The Reward Stimuli And Experiments
Although scientists knew for ages that people reacted to many stimuli in a conditioned way, it was only in the 1950s that they were able to prove that point.
So, in 1954, psychologists James Milner and Peter Milner of McGill University conducted an experiment on rats in which they discovered the reward centers in the brain.
They placed electrodes inside rats brains, after which they used a lever to create electrical stimuli inside the animals brains. Each time they would press the lever, the same area of the brain got stimulated. This was interpreted as the feeling of reward for their effort and success.
The more time the lever was being pressed, the higher level of stimulation the rats would receive. In the notes from this experiment, it was written down that one rat got so hooked up on the stimuli and the feeling of reward for pressing the lever that this particular animal pressed it more than 7500 times.
Since the rats in this experiment kept repeating the same action over and over again to stimulate the same area in the brain, Milner and Old concluded that the animals were enjoying the entire process.
Later on, other scientists took the plunge to additionally clarify the findings of these two scientists so there were some more detailed discoveries regarding the reward areas in the brain.
To be more precise, scientists found that the area around the medial forebrain bundle is one of the most sensitive parts of the brain related to rewards and pleasure.
The Lack Of Dopamine Issues
Weve already discussed the most frequent disorders connected with either the lack or excess of dopamine, such as apathy or schizophrenia.
However, these arent the only issues that can come as a result of unbalanced dopamine levels. Since most problems occur when dopamine is low, here are some symptoms that your dopamine levels might not be on a satisfied level.
Your dopamine levels might be low if you feel frequent tremors or cramps in your extremities, as well as stiff muscles. Whats more, these symptoms are often indicators of Parkinsons disease.
Thats why they require special attention and testing so that you start with the right therapy as soon as possible.
Further, people suffering from dopamine deficiency could suffer from constipation, the loss of appetite or fatigue.
All these symptoms can occur as the result of low dopamine. Simply put, when the pleasure centers in your brain dont feel that the reward is coming, in form of a pleasant taste or smell, the centers that control your appetite and the digestive system wont be inspired to eat at all.
Similarly, if you feel chronic exhaustion and low libido, your dopamine levels might not be as high as necessary for normal everyday life.
This connection is similar to the relationship between dopamine and food if the pleasure centers arent notified that theres going to be a reward for something youd initially like to do, there wont be any chemical support for the action in question.
Causal Hedonic Hotspots For Hedonic Enhancements
Yet hedonic gains of function can be produced by neural events in several forebrain structures, resulting in intense pleasure reactions. Animal affective neuroscience studies have recently identified a network for generating hedonic enhancement of liking reactions, embedded as a set of small hedonic hotspots distributed among several limbic structures throughout the brain, ranging from cortex to brainstem. Each hotspot can specifically amplify orofacial liking expressions elicited by sweetness in rats, when neurochemically stimulated by an appropriate drug microinjection. Hedonic hotspots have been found in subcortical forebrain nucleus accumbens and connected ventral pallidum, in the brainstem parabrachial nucleus of the pons, and may now be emerging in limbic areas of prefrontal cortex, including orbitofrontal cortex and insula .
The size of hedonic hotspots mapped so far is each about 1 cubic millimeter in volume in rats . By comparison, each structure that contains a hotspot is much larger. For example, the entire nucleus accumbens comprises nearly 10 mm3 in rats, but its opioid hedonic hotspot located in the rostrodorsal quadrant of medial shell constitutes only 10% of total NAc volume . In other words, as far as is known, nearly 90% of the remaining NAc may lack capacity to enhance liking reactions, even for mu opioid stimulation.
Hotspots at top and bottom of the brain?
Interaction between hotpot site and neurochemical stimulation
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Addiction And Substance Dependence
Addiction has been linked to the interaction of the brain and the substance being abused, but more specifically it is the pleasure center that conditions the body and the mind to become addicted. The NAcc is believed to be responsible for changing the way the body reacts to substances, including alcohol, drugs and even food. Some substances have the ability to increase dependence on other substances, for example one study showed that morphine injected into the NAcc increased the intake of ethanol in rats.
Repetitions: Revolution Through Revolutions87
Roy Wise still remembers the fascination with and the gravitational pull of the perpetuum during his graduate studies in the 1960s, walking down the hall and hearing the noise of the clicking of relays of electrical stimulation, and the abundant pleasure-talk, in which he, in his youth, was also caught up during one instance.
There was something irresistible about the lever-pressing, self-stimulating, insatiable rat. The pleasure revolution of the mid-twentieth century was a revolution by revolutionsa simple rattine lever press repeated hundreds of thousands of times. Perhaps it was only as a perpetuum that pleasure could be heard in the context of the behaviorism from and in which it initially emerged. Would there have been pleasure if it were not for the perpetuum, if it had emerged in terms of maze-running or electric-grid-crossing rats? The repetition of these repetitions in a growing number of laboratories was at the heart of the scientific revolution in pleasure. The behaviorists toolbox of repetitions and frequencies of repetitions materialized pleasure and made it supramaximal.
