A Limitless Working Memory
A.Jeeninga, I6065404, 2017
Abstract
For some years, researchers have tried to enhance ones cognition. Improvement in cognition can be very beneficial for several reasons. Especially working memory has been the subject of enhancement since it is one of the most significant cognitive functions used at many different levels. Several methods have been used to reach this enhancement, three of them are very commonly used; rtfMRI neurofeedback, Transcranial Magnetic Stimulation, and Smart-drugs. This paper reviews two studies done with each of these three methods and compares them to one another in terms of safety, convenience, and results. rtfMRI shows no side-effects, TMS also works relatively long-term, and Smart-drugs are the most convenient. It is concluded that neurofeedback and TMS are very promising compared to the dangers of Smart-drugs, but more research is needed for long-term effects so that enhancement is possible without the machinery required for rtfMRI neurofeedback and TMS.
Introduction
Your working memory (WM), which is a core executive function, is established to play a significant role in your life. The term working memory was used for the first time in the 1960’s by George A. Miller, Eugene Galanter, and Karl H. Pribram who made a theory around working memory figuring that the mind worked like a computer. And it became famous because of the homonymic model of Alan Baddeley and Graham Hitch (Baddeley et al., 1974). Many theories followed and now your working memory is known as a cognitive system with a limited capacity, the most important component is attention, and it is responsible for the holding, processing and, manipulation of incoming information. It uses information from your long-term memory and interconnects strongly with your short-term memory. The specific relationship between working memory and short term memory remains relatively unclear but it is known that the interaction between the two is of great significance and some models even consider the two as the same. In a way, your working memory might be considered as the lead actor of your skills, planning capacities, academic performance, contribution to society; your life (Aben et al., 2012).
An impaired working memory leads to several mild to severe difficulties concerning all your cognitions. Research has highlighted the importance of your working memory by showing the difficulties and deficiencies patients, with an impaired working memory, have, and the effects of it on their daily lives. From 2006 – 2009 working memory in patients who suffered from a stroke was researched and it was found that working memory is very closely related to attention and that stroke-induced deficits in working memory and attention are often very severe and result in impairments to vocational performance and social functioning (Westerberg et al., 2009). Major Depressive Disorder (MDD) is, besides a declining of life-quality, also associated with cognitive deficits and these attribute to a dysfunction of the central executive component of your working memory (Channon et al., 1993). Also schizophrenia patients show widespread deficits in cognitive functions including working memory (Light et al., 2005). Impairments like these, among others, highlight the importance of a normal functioning working memory which lead to research to find solutions for a ‘broken’ working memory.
A wide range of different methods varying from medication to non-invasive brain stimulation (NIBS), have been used to improve badly functioning executive functions and cognitions which include working memory and attention, and most of them had positive outcomes. These successes raised the question what those methods would do to a normal functioning working memory and what the benefits could be. An important part of current research is to find ‘cures’ for an impaired working memory, whereas other research is aimed at investigating if those methods also improve a working memory that is already working correctly. Can those methods enhance a normal functioning executive function? Cognitive enhancement has been researched and is figured to give a helping hand in, mainly, occupations where professionals can benefit from enhanced cognitions. For example, surgeons make long days, work in shifts and surgeries can continue for hours, therefore an enhanced ability to concentrate would be very advantageous (Warren et al., 2009).
Research done to enhance cognitions has shown that the same methods used for fixing the impaired can also have an effect of enhancing what is not broken. The different methods, Smart-drugs/drugs, real-time fMRI neurofeedback, and Transcranial Magnetic Stimulation (TMS), discussed in this review have shown significant effects and some can even be relatively easily used. But they differ in invasiveness, duration, side-effects, and training-methods. (Smart-)Drugs can pretty much be used at any time, for example before important academic or occupational challenges. While you need a TMS-machine or an MRI-machine for the other methods, and are, therefore, more difficult to get by. (Smart-)Drugs, however, almost always go hand in hand with, sometimes severe, side-effects, withdrawal-effects, or addiction (Partridge et al., 2011). Whereas in the 40 years of neurofeedback, no side-effects or damages have been reported.
