Abstract: It was originally thought that both the palatability and the reward value of nutrients are processed in the same brain region. However, a study conducted by Wassum et al. (2009) provides evidence that this is not the case. They found that the nucleus accumbens and the ventral pallidum are responsible for processing food palatability while the basolateral amygdala is involved in assigning incentive value of food rewards. Furthermore, these processes are interrupted when naloxone is administered into their associated regions. This research is significant because it could provide insight into why subjects continue to engage in certain behaviors despite them no longer being "palatable" or enjoyable, such as in drug addiction, and could provide the basis for more effective treatments of addiction.
Introduction: Food palatability refers to an organism 's subjective experience of food and can be either positive or aversive. As a result, this is generally associated with reward "liking". The reward value attributed to obtaining different foods plays a role in determining an organism 's actions, and is thus referred to as reward "wanting". These "liking" and "wanting" pathways were previously thought to be processed by similar, linked, neural structures including the nucleus accumbens and ventral pallidum and were thought to go hand in hand (Smith & Berridge, 2007). However, many researchers now suggests otherwise. Studies still indicate that the nucleus accumbens shell
Brain chemistry can affect different addicts more then others. Drugs and alcohol are more of the main addictions that brain chemistry affects. Once taking these addictive substances your internal natural drug dopamine is lowers causing you to seek more external addictive substances. This causes craving and makes it a lot harder for the addict to stop. In Olds and Milner’s later experiments, they allowed the rats to press a particular lever to arouse themselves, to the effect that they would press it as much as seven-hundred times per hour. This region soon came to be known as the "pleasure center". Using drugs and alcohol stimulates the pleasure center in the brain that makes your brain think, “feels good- want more“. This can make it increasingly harder for an addict to stop using, until they hit a point called “rock bottom”. This is where choice comes back into play.
It is believed that certain individuals are predisposed or vulnerable to addiction based on biological, psychological and social influences. The euphoric high produced by many addictive substances is the result of overstimulation of the “pleasure center” of the brain. This is the same area that controls emotions, fear, self-control and overall feelings of wellness. The presence of these foreign chemicals creates a response that the brain will crave as soon as it fades. The brain’s chemistry works against its own health, as it rewires its decision making faculties around the primary goal of finding and taking more of the drug” (1). Many people mistakenly believe that psychological addiction is somehow less serious or real than physical addiction. The psychological aspects of addiction are much more challenging to repair and recover from than the physical addiction. Psychological addiction can last for years or even a lifetime.
This research paper will evaluate the biological aspects of addictive substance or behavior and how it affects the brain and organs. Biological aspects include dopamine levels that are replaced in the brain due to the reward system being overtaken and the absorption rate of the drug once it is ingested will be discussed. The biological aspects are extensive and permanent if the individual does not get the help they need. Furthermore the clinical issues of addictive substance or behavior will be discussed along with medical treatments and ethical issues. This includes treatments such as counseling
According to the biological perspective, drug use may start off as casual, but through continued use, it produces changes in the brain that influences the onset and maintenance of drug addiction. (Horvath et al., 2013). Drugs have their most prominent effects on the function of neurotransmitters. Almost all major drugs of abuse activate the reward system and cause a flood in the levels of dopamine which is a neurotransmitter that is involved in pleasure. As a result, not only do people learn to associate drug use with pleasure, but the brain also starts to reduce its own natural dopamine production in adjustment to the levels of dopamine produced by the drugs. This is called tolerance, and the consequences of tolerance are highly influential
The addictive properties of cocaine are a dopamine D2-receptor researchers “indicate that these dopaminergic neural systems play an important part in rewarding effects” (Miller, Gold, Smith, 1997, p.64).
Across all addictions, there is a central theory as to how such an addiction can occur. The common mechanism of all addictive substances is the activation of the brain’s “reward system”, made up of dopaminergic neurons of the midbrain and their extensions to the limbic system (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3272277/). This system is normally used in advancing evolutionary fitness promoting activity, such as sex, food, or social interactions (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3272277/). In such normal natural behaviors, the reward system activity is relatively brief and weak. However, addictive substances abuse the system’s circuitry, causing
Dr. Anna Rose Childress performed a simple experiment with Coleman. While scanning his brain, Childress showed Coleman videos of nature and of drug use. Even after a period of “clean time,” the brains of must addicts reacted to the images of drug use. However, Coleman’s brain showed no difference. This may be a result of the Baclofen impacting his cravings, or it may be exchanging one addiction for another.
The three stages of addiction are binge/intoxication defined by consumption and reward, withdraw/negative affect due to absence of the substance, and preoccupation/anticipation relating to the stage of seeking11. As such, the brain regions associated with each stage are the basal ganglia, extended amygdala, and prefrontal cortex correspondingly. The stages of addiction are cyclical, one leading to the next. The physical and psychological damage is magnified as the cycle is reinforced and strengthened with time
In their article, “The Effects of Pharmacological Opioid Blockade on Neural Measures of Drug Cue-Reactivity in Humans,” Courtney et al. investigates the role of opioid blockade on neural systems underlying drug craving. They tested whether blockade of opioid receptors can actually reduce the salience of the methamphetamine cues.
