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The Root of Reward of Reward Deficiency Syndrome

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Biology 103
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The Root of Reward of Reward Deficiency Syndrome

Shah Aashna Hossain

"What has spawned a new way of looking at addiction is the fact that many of the potent motivational, and hence addictive, properties of different substances seem to involve a common neurochemical actionÖ" a "relationship between neurotransmitters, their receptors in the brain and addictive action."

- Bozarth, director of the Addiction Research Unit in the Department of Psychology in the College of Arts and Letters (1)

In the Hebb laboratory of McGill University in 1954, research psychologist James Olds was running a series of experiments involving the neurological alerting process of rats (2). Accidentally, he placed some electrodes inside the rats' limbic system - a part of the brain containing a group of structures that play a role in emotions. The brain was wired in a way that this area could be stimulated when the rat pressed on a lever. Curiously enough, the rats went back to pressing the connected lever time and time again - even up to 5,000 times per hour. They even denied themselves everything except sleep for the stimulation provided. Carried out in the medial hypothalmus region of human brains, this experiment was found to provide its subjects with feelings resembling orgasmic sexual arousal. And if certain other areas of the brain experienced stimulation, negative thoughts were eliminated and a feeling of light-headedness would occur. Thus was born the concept of the brain's reward pathway. In other words, the discovery that "pleasure is a distinct neurological function that is linked to a complex reward and reinforcement system" (3).

The Cascade Theory of Reward

Four regions of the brain and four neurotransmitters play a significant role and are a major part of the neurological reward pathway: dopamine in the nucleus accumbens and the hippocampus; serotonin in the hypothalamus; the enkephalins in the ventral tegmental area and the nucleus accumbens; GABA - an inhibitory neurotransmitter -also in the ventral tegmental area and the nucleus accumbens (Depression Despot , - link to map of the brain's limbic system) (3). Out of all these neurotransmitters, dopamine has been singled out as "the primary neurotransmitter of reward."

In the majority of people, the reward system begins with one of these chemicals spreading out to "network" and involve the other neurotransmitters in what resembles a cascade ( - link to cascade system diagram) (3). As a result, one feels "secure, calm, comfortable and satisfied," referred to as the "reward." In fact, a lot of research has shown that a significant amount of human behavior is aimed towards achieving such feelings. In its simplest definition, reward deficiency syndrome is what occurs when such "networking" does not occur (4).

Reward Deficiency Syndrome

Genetic abnormalities, exposure to a prolonged period of stress, and alcohol or other substance abuse leads to a corruption of the "cascade function" (3). Such a disruption in the interaction between the neurotransmitters results in the opposite of the "reward": feelings of anger, anxiety, and other emotions associated with negativity. It has also been linked with compulsive and impulsive disorders such as alcoholism and attention deficit hyperactivity disorder (5) ( - link to table of disorders associated with reward deficiency syndrome) (3). Since dopamine has been deemed the most important of all neurotransmitters in the neurological expression of pleasure, it is a defect in the gene that carries this chemical that has been primarily blamed for the incidence of this disorder.

The D2 Dopamine-Receptor Gene

The D2 receptor has been determined the producer of the "reward"-producing neurotransmitters, and there are two main variants of the gene that contains this chemical: the A1 allele and the A2 allele ( - link to diagram of gene's variants) (3). Carriers of the A1 allele are said to be predisposed to reward deficiency syndrome for the simple reason that they have about thirty percent fewer D2 receptors than carriers of the A2 allele ( 03/blum-10.html - link to diagram comparing dopamine receptor numbers in an A1 allele and an A2 allele) (3). Thus, it is more likely that there are lower levels of dopamine-related activity in the brains of A1-allele carriers than in the brains of A2 carriers. And since dopamine plays a role in reducing stress as well, individuals with the A1 allele may depend on dopamine- releasing substances such as marijuana, alcohol, chocolate, and others to respond to their own stress or cravings.

