Existential Neuroscience

Is it reasonable to fear death? If you agree with Lucretius, you will say no. In what is known as the Symmetry Argument, Lucretius contends that that the time before our existence is similar to the time of our future non-existence. And since we do not fear the time before we existed, it is not reasonable to fear our future non-existence i.e. death. (See Rosenbaum, 1989 for a more detailed exposition)

However, even if you concede to Lucretius’s argument, the fact remains that the awareness of our mortality generates a significant threat to our psychological well-being. A large corpus of research on terror management theory details how mortality saliency affects our self-esteem, worldview, among others.

In a recent fMRI study, Quilin and colleagues (2011) extends our knowledge on terror management theory by exploring the neural correlates of mortality salience. They were interested in the activity of the amygdala, rostral anterior cingulated gyrus (ACC), ventral tegmental & caudate nucleus (CN).

In this within-subjects experiment, thoughts of death were induced in the participants by requiring them to agree or disagree with a statement such as I am afraid of a painful death. Statements about dental pain were used in the control condition.

Results

The authors found higher activations in:

• Right amygdala
• Left ACC
• Right CN

They suggested that the activations in the amygdala and ACC may indicate ‘non-conscious, latent markers of threat aroused by mortality salience’ and that further investigations may reveal the role of the CN in regards to the defensive mechanisms that we employ against mortality threat.

This area seems promising to me and more research needs to be done to help us better understand how we deal with threats of mortality. It would also be interesting to look at how religious affiliations affect the way the brain deal with existential fears. If indeed 'mortality threats functions as a potential for anxiety rather than as experienced anxiety', what can neuroimaging techniques tell us about whether believing in a higher being help us deal with the potential or experienced anxiety resulting from mortality threats?



Quirin M, Loktyushin A, Arndt J, Küstermann E, Lo YY, Kuhl J, & Eggert L (2011). Existential neuroscience: a functional magnetic resonance imaging investigation of neural responses to reminders of one's mortality. Social cognitive and affective neuroscience PMID: 21266462

Rosenbaum, S. (1989). The Symmetry Argument: Lucretius Against the Fear of Death Philosophy and Phenomenological Research, 50 (2) DOI: 10.2307/2107964

Beauty-is-Good Stereotype in the Brain

Leo Tolstoy once said, “It is amazing how complete is the delusion that beauty is goodness.” And how complete is this delusion? In a recent study, Tsukiura & Cabeza (2011) provides an insight into this question by investigating the neural mechanism underlying the Beauty-is-Good stereotype. They were interested in the activity of the medial orbito frontal cortex (associated with positive stimuli, reward processing etc); the insular cortex (associated with negative stimuli, punishment processing etc) and the interaction between these two regions.

This fMRI study required participants to engage in 3 different tasks:

1. Face attractiveness rating (beauty judgment task)
2. Action goodness rating (moral judgment task)
3. Brightness rating (control condition)

The 3 tasks. Click to enlarge

Conforming to their hypothesis, the authors found that activity in the mOFC increased linearly as a function of both attractiveness and goodness rating. Activity in the insular cortex also decreased linearly as a function of both types of ratings. In both regions, the strong correlation between the activations caused by both judgments also supports the idea that similar neural regions are engaged when we are processing attractiveness and moral goodness.

Furthermore, the negative correlation between right mOFC and right insular cortex provides support for the “dual process hypothesis” of the Beauty is Good stereotype in that we display both a positive bias of attractiveness as being good and a negative bias against unattractiveness as being bad.

That is to say, the stereotype is driven by two opposing mechanism whereby we tend to think that an attractive person is more moral and an unattractive person is less moral, rather than a singular bias towards attractiveness or unattractiveness.

Click to enlarge

Our delusion that beauty is goodness then appears to have been built into how our brain processes both type of judgments and the completeness of this delusion may surprise even the great Leo Tolstoy.

Tsukiura T, & Cabeza R (2011). Shared brain activity for aesthetic and moral judgments: implications for the Beauty-is-Good stereotype. Social cognitive and affective neuroscience, 6 (1), 138-48 PMID: 20231177

Spicy food and collectivism: How the brain shapes culture

We are used to thinking of culture as a social factor and not a biological factor. We attribute dispositions such as being individualistic or being collectivist to the country that one was brought up in, but no one has really looked into why certain cultures tend to be that way. An emerging field of research called cultural neuroscience says that cultural values can be shaped by the brain and genes.