It remains unclear whether you can train your brain in such a way that you eventually do not need the fMRI-machine and feedback-system anymore to enhance a cognition, if this is the case, the surgery-example would not define neurofeedback (or TMS) as useful, compared to Smart-drugs. Is there evidence that effects can be made ‘permanent’ or do all effects eventually fade away? I hypothesize that the results of cognitive enhancement, especially for working memory and attention, do not outweigh the effort or the side-effects of the method for the enhancement will have faded away after longer periods of time while reviewing research done with the mentioned methods and healthy participant population.
Neurofeedback
Real-time fMRI neurofeedback is one of the most promising methods for training your brain. In RTfMRI neurofeedback training, the region of interest (ROI) is localized while doing a task inside the fMRI scanner that specifies for that brain area (deCharms et al., 2005). Once the ROI is determined, the participant, while inside the fMRI, views a computer screen with a moving image of, for example, a thermometer which can increase and decrease in temperature, and the participant is asked to upregulate the activity in his or her ROI. The thermometer then shows if it is successful or not. Participants up- or downregulate the activity in their ROI in a personal way, which are usually positive or negative thoughts. Neurofeedback is one of the safest methods for exercising your brain, it is non-invasive, and has little to no side-effects which is why it is considered to be a perfect method for training regions of the brain, which may lead to cognitive enhancement.
A step in improving the performance of working memory (WM) was taken when the information flow from WM to other brain regions found a lot of evidence for the dorsolateral prefrontal cortex (DLPFC) playing a crucial role in these executive control processes (Zhang et al., 2013). It was determined as the ROI in the following study from Zhang et al., in 2013. The entire experimental procedure consisted of two rtfMRI neurofeedback training sessions between pre- and post-behavioural tests. Thirty healthy participants (male and female), with a mean age of 21.67, were randomly assigned to either the experimental group or the control group. Before the experiment the DLPFC was localized for each participant. During the experiment the difference in BOLD-levels were measured as feedback signal, a graduated thermometer with increasing and decreasing bars was used as visual feedback image.
Three different types of behavioural tasks were completed as the pre- and post-test. The digit-span task measured short-term storage and manipulation of verbal information, the letter-memory task measured maintenance and manipulation of the updating of verbal information, and the spatial 3-back task and colour-word Stroop-task were assessed to monitor visuospatial information and the inhibition of conflict. Figure 1 shows a clear set-up of the experiment.
Figure 1. (Figure 1 in Zhang et al., 2013)
The results of the experiment showed that the activation of the left-DLPFC was positively correlated with the number of correct hits and negatively correlated with the reaction time of corrected hits. The comparison between the experimental and control group showed a stronger activation in the following regions: bilateral DLPFC, PPC and left middle occipital gyrus (MOG), in the experimental group. The between group analysis showed an significant increase in digit-span in the experimental group versus the control group. The letter-memory task showed a significant increase in correct response for the experimental group between the first pre-test and the second post-test. The 3-back task and Stroop task also showed an significant improvement from first pre-test and second post-test. For the last two tasks no significant difference was found between groups.
The results of the experiment showed improvements for all three behavioural tasks for the experimental groups after the neurofeedback training sessions, but only a between group difference was found for the digit-span task. This indicates that the training sessions do have an effect on the executive control processes of the WM for the experimental group, but this alone effect is not enough to get significant between-group results. The experiment did indicate the importance of the DLPFC in WM. The up- and downregulation of the activity in the DLPFC was only visible during the course of the experiment, there were no long-term effects found. This could indicate that there are more training sessions needed for a prolonged enhancement of the WM, but the enhancement is possible.
