The Obsessive Drive For Drugs: The Striato
The pathway involved in the compulsive drive for substances is the striato-thalamo-orbitofrontal circuit. This circuit is tightly interconnected with other prefrontal and limbic regions, including the anterior cingulate, insula, dorsolateral prefrontal cortex , and amygdala. Innervation includes both the mesocortical dopaminergic pathway, which projects to PFC regions that include the OFC and anterior cingulate,11 and glutamate neurons that project reciprocally between the PFC and amygdala, as well as from the PFC to the NAc and VTA.96 This striato-thalamo-orbitofrontal circuit has been implicated in obsessive-compulsive disorder , a syndrome sharing common features with the addictive disorders that is, the drive for drugs and alcohol includes a lack of control over intrusive thoughts and compulsive behaviors that are directed toward obtaining and administering substances.106,107
B Reward And Motivation
Imaging studies have also revealed decreased activation of brain reward regions to receipt of non-drug rewards, such as food, sexual stimuli, or money, in individuals addicted to drugs compared with controls . Such a reduced sensitivity to non-drug rewards is likely to impair an addicted individuals capacity to be incentivized by naturally pleasurable activities and stimuli. Intriguingly, there is also a reduced reactivity of striatal and prefrontal regions to negative reinforcers, which is associated with worse outcomes . Decreased sensitivity to negative reinforcers could impair the capacity of the addicted person to feel deterred by negative outcomes .
Ways The Limbic System Impacts Physical Emotional And Mental Health
The limbic system is a set of brain structures that plays a role in emotions, particularly those that evolved early and which play an important role in survival.
Research has linked the limbic system to feelings of motivation and reward, learning, memory, the fight or flight response, hunger, thirst, and production of hormones that help regulate the autonomic nervous system. The autonomic nervous system supports automatic, non-conscious functions such as thirst, hunger, heart rate, and regulating the bodys internal clock.
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Study Reveals How Ecstasy Acts On The Brain And Hints At Therapeutic Uses
by Sam Wong17 January 2014
fMRI scans show reduced blood flow in the visual cortex and limbic system under MDMA.
Brain imaging experiments have revealed for the first time how ecstasy produces feelings of euphoria in users.
Results of the study at Imperial College London, parts of which were televised in Drugs Live on Channel 4 in 2012, have now been published in the journal Biological Psychiatry.
The findings hint at ways that ecstasy, or MDMA, might be useful in the treatment of anxiety and post-traumatic stress disorder .
MDMA has been a popular recreational drug since the 1980s, but there has been little research on which areas of the brain it affects. The new study is the first to use functional magnetic resonance imaging on resting subjects under its influence.
Twenty-five volunteers underwent brain scans on two occasions, one after taking the drug and one after taking a placebo, without knowing which they had been given.
The findings suggest possible clinical uses of MDMA in treating anxiety and PTSD, but we need to be careful about drawing too many conclusions from a study in healthy volunteers.
Edmond J. Safra Professor of Neuropsychopharmacology
The results show that MDMA decreases activity in the limbic system a set of structures involved in emotional responses. These effects were stronger in subjects who reported stronger subjective experiences, suggesting that they are related.
Drugs Can Undermine Decision
Images of drug addicts brains show changes in areas that affect judgment and behavior control. This reflects a double-whammy of addictionintense cravings for drugs paired with a compromised ability to make decisions.
For the addicted person, every day is dominated by the compulsion to get drugs and use drugsno matter what the consequences. And, deciding to change these addictive behaviors by an act of sheer willpower becomes futile.
Understanding this fact reduces the stigma associated with addiction and underlines the need for medical treatment of the disease.
A diagnosis of addiction is not a life sentence. Treatmentbehavioral therapy and medicationscan help people manage changes in their brain function and respond to drug cravings in new ways. Group therapy and group support can enhance motivation to remain drug-free.
