User:Ben bolaji
The Pleasure Center
[edit]This interesting name is for the part of the brain that is believed to illicit and respond to the things that humans perceive as pleasurable [1]. But the name "pleasure center" is not the correct nomenclature for this part of the brain. The correct scientific and anatomical name is, Nucleus Accumbens. The Nucleus Accumbens (NAcc) is just a small bundle of neurons located near the striatum The brain is divided into two halves and each half of the brain houses its own NAcc. The NAcc in each half of the brain is thought to be responsible for the memory associated with pleasures, which lead to an intricate reward system in our brains and bodies and also it is believed to be the source of motivation and drive. Since the NAcc is thought to be pivotal to rewards and pleasures, many believe it is also tied in to addictions, ranging from alcohol and drugs, to sex and food.[2] Since the NAcc is involved in emotion, as far as rewards and pleasures are conerned, it is considered to be part of the limbic system.
Actions and Rewards
[edit]The NAcc is linked to the rewarding of human behaviors. But human behaviors or actions can only be rewarded if there are cues to remind us of what a particular action felt like [3]. The human brain and the cluster of Neurons (NAcc) partner together to provide these clues by releasing neurotransmitters. The two main neurotransmitters that are released into the NAcc upon certain stimulation are dopamine and serotonin. Serotonin is known as the neurotransmitter that gives the body the impression of satisfaction and hence the body no longer desires the stimulant that was provided initially. Conversely, dopmanine is the neurotransmitter that increases the desire for that stimulant [4] With these neurotransmitters being released into the NAcc it becomes clear that certain behaviors are driven by a reward or anticipation of a reward. The body remembers the pleasurable feeling of the reward and that particular action or behavior can be committed to memory. It is good to keep in mind that the brain's reward system is not only responsive to neurotransmitters. The brain can also take social interactions and use these to create a reward system based on the pleasure of a social interaction.[5]
Sex and the Pleasure Center
[edit]Sex is an act that can be committed to memory as a pleasurable or distrurbing act, depending on the neurotransmitter released. Dopamine is actually involved in sexual motivation and reward as discovered in male rats. [6]. Female rodents have not been extensively tested but a transcription factor named delta fos B has been shown to increase the sexual efficiency of Syrian female hamsters when injected into the NAcc.[7]
Addiction and Substance dependence
[edit]Substance abuse and drug addiction is an issue that plagues societies across the world. Addiction has been linked to the interaction of the brain and the substance being abused, but more specifically it is the pleasure center (NAcc) that conditions the body and the mind to become addicted[8] The NAcc is believed to be responsible for changing the way the body reacts to substances, including alcohol, drugs (narcotics) 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 [9].
How the Brain Interacts with the Nucleus Accumbens
[edit]The NAcc is a unique component of the brain. And a component of the brain needs to be able to interact with brain ad a whole. The NAcc cannot illicit reward and learning responses without letting the brain inject dopamine into it or without letting the brain process the stimuli received. One model known as the triadic model of neurobiology has been used to attempt to explain what initiates motivation. The triadic model is based on three components of the brain that need to interact with each other constantly, the amygdala, nucleus accumbens and medial/ventral prefrontal cortex. Current research is showing that the NAcc creates a strong reward system, while the Amygdala creates a harm avoidance system for an action and the medial/ventral prefrontal cortex supervises that particular action. With these components working in unison, the brain is able to create what we know as motivation. [10] Certain brain receptors also have the ability to alter the behavior of the pleasure center. Receptors in the NAcc have to open and close to respond to dopamine and serotonin. But there are other receptors that may open and close to other substances and these may inhibit or enhance the behavior of the NAcc. For example, group II metabotropic glutamte receptors (mGluR2 and mGluR3) may play a role in the pathology of cocaine addiction[11]. It was observed that the mGluR2 and R3 receptors decrease the body’s need for cocaine. So while the NAcc might allow the body to become dependent, these receptors may also work with the NAcc to keep the dependency at an attenuated level.
Experiments
[edit]The above information is based on pioneering research and experimental design. This research has useful benefits for the therapy and rehabilitation. The test subjects range from mice to rats to primates. Rodents are preferred because of their size and easy handling, but are mostly chosen because the effects of the NAcc seem to take effect much quicker than they do in primates. In other words they learn, become addicted or acquire a reward system at a faster rate than humans.
Current Research
[edit]Neurologists, Biologists and Psychologists continue to be interested in the effects of the NAcc. Substance abuse is a common point of research. Opiates, such as Cocaine, are the choice of drug used in trying to determine the reward and addiction response of the NAcc.[12] Cocaine not only has adverse consequences for the NAcc but it has adverse consequences for other neurotransmitters and other receptors. Memory and attention are also areas that are researched in relation to the NAcc. It is currently understood that the organic solvent toluene, interacts with the dopamine and NMDA receptors and causes memory impairment [13]. This is pertinent information due to the fact that toluene is used in many commercial products such as paint removers, rubber, ink and leather to name a few.