For example, in one striking example I read about quite recently, one hypothesis put forth for the reason why Asian people like spicy food was because spices conferred natural bacteria killing properties that was especially important in a humid climate where food went bad. Over time, the hypothesis goes, people who liked spicy food more and ate more spicy food were less prone to stomach diseases that killed the others, thus passing on their genes for the next generation. A similar finding was found when examining lactose intolerance. Lactose intolerance is far more prevalent in certain regions of Asia where the rearing of lifestock for milk is less common. In Europe however, up to 95% are able to digest lactose, and this is reflected in their preference for milk products like cream and cheese.


In this review by Way and Lieberman, they sought to answer the question as to why certain cultures tend towards individualism and collectivism. They reason that because of evolution, genes that change brain function and influence the cultural norms we adopt and we institute are selected for between people born in different regions. For people brought up in one region that was say marked by famine, grouping together and helping one another might have brought about greater survival for the people, hence the genes that promote this thinking get passed on. In a separate part of the world, marked by conflict perhaps, survival would favor people who think for themselves and for their immediate family members. Over time, those different selective pressures would have promoted different social behaviors in different regions.


What mechanisms might have promoted these behaviors? They reviewed work from scientists studying the distribution of several genetic alleles. Previous work has shown that variation in the serotonin transporter gene, a very important neurotransmitter associated with emotion and reward, was associated with individual differences in social sensitivity. People with the short version show greater reaction to social events such as death or birth of children, regardless of whether it was positive or negative. When these scientists studied the distribution of these alleles in different cultures, surprise surprise! They found that the short version of this allele was much more prevalent in collectivist cultures than individualist cultures.



*higher score on individualism collectivism scale indicates higher individualism.


The authors hypothesize that since this allele makes people more sensitive to being socially excluded, it promotes individuals to tend and befriend, leading to a cultural trend of being more collectivist. There's more to read about other such alleles in the review, but seeing as to how this post is quite wordy already, I'll stop here :)




Sherman, P., & Billing, J. (1999). Darwinian Gastronomy: Why We Use Spices BioScience, 49 (6) DOI: 10.2307/1313553

Way, B., & Lieberman, M. (2010). Is there a genetic contribution to cultural differences? ... SCAN, 5 (2-3), 203-211 DOI: 10.1093/scan/nsq059

Cognitive Inferences and Optical Illusions

Ever wondered what allows us to be so perceptive about the world around us that it's almost taken for granted? Or why it is so difficult to create a robot with human-like perception, intelligence and understanding?

The discovery that the brain forms assumptions about the world in order to facilitate our lives has been one of the most illuminating insights from psychology and neuroscience.

Assumptions, or cognitive inferences, are what separates humans from robots. One very salient instance of this is our ability to see a man and his shadow against a wall, and not perceive that there is actually another physical object next to the man. Robots need to be programmed an infinite number of rules to overcome just this problem which our brain easily solves by utilizing assumptions that have been formed based on our experiences and through learning

One very interesting way of teasing out these assumptions is by means of optical illusions. Optical illusions fool us because they violate our assumptions about what we see. A really good one I'd recommend is this illusion by Edward H. Adelson.





What is special about this, you might ask? Well, Tile A and Tile B are objectively the same colour.
Look again. It might be hard to believe at first, but it really is!

And to prove it (I couldn't believe it myself initially), I did the following. I created a brownish-green oval, copied it so that there are exactly two same coloured ovals, and shifted them into the tiles.



Amazingly, the two ovals appear different accordingly.

To shortcut the process above, here's probably what's going on.



The bar in the middle is really a uniformly grey bar.

What's happening is that our mind cannot divorce the effect of shadows from our perception. As long as the picture shows the green cylinder casting a shadow, the 'shadow assumption' module of our brains gets activated and the things in relation to it will be affected. A robot should typically see Tiles A and B to be the same.

Our assumptions fill in the gaps so that our perception of the world becomes seamless and efficient (and it doesn't feel like we're constantly bombarded with stimuli).


Adelson, E. (1993). Perceptual organization and the judgment of brightness Science, 262 (5142), 2042-2044 DOI: 10.1126/science.8266102

Adelson, E. (2001). On seeing stuff: The perception of materials by humans and machinesHuman Vision and Electronic Imaging VI, Bernice E. Rogowitz; Thrasyvoulos N. Pappas, Editors, pp.1-12

Boost your Guitar Hero skills 101 - SLEEP! Really?

We have been told that feeling well-rested while studying and reviewing your work just before bedtime enhances your memory for what you have studied. But when it comes to the role of sleep in motor memory, the answer is less clear. A recent research abstract presented at the 24th annual meeting of the Associated Professional Sleep Societies LLC by Dr Kevin Peters from Trent University suggests that sleep enhances our performance in complex motor learning tasks, as measured by an larger increase in accuracy levels obtained in playing guitar hero in the sleep condition compared to the wake condition.

