Tag Archives: Amygdala

The Role of the Amygdala in Long Term Memory

The amygdala is well renowned for its role in memory, particularly during fear conditioning. During Pavlovian fear conditioning, the lateral amygdala receives input from both the conditioned stimulus (CS) and the unconditioned stimulus (US) and is thought to be the site of plasticity for the association between the CS and the US (Phelps, 2009). The amygdala also becomes active in humans during exposure to strong aversive odorants, suggesting that the amygdala makes use of the transduction of negative odorants in some way as to lead to the consolidation of fear memories, catalyzing the retention of experience surrounding the exposure (Zald; Pardo, 1997). The amygdala also responds to identify reward representations, working with the orbitofrontal cortex to help promote behavior that can result in rewards (Gottfried et al., 2003). The amygdala, therefore, seems pivotal in labeling the retention of past experiences with an emotional tag, supplying the organism with an emotional context in which to interpret the memory, and with any luck, an adaptive advantage.

Read more…

The Role of the Hippocampal-Thalamic Circuit

In 1999, Aggleton and Brown proposed a neurological system for episodic memory that had been based upon about three decades of research. One of the intriguing features of this circuit is that it involves three different regions of the telencephalon (the frontal lobe, the temporal lobe, and parts of the limbic system), but it also includes the diencephalon (thalamus). In the late 1960s it had been known for some time that the diencephalon and the temporal lobe were involved in episodic memory (Delay & Brion, 1969). Part of the mystery, however, was that these two brain regions develop from different secondary vesicles, yet damage to one or the other of these regions results in similar forms of amnesia. This led Delay and Brion to hypothesize that the diencephalon and the temporal lobe must be a part of the same neural circuit, whereby damage to any part of it would result in a similar memory deficit.

Read more…

If you’re going to talk about the biology of potential rapists and molesters, please mention the biology of their victims, too

Senator Saxby Chambliss

Addressing sexual assault in the military, Senator Saxby Chambliss recently offered this to a Senate Armed Forces Committee hearing as an explanation, “”The young folks who are coming into each of your services are anywhere from 17 to 22 or 23. Gee whiz, the hormone level created by nature sets in place the possibility for these types of things to occur. So we’ve got to be very careful how we address it on our side.”

While I do think the senator was making an honest attempt to understand and address the problem, and by no means do I think he condones rape and sexual assault (at least intentionally), he needs to realize that the argument “from biology” can easily sway people into believing that these assaults are nobodies’ responsibility. This has been shown in court numerous times. If you can explain to the jury that the defendant’s brain is somehow different from the brains of normal law-abiding individuals, the jury is likely to downgrade the seriousness of the crime – although, there have been some exceptions to this.

As a way to address this issue, I would like to mandate that the biology of the victims is also mentioned. There have been a growing number of studies showing that abuse can seriously alter a person’s brain – the most devastatingly when the victim is a child and still undergoing neuronal development, but also very seriously in adults. Extreme stress in adults can inhibit neurogenesis (the growth of neurons) in adult hippocampi (Nibuya, 1995; Duman, 1997). Two important things that the hippocampus does is facilitate learning and memory and help to regulate aggression – things that become compromised in the victims of abuse. Rape can also lead the victims to suffer from Post Traumatic Stress Disorder, a condition that can result in a reduced medial prefrontal cortex, a hyperresponsive amygdala (could lead to experiencing fear on a frequent basis), and a reduced hippocampus (Shin et al., 2006).

By discussing the biology of the victim, therefore, we can see that rape and abuse can profoundly change their brain – in other words, the brain of the victim after the rape and abuse will NEVER be the same again.

But don’t stop with talking about the biology of the victim. Bring back the individual who experienced the abuse, and listen to the lamentations of the victims and the accounts of the clinical psychologists who have tirelessly worked to help victims of rape and abuse live and function with their experiences. If at this point a politician can’t see how useless, redundant, and offensive the de-personalized ‘hormone’ argument is, they do not deserve to represent anybody.

Sources

Huffington Post: Saxby Chambliss Attributes Sexual Assault to ‘The Hormone Level Created By Nature’

Duman RS, Heninger GR, Nestler EJ (1997). A molecular and cellular theory of depression. Arch Gen Psychiatry, 54, 597–606

Nibuya M, Morinobu S, Duman RS (1995) Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci, 15, 7539–7547

Shin, L. M., Rauch, S. L., & PITMAN, R. K. (2006). Amygdala, medial prefrontal cortex, and hippocampal function in PTSD. Annals of the New York Academy of Sciences, 1071(1), 67-79.