In the experiment done and reported in the article “Intense Sweetness Surpasses Cocaine Rewards,” by Magalie Lenoir, young adult ,male, Wistar rats that weigh 221 to 276 grams were experimented on. Before the experiment, these rats were housed in groups of two or three and were sustained in a light and temperature-controlled environment. The food provided was a standard rat chow A04 that contains 60% carbohydrates (mainly corn starch),16% proteins, 12% water, 5% minerals, 3% fat and 4% cellulose. No refined sugar was added to their food. This study researched whether the rats would rather receive sugar or cocaine as a reward. To prepare for the experiment,anesthetized rats were prepared with silastic catheters in the right jugular vein (which is the throat or pertaining to it). Catheters were flushed daily with sterile antibiotic solution containing heparinized saline and ampicillin.Behavioral testing began 7-10 days after the surgical procedure.
Consequently, individuals privy to recurring cocaine use suffer from various executive deficiencies, including “impairments of multiple measures of attention, visual and spatial memory, language, decision making, and sensory perception functions” (Bickell et al., 2015). High rates of delayed discounting, meaning decreasing value of a reward perceived by an individual as reward time progresses (impulsivity), are prevalent among cocaine using individuals. Therefore, delay discounting may function as a transient process between impulsive control disorders and addictive disorders, and a treatment that can decrease its rate would be beneficial (Bickel et al.,
Substance addiction can hugely impact on a person’s thinking, functioning and behaviour. Whilst depressant drugs such as alcohol and opioids slow down your central nervous system (CNS), stimulants such as cocaine or amphetamine increase the activity of the CNS, leading to higher blood pressure, heart rate and increased alertness. Repeated abuse of the substance leads to tolerance and withdrawal, in turn this leads to the user showing signs of irrational behaviour. Another form of substance abuse is hallucinogens; they can cause powerful changes in sensory perceptions. It works by binding to the serotonin receptors, these neurons control visual information and emotions, and this can lead to various effects on the user. Neurobiology can help us understand the reasons for addiction and the effects they have on us. Groman and Jentsch (2012) discuss key issues of differentiating the causes and consequences of addiction through neuroimaging and behavioural research on monkeys, they found that the dysfunction of the dopamine
The complexity of the human brain creates mystery when determining the influence of neurophysiological factors and their role in the process of addiction. There is a proposed relationship between drug addiction and the mesolimbic dopamine system, with the mesolimbic pathway from the ventral tegmental area to the nucleus accumbens considered the ‘reward centre’ of the human brain (Alcohol Rehab, 2011). A release of dopamine is necessary for ‘reward’ which is hypothesised to initiate the addiction cycle by providing positive reinforcement for drug self-administration (Feltenstein & See, 2009). Methamphetamine triggers the release of dopamine from synaptic vesicles which flood the synaptic cleft activating feelings of euphoria, well-being
The OFC function has been implicated in the devaluation of food rewards by satiety (Gremel and Costa, 2013). It has been implicated in various cue related behaviors modulated by changes in expected value. Furthermore, the OFC neurons hold value based information ‘online’ to guide future decision-making and therefore estimate the likelihood of specific outcomes to guide future responses (Wilson et al, 2014). Given that the OFC receives significant sensory information, the OFC likely integrates signals about sensory properties with expected outcomes (Thompson et al, 2017). Thus, the OFC registers the current value of foods and updates actions based on this information. However, several studies have indicated that obese humans and rats fed a
“The overstimulation of this reward system, which normally responds to natural behaviors linked to survival (eating, spending time with loved ones, etc.), produces euphoric effects in response to psychoactive drugs. This reaction sets in motion a reinforcing pattern that “teaches” people to repeat the rewarding behavior of abusing drugs ”(“Understanding Drug Abuse). Using addictive drugs floods the limbic brain with dopamine, taking it up to as much as five or ten times the normal level. A person with elevated dopamine levels now has a brain that begins to associate the substance with an outside neurochemical reward (“Your Brain on Drugs”). As a person continues to abuse drugs, the brain adapts to the overwhelming surges in dopamine by producing less dopamine or by reducing the number of dopamine receptors in the reward circuit. The result is a lessening of dopamine’s impact on the reward circuit, which reduces the abuser’s ability to enjoy the drugs, as well as the events in life that previously brought pleasure. The decrease in normal dopamine levels encourages the addict to keep abusing drugs in an attempt to bring the dopamine function back to normal, except now larger amounts of the drug are required to achieve the same dopamine high, an effect known as tolerance (“Understanding Drug Abuse ). That is what leads to the state of addiction, which leaves the person in a cycle of craving, using, withdrawal, and relapse.