The D4 Dopamine-Receptor Gene

The dopamine D2 receptor gene is thought to be the most instrumental in determining whether or not an individual will be diagnosed with reward deficiency syndrome or not; however, other genes - such as the D4 receptor gene - are believed to be involved in different expressions of the disorder. For instance, Israeli and National Institute of Mental Health scientists recently found that carriers of a certain form of the D4 gene are inclined to partake in novelty or sensation-seeking activities. The objective of their studies was to test Washington University scientist Robert Cloninger's hypothesis that such behavior is connected to the processing of dopamine. Indeed, the studies found that novelty-seekers tended to have a longer version of D4 than those who could not be classified as novelty-seekers. The latter group tended to be more calm, reflective, loyal, and rigid (3). A reason that has been offered to explain the similarity between these sensation-seekers and those with the A1 allele of the D2 dopamine receptor gene is because the D2 and D4 receptor-genes both have similar nucleotide sequences.

Are The Above Assertions Actually Valid?

The authors of the scientific articles above seem to be making the assertion that having a certain variant of either the D2 or D4 dopamine receptor gene will normally cause one to have reward deficiency syndrome. However, another notion that has been asserted before that is closer to the truth is that genes are not ever a direct cause of any such disorder. Defects in or variations of genes may distort cell functions and/or processes, which themselves may in turn cause a disorder, but the connection between genes and disorders has not yet been proven to be closer to that. Something else that raised suspicion and lessened the credibility of the claims made by Dr. Kenneth Blum and others was that the sites of those involved in the research or sites related to them were quite closely tied to those with a vested commercial interest in such a topic. For example, the "Partners For Change" website did provide some information on the syndrome; however, towards the end of the page, there was a definite emphasis on the selling of their "unique neuronutrient product" (4). It even mentions at the very end of the "article" that most of the material comes partially from the research carried out by Dr. Kenneth Blum. So while I believe that it is possible that such a syndrome does indeed exist, I cannot agree with the statement that it is directly linked to particular varieties of either the D2 or D4 dopamine-receptor gene.

WWW Sources

1)Depression Despot, Clear and Basic Explanations on Depression

2)The Neurobiology of Depression (Scientific American Journal), Neurobiological Views on Depression

3)Depression Information Center, A Clear Explanation of Depression and Facts and Figures Relation to Depression

4)Action Against Depresion (AAD), A Page on Seeking Help for Depressed Individuals

5)Psychology Informaiton Online, Depression as a Psychological Disorder

6)Causes of Depression, A Q and A on the Causes of Depression

7)Major Depression and the Neurotransmitter Serotonin, An Explanation on Neurotransmitters



Comments made prior to 2007

Hello, I'm doing research on reward deficiently syndrome for my grade 12 biology essay. I happened discover a contradiction between your information and another of my resources. It was about how many times the rats would activate the lever for a sensation of stimulation in James Olds's experiements. My other resource said it was 4 to 5 times per hour while the information given here said 5,000 times per hour. I'm quite sure the information on this site is the incorrect one, given the fact that there are only 3,600 seconds in an hour and for a rat to activate a switch 5,000 times in that amount of time is highly unlikely. Just thought I'd let you know of this incorrect information and hope you will change it in the near future. Other than that thank you for being a good source of information for my essay and I'll be sure to link all credit back you ... Cheryl MacLean, 7 March 2004


Richard Henry's picture

Self diagnosis

I'm a man who has struggled with addictions all my life. Without understanding I performed a self diagnosis, I came out with what I thought was A new theory in determine my short comings. Unbeknownst to me, I wasn't shure if what I was diagnoseing myself as... was "reward deficiency syndrome", or "reward deficiency disorder"??? so just for the fun, I did a search and came up with your post. Wow...I also came up with another theory for me.. Its called S.A.D.D substance, abuse, defiant, disorder.

Addictions and Dependency

" My View"

If modern society is interested in doing something important for the next generation I have a suggestion. Implement an education program in the early grades on the process of dependency and addiction. We need to break the cycle before it begins because our natural instincts can work against us. It all starts out with natural curiosity and the quest for knowledge fueled by a sense of adventure that often leads to experimentation. Every experience can be a learning event that teaches us right from wrong and the consequences of each action, its all a growing process through adolescence into adulthood. Education during the early years can teach us the things to avoid. Knowing is half the battle, we can avoid the stages that lead to the tormenting outcome of addiction.

