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Archive for the ‘emotions’ Category

How are values computed in the brain? Rewards can be as many things: the expectation when having just ordered your favourite dish; the child’s joy at Christmas Eve; the enjoyment of good music or the wonderful taste of strawberries.

But how does the brain process these many different kinds of rewards? Does it treat all types of rewards equally or does the brain distinguish between different kinds of rewards? Rewards can come in many different forms: from sex, social recognition, food when you’re hungry, or money. But it is still an open question whether the brain processes such rewards in different ways, or whether there is a “common currency” in the brain for all types of rewards.

Guillaume Sescousse and his colleagues in Lyon recently reported a study on how the brain reacts differently to money and sex. A group of men were scanned with functional MRI. While being tested, subjects played a game in which they sometimes reveiwed a reward. The reward could be money or it could be the sight of a lightly dressed woman. So there were two types of rewards. Money can be said to be an indirect reward, and the sexual images can be seen as more immediately rewarding (at least for most heterosexual men). But how did the brain process these rewards?

The researchers found that there were unique activations for both sex and money, but that there were also overlapping regions of activity. On one hand, for both types of reward was a general activation of what we often refer to as the brain’s reward system (ventral striatum, anterior insula, anterior cingulate cortex and midbrain; see figure 1). The brain thus uses the some structures to respond to both types of reward.

Regions of common activations

But there were also specific activations for erotic pictures and money. And this difference was primarily made in the brain’s prefrontal cortex, especially the orbitofrontal cortex (OfC). Here, it was found that monetary rewards engaged more anterior OfC regions, while erotic images activated more posterior OfC regions.

This could suggest that the brain also treats the two types of reward differently. The crux of this paper, however, is how one explains the difference. As noted, the researchers used two different kinds of reward, but they differ in several ways which I will try to summarize here:

  • Direct vs indirect
    • Money is indirectly rewarding, because money can not be ‘consumed’ in itself. They are rewarding to the extent they could be exchanged for other things. Erotic images are in themselves directly rewarding. Not because they symbolize sex, or the possibility of sex, but because they have an immediate rewarding effects.
  • Abstraction level
    • Another option is to say that erotic pictures and money differ in their level of abstraction: Erotic images are concrete, while money is an abstract reward.
  • Time interval
    • A final possibility is that there are differences in the time interval: Erotic images are immediately rewarding, while the money can only be converted into real value after a while (for example, after scanning, or after a few days where you spend the money). We already know that the frontopolar regions of the brain is among the regions that are most developed in humans compared to other primates, and is linked to our unique ability to think about the future, i.e. prospective memory and planning, and through this to use complex abstractions for rewards, including money.

Regions of distinct activations: orange = monetary rewards, green = sexual rewards

What the exact cause of this common currency as well as the separation between money and erotic pictures is still unclear and warrants further studies (which I am currently undertaking). The essential addition of this study is the separation between the posterior and anterior parts of the OFC in processing different kinds of rewards. By showing common and distinct regions, this study may resolve some of the ongoing debates in the decision neuroscience / neuroeconomic literature. But as always found in science, this study generates more questions than it resolves, and we can only hope that future studies can add to this knowledge.

-Thomas

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In March, the Center for Academic Research & Training in Anthropogeny hosted a conference on the “Evolutionary Origins of Art and Aesthetics”. The list of speakers was pretty impressive. Luckily, the lectures were taped and are now available on You Tube. Here is a video with lectures by Antonio Damasio on emotion, Helen Fisher on love, and Isabelle Peretz on music. I will probably post some of the other talks at a later point.

-Martin

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Picture 1Here is a heads up for a recent study demonstrating – again – that the amygdala is not merely a “fear centre” in the brain. I have previously blogged about the amygdala, first not being a single structure, and that it is not only involved in fear.

In 2007, a team of French researchers demonstrated that direct stimulation of the amygdala did evoke emotional responses, but that there was a difference between which hemisphere was stimulated. Right amygdala stimulations induced aversive responses, in particular fear and sadness. In contrast, left hemisphere stimulation induced either positive (happiness) or negative emotions (fear, anxiety, sadness). As the abstract reads:

Very few studies in humans have quantified the effect obtained after direct electrical stimulation of the amygdala, in terms of both emotional and physiological responses. We tested patients with drug-resistant partial epilepsies who were explored with intracerebral electrodes in the setting of presurgical evaluation. We assessed the effects of direct electric stimulations in either the right or the left amygdala on verbally self-reported emotions (Izard scale) and on psychophysiological markers of emotions by recording skin conductance responses (SCRs) and by measuring the electromyographic responses of the corrugator supercilii (EMGc). According to responses on Izard scales, electrical stimulations of the right amygdala induced negative emotions, especially fear and sadness. In contrast, stimulations of the left amygdala were able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions. Unpleasant states induced by electrical stimulations were accompanied by an increase in EMGc activity. In addition, when emotional changes were reported after electrical stimulation, SCR amplitude for the positively valenced emotions was larger than for the negative ones. These findings provide direct in vivo evidence that the human amygdala is involved in emotional experiences and strengthen the hypothesis of a functional asymmetry of the amygdala for valence and arousal processing.

Interestingly, there is more to say about this study. First, it may be that there is a systematic bias introduced by the way the researchers did the study. By using high-frequency (50 Hz) stimulation in 1 second, they might have induced one characteristic response of the amygdala. This structure is often seen as having quick “on-off” responses. Thus, one second pulse trains is actually a long duration for the amygdala. So a pulse of 20 milliseconds could be hypothesised to produce different responses. Also, the researchers found that GSR responses were actually larger for positive emotions, when they were reported. As the amygdala has often been implicated in unconscious emotional responses (mostly aversive responses) one may speculate that the left-hemisphere amygdala involvement in positive emotions may be related to conscious emotions.

As always, new findings leads to numerous novel questions, ideas and hypotheses. Which is why science is so much fun. But it is important to note the change we see today the role of the amygdala in emotional responses. We are moving away from the LeDouxian paradigmatic focus on fear (and some aversion)as the sole emotion of the brain, and more towards a balanced view towards a similar focus on positive emotions and (hopefully) more complex human emotions. Through this development, we can see that novel findings are breaking down the old ideas of neo-phrenology, breaking single structures into smaller parts, and into parts of a larger network of convergence and divergence structures. Keep your eyes open, more is on the way.

-Thomas

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Thomas + BecharaAntoine Bechara, the inventer of the Iowa Gambling Task, and together with Antonio Damasio the architect of the “somatic marker hypothesis” is visiting the Decision Neuroscience Research Group at the Copenhagen Business School at the moment. Here he is explaining to Thomas the role of gut feelings in making a decision to drink the bad CBS coffee or not.

-Martin

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-Thomas

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From time to time we bring you the quirky side of neuroscience here at BrainEthics. Now, we discover a funny little study in Psychiatry Research: Neuroimaging that bears the attractive title “The neural basis of unconditional love” by Mario Beauregard et al. Indeed, the study of the neural bases of preference formation, aesthetics and even love have gained much momentum since this field started just a few years ago. Fields such as neuroaesthetics and neuroeconomics seem to overlap when it comes to these studies, in which the core aim is to study the fundamental processes underlying preference formation.

In the study, Beauregard and colleagues wanted to establish the neural bases of unconditioned love. So the first tricky thing would be to define and operationalise what is meant by “unconditioned love”. IMO, such kind of love is the affectionate feelings one would call religious love, or ultimate altruism…(if such ever exists).But following the name, it does suggest a broader definition of affectionate feelings towards a person (or just any thing?) regardless of their origin, persona, deeds or misdeeds, family bonds and so forth.

Claimed amygdala activation, which rather looks like collateral sulcus/entorhinal cortex... (from Bartels & Zeki 2004)

Claimed amygdala deactivation during maternal love, which rather looks like collateral sulcus/entorhinal cortex... (from Bartels & Zeki 2004)

Similar studies of strong affectional feelings to other persons have been conducted recently. For example, in a study of maternal love (PDF) by Bartels and Zeki, mothers were scanned while looking at baby faces, in which sometimes their own newborn’s face was shown. The researchers found that when looking at their own babies, compared to looking at other infants, mothers demonstrated stronger activation in regions such as the ventral striatum/nucleus accumbens, ventro-anterior cungulate cortex and fusiform cortex.

