Neurobiology of Addiction

Hijacked Brain

-cravings reside in old brain

Amygdala

A limbic system structure involved in memory and emotion, particularly fear and aggression.

Hippocampus

A neural center located in the limbic system that helps process explicit memories for storage.

Marijuana Neurotransmitter System Action

Activates CB1 and CB2 cannabinoid receptors

Opiates Neurotransmitter System Action

Activates Mu Opiate receptors

Nicotine Neurotransmitter System Action

Activates nicotinic acetylcholine receptors

Preoccupation/Anticipation

Altered functioning of the prefrontal cortex Increased limbic activity Increased planning for use Increased activity of amygdala with negative emotional memories Increased stress and anxiety Increased cravings Relapses

Addiction APA DSM-5

American Psychiatric Association DSM-5 "The essential feature of a substance use disorder is a cluster of cognitive, behavioral, and physiological symptoms indicating that the individual continues using the substance despite significant substance-related problems." - 2013

Addiction ASAM

American Society of Addiction Medicine (ASAM) "Addiction is a primary, chronic disease of brain reward, motivation, memory and related circuitry. Dysfunction in these circuits leads to characteristic biological, psychological, social and spiritual manifestations. This is reflected in an individual pathologically pursuing reward and/or relief by substance use and other behaviors." - 2011

Three Stages of Addiction

Binge/Intoxication Withdrawal/Negative Affect Preoccupation/Anticipation

Negative Effects of Withdrawal

Decreased Dopamine dysphoria Decreased Serotonin dysphoria Decreased GABA anxiety Decreased Opioid Pain

Withdrawal/Negative Affect

Decreased stores of Dopamine Decreased Dopamine Receptors (downregulation) Tolerance - need more to get same effect Decreased release of GABA Increased anxiety Use to avoid/reduce negative experiences of withdrawal Negative Reinforcement

Alcohol Neurotransmitter System Action

Facilitates GABA receptor function Inhibits NMDA (Glutamate) receptor function

Positive Reinforcement

Increased Dopamine euphoria Increased Serotonin euphoria Increased GABA Reduced anxiety Increased Opioid Reduced pain

Binge intoxication stage

Increased release of Dopamine VTA Nucleus Accumbens Euphoric effect High level of satisfaction Pleasurable experiences Positive reinforcement

Amphetamine Neurotransmitter System Action

Increases release of dopamine (and NE) and inhibits dopamine (and NE) transporters

Cocaine Neurotransmitter System Action

Increases release of dopamine (and NE) and inhibits dopamine (and NE) transporters

Addiction (Koob and Volkow)

Koob and Volkow "Addiction is a chronic relapsing syndrome that moves from an impulse control disorder involving positive reinforcement to a compulsive disorder involving negative reinforcement." - 2010

Development of addiction

Many of the patterns of addiction are related to the activation of the reward pathway. The reward system is modulated by dopamine. Models illustrate that animals will self administer a drug or electrical stimulation in order to maintain dopamine levels in the nucleus accumbens There is also a "disconnect" between the reward pathway and the prefrontal cortex

Moral Model

Substance abuse is a moral failing, not an illness. This is the most popular substance use model.

Ventral Tagmental Area

a group of dopaminergic neurons in the ventral midbrain whose axons form the mesolimbic and mesocortical systems; plays a critical role in reinforcement sends widespread signals to many places including the nucleus accumbens

Nucleus Accumbens

a region of the forebrain that receives dopaminergic innervation from the ventral tegmental area

Positive reinforcement

anything that increases the frequency of the response immediately preceding it. Example: drug administration for the euphoric effects

Craving Pathway

prefrontal cortex, anterior cingulate, orbitofrontal cortex and basolateral amygdala involved in cue-induced and drug-induced craving. Craving type I - craving that is paired with a previous stimulus or an environmental cue. Craving type II - protracted abstinence state weeks after detoxification in drug dependent individuals.

Negative reinforcement

temporary interruption of continuous negative stimuli that increases the frequency of the response immediately preceding it. Example: administering a drug during the withdrawal state leads to temporary relief from the withdrawal symptoms.

Medical model

the concept that diseases have physical causes that can be diagnosed, treated, and, in most cases, cured. When applied to psychological disorders, the medical model assumes that these mental illnesses can be diagnosed on the basis of their symptoms and cured through therapy, which may include treatment in a psychiatric hospital.

Motivation

the driving force responsible for approach or avoidance behavior

Reward

those entities that instigate approach behavior. Can be "objects, stimuli, activities or internal physical states that have positive value for a person or an animal" (Kandel 2012)

Dopamine and Addiction

involved in drug addiction, increases pleasure and linked to reinforcers in the ventral tegmentum area. in the Nigrostriatal Pathway Rewarding activities and drugs of abuse increase dopamine in the brain's reward center. The same reward neurons encode the degree of reward, receipt of reward, reward anticipation, and errors of reward prediction. Addictive drugs are more powerful in activating the reward center than biologically essential stimuli (food, sex, socialization) and they alter the function of the reward center. This is known as the "Hijacked Brain Hypothesis"

Drug Seeking Compulsive Pathway

nucleus accumbens, ventral pallidum, thalamus, and orbitofrontal cortex Integrates reward function with motor function or drug seeking.

Prefrontal Cortex

part of frontal lobe responsible for thinking, planning, and language