Enhancing Virtues: Intelligence (Part 2)
J. Hughes
Published by the IEET on 2014–09–10
Social Change for Cognitive Enhancement
Flynn Effect While there are powerful genetic constraints on our intellectual abilities we know that there are many environmental and behavioral factors that can encourage and discourage the development of intellectual abilities. For instance we know that people around the world have become more intelligent over the last century for entirely environmental reasons. In the 1980s, New Zealand political scientist James Flynn began to look at the questions used in intelligence tests in industrialized countries. The tests had changed, but the distribution of IQ hadn’t since an IQ of 100 is by definition the average intelligence for a given population.
But was today’s 100 the same as last year’s? Flynn found that IQ tests have been getting harder, and that intelligence has been rising by about three points per decade.[1] People who would have been in the top 10th percentile of intelligence a hundred years ago would today be among the 5% least intelligent people in the population. Compared to the previous generation, the number of people who score high enough to be classified as a “genius” has increased more than 20 times. The “Flynn effect” has now been documented in dozens of countries, and it is beginning to be observed in the developing world.
There is no widely accepted explanation for the Flynn effect, but the causes are entirely environmental. Improved nutrition has contributed since there is a well documented link between malnutrition and lower intelligence. The decline in violence has reduced the stressors on children’s cognitive development. The percent of the population that can read has increased rapidly around the world, as has earlier, better and more widespread mandatory education. As family sizes shrank each child received more attention. As people moved from slow, culturally isolated farms to fast, complex cities their brains were stimulated. Especially stimulating was greater exposure to all kinds of media, including books, magazines, radio, television and the Internet. While none of these factors appears to explain the Flynn effect by itself, each appears to contribute something.
Poverty Reduction So a global effort at intelligence enhancement would start with the obvious social policy targets of reducing poverty, illiteracy, malnutrition, disease, violence and inequality, all of which impair cognitive abilities.[2] Improvments in women’s education has a double benefit since it also reduces family size, improving the attention and resources children get and the quality of their care. Even when inequality does not reduce material resources or access to education, it introduces stressors such as “stereotype threat” that impair the cognitive ability and test performance of the poor,[3] women and ethnic minorities.[4]
Improvements in cognition in return tend to support the rule of law, economic growth, democratic and accountable institutions, and support for policies that reduce inequality. In one study the average level of a nation’s cognitive ability was correlated with GDP and economic growth, the rule of law, more economic equality, smaller families, lower rates of murder and higher rates of solved murders.[5]
Increasing Literacy and Improving Pedagogical Methods There is some evidence that quality and length of education improves at least crystallized intelligence, if not fluid intelligence. Early childhood education from prekindergarten through first grade, has an effect on cognition and academic achievement through the college years.[6] But information technology and artificial intelligence now allow us to move beyond the industrial model of education that developed a century ago to more personalized and adaptive curricula, and life-long learning tools, that will hopefully identify and develop our fullest natural capacities throughout the life course.
Brain-Healthy Lifestyle and Practices
Belief in Neuroplasticity Unfortunately reading the previous essay on the genetic constraints on intelligence may have just impaired your intelligence. Research shows that groups that are told they can improve their cognitive performance improve their performance more than groups who are told that cognitive performance is largely genetic.[7] So we need to remind ourselves that there are a lot of lifestyle changes that we can make to improve our intelligence. In a paper titled “Towards a Smart Population: A Public Health Framework for Cognitive Enhancement” Lucke and Partridge[8] argue that the first and most impactful ways to enhance cognition are improvements in sleep, exercise, diet and reducing stress.
Sleep As a result of spread of electricity and the distractions of modern life many of us do not get adequate sleep, and lack of sleep has an immediate impact on reaction time, working memory and other intellectual abilities. We need at least six hours of sleep to consolidate learning from the previous day, and short naps before tests improve performance.[9]
Exercise Similarly, as we migrated from the savannah to the farm to the factory and finally to our mostly sedentary modern lives, we get much less exercise than we need for physical and cognitive health. Physical exercise improves cognition by improving cardiovascular health and boosting the amount of neural growth factor in the brain (brain-derived neurotrophic factor or BDNF) [10] [11] Exercise programs have been shown to improve performance on cognitive tests for both young and old.[12] [13] [14] Twenty to thirty minutes of aerobic exercise improves self-regulation and performance in reading and math for children with ADHD. [15] [16]
Brain Foods As to diet there is plenty of evidence that some things we eat can harm intelligence, but the evidence for actual brain foods is still thin. Environmental toxins from lead to pesticides have been found to have a widespread effect on impairing intelligence.[17] Obesity is correlated with low intelligence, but that appears to be mostly because those with more self-control and intelligence are less likely to get fat [18], so that weight loss has little impact on cognitive ability. The jury is also still out on whether calorie restriction or short-term fasting[19] are good for cognition.