Previous experiments done in cognitive enhancement upregulated activity in localized regions of interest, however most executive processing requires the functional integration of interconnected networks instead of activity solely in one region. The complex system of WM requires such connectivity, hence, can upregulating the activity within these connections result in an enhanced WM. In an experiment from 2013 it was tested if it is possible to acquire feedback information based on these connections using a visual-spatial attention paradigm (Koush et al., 2013).
The approach that was used differed from normal functional MRI data, they used a hypothesis driven approach in fMRI, namely, dynamic causal modelling (DCM). DCM defines hypotheses about neural mechanisms underlying a fMRI measurement in terms of ROIs, the connections between these ROIs, the external inputs into this network, and the context dependent manipulations of this network. Measures like DCM for neurofeedback have led to insight in the possibility to learn voluntary control over functional brain networks instead of single ROIs (Koush et al., 2013).
Thirteen healthy volunteers, with a mean age of 27,2, participated in the experiment from which six performed only localizer runs and seven performed in the actual experiment. Before the neurofeedback sessions, each participant underwent localizer runs to localize the left and right early visual cortex (VC), and the left and right superior parietal lobule (SPL). Within the neurofeedback sessions it was tested if the participants were able to voluntary control the feedback signal while shifting their visual-spatial attention. Each session consisted of eight trials, each trial consisted of 5 baseline blocks in-between either 4 block attention to the right (aR) or to the left (aL). The direction of the attention was indicated with low contrast dashed circles. Participants had to try to upregulate or downregulate their activity, the feedback signal consisted of the words UP, in red, for aL trials, and DOWN, in blue, for the aR trials. The DCM method makes it possible that the neuronal dynamics, the connectivity between regions, is translated into BOLD-signals instead of the activity of the region itself. This connectivity is the shifted attention indicating the activity of a network related to WM.
All participants were able to control the connectivity based feedback signal, and the feedback signal was in all trails significantly greater than zero. The processing speed of the attention-shifts thus increased for each participant, which could lead to an enhancement of the attention-part of WM. This experiment indicates that it is not only possible to voluntarily control activation within brain regions, but also to voluntarily up- or down-regulate the activity in the connections between brain areas. This gives new insight into future research since a connected network is one of the most important aspects of a functioning WM, and other cognitive functions.
There were no long-term results found in the experiment. Performing attentional tasks without the feedback signal did not lead to significant results of improved attention or increased processing speed.
Transcranial Magnetic Stimulation
Transcranial magnetic stimulation (TMS), introduced approximately 20 years ago, is a non-invasive brain stimulation (nibs) method of electromagnetic induction. A large magnet is held against the skull and induces a pulse which revives electricity in the brain, which activates neurons. In studies it is primarily used to either stimulate or disrupt a ROI. Although it is a non-invasive method, it can evoke side-effects, contrary to neurofeedback, TMS can lead to headaches, an irritated scalp, and, with pulses of high intensity, evoke an epileptic insult. The latter occurs mostly with patients who suffer from epilepsy, or use certain medications.
The DLPFC was established as a crucial structure of the processing of WM, in 2016 the excitability of neurons within the DLPFC was modulated with TMS to enhance WM (Bagherzadeh et al.,2016). The effects of TMS showed already positive results in patients who suffer from depression or schizophrenia within multiple studies (Levkovitz et al., 2011 and Lee et al., 2005). The effects of TMS are investigated within the healthy population. This experiment stimulates the left-DLPFC of healthy volunteers with high-frequency repetitive TMS while the participants had to perform a series of cognitive tasks (Bagherzadeh et al., 2016).
Thirty healthy participants, with a mean age of 36,8, volunteered for the experiment and all had no prior experience whatsoever with TMS. The participants were randomly assigned to either the active TMS-group (15 participants) or the sham TMS-group. The experiment consisted of the three following phases; first the participants had to perform behavioural tasks to establish a baseline, then all participants received TMS sessions (either actively or sham) different days over the course of two weeks, and finally the behavioural tasks had to be performed again 5 days after the last TMS-session. The difference between the active TMS group and the sham TMS group was measured. Figure 2 shows the set-up of the experiment (2A), and the behavioural tasks that were used (2B).