The affects of abuse in the brains of children

Brain scan when viewing photos of angry faces

Brain scan when viewing photos of angry faces

We’ve known for a long time that childhood abuse can leave long term damage and profoundly impact the life of an abused individual on into their old age. If you glance at any abnormal psychology textbook, and you look at suspected ideas of what causes personality disorders, childhood abuse is always on the list.

However, understanding what changes are actually taking place in the brain as a result of abuse have only really come to light over the last few years. This is mainly due to the bold and daring work of a number of neuroscientists – people like Dr. Eamon McCrory at the University College London.

Using fMRI, McCrory and his team found that children who had been exposed to family violence showed the same brain activity as combat soldiers, when exposed to an exercise where they viewed pictures of angry faces. If you just stop to think about that for a few seconds, it’s really very unsettling. The two brain areas that showed heightened activity in both abused children and soldiers were the amygdala (involved in fear recognition and memory formation), and the anterior insula (involved in emotion and self-recognition). McCrory suggested that perpetual exposure to negative stimuli, such as being subject to continued abuse or having to survive in a war zone, actually causes the hypersensitization of these two areas in the brain.

Hypersensitization means that those areas have essentially been trained to respond with a lot of activity, which over time means that there will be a large response, even when the stimulus is not as threatening or negative as the original (the abuse / the war zone). When the various parts of the brain have been calibrated to respond this way, the individual is likely to suffer from an anxiety or a stress disorder, or perhaps in the case of childhood abuse, a long term personality disorder.

A key difference, with regards to brain activity, between abused children and combat soldiers, is that the brain of the child is still developing. Brain maturation is complete at about the age of 25, but there are some crucial developmental stages during childhood. After the child is born to the age of 6, very important areas in reasoning and emotion are still growing and developing. So if a child experiences extreme stress, certain areas of the brain that have not matured yet will still respond to the environment, only the over activity and the stress could cause neurochemical changes that stymie neuronal growth, meaning that these areas will never develop correctly.

When this happens the child could end up with a personality disorder – the worst case scenario being antisocial personality disorder, or psychopathy.

Fear and the Amygdala

The experience of fear has often been closely tied to activity in the brain structure called the amygdala, which is itself a cluster of nuclei and highly involved in the processing of memory. There are two amygdalae, one on each side of the brain.

There is ample evidence that the amygdala is heavily involved in fear conditioning, the procedure whereby we learn to tag aversive experiences with feelings of fear. Fear conditioning is perfectly natural, and functions to help you avoid aversive experiences in the future. There are numerous problems that can arise because of fear conditioning, however, such as tagging healthy and innocuous experiences with a fear response (perhaps because of past trauma), making one susceptible to perpetual fear, paranoia, and misanthropy. On the whole, though, fear conditioning should facilitate your passage through life.

A recent study by Feinstein et al. found that while the amygdala is active during fearful occurrences, it is not responsible for our subjective experience of fear. Feinstein et al. found that a lady, who suffered a condition that resulted in a reduced amygdala, and subsequently seemed to lack a fear response, could be induced to experience fear by increasing her carbon dioxide intake. In fact, people who have a reduced amygdala become even more fearful than those with a healthy amygdala during these negative experiences. I would expect that CO2 triggers fear because of the impending threat of suffocation; if the body is becoming low on oxygen, any mechanism or experience that motivates the organism to take action will promote survival.

On the surface, this experiment seems to suggest that you can induce fear in those who do not typically experience it.

Naturally, this peaked my curiosity because of my interest in psychopaths. Those with psychopathy typically have a reduced amygdala and cannot experience fear. I would be curious to know if this method of inducing fear could be used to help psychopaths develop a conscious and emotional understanding of what it is to experience fear. There are still no treatments for psychopathy, but if we could induce fear in these individuals, perhaps we could trigger the beginning of a conscience?

Jack Pemment, 2013

 

Sources

Nature News: Researchers scare ‘fearless’ patients – Feelings of terror did not involve the brain’s fear center.

Feinstein, J. S., Buzza, C., Hurlemann, R., Follmer, R. L., Dahdaleh, N. S., Coryell, W. H., … & Wemmie, J. A. (2013). Fear and panic in humans with bilateral amygdala damage. Nature neuroscience.

Mind Whimsy

Kevin Dutton on psychopathy: A bright side?