The evidence is good that a Mediterranean diet rich in plants, olive oil, yogurt and fish, slows cognitive decline in old age and reduces the risk of dementia.[20] [21] Unfortunately, while there is good evidence that omega-3s from fish and other foods are good for cognition,[22] we still don’t understand which other aspects of the Mediterranean diet provide cognitive benefits. It doesn’t seem to be the antioxidant content of the diet for instance. Foods high in antioxidants and antioxidant supplements do nothing for cognition.[23] [24] [25] [26] [27]
Activities that Build Cognitive Reserve One idea that has gained support is that a lifetime of intellectual engagement strengthens our neural architecture and builds a “cognitive reserve” that slows cognitive decline in old age.[28] The amount of education you acquire reduces your lifetime risk of developing dementia, and slows its progression.[29] People who read a lot, stay engaged in recreational activities, learn a musical instrument, or learn more than one language perform better on cognition tests throughout their life, and develop dementia more slowly.[30] [31] [32] [33] Teaching is especially beneficial; learning something with the expectation that you will be teaching others improves memory of the material.[34]
Socializing The benefits from socializing appear to complement the benefits of solitary cognitively demanding activites.[35] In one experiment seniors were taught either digital photography or quilting, or both, and practiced these hobbies for three months, while control groups either socialized or practiced less cognitively demanding hobbies by themselves. After three months all five groups had seen some improvements in working memory, with the biggest gains in the digital photography group. But surprisingly the group that just socialized had improved in speed of thought and “mental control” more than the photography or quilting groups.
Mindfulness Meditation In a previous essay we reviewed the evidence for benefits to executive function from meditation, and those functions are also important to intelligence and cognition in general. One of the features of high IQ is the ability to focus on important information and ignore irrelevant information,[36] and mindfulness meditation helps train this ability.[37] Mindfulness meditation improves memory capacity and performance on tests, [38] and introduces more thoughtful deliberation into decision-making, reducing the influence of cognitive biases. [39] [40] [41] I’ll talk more about the importance of learning to recognize one’s own cognitive biases in the next essay on fairness.
Multitasking and Brain Games I am a chronic multitasker, which is embarrassing since the research shows that for most of us multi-tasking and digital distraction significantly impair attention, memory and performance. Multitasking is a form of attention deficit disorder, motivated by the brain’s search for dopamine hits, Of course I assume that I am among the few who can successfully multitask, but the research also shows that people who think they do it well are generally performing significantly worse.[42] In the last year I have at least learned to only have my email open five minutes per hour.
Help for multitaskers may be on the way however. About five percent of people are capable of multitasking, people with superior executive control and working memory. With targeted brain games and neurofeedback these cognitive skills can be trained. A lot of games and puzzles — sudoku, crosswords, scrabble — only train your brain to do that particular task better, and even then the improvements don’t last long.[43] But some forms of brain training are being found to have persistent benefits across a number of cognitive abilities.
For instance n-back is a challenging memory training game that was invented in the 1950s. It presents you with a series of letters, numbers, colors and sounds, and asks you to remember them well enough to match them several steps ahead. It exercises many parts of the brain[44] and recent meta-analyses of twenty three studies found that it had a small positive effect on improving working memory[45] and fluid intelligence.[46] Other programs are looking at targeting the games at improving core cognitive abilities, or combining physical exercise with brain training games[47] and environmental enrichment[48] which also seems to have a promising impact on improving general cognitive functions.