Figure 2. (Figure 1 in Bagherzadeh et al., 2016)
The digit-span task measures the capacity of the verbal short-term memory, The 2-back task evaluated storage and executive processes, including selective maintenance, monitoring, and updating of spatial information in WM (Owen et al., 2005), the delayed match-to-sample task tests the visual domain of memory and decision-making, the pattern recognition memory task tests abstract visual pattern recognition, the spatial recognition memory task is a 2-choice test of spatial recognition memory, the spatial span task tests the ability to remember visual stimuli, and the stockings of Cambridge task measures the executive function, spatial abilities, and strategic planning.
For all tasks they tested on accuracy and the reduction of latencies. The results showed that, for nearly all tasks, the performance of the participants improved after receiving TMS-intervention. Then, these outcomes were used to see which of the tasks gave a significant improvement of WM. Only two tasks gave corrected significant results after TMS-intervention, the digit span task and the spatial 2 back task. This result is simultaneously promising and moderate. For two tasks, the activity in the left-DLPFC was stimulated enough to increase the performance, but for the remaining 5 tasks no significant results were found yet. This could indicate that, for example, the cognitive load between tasks differs too much to bring about significant results or that the intensity or duration of the TMS sessions needs to be adapted per task. The results do indicate some long-term effects since the behavioural tasks had to be performed again 5 days after the final TMS-session. The enhancement, thus, maintained at least 5 days after treatment in the tasks which gave the significant results.
The enhancement of WM after rTMS stimulation to the DLPFC was also researched with direct TMS (Preston et al., 2010). Instead of two weeks of TMS-interventions, the stimulation of the DLPFC happened 10 seconds before the participants had to perform a behavioural WM task. Thirty-four healthy participants volunteered for the experiment aged 18-50 and were divided into an active stimulation group and a sham group. The experiment consisted of four phases; the stimulus phase, the delay phase, the probe phase, and a response phase. In the stimulus phase a 5- or 7-item string of uppercase consonants and vowels was presented on a screen, this was followed by the delay phase were the participants had to fixate on a marker while remembering the items from the stimulus phase, in the probe phase a single uppercase letter appeared and the participants had to indicate whether this letter was also presented in the first string in the response phase by pressing a key. Figure 3 shows the experimental design with indications when the participants received rTMS pulses.
Figure 3. (Figure 1 in Preston et al., 2010)
The results of this experiment were analysed from thirty-two participants. Two participants, who were in the active stimulation group, were unable to complete the study due to spontaneous arising headaches. In both cases, the headaches resolved after a few hours. For the remaining participants, a mean decrease in reaction times of approximately 219ms was found compared to pre-stimulation baseline in the active TMS group. In the sham TMS group, results showed a mean increase in reaction times of 30ms compared to their baseline. The experiment was performed on one day, it is unknown if there were any long-term effects found of the TMS stimulation.
The results of this experiment do show an improvement in performance in the group who received active TMS stimulation, and surprisingly a deterioration in the sham group. The latter could indicate that, for example, the sound of the TMS machine distracted the participants from performing the same as before the sham stimulation. In the active stimulation group the results indicate that the TMS pulses did increase the activity mainly in the left-DLPFC and its connections, more neurons in this region had an increased excitability which lead to an improved performance on the WM task. Contrary to neurofeedback, this TMS experiment showed some minor side-effects with two participants who, on that account, had to opt out of the experiment.
Smart-drugs
The term Smart-drugs or nootropics has become a vague understanding over the last years. At first, smart-drugs were seen as pharmaceutical products to improve your cognitive functions such as γ-Hydroxybutyric acid (GHB) or 4-methyl methcathinone (mephedrone or 4-MMC). Because of sever side-effects and addiction-risks products like these were made illegal. Recently, it took the other direction and the term smart-drugs went from very severe to, overreacted since currently coffee (caffeine) and candy (sugar) are considered as smart-drugs.