Because addiction treatment aims to change deeply embedded habits, relapse can be part of the process. However, this is a well-known feature of diabetes, hypertension, asthma, and other chronic diseases with treatment plans that depend on behavior change. Just as science is unraveling the causes of addiction, it is also revealing what works in helping people return over time to drug-free lives .
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Priming: The Nucleus Accumbens And Dopamine
D2 receptor ligands have not proven useful in the treatment of stimulant dependence D2 receptor agonists are reinforcing in animal models, and D2 receptor antagonists are not effective in human studies. However, since D2-agonists appear to be especially potent in the induction of priming, medications targeting D2-like D3 and D4 receptors have been explored. In addition, whereas D1 and D2 receptors are more diffusely concentrated throughout the brain, D3 receptors are preferentially expressed in the mesolimbic system, particularly in the NAc, and D4 receptors have their highest densities in the prefrontal cortex and suprachiasmatic nucleus of hypothalamus.11 Preclinical studies reveal that D3 receptor antagonists block both cocaines reinforcing actions and cocaine-induced reinstatement of cocaine-seeking behaviors 82,83 a partially selective D3 receptor ligand is now undergoing assessment for human trials.84 In an exciting human study assessing the interaction between genetic factors and drug use, healthy subjects with different D4 variable-number-of-tandem-repeats polymorphisms were administered a priming dose of alcohol and then assessed for craving. Groups with different D4 VNTR polymorphisms demonstrated a differential response to the D4 antagonist,85 portending the developing importance of pharmacogenetics to inform the targeted use of medications based upon an individuals genotype.
The Disease Concept Of Addiction
When the brain is polluted, the brains chemistry changes. A change in chemistry over a short period of time may not create a permanent change. But, increasing the frequency at which chemical reactions are altered would proportionately increase the development of a disorder or illness.
For instance, prolonged spikes in blood sugar levels could eventually create insulin resistance. And, insulin resistance can lead to diabetes. This disease results from a permanent change in DNA. Diabetes can result in the loss of a limb.
Since the parts of the brain work together as a team, when one part is struggling, the effects are felt throughout the entire bodyas seen with the diabetes example. The disease of addiction works the same way.
Addiction is considered to be a disease because drugs change the brain structure and how it works.
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Controlling Behavior Memory And Mood
While the addiction theories have traditionally focused on the interaction among the mesolimbic system and the dorsal striatal regions, the limbic brain regionssuch as the prefrontal cortex, the hippocampus, and the amygdalahave gained increased attention in addiction . As exposed before, the prefrontal cortex, the hippocampus, and the amygdala are mainly glutamatergic structures all reciprocally interconnected that are closely integrated into the reward brain circuit by receiving direct dopaminergic inputs from the VTA and, conversely, by regulating accumbens and VTA activity .
The initial experiences with drugs would use the regular learning mechanisms in the limbic regions to be acquired and stored in memory . In this way, the prefrontal cortex guides the dorsal striatum and acts as an ON/OFF switch for drug-seeking, deciding when this behavior should be allowed or inhibited . Regarding the hippocampus and the amygdala, they interact with the prefrontal cortex and the accumbens for the learning of drug-stimuli associations and these limbic regions collaborate for the subsequent retrieval, extinction, or reinstatement of the drug-related memories . Since the drug-related experiences are rewarding and emotionally arousing, they activate neurobiological pathways involved in the emotional enhancement of associative memory, which may potentiate their acquisition and subsequent long-term maintenance .
The Dorsal Striatum: Where Goal
Together with the mesolimbic system, the dorsal striatum is a key brain region to explain addiction. The dorsal striatum, composed by the caudate nucleus and putamen, is a center for sensorimotor integration. It receives excitatory inputs from the thalamus, which is a major relay for sensory signals, and extensive excitatory inputs from cortical areas that are distributed across the striatal subdivisions through the cortico-striatal circuit . In this regard, the dorsomedial striatum is mainly innervated by cognitive-related prefrontal cortical regions supporting executive functions , while the dorsolateral striatum mostly receives input from primary sensory and motor cortices . Furthermore, the so-called spiraling nigrostriatal circuit allows functional and bidirectional serial connections among the dorsal striatum and the reward centers including the accumbens and the dopaminergic neurons in the midbrain .