The Exocortex and Collective Intelligence Whether games turn out to be a powerful way to broadly improve intellectual abilities it is clear that we are all now orders of magnitude smarter as a consequence of information technology. We carry around devices that allow us to store more information than anyone could possibly remember, and to access the rapidly growing body of human knowledge with a few clicks. The mining of consumer behavior data by firms like Netflix, Amazon and Facebook allow to discover films, books and news that we otherwise would never have seen. Wearable interfaces like Google Glass, and virtual assistants like Google Now and Siri, will become increasingly miniaturized, inconspicuous and contextually helpful, giving us information we may not even know that we need. A large amount of effort is being put into online and computerized forms of education, validated with concrete learning outcomes, that will undoubtedly clarify which types of exercises do improve real-world decision-making skills. These will all start as part of our wearable exocortical assistants and ubiquitous computing environment, then be integrated with “augmented cognition” devices that finetune our attentiveness and learning, and then be integrated into the brain-machine interfaces to come.
Pharmaceutical Cognitive Enhancement
The potential for intelligence enhancement globally through poverty reduction and improved pedagogies are still enormous, and in the developed countries most of us can substantially improve our cognitive faculties with lifestyle changes. But our capacity to improve intelligence simply through environmental enrichment and behavioral change may be reaching its limits. We see for instance that among affluent families in industrialized countries inherited genetic differences in brain structure and neurochemistry is a much stronger predictor of intelligence than among the poor.[49]
In other words, the enrichment differences among poor families are holding many kids back from developing their full potentials as adults, while most affluent kids are nurtured and stimulated to achieve much most of their full, innate intellectual potentials, whatever those may be. If this is the case, further improvement in intellectual capacities for those in enriched environments will largely depend on the use of drugs and technology to tweak neurology.
Caffeine, Coca and Qat Stimulants of various sorts have been in use for thousands of years, and specifically have been used to enhance intellectual activity and moral self-control. The drinking of tea has a long tradition in Chinese culture, which celebrated its reputed beneficial effects for scholarly work and meditation. Confucius edicts say “Tea tempers the spirits and harmonizes the mind, dispels lassitude and relieves fatigue, awakens thought and prevents drowsiness, lightens or refreshes the body, and clears the perceptive faculties.” Buddhist monks were forbidden intoxicants, but drank a lot of tea to keep awake for meditation and rituals. The Japanese Zen tradition developed a tea ceremony which makes the making and drinking of tea itself into a meditation.
Evidence points to the widespread chewing of coca leaves (the source of cocaine) in the Andes as far back as 8000 years ago, where it was believed to be of divine origin. Similarly Egyptians, Ethiopians and Yemenis have been chewing the stimulant qat plant for thousands of years, and in ancient Egypt it was believed to be an ingredient in a ritual to make the user into a god.
Coffee and coffeehouses have a long tradition in Arab and Turkish culture where they were hubs for entertainment and conversation, and were referred to as “schools of the wise.” Sufis drank coffee to stay awake during their dervish devotions, and Pope John Paul II beatified the 17th century Franciscan friar that invented cappuccino.
Before the introduction of coffee, tea and chocolate into Europe the average European drank alcohol from morning until night. In the 17th and 18th centuries the coffeehouses became exciting hotbeds of learning, debate and reading, so that they were called “penny universities,” since a cup of coffee cost a penny. In sharp contrast to the pacifying debauchery of the alehouses, coffeehouses were the key vector for the spread of Enlightenment ideas of reason, democracy and human rights, so much so that they came under political attack from monarchists.
Clinical research supports the cognitive benefits from caffeine. Caffeine improves attention, executive control, working memory and learning.[50] [51] [52] Taking caffeine right before a fifteen to twenty minute nap provides even more alertness than either the nap or the caffeine by themselves. The trick is to fall asleep quickly since the caffeine kicks in after about twenty minutes.[53]
Coffee and tea also appear to have a long term benefit of protecting the brain from age-related cognitive decline. Consumption of caffeine, especially coffee,[54] is associated with lower risks of developing Alzheimers disease[55] [56] and Parkinson’s disease.[57] Drinking tea is associated with a lower risk of stroke.[58]
Some critics assert that the only benefit we get from caffeine once we acclimate to it is to prevent caffeine withdrawal.[59] This turns out not to be the case; even after the brain adapts we still get cognitive benefits that aren’t withdrawal related.[60] [61] The problem with caffeine and other stimulants is that their benefits for cognition are U shaped, and wear off for the habitual user.[62] Caffeine in moderation has a temporary benefit for attention and speed, but too much degrades performance.
