Perhaps few findings in the cognitive sciences have received more press in recent years than the discovery by Rizolatti and colleagues in macque monkeys of mirror neurons; that is, neurons that preferentially activate both when a monkey performs some action and when observing someone else perform the same action. There is evidence that these neurons exist in humans, although it’s indirect (however, see Keysers 2010). They’ve quite captivated the publics’ attention, these crafty little neurons.
The mirror neuron system is thought to help primates, non-human and human, understand what others are doing by simulating the motor plan of an observed action and also allowing for prediction of the most likely outcome of an observed action. In other words, mirror neurons are sensitive both to actions and outcomes, and to some extent, inferring the why behind the what. Many have suggested that they play a significant role in comprehending mental states and empathic processes. But it’s in regards to these latter claims where the evidence is not as clear.
So, how does the brain intuit others’ inherently unobservable mental states in the absence of biological action? Much of the research evidence points to the mentalizing system, also known as the theory-of-mind network, as the neural network tasked to the job (see meta-analysis by Van Overwalle and Baetens, 2009). Anatomically speaking, these networks are distinct, with the mirror neurons located primarily in the ifraparietal sulcus, superior temporal sulcus and the prefrontal cortex, while the mentalizing system constitutes a distinct set of brain regions that lie along the cortical midline and in the temporal lobes, including the mPFC, TPJ, temporal poles, PCC and posterior STS.
One of the big challenges in this area of research is in designing tasks that are able to effectively disentangle processing of motor action from mentalizing. This is quite a challenge because it’s difficult to know what kind of mental process participants are applying to any given set of social stimuli. Do participants engage in higher-order abstract mentalizing automatically, and even when the stimuli might not necessarily demand it? How can we know what mental process subjects are engaging in? In other words, how might one capture the distinction between perceiving what others are doing vs. obtaining a more abstract representation of why they might be doing it?
UCLA’s Bob Spunt and colleagues (2011) designed a study that would attempt to do just that. They had participants observe short video clips of a human performing an action and directed the participants, in the scanner, to covertly describe each video clip in terms of (1) what an actor was doing, (2) why he was doing it, (3) how we was doing it or (4) to just passively view the video. They were to start the process of covert description once the video started playing, begin their description with the word “he” (e.g. he is reading) and to press a button once they were done.
(Thanks to the researchers for providing the video)
For example, in the above example, participants might have covertly described that the man is reading (WHAT), that he wants to learn or is bored (WHY), or that he is flipping pages or gripping the book (HOW).
This had the effect of creating three levels of mentalizing “depth” while holding the action component constant. If the mirror neuron network was involved in the mentalizing process, then one would expect to see neural activation increases in the mirror neuron network covarying with the increase in participants presumed mentalizing about the actor. And if the mirror neuron network was involved in mentalizing, then one would expect to see increased activations in neural regions which have been previously suggested to contain mirror neurons.
In support of the theory that mirror neurons don’t play a significant role in mentalizing, the researchers found no increase in the mirror neuron network in response to increases in mentalizing. But they did find increased activation in brain regions associated with mentalizing, including dorsal and ventral medial pFC, posterior cingulate cortex, and the temporal poles.
The study does provide another piece of support to the position that although the mirror neuron system might be necessary in understanding actions of the body, it’s not sufficient to explain the cognitive processes required to infer unobservable mental states.
Spunt, R., Satpute, A., & Lieberman, M. (2011). Identifying the What, Why, and How of an Observed Action: An fMRI Study of Mentalizing and Mechanizing during Action Observation Journal of Cognitive Neuroscience, 23 (1), 63-74 DOI: 10.1162/jocn.2010.21446
Keysers, C., & Gazzola, V. (2010). Social Neuroscience: Mirror Neurons Recorded in Humans Current Biology, 20 (8) DOI: 10.1016/j.cub.2010.03.013
Van Overwalle F, & Baetens K (2009). Understanding others’ actions and goals by mirror and mentalizing systems: a meta-analysis. NeuroImage, 48 (3), 564-84 PMID: 19524046
Nice piece from the Boston Globe on the positive benefits of solitude. (My friend Adam Waytz, from the Harvard psychology department, gets a mention.)
Congenitally blind people use visual cortex to do language processing
An essay by June Carbone regards the role of neuroscience in determining punishment for adolescents who commit crimes such as murder. Focused on a recent US Supreme Court decision on the juvenile death penalty, the piece points out some of the limitations of applying neuroscientific findings to issues of jurisprudence.
A new study from researchers at Northeastern University says day traders make more money when they stay with the herd.