In addition, and to the researchers’ surprise, they also found stronger bilateral activation of the anterior insula, a structure typically involved in aversive functions (but I will not follow the speculative account of the researchers on this activation). Deactivations were claimed to be found in regions such as the amygdala – which really is not amygdala, but rather collateral sulcus, judging from their figure (see figure on right). Isn’t is strange that prominent researchers such as Semir Zeki goes so wrong in neuroanatomy? The consequences from arguing for deactivation in the entorhinal cortex, compared to the amygdala, is dramatic. Instead of talking about emotions, one would be more prone to talk about complex visual processing. Yes, it does matter where you think your blobs are…

So what did Beauregard and colleagues do differently? First, they needed to describe the uncondition love construct, which they describe as:

(…) distinct from the empathy and compassion constructs. Empathy is commonly defined as an affective response that stems from the apprehension of another’s emotional state (e.g., sadness, happiness, pain), and which is comparable to what the other person is feeling (Eisenberg, 2000). This affective response is not unconditional and does not involve feelings of love. Compassion refers to an awareness of the suffering of another coupled with the desire to alleviate that suffering (Steffen and Masters, 2005). In contrast to compassion, unconditional love is not specifically associated with suffering.

Hm, not a particularly good definition to go hunting for neural correlates to. Nevertheless, the aim was to study the neural basis of unconditional love, something that has not been done before. So how did they do it? First, the authors had to select the subjects:

Participants were assistants in two l’Arche communities located in the Montreal area. L’Arche communities (founded by Jean Vanier in 1964) are places where those with intellectual disabilities, called core members, and those who share life with them, called assistants, live together. This special population was selected on the basis that one of the most important criteria to become an assistant is the capacity to love unconditionally. (We recruited) assistants with a very high capacity for unconditional love. We ensured that all recruited individuals understood the meaning of this form of love (based on the construct presented in Section 1) and found their work at l’Arche (community help service) very gratifying.

The hypotheses were 1) unconditional love is rewarding, and therefore it was expected to be associated with activation of the VTA and dorsal
striatal regions; and 2) since unconditional love experientially differs to a large extent from romantic love and maternal love, it was predicted that this form of love would be mediated by brain regions not involved in romantic love and maternal love. I particularly hate this second hypothesis: it’s not really a hypothesis, because ANY activation that is “different” can confirm this hypothesis. If it’s a fishing trip, let us know…

Let me try a bit of further deconstructionism of this study. In the methods section, it is described how the subjects were instructed to look at unfamiliar faces and either attempt to feel unconditioned love or think about the person’s intellectual capacity (sic.).

A blocked-design was used to examine brain activity during a passive viewing (PV) condition (control task) and an unconditional love (UL) condition (experimental task).

Note: using block designs are typically used to study differences in state (e.g. comparing neural activation during different attentional states).

Five blocks of pictures were presented during both conditions. Each block consisted of a series of four pictures. Each picture was presented during 9 s (pre-experimentation revealed that, on average, participants needed that long to feel unconditional love toward the individuals depicted in the pictures).

OK, so some of the activation differences between the UL condition and the PV condition may be due to task difficulty and reaction time, and not, as they would have wanted, the nature of the task.

Blocks were separated by periods of 30 s. Pictures depicted individuals (children and adults) with intellectual disabilities. These individuals were unfamiliar to the participants. Instructional cue words (“View”, “Unconditional love”) printed in white first appeared in the center of a black screen for 2 s. While the picture remained on the screen, participants performed the tasks specified by the prior cue. In the PV blocks, participants were instructed to simply look at the individuals depicted in the pictures. In the UL blocks, participants were instructed to self-generate a feeling of unconditional love toward the individuals depicted in the pictures.

OK, there are many assumptions here… Just to illustrate, do the following for me: close your eyes and for 20 seconds DO NOT THINK ABOUT AN ELEPHANT!!! What happens? Well, you’d probably be surprised to see that elephant does really appear in your mind even if you try to suppress it. Thought suppression studies have demonstrated this through the past many decades. So IMO, what the study might also be about is thought suppression – or comparing elephant thinking to elephant-suppression activation. IOW, I’m not sure that the viewing condition did not evoke some “unconditioned love”-suppression.

Therefore, the UL task involved both a cognitive component (self-generation) and an emotional–experiential component (feeling). Blocks were presented in alternation (PV, UL, PV, UL, etc.). At the end of each block for both experimental conditions, a four-point scale (1 = “No feeling”, 2 = “Some feeling”, 3 = “Moderate”, 4 = “Very intense”) for rating the extent to which they currently felt unconditional love was presented for 3 s.