Over the last few years, society has become more and more competitive, especially among students and people with occupations with a high cognitive load, primarily for WM. Those people seized the opportunity to try a new category of smart-drugs to keep up with their always faster ongoing lives. This category of smart-drugs is a category in which the drugs are actually medications for people who suffer from a mental disorder, such as ADHD, narcolepsy, or sleep-disorders. For the people who suffer from such disorders, medications like these should bring the too high or too low level of corresponding neurotransmitter release back to normal. For healthy people these medications tend to bring the level of neurotransmitter release to a higher, enhanced level, which helps them concentrate more, stay awake longer, or get through working different shifts better.
A lot of research have been done to test the effect of smart drugs in healthy volunteers, especially because of the addiction-risk and possible side-effects which you do not or minimally have in NIBS or neurofeedback.
One of the most familiar smart-drugs, mostly used among students, is methylphenidate (MPH) or Ritalin, which is normally used to control the dopamine levels in ADHD-patients.
In ADHD-patients, methylphenidate controls the release and reuptake of dopamine which makes the patient calmer, he or she can concentrate better, and does not get distracted so easily. For healthy adults, methylphenidate tends to enhance their ability to concentrate (Husain et al., 2011). An experiment conducted in 2012 with fourty healthy women with a mean age of 23 years tested the effects of methylphenidate on decision making and strategic planning, both cognitive functions in which WM plays a significant role (Campbell-Meiklejohn et al., 2012). Twenty women assigned to a placebo groups, the other twenty women were assigned to the methylphenidate (2×10 mg) group. The participants received the placebo or methylphenidate one and a half hour before the behavioural test.
The participants had to perform the ‘loss-chasing task’. All participants started the task with a fictional amount of 192.000 Danish kroner (± €26.000), the main goal of the game was to lose the least amount of money. The game has 30 rounds and each round consist of one to six trials. In the first trial of a round, an amount of money appeared on the screen below two options ‘quit’ or ‘play’ from which the participants had to choose one. The amount of money that appeared is the amount the participant could either lose or win during that trial. Participants started with an amount they lost, they could accept that loss and press ‘quit’, or they could try and recover that loss when the next ‘double-or-nothing’ option appeared and press ‘play’. The chance of a win was set at 15% of all trials. Participants could lose up to a maximum of 6400 kroner, then a next round would start, or a next round would start when the participant chose the ‘quit’ option. The total amount lost during one round would then be subtracted from the total 192.000 kroner. The game requires undivided attention throughout. Figure 4 shows a visual description of the game.
Figure 4. (Figure 1 in Campbell-Meiklejohn et al., 2012)
The results from this experiment were analysed from 37 participants. Two participants, who were both in the methylphenidate group, were prematurely excluded from the experiment because of spontaneous severe headaches. One participant, also from the methylphenidate group, was excluded because of an outlier-score. The results were divided into different categories; the choice to continue gambling, the effect of the stake (the amount of money which appeared on the screen), the effect of continuous losses, responsiveness to rewards, and consideration time. The categories stake-effect, continuous-losses effect, and responsiveness to reward effect found significant between-group results. The methylphenidate group continued to gamble more even when the amount of money kept rising compared to the placebo group. The placebo group stopped gambling after many losses in a row, the methylphenidate group continued also when losses increased. Within the methylphenidate group there was a significant interaction found between responsiveness to rewards which was associated with a decreased influence of stake magnitude on choice.
The results show us that methylphenidate does have an effect on decision making and strategy planning however in this experiment not in a positive way. Instead of enhancing the ability to concentrate and controlling your attention, the categories which had significant results show that the methylphenidate group failed to inhibit their risky behaviour compared to the control group. This finding does give a new insight in risky behaviour and decision making.