However, an earlier paper by Cai & Rickard (2009) suggests that after controlling for circadian (time of day) and homeostatic (time since sleep) confounds, participants in the sleep conditions did not display any benefits in a motor sequence task.

The participants in their research were categorized into 3 conditions - a wake group, a 1 night sleep post-training group and a 2 night sleep post-training group. Participants were tasked to tap a number sequence, 4-1-3-2-4 repeatedly and reaction times (RTs) were measured. All participants trained at about 9.30am and were tested on 5.30pm on the day itself or on Day 2 and Day 3 depending on which conditions they were in.

Comparing difference scores of their RTs for the 3 different groups revealed no significant differences between them. If sleeping does indeed improve motor memory, we would expect a significant reduction in RTs for the sleep groups compared to the wake group. Therefore, it appears that after controlling for circadian and homeostatic factors, sleeping after training does not improve motor sequence performance.

Unfortunately, I do not have access to the exact methodology and results of Peter's study to verify if the concerns about the relevant confounds raised by Cai & Rickard (2009) are adequately addressed. Therefore, as far as I'm concerned, the jury is still out on the specific benefits (if any) conferred to motor memory by sleep. But I must say that Peter's design holds much promise (he certainly won't have any trouble finding willing and good subjects).

Well, regardless of whether sleeping helps you perfect that golf swing or ramp up your skill level on guitar hero, it’s still a good idea to get a good night's rest to ward off the negative effects associated with sleep deprivation in other domains of our lives. Afterall, according to a study by Falleti, Maruff, Collie, Darby & McStephen (2003), driving after being awake for 24hrs is like driving with a blood alcohol concentration of 0.05%. Not quite enough to get you arrested but probably more than enough to make you think twice about pulling that all-nighter.

Cai, D., & Rickard, T. (2009). Reconsidering the role of sleep for motor memory. Behavioral Neuroscience, 123 (6), 1153-1157 DOI: 10.1037/a0017672

Falleti MG, Maruff P, Collie A, Darby DG, & McStephen M (2003). Qualitative similarities in cognitive impairment associated with 24 h of sustained wakefulness and a blood alcohol concentration of 0.05%. Journal of sleep research, 12 (4), 265-74 PMID: 14633237

Link between Sexual Motivation State and Dopamine Release in the mPOA?

Is an increase in dopamine release in the medial preoptic area (mPOA) specifically related to male physical arousal and sexual behavior or does it have a bigger role in sexual motivation?

Kleitz-Nelson, Dominguez, Cornil & Ball (2010) investigated this question by using the Japanese quail (Coturnix japonica). The male quail does not an have an intromittent organ and therefore does not require an erection to successfully copulate. The researchers collected and measured the dopamine content from extracellular samples from the adult male quails’ mPOA every six minutes before, during and after exposure to a female quail.

What they found was that for male quails that copulated, their levels of extracellular dopamine increased dramatically past baseline levels (BL1-3) when the female quail was introduced (F1-F6) and decreased after the female quail was removed (POST1-POST6). Non-copulators did not exhibit an increase in extracellular dopamine levels.

In addition, for copulators, the researchers did not find any changes in extracellular dopamine levels between sampling periods during which the quails either engaged in the actual mating behavior or not. That is to say, during the sampling period, regardless of whether the male quail was engaging in coitus or not, their levels of extracellular dopamine levels showed increased levels as long as they are in the presence of the female.

The authors thus concluded that the rise in extracellular dopamine in the mPOA is not only involved in erection and ejaculation, as the copulators had high levels of extracellular dopamine regardless of whether they were actually engaging in mating behavior at that moment. And given that the quails do not require an erection for copulation to occur, the evidence suggests strongly that extracellular dopamine in the mPOA is specifically associated with sexual motivation and not just physical arousal.


Kleitz-Nelson, H., Dominguez, J., Cornil, C., & Ball, G. (2010). Is sexual motivational state linked to dopamine release in the medial preoptic area? Behavioral Neuroscience, 124 (2), 300-304 DOI: 10.1037/a0018767

"Can't Touch This" - The neurophysiology of pleasant touch

Touch is crucially important for social communication, mediating how we perceive and interpret the actions of others. For example, waitresses who touch customers get better tips (Crusco & Wetzel, 1984). However, touch alone does not always lead to positive outcomes. For many years researchers have known that touch is moderated by factors such as type of touch, location of touch, situational context, and many others. Until recently however, they were uncertain as to how the social effect of touch was achieved. In this review by Olausson et al., the authors shed light on how pleasant and socially relevant aspects of touch are possibly mediated by a new distinct type of receptors called C-Tactile afferents.

