What we don't know about cognitive enhancement

The use of prescription drugs such as Ritalin, Adderall and Provigil for increasing attention and work capacity has been controversial. However, in the context of such back and forth fights about the desirability of pharmaceutical cognitive enhancement, we must step back and ask some basic scientific questions:
- Do these drugs enhance brain function in people without ADHD or narcolepsy?
- Do they work equally well in everyone?
- Are there any cognitive trade-offs for using these drugs?

This is why this review by Husain and Mehta is both timely and important. Some of the great points made include:

1. We do not understand cognitive systems well enough to understand the potential trade-offs that may exist from taking a cognitive enhancing drug. There are counter-intuitive findings everywhere. For example, young adults who carry the APOE-4 allele (which has been associated with a higher risk of dementia later in life) actually have better performance on decision making tasks than those carrying the APOE-3 version. Therefore, it is plausible that drugs targeting memory systems might have detrimental effects on decision making tasks.

2. It's difficult to know how well cognitive enhancing drugs work in healthy people in the "real world". Although several studies have shown increased performance for certain laboratory tests of cognitive ability, there is no clear consensus about how these tasks translate into real-world academic or job performance. Furthermore, as most studies show small effect sizes and results in some, but not all tasks, there is a very real possibility that these drugs have no measurable effect outside of the laboratory.

3. A small overall cognitive enhancing effect of a drug can come either from a small effect observed in all participants, or large effects in some participants and no effects in others. Previously, these authors have shown large individual difference in cognitive enhancers (I wrote about this here). In particular, participants with lower working memory capacity seem to have more enhancement from these drugs than those with larger working memories.

4. A common complaint, but relevant nonetheless: the long-term effects of these drugs, taken for enhancement purposes, is unknown.

What I particularly like about this paper is that it both outlines a needed future research plan while staying above the ideological ethical fray.  

Husain M, & Mehta MA (2011). Cognitive enhancement by drugs in health and disease. Trends in cognitive sciences, 15 (1), 28-36 PMID: 21146447

Electrical enhancement of mathematical ability

Mathematical ability is highly linked to earning power and career success.  A new paper  in Current Biology demonstrates that six days of 20 minute sessions of electrical stimulation over the parietal lobe can increase some numerical literacy tasks, even six months after the stimulation was applied!

The electrical stimulation is called transcranial direct-current stimulation (TDCS). In this paradigm, electrodes are placed on the scalp as in EEG, and then a small amount of current (1-2 mA) is applied. In this paper, electrodes were applied to the parietal lobe as injuries to this region can lead to numerical difficulties. Three groups of participants were tested: two experimental groups who received stimulation, with the current going in each direction, and a control group who had electrodes applied, but without electrical stimulation (sham stimulation).

During the stimulation, participants were presented with pairs of novel symbols that stood for digits. Participants would learn the value of these symbols by indicating which symbol represented the larger value.

 As you can see from this figure, all three groups learned the task over the six experimental sessions.

Following the learning task, participants would then be given a "numerical Stroop" task to determine the automaticity of the symbol-value relationships. In this task, pairs of symbols are presented with one larger than the other. The larger symbol could be the symbol representing the larger value (congruent condition), could be the same value as the smaller value (neutral condition), or the larger symbol could represent the smaller value (incongruent condition). If the newly learned symbols were being processed as numbers, then the reaction times in the incongruent condition should be longer than neutral while congruent trials should lead to faster reaction times.

 It turns out that the stimulation did lead to an increased congruity effect, but only when the current was going in one direction (right-annode, left-cathode). In fact, current in the opposite direction seemed to decrease the learning of the symbols!

As illustrated in the left-hand figure, sham stimulation led to a ~65ms congruency effect (because even without stimulation, the participants were still learning the task). However, in the right-annode, left-cathode stimulation, the effect was about twice as large, while the opposite stimulation provided no learning at all.

