Tuesday, June 29, 2010

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

Saturday, June 19, 2010

"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

Wednesday, June 16, 2010

Is your best friend’s relationship advice/decision really the best for you?

When you have a relationship decision to make and you are at a loss as to which is your best available option, are your friends the ones you turn to? If your answer is yes, the following article may make you think twice in the future.

In the article Risk-Taking in Relationships: Difference in deciding for Oneself Versus for a Friend, the authors explored the idea that people tend to make riskier decisions or give riskier advice for their friends as opposed to when they are making one for themselves. Most existing research has so far focused on people making decisions for themselves. However, there is a lack of empirical research on decision making for others, which is a rather common situation in life. Examples include doctors making decisions for patients or politicians for their constituents. The authors decided that decision making in relationships would be a good starting point as participants are undergraduates, often with a good chance of encountering such relationship choices.

The first experiment asked 201 participants to fill in a questionnaire of 11 scenarios concerning real-life relationship problems. There were two options for each scenario, one that was risk-averse (e.g. a fun time with friends) and another that was risk-taking (e.g. potentially having a fun time with an attractive member of the opposite sex). All participants were grouped into 3 categories: (1) deciding for themselves, (2) deciding for a same-sex friend, and (3) advising a same sex friend. A risk-averse option receives a score of 0 and the alternative gets a score of 1. Therefore, if a participant chose the risk-taking option for all 11 situations, the score would be 11.

The results indicated that participants made riskier choices for their friends as opposed to for themselves. Moreover, results showed that there were no differences for the other-decision group and the other-advice group. However, a life impact analysis of the scenarios reveals that the impact of the situation on the person’s future life could influence the self-other difference. Therefore the second experiment was conducted to investigate this possibility.

In the second experiment, 20 scenarios were pre-rated with 12 chosen. Six of them were of the highest score for low life-impact and vice versa for the high impact scenarios. In general, the results concurred with the first experiment and the possibility of self-other difference from low or high impact scenarios was also confirmed. Participants were more risk-taking in low impact scenarios and more risk-averse in high impact scenarios. However, a non-linear analysis suggested that the conclusion might not be as straightforward. Evidence from the non-linear analysis indicated that not every low-impact scenario had participants choosing a more risk-taking decision for their friend. Self-other difference was non-existent or reversed in three of the six low-impact scenarios. For example, when asked if they would give their phone number to someone they just met at a party, 80% said they would but only 67% said they would tell their friend to do the same thing. Experiment 3 sought to find out why people take more risk in some scenarios when it comes to deciding for a friend while other scenarios produce a completely different set of results.

Before discussing Experiment 3 proper, a brief review of some literature to provide rational explanations will prove useful. People in general take into account more information when deciding for oneself than for others. One way to interpret this is that positive consequences are accounted for in oneself and others but people will also focus on the negative consequences only when deciding for themselves. The corollary is that there is a bias towards riskier decisions for one's friend since positive consequences weigh more in the decision-making process. Insofar as this explanation is true, we can reasonably expect self-other differences to disappear for high-impact scenarios, but what about the three low impact ones previously mentioned?

Each scenario (giving out a phone number, going to an out-of-town concert and buying a gold chain for a significant other) has the potential to produce negative outcomes. For example, going out of town for a concert may be dangerous if you find yourself too far from home with a person you've just met. As a consequence, there might be a chance that such considerations are not completely ignored despite the scenario being generally of a low impact.

There are generally two mechanisms by which negative information can be directed when making decisions. The first states that such information is not even brought to mind when deciding for others. If this is the case, explicitly stating the negative consequence would serve to negate the self-other difference. The second possibility is that the consequences, albeit being brought to mind, are given less weight.

Experiment 3 tested both versions. For this experiment, each scenario was provided with both positive and negative consequences for each risk option (same questionnaire as Experiment 2) for one group and no such consequential information for another group. If this inclusion eliminates the self-other difference, the first mechanism is supported. In addition, the conclusion of this experiment asked participants to provide reasons for their choices in the three low-impact scenarios with the largest self-other differences as in Experiment 2. If participants stated more negative reasons, it would mean they were aware but chose to ignore the consequences.

Results of Experiment 3 indicated that, regardless whether consequential information is present, the self-other difference is not removed for the low-impact scenarios. For the open-ended questions at the end, participants gave more negative reasons when deciding for themselves than for others. This raises an interesting question because it contradicts the prospect theory where people in general place more importance on losses than on gains. Maybe we place a different emphasis on our decisions when it comes to deciding for others.

With these results in mind, we definitely do know that people take more risks for their friends in decisions, at least with respect to relationships. So, before the next time you go banging on your friend’s door regarding your relationship problems, do bear in mind what their decision could mean to you.

Beisswanger, A., Stone, E., Hupp, J., & Allgaier, L. (2003). Risk Taking in Relationships: Differences in Deciding for Oneself Versus for a Friend Basic and Applied Social Psychology, 25 (2), 121-135 DOI: 10.1207/S15324834BASP2502_3

Monday, June 14, 2010

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

Friday, June 4, 2010

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