To give a little background, human touch is generally considered to be mediated by 3 different type of receptors:

1. Thermal Receptors allow us to feel warmth and heat.
2. Mechanoreceptors allow us to feel pressure.
3. Nociceptors allow us to feel pain from chemical or heat damage.

For the most part, the mechanoreceptors are myelinated afferents. "Myelinated" means that the part of the neuron that transmits the signals are covered with an electrical insulator that allows it to conduct impulses at high speed (50m/s). Myelination is essential for quick reaction. "Afferent" neurons are neurons which carry information towards the central nervous system.

In the early part of the 20th century, mechanoreceptors that were unmyelinated were identified in various mammals like cats. They were termed C tactile (CT) afferents. For a time it was thought that humans did not share this primitive and slower tactile system, which conducted impulses at a speed of 1m/s. However in the 1990s they were soon found in abundance in hairy skin around the arms and legs, but not on the hairless surface of the palm.

The only appropriate time to use a lolcat.

Immediate testing of the sensitivity of these CT afferents found that they were for lack of a better word, wierd. They could not discriminate between pin pricks and smooth probe pressure, but however responded best to a slow stroking with a soft brush.

Direct evidence for the specific role of CT afferents was however, hard to achieve, because it was not possible to stimulate CT afferents without also activating myelinated afferents in normal subjects. The authors studied subjects who suffered from sensory neuronopathy, a condition where subjects lacked myelinated afferents but have intact C fibres. These subjects were long thought to have lost all tactile sensations but they detected soft brush stroking. Much of the CT effect was however, below conscious level. They could not effectively locate where the touch was delivered, and were not able to describe it, only saying that it was slightly to moderately pleasant.

FMRI imaging of the neuronopathy subjects also found that the posterior insula cortex was activated, but not traditional somatosensory systems identified with other tactile stimulation. This region is considered important for integrating converging information and passing it on to emotional systems. For one thing, it has been shown to be involved in the perception of pain.

Based on the evidence, the authors believe that CT system is involved in social touch. For one, the poor conduction velocity and poor discriminative properties of CT afferents make them ill-suited for processing the complex features of touch, features which are easily handled by other mechanoreceptors that are myelinated. Why then would they be present in humans? For another, the CT system appears to be tuned to slow, light touch, which occurs most often during close interactions with loved ones. The evidence from the sensory neuronopathy patients appears to confirm this fact.

So, what does this tell us? For the scientist, this research opens up new areas of research into the biological foundations of the social and emotional aspects of touch, which has longed focused purely on physical sensations. For the layman, not much. Intuitively we already reach out to stroke someone who is upset when we have no idea how to comfort that person, even if we do not know whether it would help. This review, and the research that has been done, confirms that physiologically, there is an effect. So, keep touching (as long as its appropriate, of course) :)

Ed's note: For another noteworthy study which was not mentioned in this review, but which I'm guessing was done by a postgraduate student of the author, you can refer to http://www.sciencedaily.com/releases/2009/04/090414084453.htm.

Olausson, H., Wessberg, J., Morrison, I., McGlone, F., & Vallbo, �. (2010). The neurophysiology of unmyelinated tactile afferents Neuroscience & Biobehavioral Reviews, 34 (2), 185-191 DOI: 10.1016/j.neubiorev.2008.09.011

Sorry honey, I just had to buy that dress! - When cognitive overload undermines our self-regulatory ability.

Counterintuitively, people who exercise self control in some way, such as dieting or trying not to look at or think about something, might end up buying things more impulsively instead if given the opportunity.

Vohs & Faber (2007) explain in their study, Spent Resources: Self-Regulatory Resource Availability Affects Impulse Buying, that opportunities for impulse purchasing have increased with the proliferation of ATMs, shopping on the Internet, and shop-at-home television programs. Depletion of cognitive self-regulatory resources coupled with ever-increasing avenues for impulse buying might just be the answer.

In one experiment, 35 undergraduate participants were made to watch a video of a woman talking on the pretext that they were going to judge her personality later. To suppress one group's attentional resources, irrelevant words were flashed at the bottom of the screen and participants were told to ignore the irrelevant words and focus instead on the woman. Another group was given no such instruction to divert their attention away from the words, and thus served as the control group. After the video, participants were told that they were taking part in a marketing study to determine the prices that students would pay for various products.