Often referred to as the “love drug” or “love hormone”, oxytocin has attracted increasing interest from researchers in recent years. It was originally shown to modulate aspects of social attachment and pair bonding in animals such as the female prairie vole, whose monogamous nature is dependent on oxytocin. Recent research in humans has shown that oxytocin increases trust behavior in economic exchanges and increases perception of trustworthiness in human faces, as well as promoting emotion recognition and altruism. This evidence inspired hopes among some, particularly in the mainstream media, that science might have found a possible pharmacological target for humans who show deficits in prosocial behavior.
But recent evidence has complicated the narrative a bit.
Research has shown that oxytocin plays a role in increased emotional reactivity to both positive and negative social cues. For example, one study from 2009 (Shamay-Tsoory et al) had participants engage in a game of chance with another player (the actor). In one condition, the actor was made to win more than the participant, evoking feelings of envy in the participant. In another condition, the actor was made to lose more than the participant, evoking feelings of “schaudenfrude” or gloating. Participants who were administered oxytocin before playing showed increases in both envy and schaudenfrude (if oxytocin was involved only in enhancing prosocial behavior, we would expect to see the opposite result.) Other research has shown oxytocin increased approach behavior or affiliative drive rather than regulating positive or negative responding per se. And one recent study showed that oxycotin led humans to self-sacrifice for their own group while showing increased aggression toward out-group members. The gist of this set of findings is that oxytocin doesn’t seem to bias individuals toward the positive, but rather can magnify whatever “stimuli” happens to be in someone’s attentional spotlight, be it bad or good, thereby generating an increase in corresponding positive or negative emotional responses.
Jennifer Bartz and colleagues (2010) were curious to explore whether oxytocin could “correct” deficits in pro-social behavior in individuals with borderline personality disorder (BPD), a population famous for emotional instability, extreme impulsive behavior and identity confusion. People with BPD tend to be involved in intense, emotionally volatile relationships characterized by frequent arguing, repeated breakups and extreme aggression. This behavior often extends beyond their romantic relationships, as BPD individuals have also been shown to have difficulty cooperating with strangers. The existing body of research, Bartz et al suggested, offers up contrary predictions. On the one hand, oxytocin could be helpful in reducing the negative behaviors normally associated with BPD in favor of kinder, gentler behavior towards others. Alternatively, oxytocin might have increasingly negative effects for people with BPD, who are chronically concerned with (lack of) trust and abandonment and have difficulty cooperating with others. They’re essentially fixed in a constitutively negative state when it comes to social interactions and increased oxytocin could decrease prosocial behavior even further. Additionally (or alternatively), the oxytocin system might be dysregulated in BPD and could produce different responses (vs. control) to oxytocin as a result.
Bartz and company designed an experiment in which the participant was paired with a partner (in reality, a virtual “computer” partner) to engage in an economic game. In this game, the participant was to make one of two choices that involved financial rewards. The catch was that the amount of the reward was also dependent upon the choice that their “partner” made.
Both players clearly make the most money if they both choose strategy A. But because the player has to make the choice before the partner, the decision involves an element of trust (if your partner defects, you get nothing. If your partner trusts you and you defect, you get $4 and she gets nothing.)
So, what did they find?
Results showed the following:
1. BPD people trusted their partners in an economic game less after they received oxycotin than when they received a placebo.
2. Additionally, when asked if they would be more likely to make a hypothetical decision that would punish their partner, even when they knew their partner had extended trust toward them, they were more likely to punish after Oxytocin than placebo.
Administration of oxytocin to BPD individuals actually decreased pro-social behavior (and increased antisocial behavior). As the experimenters suggest, increasing the salience of a social cue that makes trust issues salient may have caused BPD participants to rely on their normal strategy for trust-dependent social interactions; that is, defect and punish the partner. Or it might have motivated approach/affiliative behaviors which triggered memory of past experiences gone awry and set off chronic and ever-present concerns about trust and rejection (e.g. “reject and punish them before they can do the same to me.”). Finally, the experimenters suggest the possibility that the oxytocin system itself may be dysregulated.
In short, the evidence doesn’t offer overwhelming support for the notion that exogenously-administered oxytocin will be a useful clinical treatment for people with pro-social deficits, such as those with BPD. Additionally, it’s difficult to imagine long-term benefits of oxytocin given that it’s half life when administered intranasally is only about three minutes. It’s been said that the most of the real action with regards to oxytocin is on the receptor end.
Bartz, J., Simeon, D., Hamilton, H., Kim, S. Crystal, S., Braun, A., Vincens, V., & Hollander, E. Oxytocin can hinder trust and cooperation in borderline personality disorder. (2010). Social Cognitive & Affective Neuroscience
Shamay-Tsoory SG, Fischer M, Dvash J, Harari H, Perach-Bloom N, Levkovitz Y (November 2009). “Intranasal administration of oxytocin increases envy and schadenfreude (gloating)”. Biological Psychiatry 66 (9): 864–70.
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