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Showing entries tagged amygdala.  Show all entries

December 5, 2011

Morphine: Friend or Foe for People Dealing with Long-Term Pain?


Lights reflect off of the gleaming road in the rain. The highway embankment funnels traffic into a valley where pools of black water flood the lanes. Your car suddenly hydroplanes and you veer into the other lane. The sound of metal wrinkling like tin foil ricochets in your ear. You wake up in the hospital with a horrendous pain emanating from your broken legs. Morphine is dispensed to ease the pain. Rehabilitation is slow and the pain is incessant. Tolerance develops. Withdrawal symptoms like abdominal cramps and depression begin. You want to stop taking morphine, but the pain in your legs persists and makes it difficult to walk. What do you do?

Morphine has the possibility to help those in pain, but it also has the potential to create a dangerous addiction. Morphine has been in use since Byzantine times because it's a powerful and effective painkiller. Research is now looking into morphine's mode of action in the body, to better mitigate the unfortunate side effects of tolerance and addiction for long-term pain control. In the November 30th issue of the Journal of Neuroscience, a group led by Dr. Ping Zheng in China found that chronic morphine treatment actually switches the effect of dopamine from inhibition to excitation on pyramidal cells of the basolateral amygdala. Pyramidal cells in the BLA are involved in emotion. Excitation of these cells could change the emotional response, which is especially important in withdrawal, when negative feelings can contribute to a relapse.

The researchers used rats to test the effects of chronic morphine treatment. They induced morphine tolerance in rats and then used brain slices to study excitatory postsynaptic currents (EPSC) using the whole-cell patch clamp method. Compared to the control group injected with saline, the morphine treated rats had higher amplitude EPSCs by 50%. After this observation, the team wanted to investigate the reason behind this change. They used a dopamine D1 receptor antagonist in the morphine treated rats, and the EPSC was now the same as the saline control group. Thus they concluded a change in D1 receptors is responsible for the excitatory response.

But what changed about the dopamine D1 receptors at the molecular level? The researchers determined that morphine treated rats had a higher release of glutamate from the presynaptic neuron. Looking at the expression of D1 receptors using Western blotting, they saw there was increased expression of D1 receptor, versus saline. The researchers hypothesized this increased expression might be dependent on protein kinase A (PKA) so they tested this with a PKA inhibitor. They indeed found that the increased release was due to PKA activation.

To supplement these studies, a behavioral test called conditioned place aversion (CPA) were performed on the rats. In this test, rats were placed in one section on days when they received the drug, and in another section on days when they did not receive the drug and were experiencing unpleasant withdrawal symptoms. The rats were then allowed to freely go into either section, plus a third section. Time was clocked for how long the rats spent in each section and the CPA score was determined by the difference between the time spent in the withdrawal-paired compartment divided by the time spent in the drug-paired compartment. The researchers used this to test to determine whether the increase of D1 receptors is responsible for the withdrawal induced conditioned place aversion. The morphine rats strongly avoided the withdrawal compartment, but when a D1 receptor antagonist was injected into their BLA, they no longer avoided that compartment. Therefore, D1 receptors are responsible for part of the withdrawal process.

This study could lead us to understand more about the molecular nature of morphine tolerance and addiction. Using these findings, new ways to combat the negative side effects of morphine use could be implemented.

Li, Z., Luan, W., Chen, Y., Chen, M., Dong, Y., Lai, B., Ma, L., Zheng, P. (2011). Chronic Morphine Treatment Switches the Effect of Dopamine on Excitatory Synaptic Transmission from Inhibition to Excitation in Pyramidal Cells of the Basolateral Amygdala. Journal of Neuroscience, 31(48): 17527-17536.
Posted by      Amanda W. at 1:42 PM MST

Why Keep A Promise?


It is interesting to see the importance humans place on a promise. A promise is not visible or tangible yet it still seems to have a strong, compulsory quality to it. Why is that? The truth of the matter is humans have the exceptional capacity to establish social norms and create understood cooperation among each other that is not seen elsewhere in the animal kingdom. Before society's infrastructure of rules and laws existed, promises were still made as a way to ensure trust, teamwork and partnership. Furthermore and perhaps the most intriguing aspect of a promise is that it is a verbal, nonbinding agreement. Yet despite the lack of concrete liability we still make promises every day.