It was found that participants who had their attention manipulated assigned significantly higher prices to the products than participants in the control group.

In the second experiment, 73 undergraduates participated by first completing the trait Buying Impulsiveness Scale (BIS), a scale developed by Rook and Fisher (1995) which measures generalized urges to spend impulsively. This was followed by a thought suppression exercise where participants were induced with the thought of a 'white bear', an interesting experimental technique developed by Wegner in 1989 that has been proven to drain considerable cognitive resources. Participants were told to write down their thoughts for the next few minutes. Participants in the Thought Suppression condition were told that they should try and avoid thinking of a white bear and if they did think of a white bear, they should place a check mark on their paper and then resume recording their thoughts. Participants in the No Suppression condition could think of anything they wanted, including white bears.

After this, participants were told that they were going to be involved in a study about introducing new products at the university bookstore. Participants would be given $10 for their participation in the study, after which they could either leave with the money, or they could make a purchase with the items that were available as part of the bookstore's product study.

It was found that spontaneous buying behaviour is once more predicted by mental resource depletion, as students who did not have to suppress their thoughts were more likely to keep the $10 and leave. Additionally, an interaction effect between dispositional buying impulsiveness (as determined by the BIS) and the self-regulatory resource condition was found. As the authors assert, "Among people who are prone to buying impulsively, temporary lapses in self-control ability signal a strong possibility that impulsive, unplanned, and perhaps unwanted spending may occur."

In the last experiment of the study, 40 undergraduate subjects took a variant of the second experiment to determine that the results were not confounded by other cognitive or affective traits, such as the desirability of the items being purchased.

This study extends the research on impulse buying, which has come a long way since the 1980s where people were simply labeled as either impulsive or nonimpulsive purchasers, effectively indicating that there is an interaction between both dispositional and environmental influences that determines impulse-buying. In other words, personality and social factors both play a part. The authors conclude: "Self-regulatory resource availability would be an important element in determining when and why people engage in impulsive spending." Without enough self-regulatory resources, people will be less able to overcome urges and substitute desirable behaviours with undesired ones. Thus, temporary reductions in the capacity to self-regulate leads to stronger impulsive buying tendencies.

From this research, it appears that people in modern contexts do not stand confidently in the ability to control their temptations, as contemporary city-living inundates our senses with a twin barrage of cognitive overload as well as opportunities to spend.


Vohs, K., & Faber, R. (2007). Spent Resources: Self‐Regulatory Resource Availability Affects Impulse Buying Journal of Consumer Research, 33 (4), 537-547 DOI: 10.1086/510228

Sorry, what's your name again? - How stress impairs our social memory.

Ever felt that someone hasn't been paying attention to what you were saying in previous conversations because he/she forgets biographic information about you that you had mentioned countless times? Well, it turns out that it might just be that they're stressed out by something else.

In their paper, Stress Impairs Retrieval of Socially Relevant Information, Merz, Wolf & Hennig (2010) investigated the hypothesis that parts of our social memory (memory about names, birth dates, parts of other people’s life) fail because of stress.

15 women and 14 men were recruited to take part in an experiment whereby they were randomized into either the Stress or Control conditions. All participants started the experiment by memorizing two biographical notes (one from each gender) which includes photos, home towns and parts of their life stories.

Stress was then induced on the participants in the stress condition by instructing them that they would have to give a public speech 10 minutes later. Cortisol levels in saliva samples collected during 5 different time intervals during the whole experiment were used to quantify their stress levels.

All participants were then tested on the biographical notes that they learnt at the beginning of the experiment. Participants were tested on recognition (selecting the correct answer out of 5 choices), correction (marking the incorrect answer out of 5 choices) and reproduction (answering semi-open ended questions). Global Memory indicates the average of the three tests.

The authors found that participants in the stress condition had significantly lower recognition, reproduction and global memory scores than participants in the control condition.

Mean cortisol response during memory retrieval of responders (participants who show stress induced cortisol increase) also had a significant negative correlation with the recognition task and global memory score.

The authors conclude that acute stress reduces our ability to retrieve socially relevant information and that there was an association between these stress-induced retrieval deficiencies and cortisol response to the stressor.

So, cut that person some slack when he/she forgets something about you; it might just be the cortisol, or even the pressure you're inducing on the person to remember stuff about you!


Merz, C., Wolf, O., & Hennig, J. (2010). Stress impairs retrieval of socially relevant information. Behavioral Neuroscience, 124 (2), 288-293 DOI: 10.1037/a0018942