Nicotine Of course smoking tobacco does not enhance cognition long-term, and is a risk factor for cognitive decline. But nicotine by itself has long been known to have stimulant effects, and to boost memory, learning and attention. Now nicotine, and drugs that effect nicotine receptors in the brain (α4 and α7 agonists), are being investigated as cognitive enhancement therapies for people with schizophrenia[63], Alzheimers disease and ADHD. [64]
Methylphenidate and Modafinil The drugs methylphenidate and modafinil improve attention, learning and memory primarily by boosting dopamine. Methylphenidate has been shown to encourage brain maturation and the differentiation of neural stem cells, and to enhance synaptic plasticity.[65] [66] [67] Methylphenidate also boosts norepinephrine levels which helps to focus attention, while suppressing nerve transmissions in sensory pathways so that it is easier to block out extraneous stimuli.
Modafanil was originally developed as a treatment for narcolepsy, but is now prescribed for night-shift workers. It has been shown to be an effective treatment for some adults with ADD, and is displacing the use of amphetamines by the military. Modafanil has far fewer side effects than methylphenidate or Adderall, and an even lower addiction profile, but has many of the same benefits, such as reducing fatigue, and improving focus and working memory.
As with caffeine the benefits of methylphenidate (and other amphetamines) or modafinil for learning and memory are greater for those on the low end of those abilities than for those who are already perform in the top range cognitively.[68] [69]
Ampakines Ampakines are another class of non-stimulant drugs that have cognitive enhancement benefits by boosting neural transmission, neural growth factor (BDNF) and neural differentiation.[70] Intriguingly some of the cognitive enhancement effect from ampakines appear to be the result of its allowing the brain to recruit parts of itself for thinking and problem-solving that it does not usually use.[71]
Treatments for Downs and Dementia The development of therapies to treat Downs syndrome and dementia are one of the avenues for cognitive enhancement, both for those with those disorders and for the rest of us. Dramatic improvements in memory have been found in mice models of Downs treated with drugs that boosts the brain chemical GABA,[72] and there are trials proceeding on drugs to boost nerve growth and modulate half a dozen other neurological systems that may improve cognition.[73] So far two types of drugs have been developed that slow memory loss in dementia, cholinesterase inhibitors and NMDA receptor antagonists,[74] and these are also a potential target for cognitive enhancement in healthy people,[75] although a recent meta-analysis found little evidence that they improve health people’s memory.[76]
Of course, these drugs are effective for some people and not others. If you are already on the lucky end of the bell curve of neurochemistry boosting your dopamine or norepinephrine actually impairs your attention, memory and learning. Once the brain has been neurochemically optimized, achieving further cognitive enhancement may require more radical modifications with machines and genetic engineering.
References
[1] Nisbett RE, et al. Intelligence: New Findings and Theoretical Developments. American Psychologist. 2012; 67(2): 130–159.
[2] Hunt E. What Makes Nations Intelligent? Perspectives on Psychological Science. 2012; 7(3) 284–306.
[3] Mani A, Mullainathan S, Shafir E, Zhao J. Poverty Impedes Cognitive Function. Science. 2013; 341: 976–980.
[4] Nisbett RE, et al. 2012 ibid
[5] Rindermann H. Relevance of education and intelligence at the national level for the economic welfare of people. Intelligence. 2008; 36, 127–142.
[6] Nisbett RE et al. 2012 ibid
[7] Schroder HS, Moran TP, Donnellan MB, Moser JS. Mindset induction effects on cognitive control: A neurobehavioral investigation. Biological Psychology. 2014; 103: 27–37.
[8] Lucke J, Partridge B. Towards a Smart Population: A Public Health Framework for Cognitive Enhancement. Neuroethics. 2013; 6:419–427. DOI 10.1007/s12152–012–9167–3
[9] Dresler M, et al. Non-pharmacological cognitive enhancement. Neuropharmacology. 2013; 64: 529–543.