In conclusion, striatal neuroplasticity supports the progressive transformation of conscious and voluntary drug-taking actions into habits . Habits are an important cause of relapse as they are compulsive and uncontrollable by the individual and automatically elicited by drug-associated cues. This explains that drug-related stimuli would trigger drug useusually accompanied by intense craving feelingsdespite of efforts to remain abstinent .
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Experiencing Rewards And Learning To Predict Them
The mesolimbic system has been a traditional focus of drug addiction research, since it is a key substrate for reward and motivated behavior. The mesolimbic system comprises the accumbens and the midbrain ventral tegmental area as its main brain nodes and dopamine as its major neurotransmitter . The dopaminergic projection neurons in the VTA release dopamine to the accumbenseither at its core or shell subdivisionsas well as to memory-related limbic brain regions such as the prefrontal cortex, the hippocampus, and the amygdala . Conversely, these brain regions regulate VTA activity. Specifically, GABAergic inhibitory pathways from the accumbens may either stimulate or exert inhibitory feedback control over dopamine release by targeting either the dopaminergic VTA projection neurons or the inhibitory VTA interneurons . For their part, the glutamatergic limbic regions are all reciprocally interconnected, and they also project to the accumbens and to the VTA either directly or by indirect polysynaptic pathways, to stimulate dopamine release . This illustrates that reward and memory systems in the brain are closely interrelated, which makes sense considering that learning is often driven by rewards, punishments, and their anticipation .
Drugs Of Addiction Act Upon A Portion Of The Brain Called The Limbic System
The question of is drugs of addiction bad or good arises when people who are dependent on these substances do not understand how addiction leads to physical dependency. For them, an addiction means using a substance day after day, week after week, month after month and year after year. The substance they are addicted to is habit forming. Once the substance is acquired, it is often difficult if not impossible to get rid of it. Many who become addicted to drugs of addiction do so because of the influence of friends and family that may be physically present but cannot be trusted with the use of such addictive substances. The drugs of addiction act upon a portion of the brain called the limbic system of the brain. This portion of the mind controls emotion and mood. People who are addicted to drugs of addiction show a strong response to triggers of certain emotions. When you think about it in this way, does it not make sense that if you have emotional problems and are dependent on drugs of addiction, then there must be a part of your mind which is inappropriately triggered by the use of the substance and this is where drugs of addiction come into play. The limbic system takes pleasure in the drugs of addiction as a result of the stimulation it gets from these substances.
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Struggling With Addiction The Palm Beach Institute Can Help
If you or a loved one is battling the disease of addiction you dont have to do it alone. Contact us today at the Palm Beach Institute to get a free consultation and assessment. Our caring staff will work alongside you help you determine which treatment programs work best for your unique situation. Start on the road to addiction recovery today.
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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Incentive Salience Learning And Novelty: A Reconsideration Of Mesolimbic Dopamine
In addition to the disappointing clinical response to dopaminergic agonists and antagonists, a paradigm shift in the role of DA in the addictive process occurred with the recognition that DA does not, in and of itself, induce pleasure, mesolimbic DA efflux increases not only in response to a reward, but also in anticipation of a potential reward and during aversive states, including foot shock, restraint stress, and the administration of anxiogenic drugs,17,24,34 extracellular increases in accumbens DA are attenuated in rodents self-administering cocaine relative to yoked littermates ,67 revealing that the self-administration of cocaine elicits less mesolimbic DA efflux compared to the passive administration of cocaine, and DA plays critical, and overlapping, roles in the interpretation of stimuli and the acquisition of behaviors reinforced by natural rewards and drug stimuli.
