reward and addiction (4.2) Flashcards
motivation
a theoretical construct; used to explain why people do what they do
what we are motivated toward (2)
survival, reward
what influences motivation (3)
memory, executive functions, emotional state
reward
the positive/pleasurable consequence of an action; a potent motivator; typically serve as reinforcements (increase probability of behavior when presented)
primary (natural) vs secondary rewards
primary: necessary for the survival of the species (i.e. sleep, thirst, food, temperature, sexual reproduction)
secondary: objects that derive their value from primary rewards (i.e. money -> food)
mesotelencephalic dopamine system
plays an important role in intracranial self-stimulation; neurons project from mesencephalon (midbrain) to telencephalon
midbrain areas in the mesotelencephalic dopamine system (2)
substantia nigra, ventral tegmentum
nigrostriatal vs mesocorticolimbic pathway
nigrostriatal: substantia nigra neurons project to the dorsal striatum
mesocorticolimbic pathway: VTA neurons project to cortical and limbic sites, including the nucleus accumbens; the major “reward” pathway for ICSS and natural rewards; anticipatory pleasure
nucleus accumbens
receives direct dopaminergic input from the VTA; indirectly excites the prefrontal cortex via the ventral palladium (part of basal ganglia) and DM nucleus (part of thalamus); lesions eliminate self-administration of addictive drugs
drug addicts
those who continue to use a drug despite its adverse effects on their health and social life
drug administration (4)
ingestion: easy, but unpredictable
injection: fast and predictable, but need needle and potential for scar tissue, infection and overdose
inhalation: fast, but hard to regulate and may damage lung tissue
absorption: easy, but damage to nasal, oral and rectal mucosa
mechanisms of action for drugs
once a drug enters the bloodstream, it must pass through the BBB to have its effects; drugs influence the NS by altering the way nerve cells send, receive and process information
liver
where the actions of most drugs are terminated [by enzymes]
drug tolerance
decreased sensitivity to a drug as a result of exposure to it; (1) a given dose has less effect or (2) a larger dose is needed to produce the same effect; metabolic (less drug gets to site of action) or functional (reduced sensitivity; fewer receptors or less responsive at sites of action)
withdrawal syndrome
an adverse physiological reaction triggered by a sudden elimination of a drug after significant amounts of it have been in the body for a period of time
tobacco (ingredient, health, effect)
ingredient: nicotine
health: smoker’s syndrome (chest pain, labored breathing, wheezing, coughing), cancer
effect: nicotine binds to acetylcholine receptors on dopaminergic neurons in the VTA; sodium influx and increased release of dopamine in NAc
alcohol (ingredient, health, effect)
ingredient: ethanol
health: alcohol withdrawal syndrome (vomiting, convulsions, delirium tremens), Korsakoff’s syndrome, cirrhosis
effect: ethanol reduces activity of voltage-dependent potassium channels in VTA neurons; relative refractory period of VTA dopaminergic neurons is reduced (fire more often); increased release of dopamine in NAc
marijuana (ingredient, health, effect)
ingredient: THC, cannabis sativa
health: short-term memory impairment (DLPFC), interference with tasks involving multiple steps, respiratory problems
effect: THC binds to CB1 receptors on GABAergic inputs in the VTA, reducing calcium influx and thus transmitter release; VTA dopaminergic neurons fire more often; increased release of dopamine in NAc
amphetamines (ingredient, health, effect)
ingredient: levo- and dextro-amphetamine
health: short-term working memory impairment; altered cognitive (executive) control
effect: competes with dopamine for reuptake in the NAc; causes reuptake transporters in the terminal button to reverse their mode of operation; increased dopamine in the NAc
cocaine (ingredient, health, effect)
ingredient: cocaine, anesthetic
health: cocaine psychosis from binges or sprees (unconsciousness, seizures, heart attack, stroke)
effect: acts as a serotonin-norepinephrine-dopamine reuptake inhibitor (triple reuptake inhibitor (TRI)); prevents dopamine reuptake and thus increases levels in the NAc
opiates (ingredient, health, effect)
ingredient: morphine, codeine, heroin
health: relatively minor health hazards (indirect related to needle use)
effect: bind to endogenous opiate receptors on VTA GABAergic neurons, enhancing potassium efflux and thus reducing transmitter release; VTA dopamine neurons are disinhibited; increased release of dopamine in the NAc