Some research looking into the systems of the brain involved in nonbinding agreements has been done but there are still more questions than answers regarding of this topic. Using promises as a premise for research opens a unique door because promises can either be kept or broken. They can be made for many reasons but there are two justifications for keeping a promise. The first is to ensure future trust and cooperation and is referred to as an instrumental reason. The second rational is because it is the right thing to do and is called the intrinsic reason. The study in this paper focuses on the latter of these two explanations.

Each trial of the experiment had two subjects, a trustee and an investor. The trustee's brain activity was measured. First the trustee promises the investor to always, mostly, sometimes, or never keep their promise. In this study to be trustworthy means sharing the money made equally. The investor could choose to invest or not and then the trustee could choose to keep or break their promise to share the money. The trustee could choose both the strength of their promise and whether or not to keep their promise. These freedoms of choice led to two main groups of trustee subjects: both groups almost unanimously promised to "always" keep their promise but when it came to keeping the promise the subjects split into either the group who honored their promise or who was dishonest.

This study was the first to create a design looking at three different processes that play a role in promises. The first stage is the promise stage where the promise is made, then there is what is called the anticipation stage while they wait for the commitment of the investor, and finally the decision stage where the promise is either kept or broken. Researchers could differentiate subjects who will keep their promise and who will break it by brain activity during the promise stage, when the deceitful act is already planned.

This study found that all stages of the paradigm revealed different, highly specific activation patterns in the brain. The promise stage is where the dishonest act may be already planned but not yet implemented and researchers hypothesize if the subject already plans to break a promise, this misleading gesture will induce an emotional conflict. This emotional clash shows activity in parts of brain involved in conflict and negative emotional process such as the anterior cingulated cortex or amygdala. The anticipation stage showed parallels in brain activity to personality traits such as depression and neuroticism, both of which are associated with negative expectations of the future. When the subject had to decide to keep or break the promise, breaking the promise showed similar brain activity to the emotional process of telling a lie and the guilt that that involves. This study showed plausible evidence tying nonbinding agreements to emotional and logical processes of the brain. This evidence is critical in explaining why humans value and venerate the simple idea of a promise.



Baumgartner, Thomas, Urs Fischbacher, Anja Feierabend, Kai Lutz, and Ernsty Fehr. "Broken Promises." Neuron 64.5 (2009): 756+. Science Direct. Elsevier Inc, 10 Dec. 2009. Web. 5 Dec. 2011. .
Posted by      Bethany B. at 10:48 AM MST
  Sarah Bennet  says:
Amazing blog and very emotional. A promise is not a concrete thing but it has feelings and quality to bond two people with trust. Everyone should need to read this and learn the important message from this. dba writing help
Posted on Wed, 3 Jul 2019 3:34 AM MDT by Sarah B.

October 24, 2011

Caught in a Lie: The Role of the Brain in Detecting Deception


Vital to everyday social and economic interactions is the ability to accurately discern whether other individuals are being honest or deceitful. While recognizing dishonesty is no easy matter, it is nonetheless possible even in the absence of signals from facial expression, through careful attention to nonverbal cues. Researcher Julie Grèzes and her colleagues have identified the brain mechanisms that underlie detection of deceptive intent through the use of fMRI technology.

The study involved imaging 11 participants as they viewed videos of actors with blurred faces lifting boxes, and evaluated whether the actors were attempting to deceive them regarding the weight of the box. The results from this experiment were compared to the results from a previous study in which participants were asked to judge whether actors' expectations of a box's weight were false. The key contrasting variable was the judgment of of deceptive intent in the current study, versus the judgment of a false belief resulting in accidental deception in the previous study.

Their research concluded that the amygdala and rostral anterior cingulate cortex were both significantly activated when the participants judged the actors as being intentionally deceptive, yet not when the actors were judged to have unknowingly erroneous beliefs that led to accidental deception.

The amygdala is known to be a critical aspect of the neural circuitry concerning emotion and value appraisal. Additionally, the anterior cingulate cortex is activated when there is intent to directly communicate with the participant, indicated by eye contact and use of the participant's name. Based on such, the researchers speculate that activation of the amygdala and anterior cingulate cortex may be suggestive of the observers' valuation of social intentions towards themselves, and could thereby reflect an emotional response to being misled.