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Neuroscientists Identify How Reward Signals Are Transmitted In The Brain
The new findings by Jonathan Britt, from McGill University, were presented in a lecture titled, “Investigating the Pleasure Centers of the Brain: How reward Signals Are Transmitted” at the 2014 Canadian Neuroscience Meeting, which took place in May of 2014.
The so-called pleasure center of the brain was co-discovered in 1954 by James Olds, who was an American psychologist, and Peter Milner while he was a postdoctoral fellow at McGill University. Olds and Milner stumbled on the pleasure center after they implanted electrodes into the septal area of the rat and found that rats became addicted to pushing a lever that was stimulating the nucleus accumbens .
What Role Does the Nucleus Accumbens Play In Seeking Pleasure?
Electrical stimulation of the ventral tegmental area triggers the release of dopamine in the nucleus accumbens much in the same way that addictive drugs and natural reinforcers, such as sex, drugs, alcohol, foodor anything pleasurablealso triggers the release of dopamine in the nucleus accumbens.
The rats in Olds and Milner’s experiment would continue to press this lever incessantly even at the expense of eating and drinking for sustenance. This suggested that the area is the “pleasure center” of the brain and is involved in the reward-driven reinforcement of learning and addiction.
Where Is The Pleasure Center Of The Brain
Similarly one may ask, where are the pleasure centers located?
Located near the center of the brain, the nucleus accumbens is connected, by intermingled populations of cells, to many other brain structures having roles in pleasure seeking and drug addiction.
Additionally, what does pleasure do to the brain? Pleasure itself that good feeling you get in response to food, sex and drugs is driven by the release of a range of neurotransmitters in many parts of the brain. But dopamine release in the brain’s reward system is particularly important.
Thereof, what part of the brain controls pain and pleasure?
The prefrontal and limbic regions of the neocortex, particularly the orbitofrontal region of the prefrontal cortex, anterior cingulate cortex, and the insular cortex have all been suggested to be pleasure causing substrates in the brain.
Is the hypothalamus the pleasure center?
The expression “pleasure centres of the brain”, introduced by Olds in a 1956 article, is still a good way to describe the neuronal substrates of rewards for behaviour. The lateral and ventromedial nuclei of the hypothalamus are especially involved in this reward circuit.
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Scientists Identify Brain Circuit That Drives Pleasure
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Scientists have long believed that the central amygdala, a structure located deep within the brain, is linked with fear and responses to unpleasant events.
However, a team of MIT neuroscientists has now discovered a circuit in this structure that responds to rewarding events. In a study of mice, activating this circuit with certain stimuli made the animals seek those stimuli further. The researchers also found a circuit that controls responses to fearful events, but most of the neurons in the central amygdala are involved in the reward circuit, they report.
Its surprising that positive-behavior-promoting subsets are so abundant, which is contrary to what many people in the field have been thinking, says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory.
This finding contradicts the consensus that the central amygdala is involved primarily in fear-related behavior, the researchers say.
Desire To Dread: An Affective Keyboard In Nac Shell
The anterior NAc opioid hedonic hotspot and posterior suppressive coldspot fit within a broader anatomical NAc pattern of front-to-back valence organization in shell that generates additional emotions beyond liking and disgust. This NAc pattern resembles an affective keyboard arranged rostrocaudally within medial shell, which can generate intense desire or even dread as well as hedonic impact . The keyboard pattern is arranged from anterior to posterior ends of medial shell. At its anterior end, it generates predominantly positive-valenced motivations in response to localized neural events such as microinjections of a GABA agonist or of a glutamate AMPA antagonist : eating more than twice normal amounts of food, increasing appetitive seeking for food rewards , inducing a conditioned preference for a place paired with the microinjection, and even increasing liking reactions to sweet tastes . However, as the microinjection site moves more caudally in NAc shell, appetitive behaviors decline. Instead negative fearful behavior becomes increasingly intense, and sweet tastes become also disgusting .
Affective keyboard in nucleus accumbens for desire and/or dread
Multiple anatomical modules in NAc shell
Retuning the affective keyboard
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New Insights Into A Common Problem
Nobody starts out intending to develop an addiction, but many people get caught in its snare. Consider the latest government statistics:
- Nearly 23 million Americansalmost one in 10are addicted to alcohol or other drugs.
- More than two-thirds of people with addiction abuse alcohol.
- The top three drugs causing addiction are marijuana, opioid pain relievers, and cocaine.