[10] Vaughn S, et al. The effects of multimodal exercise on cognitive and physical functioning and brain-derived neurotrophic factor in older women: a randomised controlled trial. Age and Ageing. 2014; 0: 1–6
[11] Dresler M, et al. 2013; ibid
[12] Tseng CN, Gau BS, Lou MF. The Effectiveness of Exercise on Improving Cognitive Function in Older People: A Systematic Review. Journal of Nursing Research. 2011; 19(2): 119–130.
[13] Voss MW, Nagamatsu LS, Liu-Ambrose T, Kramer AF. Exercise, brain, and cognition across the life span. J Appl Physiol. 2011; 111: 1505–1513.
[14] Bherer L, Erickson KI, Liu-Ambrose T. A Review of the Effects of Physical Activity and Exercise on Cognitive and Brain Functions in Older Adults. Journal of Aging Research. 2013; DOI: 10.1155/2013/657508
[15] Pontifex MB, et al. 2013; ibid
[16] Grassman V, et al. Possible Cognitive Benefits of Acute Physical Exercise in Children With ADHD: A Systematic Review. Journal of Attention Disorders. 2014; DOI: 1087054714526041
[17] Grandjean P, Landrigan PJ. Neurobehavioural effects of developmental toxicity. Lancet. 2014; 13: 330–338.
[18] Belsky DW, et al. Is Obesity Associated With a Decline in Intelligence Quotient During the First Half of the Life Course? American Journal of Epidemiology. 2013; 178(9): 1461–1468.
[19] Benau EM, et al. A systematic review of the effects of experimental fasting on cognition. Appetite. 2014; 77(1): 52–61.
[20] Lourida I, et al. Mediterranean Diet, Cognitive Function, and Dementia: A Systematic Review. Epidemiology. 2013; 24(4): 479–489. doi: 10.1097/EDE.0b013e3182944410
[21] Opie RS, Ralston RA, Walker KZ. Adherence to a Mediterranean-style diet can slow the rate of cognitive decline and decrease the risk of dementia: a systematic review. Nutrition and Dietetics. 2013; 70(3): 206–217.
[22] Luchtman DW, Song C. Cognitive enhancement by omega-3 fatty acids from childhood to old age: Findings from animal and clinical studies. Neuropharmacology. 2013; 64: 550–565.
[23] Crichton GE, Bryan J, Murphy K. Dietary Antioxidants, Cognitive Function and Dementia — A Systematic Review. Plant Foods Hum Nutr. 2013; 68:279–292.
[24] Devore EE, et al. The Association of Antioxidants and Cognition in the Nurses’ Health Study. American Journal of Epidemiology. 2013; 177(1): 33–41.
[25] Guallar E, et al. Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements. Ann Intern Med. 2013;159(12):850–851. doi:10.7326/0003–4819–159–12–201312170–00011
[26] Crichton GE, Bryan J, Murphy KJ. Dietary Antioxidants, Cognitive Function and Dementia — A Systematic Review. Plant Foods Hum Nutr. 2013; 68:279–292.
[27] Devore E, et al. Total antioxidant capacity of the diet and major neurologic outcomes in older adults. Neurology. 2013; 80(10: 904–910.
[28] Stern Y. Cognitive Reserve: Theory and Applications. 2013; Psychology Press.
[29] Beydoun MA, et al. Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis. BMC Public Health. 2014; 14: 643.
[30] Guzmán-Vélez E, Tranel D. Does Bilingualism Contribute to Cognitive Reserve? Cognitive and Neural Perspectives. Neuropsychology. 2014. doi: 10.1037/neu0000105
[31] Gold BT, et al. Lifelong Bilingualism Maintains Neural Efficiency for Cognitive Control in Aging. Journal of Neuroscience. 2013; 33(2): 387–396. doi: 10.1523/JNEUROSCI.3837–12.2013
[32] Brewster PWH, et al. Life Experience and Demographic Influences on Cognitive Function in Older Adults. Neuropsychology, 2014; DOI: 10.1037/neu0000098
[33] Gooding LF, et al. Musical Training and Late-Life Cognition. American Journal of Alzheimer’s Disease & Other Dementias. 2014; 29(4) 333–343.