Whether activated by an internal sense of fairness or rather an assessment of social intention, the amygdala and rostral anterior cingulate cortex are working together to help catch liars everywhere, red handed.

The original paper can be viewed at: http://www.jneurosci.org/content/24/24/5500.full?sid=4dc151cf-6709-4dae-b031-69ba24dc61c4
Posted by      Anjali C. at 12:00 AM MDT
  Gino Ciarroni  says:
Interesting Anjali,
I find this article to be very intuitive. I question if the concept of deception is an evolved basic instinct. The Amygdala and and rostral anterior cingulate cortex both are triggered in basic survival based learning. The dorsal and rostral areas of the ACC both seem to be affected by rewards and losses associated with errors. The rostral ACC seems to be active after an error commission, indicating an error response function.

While the Amygdala, as part of the limbic system, deals with emotional learing, memory modulation, and social interaction. In regards to social interaction, The amygdala volume correlates positively with both the size (the number of contacts a person has) and the complexity (the number of different groups to which a person belongs) of social networks. Individuals with larger amygdalae had larger and more complex social networks. These people were also better able to make accurate social judgments about other persons' faces. It is hypothesized that larger amygdalae allow for greater emotional intelligence, enabling greater societal integration and cooperation with others. Can Deception be a survival interpretation of where or not we see a stimuli/person as threatening or benefiting? I wonder using the basic parameters, if animals can detect deception.

The amygdala processes reactions to violations concerning personal space. These reactions are absent in persons in whom the amygdala is damaged bilaterally.[42] Furthermore, the amygdala is found to be activated in fMRI when people observe that others are physically close to them, such as when a person being scanned knows that an experimenter is standing immediately next to the scanner, versus standing at a distance
Posted on Fri, 28 Oct 2011 12:02 PM MDT by Gino C.

October 23, 2011

The Urge to Experience, How We Respond to Novelty


Human beings once were localized to a a few locations on earth, and yet over time they explored and expanded. The need to travel and experience new areas and landscapes and discover new worlds is what led the polynesians to discover all the islands in the south pacific, Columbus to the new world, and Niel Armstrong to our own moon, and that same desire to experience the unknown is the topic of interest in Brian Knutson's and Jeffrey C. Cooper's article The Lure of the Unknown in the 51 volume, issue 3 of the August 3 2006 copy of the Neuron.

Before this study, the Ventral Tegmental Area and the Substantia Nigra were heavily implicated in the process of conferring salience onto a stimuli. For the purpose of this experiment, the researchers defined salience as one of 4 different pictures presented. One set of pictures depicted novel scenes, one set showed negative scenes, one set was behavioral in nature, as when showed the picture the subjects then were expected to perform a simple action, and one set were simply neutral, and repeated for the last portion of the experiment. These different pictures represented the different forms of salience that could be conferred onto such stimuli. It turns out that the novel pictures through use of fMRI showed the most activity in the VTA and SN, as well as portions of the striatum and the hippocampus, implicating that we place the most salience onto novel pictures and stimuli as opposed to others. Other pictures then showed increased activity in different regions of the brain, such as the negative stimulus activating the locus coeruleus and the amygdala while the neutral pictures activating the hippocampus and the anterior cingulate.

The question of memory stimulation was raised, and contrary to the prediction made due to the fact that the hippocampus was stimulated by novel pictures, memory of novel pictures was not higher than that of repeated pictures. However, an interesting outcome of a related study showed that repeated pictures with the prescence of a few novel pictures thrown in were granted a temporary memory boost, undetectable 1 day later but present after 20 minutes. This contrasted with studies showing that stimuli coupled with reward cues also received memory enhancements implies the possibility that novel stimuli elicit a reward response throughout the brain. Unfortunately the study did not have a category designated for positive pictures which could have played the role as the reward response and then compared to the novel pictures to look for any similarities in the response of the VTA and the SN, as well as the effect it has on memory to see whether novel pictures play reward roles.

These studies collectively form a new basis for further study into the human response to novelty, potentially discovering whether we gain a reward sensation from novelty and whether that even makes us go in search of it, just as historical examples such as Galileo and Niel Armstrong would seem to suggest in their descriptions of experiencing the novelties of space and the limits of the world.