In a two-part podcast (Part 1 : Part 2) on the Scientific American website, Kevin Dutton, a psychologist from Oxford University in the UK discusses why psychopathic traits could be a good thing. Dutton has recently written a book entitled The Wisdom of Psychopaths: What Saints, Spies, and Serial Killers Can Teach Us about Success. This line of thought is obviously a little shocking, not in the least because of the immense societal and personal damage that can happen in the name of psychopathy. On the podcast, however, Dutton is clearly an expert on the subject and has clearly put an immense amount of work into this book.

So what are some of the points that get raised in the interview?

There are two points made clear that I believe are done to ease us into accepting the benefits of psychopathy, as well as to educate us about psychopathy and dispel some of the myths. Firstly, psychopathy is a dynamic scale and is far from a black and white issue, and secondly, many psychopaths are not violent. These are perfectly valid points.

Dutton also draws a distinction between successful and unsuccessful psychopaths. This distinction has been made for a while; in neurological studies of psychopaths, success is measured by determining time in prison (more time, less success), and researchers have tried to see if there are brain differences between these groups of psychopaths. Yang et al. (2005) found that unsuccessful psychopaths seem to have a reduced amount of prefrontal gray matter (less neuronal cell bodies) when compared to their successful counterparts. Dutton discusses success in terms of impulsivity; if the psychopath is too impulsive, then their actions are more likely to land them in trouble or veer them away from their ultimate goals. The neurological aspect could actually reinforce this view, because the prefrontal cortex does play a role in impulse control; a reduced amount of neurons in the prefrontal cortex could result in low impulse control.

Dutton goes on to mention that a successful psychopath, i.e. with good impulse control, could make a good politician. Impulse control, coupled with manipulation, a lack of empathy, grandiosity and charisma, could indeed make you a great politician or political leader. However, I think it must be noted that many people are likely to distrust politicians if some of those characteristics become evident, and so even if they are natural to the psychopath, exposing these true colors could mean that they will not be re-elected. The dirty deeds of politicians are also enough to give most people scruples, and I’m sure many would elect to be moral individuals rather than a heartless and two-faced politician. Having said that, I’m sure the argument could be made that these people are a necessary evil that do ultimately push progress, even if it is at the expense of others (someone has to get their hands dirty).

In fact, Dutton does allude to the necessary evil that perhaps societies have to have by mentioning the utilitarian argument, which is essentially acting in a way that will benefit the most. It turns out that non-psychopaths can actually be very bad at this, and Dutton uses a couple of moral dilemma questions to demonstrate the point. A train is hurtling out of control down a track and on course to hit 5 people. You can divert the train by pulling a switch, but by doing so the train will hurtle down another track and kill 1 person. Assuming that 1 person is a stranger to you, most people would agree that pulling the switch is the right thing to do. However, in a different scenario, what if the only way to stop the train from killing the 5 people was to push a large stranger from a footbridge in front of the train? Not many people would elect to do this, but a psychopath makes no distinction between these two scenarios, and this has been tied to a lack of cellular activity that takes place in the prefrontal lobes of psychopaths.

Using this example, clearly pushing somebody in front of a train is not something we should ‘learn’ from the psychopathic, but it does raise the interesting point that perhaps in more complex situations, where the consequences may not be quite as severe as murder, perhaps we do need people who do function and think this way. Many political leaders and CEOs often make decisions that increase the profit margin at the expense of making many workers redundant. Successful and intelligent psychopaths are clearly made for these kind of jobs. But again, is this something we should learn from psychopaths or just accept that in order for the world to work it is a necessary evil?

Dutton also mentions that psychopaths do not procrastinate, they are cool under pressure, and they do not care what people think of them. On the surface it could seem like these are great qualities, but it must be pointed out that the  reasons they do not procrastinate, are cool under pressure, and do not care what people think of them is because their brain has not developed correctly.

I would argue that the reason psychopaths do not procrastinate is actually related to Adrian Raine’s hypothesis, which is that as psychopaths also have a low-resting heart rate (something that could feel uncomfortable as it is a struggle to feel aroused), they are prone to seeking stimulation. Psychopathy is often comorbid with alcoholism and cocaine addiction, but these are clearly things we would not want to learn from them. However, with good impulse control, the psychopath will be seeking a huge physiological pay-off if they succeed in their plans -which will no doubt be experienced at the considerable expense of others.