It has been over two years and I still struggle with addiction. I am no longer dependent on any mind-altering substance or mood-enhancing medication. But addiction still plays a part in my daily life. It's still difficult to become and stay totally clean. Its important for me to clarify what I call "dependent". Its one important step in becoming addicted.

It all starts at the experimental stage while trying something new and experiencing the rewards of that action. Some rewards are unpleasant and we avoid that experience from that point on in our life. Like touching a hot stove. The experience is imbedded in our brain as memory and our brain reminds us of the unpleasant reward leading to avoidance. Like spankings. You know its wrong but go ahead and do it anyway. You know if you get caught you could get a spanking. For some the risk is worth it, for others its a deterrent.

Its our natural instinct to avoid sadness and seek out rewards of happiness or fullfillment. Contentment. This is how we lived in the wild during our hunter-gatherer times. We hunted and fed our families which gave us fulfillment so we repeated this over and over to survive. This is one of the reasons a person is so easily entertained and attracted to those false stimulants that give us the reward of fulfillment in today's world that is cold and empty to some. Everybody's pressed for time. The quicker and easier the reward the better and with many that comes in the form of alcohol or drugs. They trigger that same reward experience in the brain, it satisfies that feeling of comfort and joy we all seek; it disguises all other unhappy feelings.

As a result it becomes difficult to endure those unhappy feelings. We are frustrated by our inability to bring closure to issues in our life. The feelings become so overwhelming that we become dependant on our choice method of escape, comfort and security. This type of behavior is sometimes handed down through generations as a coping tool. I remember after a funeral we would all gather for a reception and get drunk to forget about it. That's not the way it works, this only creates a cycle of avoidance. All thoughts and unhappy feelings become "the root of all evil".

For myself the need to self medicate was increasing more and more as I dwelled on the past. The "could haves", the "should haves" needed constant suppression. Otherwise I would become overwhelmed with unhappy feelings and thoughts of suicide would enter my mind. I had lost so much. Without intervention and proper detoxification and or appropriate medication, it becomes a battle for survival. Not for good as in hunter-gatherer days but to the drugs or alcohol. It becomes a constant struggle to maintain a regular intake to maintan a survival mode. The relative stability comes at a high price with the effects of the drug or alcohol usage. Now, in addition to dealing with the underlying issues but the effects of dependency.

Dependency is now a full-blown addiction. Ultimately, your involvement in the drug/alchohol culture may lead to jail, an institution or death. This is why its so important to reach out to our young ones and educate them at an early stage. There will always be some experimentation but today the choices are becoming endless and in abundance. Some have ever-lasting effects and consequences like methamphetamine, cocaine, crack cocaine. In my experience crack has become the ultimate escape, a tool with the most overwhelming reward that addicts the brain.

Today I'm no longer dependent on the use of crack cocaine but the triggers in my brain are a constant reminder of days past. A person who smokes can easily relate to this reward. In times of stress the first thought that comes to mind is "I need a cigarette". Today I'm dealing with all the issue in my life as they come and bring closure whenever possible, but the need to reach that ultimate satisfaction still awakens my inner self and makes me vulnerable to relapse.

Recovery will be ongoing for many years to come, receiving that high may never happen naturally but each day I cherish the little things that bring me happiness and comfort. With Gods help I'm keeping the little things in the forefront of my brain and learning alternate coping tools. My faith in God and commitment to help the young will satisfy my cravings in the future. God Bless
Richard Henry

Anonymous's picture

how to fix it?

I strongly suspect that I have a brain wiring which is similar to the A1 allele.
Is there any way to figure this out?
I have never been able to sleep well, or handle emotions well.
I solved my emotions problem by not handling them at all (ie. repressing them permanently) and the sleeping/stress problems by massive use of drugs.
However, I have quit the use of drugs a couple of days ago, and now all those negative effects kick in once again.
Is there any to handle this, without damaging my health?

SJS's picture

Slightly confused here

5,000 times per hour really sound quite huge number.How can there bbe so much variation between your specified number & Cheryl MacLean's numbers.I am really confused.Please somebody let know that which one is true....