Full Article: http://www.sciencedirect.com/science/article/pii/S0896627306005575
Posted by      Christopher R. at 11:22 PM MDT
Tags: amygdala, fmri, memory

The Neuroanatomy Behind Sociability


The Neuroanatomy Behind Sociability

People, like all primates, are inherently social animals. We live, work, and play together. We are defined by our relationships. However, individuals have varying degrees of sociability. The size and shape of our social networks varies from person to person. There are social butterflies - people who seem to know someone wherever they go. Who boast large numbers of contacts and network effortlessly. On the other end of the spectrum, there are the wallflowers - those with more modest social networks, who interact mainly with a select handful of people. A person's sociability - whether they are a social butterfly, or a wallflower, or somewhere in between - seems innate. It seems to be a fundamental characteristic of a person.

As a strong introvert, I've often wondered, what makes one person a social butterfly and another a wallflower? What's the difference between a person with 5 friends and person with 50?

According to an article published in the journal Nature Neuroscience in February, the answer lies in part with the Amygdala. Researchers took 58 healthy men and women ages 19 to 83 and measured both the size and complexity of the subjects' social networks using something called the Social Network Index. The results of the analysis were then compared with the relative size of the subjects' amygdalas. There was significant correlation. The authors state,

"We found that amygdala volume correlates with the size and complexity of social networks in adult humans. An exploratory analysis of subcortical structures did not find strong evidence for similar relationships with any other structure, but there were associations between social network variables and cortical thickness in three cortical areas, two of them with amygdala connectivity. These findings indicate that the amygdala is important in social behavior."

In addition, while amygdala volume was found to be correlated specifically with social network size, "amygdala volume did not relate to other measures of social functioning such as perceived social support and life satisfaction." This is important because it means that the findings of correlation are more specific than social functioning as a whole.

These results were not entirely surprising to the researchers. Previous studies in other (nonhuman) primates "strongly support a link between amygdala volume and social network size and social behavior." This latest research is, however, the first study to show correlation within a certain species and between individuals of that species.

So, does this mean that a person's social fate is sealed? That their social network size was dictated at conception along with eye color? Luckily, the answer is no; at least not entirely. Within the study, there were individuals with small amygdalas and enviable social networks as well as individuals with larger amygdalas, yet smaller network sizes. In addition, the results are corollary, and say nothing about social learning or nurture (as opposed to nature). (So, those Dale Carnegie books might prove useful yet!)

The authors' analysis of the study does not seem very focused on the individual. The important thing appears to be the trend - the statistical correlation. The authors hold that the findings are important because they support an evolutionary view called the 'social brain hypothesis'. The social brain hypothesis states that mammals evolved larger brains in part as a response to selective pressures to be more social, which required greater processing capacity. The authors also expect these results to act as preliminary data in future studies looking at larger brain networks that dictate social network size and complexity.

In spite of these more lofty applications, the individual correlation still remains. So, the next time you assess your Facebook friend quota, whether its admirable, or not so much, remember, it might simply reflect your respective amygdala.
Posted by      Kyle K. at 11:16 PM MDT
  Kyle Kimble  says:
I've tried to reformat the quotation marks. It ain't happenin'.
Posted on Sun, 23 Oct 2011 11:35 PM MDT by Kyle K.
  Don Cooper, Ph.D.  says:
Posted on Mon, 24 Oct 2011 8:13 PM MDT by Don C.

Predator or prey, your amygdala doesn't care


As a child, did you ever come across an animal you had never seen before, say a small, harmless mouse, and felt highly alert, maybe your heart started racing or you felt nervous, despite knowing nothing about the animal? Or perhaps you remember being strongly drawn to an animal like a puppy at a young age, more so than an object like a toy? A recent study published in 2011 has found that there may just be a neurological explanation for our heightened emotional responses to animals.

This experiment recorded neuronal activity from three regions (the amygdala, hippocampus and entorhinal cortex) of the medial temporal lobe in 41 neurosurgical patients as they viewed a series of four different stimuli, either landmarks, people, objects or animals. The results researchers observed were quite interesting. Of all three medial temporal lobe regions, the only region to show significant selectivity to any stimulus was the amygdala. Knowing this, what stimulus would we think the amygdala might be most highly specific for? Well, we know that the amygdala plays a primary role in arousal, emotional responses and fear, so it shouldn�??t be surprising that results concluded there to be a highly significant selectivity (P< 10-15) for animal images in the neurons of the amygdala. These neuroscientists then tested for differences in neuronal responses between the left and right amygdala by repeating the above experiment separately on each section of the amygdala, concluding that the observed category-specific response arose solely from the right amygdala.