The reason they are cool under pressure is because their amygdala is either under-active or/and maldeveloped. One of the things the amygdala is responsible for is fear conditioning – things that shock and scare us cause the amygdala to become active and it increases the saliency of memory at that moment, which helps us remember in the future what in the past caused us to be scared. Psychopaths do not feel fear, at all, meaning they cannot be fear conditioned. I would argue that this is actually a bad thing and is likely to cause more problems than advantages. For one, you cannot grow up and assimilate into society with a sense of morality if you are a psychopath; however you can completely fake it. To be a successful psychopath, therefore, and go unnoticed and unchallenged, you had better also be very intelligent.

Having no empathy will of course lead you to not give a damn about what other people think. However, surely the merits of this are situational? You should always care about what your loved ones and friends think about you, because that helps you to grow and mature, and opens you up to certain kinds of wisdom. So while it is important that you know who and what to ignore, you also need to know when to pay attention.

These qualities are not decidedly psychopathic and can be learned from life experience. It’s almost accidental that psychopaths show those traits – given their neuronal deficits, they don’t have a choice.

Personally, I think that Dutton has raised some great points about the role of psychopathy and how culturally we do seem to have a niche where these people can flourish – this probably tells us a lot about human nature and society. But from this cursory introduction to his work, I would be careful of blurring the line between taking life lessons from a psychopath and accepting that our culture needs/rewards them.

I do, however, look forward to adding his book to my collection, and benefiting from his wealth of knowledge on the subject of psychopathy.

Copyright Jack Pemment, 2013

Bundy vs. Einstein: Whose brain is more important?

The post-mortem studies of Einstein’s brain have recently re-appeared in the media (Huffington Post / NBC News / Fox News), and to be sure, the story of the physicist’s brain from when it was removed in 1955 by Thomas Harvey to its current state in many many pieces is fascinating. The drive behind this ongoing analysis is to no doubt find the neurological correlates of not just intelligence, but genius – and I mean this in the sense of profound thinker, because clearly genius could be applied to anyone with exceptional skills in the entire gamut of all human activity.

Like anyone interested in the great thinkers, I think the ongoing studies are amazing, and sure, as neuroscientific procedures become more sophisticated, there is no doubt we can learn more and more about what helps to shape the brain of an Einstein.

But what about the brain of a Bundy?

Ted Bundy was a serial killer from the Pacific Northwest who murdered at least thirty women, and after a rather chaotic flight across the country, was executed in Florida by the electric chair in 1989. There are at least two important notes about Bundy that would have made a study of his brain invaluable. Firstly, he was very good at what he did. Keppel, one of the detectives who were instrumental in Bundy’s apprehension, writes of his intelligence and patience; qualities that helped him evade capture for years. And secondly, Bundy eventually told Keppel (during an interaction that was supposed to aid in the capture of the Green River Killer), the dark desires that led him to kidnap, murder and necrophilia, were like a chemical tidal wave washing through his brain, like an addiction to a narcotic.

These two important points about the behavioral characteristics of Bundy could very well have been reflected in his brain. Bundy had numerous psychological tests once he was apprehended, but the exact nature of his pathology is still unknown. The likely candidates, two conditions in this case that go hand in hand, are Antisocial Personality Disorder (APD) and Psychopathy. To be sure, we know that people with these disorders have different brains – deficits have been found in the frontal cortex, the amygdala, and regions in between: And behaviorally, these are the people who rate highly on Hare’s Psychopathy Checklist, meaning that they do exhibit violent tendencies, have limited or frustrating emotional experiences, and have no conscience.

We would perhaps expect Bundy’s brain to demonstrate some of the neurological deficits mentioned above, but Bundy was more than a psychopath – he was a serial killer. Given that serial killers are only a minute fraction of the population and that when they are caught they are either executed or left to live out their lives in a maximum security penitentiary, access to their brain is very limited. In my opinion, this makes their brain even more academically valuable, and if access to the brain is denied it also denies any real neurobiological understanding of the serial killer brain – something that is perhaps as equally valuable as knowing what contributed to Einstein’s genius.

I do not think it would be difficult to persuade a serial killer to donate their brain to science after their death. If they are indeed psychopathic, then their ego could very well be coaxed into handing over “the center of their criminal genius” to researchers after death. When listening to this interview with Bundy, the day before his execution, it is not hard to imagine that his own intellectual curiosity and his ego would have turned his brain over to science.

Perhaps somebody could persuade the state of California and Richard Ramirez to preserve Ramirez’s brain for study after death, or Gary Ridgway (the Green River Killer) to give up his brain to science after he lives out his life?

Copyright Jack Pemment, 2012