[34] Nestojko JF, et al. Expecting to teach enhances learning and organization of knowledge in free recall of text passages. Memory & Cognition, 2014; DOI: 10.3758/s13421–014–0416-z
[35] Park DC, et al. The Impact of Sustained Engagement on Cognitive Function in Older Adults: The Synapse Project. Psychological Science. 2014; 25(1): 103–112.
[36] Melnick MD, et al. A Strong Interactive Link between Sensory Discriminations and Intelligence. Current Biology. 2013; 23: 1013–1017. http://dx.doi.org/10.1016/j.cub.2013.04.053
[37] Malinowski P. Neural mechanisms of attentional control in mindfulness meditation. Frontiers in Neuroscience. 2013; 7: 1–11.
[38] Mrzaek MD, et al. Mindfulness Training Improves Working Memory Capacity and GRE Performance While Reducing Mind Wandering. Psychological Science. 2013; DOI: 10.1177/0956797612459659
[39] Karelaia N. How Mindfulness Improves Decision-Making. Forbes. 2014. http://www.forbes.com/sites/insead/2014/08/05/how-mindfulness-improves-decision-making/
[40] Hafenbrack AG, et al. Debiasing the Mind Through Meditation: Mindfulness and the Sunk-Cost Bias. Psychological Science. 2014; 25(2): 369–376.
[41] Kirk U, Downar J, Montague PR. Interoception drives increased rational decision-making in meditators playing the ultimatum game. Frontiers in Neuroscience. 2011. 5(49): 1–11.
[42] Sanbonmatsu DM, Strayer DL, Medeiros-Ward N, Watson JM. Who Multi-Tasks and Why? Multi-Tasking Ability, Perceived Multi-Tasking Ability, Impulsivity, and Sensation Seeking. PLOS One. 2013; 8(1): e54402.
[43] Melby-Verlag M, Hulme C. Is Working Memory Training Effective? A Meta-Analytic Review. Developmental Psychology. 2012; 49(2): 270–291.
[44] Owen AM, McMillan KM, Laird AR, Bullmore E. N-back working memory paradigm: A meta-analysis of normative functional neuroimaging studies. Human Brain Mapping. 2005; 25 (1): 46–59. doi:10.1002/hbm.20131.
[45] Melby-Verlag M, Hulme C. 2012 ibid
[46] Au J, et al. Improving fluid intelligence with training on working memory: a meta-analysis. Psychon Bull Review. 2014; DOI 10.3758/s13423–014–0699-x
[47] Law LLF, Barnett F, Yau MK, Gray MA. Effects of combined cognitive and exercise interventions on cognition in older adults with and without cognitive impairment: A systematic review. Ageing Research Reviews. 2014; 15: 61–75.
[48] Pang TYC, Hannah AJ. Enhancement of cognitive function in models of brain disease through environmental enrichment and physical activity. Neuropharmacology. 2013; (64): 515–52.
[49] Nisbett RE, et al. Intelligence: New Findings and Theoretical Developments. American Psychologist. 2012; 67(2): 130–159.
[50] Einöther SJL, Giesbrecht T. Caffeine as an attention enhancer: reviewing existing assumptions. Psychopharmacology. 2013; 225:251–274.
[51] Borota D, et al. Post-study caffeine administration enhances memory consolidation in humans. Nat. Neuro. 2014; 17, 201–203
[52] Nehlig A. Is Caffeine a Cognitive Enhancer? Journal of Alzheimer’s Disease. 2010; 20: S85–S94.
[53] Reynar LA, Horne JA. Suppression of sleepiness in drivers: combination of caffeine with a short nap. Psychophysiology. 1997 Nov;34(6):721–5.
[54] Eskelinen MH, Kivipelto M. Caffeine as a Protective Factor in Dementia and Alzheimer’s Disease. Journal of Alzheimer’s Disease. 2010; 20(1): 167–174.
[55] Cantos C, et al. Caffeine Intake and Dementia: Systematic Review and Meta-Analysis. Journal of Alzheimer’s Disease. 2010; 20(1): 1387–2877.
[56] Carman AJ, et al. Current evidence for the use of coffee and caffeine to prevent age-related cognitive decline and Alzheimer’s disease. Journal of Nutrition, Health & Aging. 2014; 18(4): 383–392.