Over at Practical Ethics, this paper is being discussed in terms of the societal benefit that could come from increased mathematical ability. Indeed, increasing numerical literacy could indeed decrease poverty and lead to increased innovation as they suggest. I also agree with their general unease about the possibility of "anti-enhancement" of mathematical abilities that is suggested from the right-cathode stimulation condition.

Cohen Kadosh, R., Soskic, S., Iuculano, T., Kanai, R., & Walsh, V. (2010). Modulating Neuronal Activity Produces Specific and Long-Lasting Changes in Numerical Competence Current Biology DOI: 10.1016/j.cub.2010.10.007

Cognitive enhancers: leveling the playing field?

A hot topic in neuroethics surrounds the use of drugs to enhance human intelligence.  Outside of the two most obvious issues (‘do they work?’ and ‘are they safe?’), ethicists have expressed concern over the possible unequal distribution of enhancers. Consider this statement from the President’s Council for Bioethics’ report on human enhancement (“scare quotes” are original):

“The issue of distributive justice is more important than the issue of unfairness in competitive activities, especially if there are systemic disparities between those who will and those who won't have access to the powers of biotechnical "improvement." Should these capabilities arrive, we may face severe aggravations of existing "unfairnesses" in the "game of life," especially if people who need certain agents to treat serious illness cannot get them while other people can enjoy them for less urgent or even dubious purposes. If, as is now often the case with expensive medical care, only the wealthy and privileged will be able to gain easy access to costly enhancing technologies, we might expect to see an ever-widening gap between "the best and the brightest" and the rest. The emergence of a biotechnologically improved "aristocracy"-augmenting the already cognitively stratified structure of American society-is indeed a worrisome possibility, and there is nothing in our current way of doing business that works against it.”

Is this a realistic worry? One counter to this argument, as pointed out by Anjan Chatterjee is that distributive justice is only a problem for cases where there are clear winners and losers (i.e. in a zero-sum game situation). Performance enhancing drugs are a big deal in sports because there is one winner and one loser. In other cases, enhancement of some can benefit more than just the enhanced individual, such as the case of subtle anti-theft devices such as LoJack: fewer cars are stolen in neighborhoods where LoJack use is higher because would-be thieves cannot tell which cars have the system, and will therefore look in LoJack free neighborhoods for victims.

Beyond the question of whether our current economic environment spawns competitive, zero-sum situations, we need to ask whether putative cognitive enhancing drugs provide the same effect size in all those that try them. Interestingly, a study by Mehta and colleagues in 2000 demonstrated that the degree of cognitive improvement with Ritalin in a spatial working memory task was negatively correlated with baseline working memory capacity at r = -0.78! This means that over 60% of the variance in the enhancing abilities of Ritalin could be explained by the subjects’ working memory capacities: those with lower working memories got more benefit than those with higher capacities. Similar results have been found in other studies using dextroamphetamine, and bromocriptine (a drug used to treat pituitary tumors and Parkinson’s disease).

Why is this effect not being mentioned in the ethical debate over cognitive enhancements? Partially, it is because many experiments are designed not to show the effect. The “lab rat” for most academic research is the undergraduate student. Although researchers assume that samples from this population are representative of all people, we know that they are young, educated, and have self-selected to be in universities with people of similar interests and backgrounds. Given this, it is perhaps not surprising that some studies of cognitive enhancers have not found this relationship: in a mostly homogenous population, the degree of enhancement would be similar.

Of course, the ethical debate we should be having in light of this data surrounds how we would deal with a more intellectually leveled playing field. Of course, there would be a great number of benefits to society as more people might be doing more important work, and developing new solutions at a more rapid rate. However, we should also ask how we would evaluate people for a job or academic position if all had the same intellect. Would we then put more emphasis on other traits such as creativity or cooperativeness? How would we deal with issues of nepotism, sexism and racism if there were no plausible arguments against the candidate’s intellect?