Another commonly known smart-drug is modafinil, which is mostly used in sleep-disorders of tiredness or fatigue because it promotes wakefulness. As a smart-drug it is mostly used among people who travel a lot and suffer from jet-lags, or people with a profession with long and/or irregular shifts. In 2013 the effects of modafinil were tested on healthy volunteers who had to perform cognitive tasks related to WM and creativity (Müller et al., 2013). Sixty-four healthy participants aged 19-36 signed up for the experiment and were divided in a modafinil group and a Placebo group.
A single dose of 200 mg modafinil or placebo was given to every participant 2 hours before the had to perform on behavioural tasks. Beforehand, the participants completed a series of behavioural tasks which resembled the actual tasks. Six behavioural tasks had to be performed by the participants after modafinil or placebo intake; the 12-pattern task, pattern recognition memory task, digit span task, the tower of London, spatial planning task, and spatial working memory task. Results were analysed over all 64 participants, there were almost no complications or side-effects found within the modafinil group, and the modafinil was overall well tolerated. One participant complained of headaches at the end of the testing sessions.
Significant effects of modafinil were found in only the difficult stages of the spatial working memory (SWM), ‘one-touch’ Stockings of Cambridge (SOC) and delayed visual pattern recognition memory (PRM) tasks. These tasks showed an improvement of the modafinil group compared to the placebo group and compared to the results of the pre-tests. The remaining tasks showed no significant effects or improvements within the modafinil group compared to the placebo group. Task motivation was also measured and it was found that the modafinil group found completing the tasks more pleasurable at first, but as the tasks continued the difference in task motivation between modafinil and placebo faded away.
The results of this study show that a single dose of modafinil can improve concentration on cognitive tasks related to WM. This experiment found little to no side-effects with a single dose and one-time use. The short delay of 2 hours which it takes modafinil to reach its peak is an ideal situation for students, for example, who are taking exams, or the surgeon who has to prepare for a difficult procedure. Actual long-term effects have not been reported in this study. Effects of higher dose or long-term use or over-excessive use are also unknown.
Discussion
Neurofeedback is considered as one of the most promising methods for enhancing WM due to the lack of side-effects. In 2013, Zhang et al., tried to improve the performance of the WM with rtfMRI neurofeedback training sessions. The DLPFC was determined as ROI because of its great significance in the process of WM. Participants performed a behavioural pre-test, received two neurofeedback sessions, and performed on a behavioural post-test. Their results of the post-test were compared with the results of the pre-test and with the results of a control-group. In the neurofeedback sessions participants were asked to deliberately upregulate the activity in their DLPFC and results showed that the participants in the experimental group did managed to upregulate that activity, and performance improved on their post-test and compared with controls. The neurofeedback sessions allowed the participants in the experimental group to enhance their WM, although both the neurofeedback sessions and the pre- and post-tests were carried out on the same day, no conclusions can be made on long-term effects.
Your working memory is not located in one particular brain region, it is a network of connecting brain regions who interact with one another. Koush et al., therefore tested if it was also possible to enhance WM by training these connections instead of one brain region with neurofeedback sessions. Thirteen volunteers participated in the experiment and were divided in an experimental and a control group. The results show that it ,in fact is possible to upregulate or downregulate the activity in connecting brain networks. The processing speed increased for each participant in the experimental group which makes the enhancement of WM possible. This experiment, however, also does not contains information about long-term results.
The second method was Transcranial Magnetic Stimulation (TMS), which consisted of experiments where the participants received electric stimulation to one brain region, the DLPFC. Bagherzedah et al., tried to enhance WM by exciting the neurons within the DLPFC. Thirty participants were assigned to either an active TMS group or a sham group. This experiments highlights the long-term effects of the method since the post-test was two weeks after the pre-test, within those two weeks the participants received TMS or sham stimulation on random days, the last one five days before the post-test. The results showed that the active TMS group improved an all tasks, two of them were also significant. For these two tasks the experimenters succeeded in stimulating the neurons in the DLPFC enough to improve performance after 5 days. Enhancement of the WM is possible via TMS and long-term effects are taken into account.