[57] Costa J, et al. Caffeine Exposure and the Risk of Parkinson’s Disease: A Systematic Review and Meta-Analysis of Observational Studies. Journal of Alzheimer’s Disease. 2010; 20(1)221–238.
[58] Arab L, Liu W, Elashoff D. Green and Black Tea Consumption and Risk of Stroke: A Meta-Analysis. Stroke. 2009; 40: 1786–1792.
[59] Dresler M, et al. 2013; ibid
[60] Smith AP, Christopher G, Sutherland D. Acute effects of caffeine on attention: a comparison of non-consumers and withdrawn consumers. J Psychopharmacology. 2013 vol. 27 no. 1 77–83
[61] Einöther SJL, Giesbrecht T. 2013; ibid
[62] Wood S, et al. Psychostimulants and Cognition: A Continuum of Behavioral and Cognitive Activation. Pharmacological Reviews. 2014; 66(1): 193–221.
[63] Freedman R. α7-nicotinic acetylcholine receptor agonists for cognitive enhancement in schizophrenia. Annual Review Med. 2014;65:245–61. doi: 10.1146/annurev-med-092112–142937.
[64] Potter AS, et al. AZD3480, a Novel Nicotinic Receptor Agonist, for the Treatment of Attention-Deficit/Hyperactivity Disorder in Adults. Biological Psychiatry. 2014; 75(3): 207–214.
[65] Tye KM, et al. Methylphenidate facilitates learning-induced amygdala plasticity. Nature Neuroscience. 2010; 13: 475–481.
[66] Bartl et al. Methylphenidate enhances neural stem cell differentiation. Journal of Molecular Psychiatry. 2013, 1:5. http://www.jmolecularpsychiatry.com/content/1/1/5
[67] Amiri A, et al. Changes in plasma Brain-derived neurotrophic factor (BDNF) levels induced by methylphenidate in children with Attention deficit–hyperactivity disorder (ADHD). Progress in Neuro-Psychopharmacology and Biological Psychiatry. 2013; 47(2): 20–24.
[68] Smith ME, Farah MJ. Are Prescription Stimulants “Smart Pills”? The Epidemiology and Cognitive Neuroscience of Prescription Stimulant Use by Normal Healthy Individuals. Psychol Bulletin. 2011; 137(5): 717–741. doi: 10.1037/a0023825
[69] Agay N, Yechiam E, Carmel Z, Levkovitz Y. Methylphenidate Enhances Cognitive Performance in Adults With Poor Baseline Capacities Regardless of Attention-Deficit/Hyperactivity Disorder Diagnosis. Journal of Clinical Psychopharmacology. 2014; 34(2): 261–265. doi: 10.1097/JCP.0000000000000076
[70] Pieramico V, et al. Effects of non-pharmacological or pharmacological interventions to promote cognition and brain plasticity in aging individuals. Frontiers in Systems Neuroscience. 2014; 8: 153. doi:10.3389/fnsys.2014.00153
[71] Lynch G, Palmer LC, Gall CM. The likelihood of cognitive enhancement. Pharmacology, Biochemistry and Behavior. 2011; 99: 116–129.
[72] Potier MC, Braudeau J, Dauphinot L, Delatour B. Reducing GABAergic inhibition restores cognitive functions in a mouse model of Down syndrome. CNS & Neurological Disorders Drug Targets. 2014; 13(1):8–15.
[73] Costa ACS, Scott-McKean JJ. Prospects for Improving Brain Function in Individuals with Down Syndrome. CNS Drugs. 2013; 27(9): 679–702.
[74] Tan CC, et al. Efficacy and Safety of Donepezil, Galantamine, Rivastigmine, and Memantine for the Treatment of Alzheimer’s Disease: A Systematic Review and Meta-Analysis. Journal of Alzheimer’s Disease. 2014; 41(2): 1387–2877.
[75] Furey ML. The prominent role of stimulus processing: cholinergic function and dysfunction in cognition. Curr Opin Neurol. 2011, 24:364–370.
[76] Repantis D, Laisney O, Heuser I. Acetylcholinesterase inhibitors and memantine for neuroenhancement in healthy individuals: a systematic review. Pharmacol Res. 2010; 61:473–481.
