalipine, known to impair working memory also have profound effects and remove any improvement in performance attained from the full Cogmed program?
….would meta-analyses of other training programs show the same result trend as Cogmed or would investigation of specific cognitive areas provide more information as to where the training programs effects actually lie?
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