Strangely, what the researchers found when doing the UL minus PV comparison, was stronger activation in “the middle insula, superior parietal lobule, right periaqueductal gray, right globus pallidus (medial), right caudate nucleus (dorsal head), left ventral tegmental area and left rostro-dorsal anterior cingulate cortex.” This can be seen in the figure below:

Regions showing stronger activation during "unconditional love" condition

Regions showing stronger activation during "unconditional love" condition

So what are the interpretations of these results? Does it surprise you that both hypotheses were confirmed? First, that unconditioned love was related to reward structure activation was not surprising. But the researchers over-interpret the results: they claim that this is prima facie proof that unconditioned love is rewarding. But hey, the results can just as well suggest that the unconditioned love state is just a framing of how we look at faces (for example, imaging you are either told that person/face X is a wonderful person OR an evil sadistic terrorist).

Second, is it surprising that they also found “activation not found for maternal or romantic love”? Not to me: the tasks are different, the selection of subjects are different, the confounds are plenty…

And what about that strong and bilateral insula activation? Yes, it’s right that it confirms the second hypothesis…but how does the insula play a role in unconditioned love? As I noted in my previous post, it does seem to play an important role in negative emotions and aversion. Here, the authors assert:

There is increasing evidence that the insula is implicated in the representation of bodily states that colour conscious experiences (or “background feelings”) (…) it is plausible that the middle insular activation noted during the UL condition was associated with the somatic and visceral responses elicited by the presented pictures.

Uh yes, but this is typically reflected in negative emotions. So how is unconditioned love related to aversion? Or maybe one could relate the findings to a recent review that suggest a role for the insula in addiction and urges? I don’t know, if you’re into speculating, go with whatever seems to work… Basically, this handwaving interpretations is not much better than old-style phrenology or hand-reading. They may be right, but only because they make the right guesses from previous studies.

Briefly put, although we enjoy the quirky side of neuroscience, and how it can be used to explore human nature, we at BrainEthics are also sceptical at the level at which quirky science turns into flaky science.

-Thomas

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The role of the insula in many human behaviors

The role of the insula in many human behaviors

Following up on my lead on Antoine Bechara’s upcoming visit, it is worthnotinv one of the new trends in decision making research. In particular, working from an extension of the somatic market theory and the role of ventromedial prefrontal cortex (vmPfC), Bechara and colleagues have recently demonstrated how the role of the insula seems to play an important role in decision making involving risk and aversion.

In the article entitled Differential effects of insular and ventromedial prefrontal cortex lesions on risky decision-making, the researchers compared patients with lesions to vmPfC and the insula to healthy controls and lesion controls on the Cambridge Gamling Task (nice demo here). The authors note that:

The vmPFC and insular cortex patients showed selective and distinctive disruptions of betting behaviour. VmPFC damage was associated with increased betting regardless of the odds of winning, consistent with a role of vmPFC in biasing healthy individuals towards conservative options under risk. In contrast, patients with insular cortex lesions failed to adjust their bets by the odds of winning, consistent with a role of the insular cortex in signalling the probability of aversive outcomes. The insular group attained a lower point score on the task and experienced more ‘bankruptcies’.

The results thus confirmed previous findings of a role of the vmPfC in gambling tasks, while the surprising finding was that insular lesions would also have detrimental effects on decision making. in particular, while vmPfC patients responded to reduced likelihood ratios of the gambles, betting behaviour in insular patients did not show much response to decreasing probabilities. This is demonstrated nicely in the following figure:

picture-11

The effect of ratio on betting behaviour in the four groups of participants: healthy controls, vmPFC lesions, insular cortex lesions and the lesion control group.

Furthermore, over the course of the entire gambling task, insular patients suffered significantly more bankrupcies than both the vmPfC group and control groups. This does suggest that one role of the insula is guiding behaviour through aversive coding. In other words, it may be that the insula is responsible for loss aversion (as well as risk aversion, judging from the task).

The researchers further suggest that the findings were expected from the somatic marker theory:

The detrimental effect of insular cortex damage on emotional decision-making is also predicted by the Somatic Marker hypothesis (Damasio, 1994; Bechara and Damasio, 2005), which posits a crucial role for the insular cortex in holding the representations of bodily states associated with different choice options.

The results are also relevant to other studies, including Lawrence et al. (2009), who report that using the Iowa Gambling Task, choices from disadvantageous versus advantageous card decks produced activation in the medial frontal gyrus, lateral orbitofrontal cortex, and insula. So does the insula play a role in other forms of decision making, and is it a cause in pathological gambling? To date, no conclusive studies have emerged, which is why our own research has now turned to aversion-related activations in gambling, and the study of the dynamics (and overlap) between aversion related and reward related neural functions. The recent study by Clark et al demonstrates that the insula is a structure – long ignored – to take into considerations in decision making studies.

-Thomas

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