The causes of stress and the body’s response to stress are a well known and researched subject. The NAcc may also play a role in initiating and maintaining stress.[14] Again, this is probably determined by the amount of neurotransmitters and their receptors that can interact with dopamine and serotonin. Trying to reduce the activity of the NAcc during a stressful scenario has showed a decrease in the dependence of cigarettes[15] and may have the same effects on other substances that individuals have become dependent on. Video games may present a form of addiction for some. There is research that is making strides in trying to determine the similarities between the pathway of regular substance abuse in relation to the NAcc and in the pathway of video gaming addiction. The activation of nucleus accumbens under gaming cue suggests that it may reactivate the emotional memory of previous gaming and enhance the motivation for game-seeking behavior [16]
Future Research
[edit]There are steps being made to get a greater understanding of the NAcc and its interactions with other components of the brain. Brain imaging has seen the most advances in this area. fMRI has been used to show what regions of the brain are also involved in the reward, motivation and addiction pathways. Brain imaging techniques have been used to decipher the mental demeanor of stock traders as they make daily trades. Brain imaging showed an interesting trend. The participants that were shown a picture of a smiling face were more likely to invest in risky stocks than those who were shown a picture of a serious face. Brain imaging showed that the NAcc was activated after the smiley face was shown and before the risky stock was picked. [17].
Depression has adverse effects on the psychological activities of the brain and the physical activities of the human body. It could be that the NAcc can be regulated to treat depression by a means other than medication. Music has been used to stimulate the NAcc of depressed patients, showing a positive correlation between the stimulation of the NAcc and a patient’s favorite song. [18]
See Also
[edit]Footnotes
[edit]- ^ Knutson, B (2001). "Anticipation of Increasing Monetary Reward Selectively Recruits Nucleus Accumbens". The Journal of Neuroscience. 21 (16): RC159. doi:10.1523/JNEUROSCI.21-16-j0002.2001. PMC 6763187. PMID 11459880.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ M. Brundege, James (2002-7-1). [www.biopsychiatry.com/nucleus-accumbens.htm "Differential Modulation of Nucleus Accumbens Synapses"]. Retrieved 2009-11-24.
{{cite web}}: Check|url=value (help); Check date values in:|date=(help) - ^ http://www.benbest.com/science/anatmind/anatmd10.html
- ^ http://thebrain.mcgill.ca/flash/i/i_03/i_03_cr/i_03_cr_par/i_03_cr_par.html
- ^ Yacubian, J. 2009. THE GENETIC BASIS OF INDIVIDUAL DIFFERENCES IN REWARD PROCESSING AND THE LINK TO ADDICTIVE BEHAVIOR AND SOCIAL COGNITION
- ^ 2001. Dopamine and male sexual function. Giuliano F, Allard J.
- ^ Hedges VLDelta FosB overexpression in the nucleus accumbens enhances sexual reward in female Syrian hamsters (vol 8, pg 442, 2009)
- ^ Gaetano Di Chiara. 2004. Dopamine and drug addiction: the nucleus accumbens shell connection
- ^ Barson, Jessica R.Opioids in the nucleus accumbens stimulate ethanol intake(2009)
- ^ Ernst, M (2009) Triadic model of the neurobiology of motivated behavior in adolescence
- ^ Megan M Moran. Cystine/Glutamate Exchange Regulates Metabotropic Glutamate Receptor Presynaptic Inhibition of Excitatory Transmission and Vulnerability to Cocaine Seeking. Journal of Neuroscience 7/6/2005, Vol. 25 Issue 27, p6389-6393 5p; 4 graphs 02706474
- ^ Sun, Wei-Lun Cocaine effects on dopamine and NMDA receptors interactions in the striatum of Fischer rats
- ^ Lo, Pi-Shih (2009) Acute neurobehavioral effects of toluene: Involvement of dopamine and NMDA receptors
- ^ The beta-Endorphin Role in Stress-Related Psychiatric Disorders
- ^ An acute psychosocial stress enhances the neural response to smoking cues Alain Daghe. Vol 1293. 1 October 2009, Pages 40-48 Stress, Coping, and Disease
- ^ Brain activities associated with gaming urge of online gaming addiction Chih-Hung Ko.(2009)
- ^ Happy traders take more risks. Peter Aldhous. New Scientist 4/4/2009, Vol. 201 Issue 2702, p9-9 1p 02624079
- ^ EA Osuch. NEUROREPORT 20 (13): 1204-1208 AUG 26 2009. Brain Activation to Favorite Music in Healthy Controls and Depressed Patients