In the 1930s, when researchers first began to investigate what caused addictive behavior, they believed that people who developed addictions were somehow morally flawed or lacking in willpower. Overcoming addiction, they thought, involved punishing miscreants or, alternately, encouraging them to muster the will to break a habit.
The scientific consensus has changed since then. Today we recognize addiction as a chronic disease that changes both brain structure and function. Just as cardiovascular disease damages the heart and diabetes impairs the pancreas, addiction hijacks the brain. This happens as the brain goes through a series of changes, beginning with recognition of pleasure and ending with a drive toward compulsive behavior.
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Pleasure Centers In The Brain
Rats can be made to gratify the drives of hunger, thirst and sex by self-stimulation of their brains with electricity. It appears that motivation, like sensation, has local centers in the brain
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Investigating The Pleasure Centers Of The Brain: How Reward Signals Are Transmitted
- Canadian Association for Neuroscience
- Research helps to better understand how reward signals, such as those produced by addictive drugs, travel through the brain and modify brain circuits. Researchers obtained results using optogenetics, which use light-responsive proteins to study the activation of neural circuits in distinct locations. The study has revealed circuits that are responsible for habitual behavior, which could be suitable targets for pharmacotherapies designed to treat drug addiction.
New research presented by Dr. Jonathan Britt, from McGill University, helps to better understand how reward signals, such as those produced by addictive drugs, travel through the brain and modify brain circuits. Dr. Britt obtained these results using optogenetics, which use light-responsive proteins to study the activation of neural circuits in distinct locations, allowing the researcher to precisely dissect the roles of different neural circuits in the brain. Dr. Britt’s studies have helped reveal circuits that are responsible for habitual behavior, which could be suitable targets for pharmacotherapies designed to treat drug addiction.
These results were presented at the 2014 Canadian Neuroscience Meeting, the annual meeting of the Canadian Association for Neuroscience — Association Canadienne des Neurosciences which takes place May 25 — 28th 2014.
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The Mesolimbic Pathway And Motivation
As the dopamine is produced, its released into the nucleus accumbens. The level of dopamine in this pleasure and reward center regulates the level of motivation and desire for rewards in our brain.
As such, it also plays a certain role in our subjective feeling of pleasure. Hence, when the level of dopamine is high in the nucleus accumbens, people feel satisfied, motivated and fulfilled.
When they get the reward for something theyve done, the dopamine level remains high, extending the feeling of satisfaction and exaltation.
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The Nucleus Accumbens The Pleasure Center Of The Brain
Danial Arslan 11/07/17
RESEARCH UPDATE: I am currently learning about the current and past research being conducted in my lab and in other similar labs at Emory by attending talks held on campus as well as through weekly lab meetings where graduate students in the lab share articles they find interesting and discuss their recent findings. I am also going through the long, arduous process of gaining clearance at Yerkes to work on prairie voles, which includes learning how to operate on them in the most humane way while following aseptic techniques. However, to completely understand the complexity and significance of the research being pursued in the lab, my graduate mentor assigns a review paper to me on a weekly basis to bolster my basic understanding of Neuroscience. We then get together and discuss the paper after the weekly lab meeting. This week I read about the Nucleus Accumbens and the following blog is a brief introduction into the role and significance of this portion of the brain. To view my previous blog to read more about my research and goals click here.
To access the paper, I was assigned to read and from which the information below is taken, click here.
The brain is divided into 3 portions. The cerebrum, which is the largest part of the brain, is responsible for controlling all voluntary actions, and is broken down into a series of lobes. Each lobe has a different brain function. .
Figure adopted from the review paper.
How Pleasure Affects Our Brain
This is part of our series on Changing the Brain, about whats happening in our brain in various mental states and how we can change it for the better and worse. You can read the other articles here.
Every day we make a range of choices in the pursuit of pleasure: we do things that make us feel good or work in a specific job because its rewarding or pays well. These experiences help shape our perspectives on life and define our personality.
Consequently, problems with our ability to manage or maintain our pursuit of pleasure often lie at the root of many neuropsychiatric disorders such as addiction and depression.
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Understanding Addiction Reward And Pleasure In The Brain
Last Updated on February 10, 2019 by Inspire Malibu
Learning how the brain responds to pleasure has blasted the doors of addiction research wide open. Though theres still a vast amount of unknowns where the neuroscience of substance abuse is concerned, researchers understand how the brains reward and pleasure centers are hijacked by drugs and alcohol.
In addition, doctors and scientists recognize addiction as a chronic disease that changes both the function and structure of the brain.
The hold that addiction has on the brain is extreme and powerful. Without a significant disruption of the disease, such as long-term abstinence or sobriety, the risks to an individuals health are dire.