Brain regions relevant to the addictions . Right panel represents an MRI of the sagittal brain at Talairach coordinates x = 416 left panel, at x = 3446. Each Talaraich coordinate represents a one mm MRI sagittal slice, and 13 slices were averaged for each displayed image. Amyg, amygdala ant cing, anterior cingulate DLPFC, dorsolateral prefrontal cortex LOFC, lateral orbitofrontal cortex MOFC, medial orbitofrontal cortex NAc, nucleus accumbens VTA, ventral tegmental area. The MRI template was obtained from SPM96-MRI.
The Neuroscience Of Drug Reward And Addiction
Drug consumption is driven by a drugs pharmacological effects, which are experienced as rewarding, and is influenced by genetic, developmental, and psychosocial factors that mediate drug accessibility, norms, and social support systems or lack thereof. The reinforcing effects of drugs mostly depend on dopamine signaling in the nucleus accumbens, and chronic drug exposure triggers glutamatergic-mediated neuroadaptations in dopamine striato-thalamo-cortical and limbic pathways that, in vulnerable individuals, can result in addiction. In parallel, changes in the extended amygdala result in negative emotional states that perpetuate drug taking as an attempt to temporarily alleviate them. Counterintuitively, in the addicted person, the actual drug consumption is associated with an attenuated dopamine increase in brain reward regions, which might contribute to drug-taking behavior to compensate for the difference between the magnitude of the expected reward triggered by the conditioning to drug cues and the actual experience of it. Combined, these effects result in an enhanced motivation to seek the drug and an impaired prefrontal top-down self-regulation that favors compulsive drug-taking against the backdrop of negative emotionality and an enhanced interoceptive awareness of drug hunger. Treatment interventions intended to reverse these neuroadaptations show promise as therapeutic approaches for addiction.
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Drugs Of Addiction Act Upon A Portion Of The Brain Called The Limbic System Effects
As mentioned earlier, the drugs of addiction act upon a portion of the brain called the limbic system and this is part of your thinking center. The limit is associated with memory and the cause of death comes from a part of our brain called the amygdala, which is part of the limbic. The amygdala is part of the forebrain, which is responsible for the storage of emotion and memories. It is also responsible for generating a response to stress, which causes us to have an urge to consume drugs which will relieve the stress and stimulate a pleasurable response in the addict. Once the drugs of addiction enter the bloodstream, they will travel to the lungs and the cells of the lung. This is where they will be stored until the time the substance is needed again. When the drugs of addiction are ingested, the effect produced by the substance reaches the brain through the blood stream and the person becomes addicted. However, this does not mean that the person will necessarily become dependent upon the substance. They could be occasional drinkers or heavy users but because they have become dependent upon the substance, this means that they will require it in order to survive, which can lead to a loss of control over the person and can lead to withdrawal symptoms if the dosage level is not kept at a constant.
Brain Areas Involved In Addiction
Amygdala:Amygdalar activity is related to memory consolidation for emotionally arousing events. The amygdala is involved in assigning a reward value to stimuli and in the conditioning of fear to novel stimuli. For example, rodents favoring a specific cage that is identified with drug administration will lose this conditioned stimulus if the amygdala is ablated.
Anterior cingulate: Implicated in human disorders of emotion and attention, the anterior cingulate is involved in emotional self-control, focused problem-solving, error detection, performance monitoring, and adaptive response to changing conditions.75 It plays a role in the detection of processing conflicts, particularly when low-frequency responses are executed,76 but is influenced by both motivation and affective state.
Bed nucleus of the stria terminalis : Involved in autonomic and behavioral reactions to fearful stimuli, including the stress response, the BNST is considered part of the extended amygdala and shares with the nucleus accumbens a sensitivity to dopamine stimulation. In rats, the BNST is involved in the reinstatement of cocaine seeking after foot shock.77
Dorsolateral prefrontal cortex : Implicated in difficulties holding/maintaining several pieces of information on line or in short-term storage , the DLPFC is crucial for the control and regulation of cognitive activities, including the sequencing of events, planning, and the selection of goals.
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