The short-term effects of TMS were researched by Preston et al., who conducted participants TMS stimulation 10 seconds before they had to perform a behavioural task. The thirty-four participants were divided into an experimental or a control group. Two participants were excluded from the experiment because of headaches, both participants were in the experimental group. The results for the other participants in the experimental group showed a decrease in their reaction times compared to the control group. The experimental group did show an enhancement of WM, no long-term effects were tested.
The third method, is considered as the most less-promising method because of its risks. Medications are used as smart-drugs to reach cognitive enhancement. Campell-Meiklejohn et al., took one of the most used smart drugs to the test. Fourty women were divided into either a placebo group or a methylphenidate group. the participants had to perform a complicated gambling task which challenged their WM and between-group results were compared. Two participants were excluded from the experiment because of severe headaches, both were in the methylphenidate group. Another participants from the methylphenidate group was excluded because of outlier-results. The remaining results did not show an enhanced working memory but an increase in risky decision making. Also, no long-term effects were measured.
Müller et al., tested if modafinil can enhance WM. Sixty-four participants were divided into either a placebo or modafinil group. The behaviour tasks that had to be performed consisted of multiple stages and the results showed that the modafinil group did improve, but only on the more difficult stages of the task. This could mean that WM-enhancement is possible with the intake of modafinil but that it is only significantly visible when the cognitive load increases. The modafinil group also subjectively enjoyed task-completion more compared to the placebo group, but only at the beginning of each task. This could be an indication that the reward-system of the brain is also altered by the intake of modafinil, but this also eventually fades away. No long-term effect was found within this study.
It is established that all methods described above require more research, especially to find out the long-term effects. None of the experiment integrated a post-test a few days or weeks after the experiment. It therefore remains unclear if any of the methods are suitable for use in society. The preference, however, goes out to neurofeedback. As mentioned, it exists for fourty years and no side-effects whatsoever have been reported over those fourty years. Because neurofeedback does not utilise anything other than the human brain to obtain this enhancement, it might be considered as a gym for your brain. In a normal gym, you use equipment to train your muscles. Neurofeedback trains your brain-muscle to acquire this feedback signal with the help of an fMRI and a screen which provide this signal. As you can also exercise at home to train your muscles, without any equipment, the possibility needs to be researched if this is also possible with the brain. Can you train your brain enough to such a level where you eventually do not need the equipment anymore?
TMS on the other hand did show some long-term effects, namely the results from a behavioural test which was conducted five days after TMS-stimulation. We, because of that, know that TMS-stimulation can make alterations in the DLPFC which at least last up to five days, which is promising. But both experiments did not test after the experiment was over to investigate whether TMS can make the alterations in the brain permanent. Still, TMS does always carry along the possibility of side-effects which, in some cases, can cause someone to no longer be able to finish the goal for which they initially enhanced for.
Smart-drugs are the least favourable among researchers because the universal knowledge of addiction. All researches are conducted with individuals who have no history of addiction whatsoever yet for student who initially get ‘addicted’ to the higher grade they received after taking one innocent ‘smart-pill’, it can be very dangerous. The advantage of smart-drugs is the convenience, no equipment necessary, and that it can be measured exactly when the drug reaches its peak.
Conclusion
The possibility of cognitive enhancement has been explored by many researchers over the past few years. The cognitive function working memory is one of the most experimented cognitive functions when it comes to enhancing. The benefits of an enhanced working memory go beyond individuals such as the student or the surgeon. Some ponder that an enhanced WM supports the greater good and that it can also be beneficial for, for example, government agencies. Therefore, it is of great importance that a suitable method is used for enhancement of your working memory, one of the most important and complex networks in the brain. Neurofeedback is the safest, TMS shows evidence for long-term effects, and smart-drugs are the most convenient. This indicates that further research is needed to establish if it is beneficial enough to enhance your working memory considering the defaults that exist till present-day.
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