Now that we know the amygdala is selective to animal images, we might wonder, do some animals generate a more significant response than others? For example, does an image of a lion or other dangerous, life-threatening animal evoke a higher response than an image of a small, cute animal like a rabbit or a kitten? Surprisingly, no! Researchers found no relationship between the amygdala responses and the characteristics of the animal. So if some stimuli are more threatening than others, why don�??t they evoke a higher response? An evolutionary explanation for this is the concept of predator vs. prey, where each stimulus has its own significance as either posing as a threat, or posing as a potential meal. Because each of these is so crucial to survival, our brains have evolved to hold specific processing for this category of stimuli.

With this knowledge, the next question is, is there a category-specific response in other animals as well? And if so, does it differ among animals based on their hierarchal position as a predator or prey?

Source: Nature Neuroscience: A category-specific response to animals in the right human amygdala
http://www.nature.com/neuro/journal/v14/n10/full/nn.2899.html
Posted by      Hannah M. at 8:14 PM MDT
Tags: amygdala

True or False: Emotions and Electrons Are Alike (Answer: true)


Remember that one time your girlfriend or boyfriend got ketchup on their nose while eating French fries and you thought it was hilarious, but immediately afterwards you felt guilty because they glared at you and growled for a napkin?

There is a word for that: ambivalence. The word ambivalence means that you feel two contradictory emotions (hilarity and guilty) simultaneously. Look a little more closely at the word ambivalence and you can probably guess what electrons and emotions have in common: valences. Emotional valences, like valence electrons, are shown outwardly on a persons face and they either attract (positive valence) or repel (negative valence) the person at which they are directed.

Many studies, since the advent of the fMRI, have examined the underlying circuitry involved in the expression and perception of emotion, especially negative valence emotions such as anger, sadness, and fear. The paper I analyzed is no exception to this rule: researchers from Kings College London, University College London, and the University of Zürich worked together to a) ascertain the circuitry that underlies the processing of emotionally negative facial expressions, and b) determine whether or not the amygdala is involved in the conscious processing of emotive faces. Basically, they wanted to know if our first response to facial expressions is to think or react.

In the study, a pool of 40 subjects (selected based on a range of nonspecific qualities) were shown a set of 60 faces and a corresponding number of fixation crosses (an image of a white screen on which a + is superimposed), while in an fMRI. Each of the 60 faces displayed either a neutral expression or a negative expression (anger, fear, or sadness) and the subjects used a clicker to indicate whether the face did or did not show an emotion. For each face, the response time and accuracy was recorded and was used in concert with the data provided by the fMRI images. In addition to the tests performed using the fMRI, a battery of statistical tests corrected for noise and anatomical dissimilarities among participants.

The findings are significant: the amygdala is not the only cranial structure that modulates facial processing. To be more specific, their results show that while the amygdala is involved in the processing of facial affect(Dima et al 1) there are also pathways to and from the fusiform gyrus, the inferior occipital gyrus, and the ventrolateral prefrontal cortex, which do not involve the amygdala. Most notably, anger was mediated by the inferior occipital gyrus and ventrolateral prefrontal cortex, not the amygdala.

What does all of that mean?

Basically, our brains have evolved for cognition for so long that we now respond to physical or emotional danger (anger in this case) in a cognitive fashion. We think before we react to a potentially harmful event.

Now think back for a second to your girlfriend or boyfriend with ketchup all over their nose. If this research holds, you will not immediately react and give them the napkin; you will, in fact, think about the potential harm that could come to you if you do not (minimal: they probably will not punch you), and the potential benefits you will reap if you do not (photographic evidence of the event). As far as I am concerned this decision is easy: memory is leaky; emotions are transient; but a picture lasts a lifetime.

What would you do?

Source: https://cuvpn.colorado.edu/content/31/40/,DanaInfo=www.jneurosci.org+14378.full.pdf+html?sid=20ba56d1-84f2-4fdb-b108-83aed6437270
Edited by      Christina U. at 2:03 PM MDT




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