Stimulus precedes the reward
Reward follows the stimulus
Operant conditioning (instrumental).
What part of the brain where dopamine focuses as a part of the reward system
Nucleus accumbens (NAc)
Region of the brain responsible for the impulsivity that happens with drug abuse?
Orbital frontal cortex
Humans associate environmental and cognitive stimuli based on space and time
Learning process involved when an abstinent ex-opiate has withdraw symptoms when in a group of ex-opiate patients
Classical conditioning: the body responds by changing homeostatic systems from external stimuli. This is why withdraw from opiates were short in soldiers coming back from Vietnam.
Opponent Process Theory
The subjective experience of drugs is a summation of a processes (positive experiences) and b processes (negative experiences). This happens when patients say they really enjoyed the drug to start with, but now they hate it.
Incentive Sensitization Theory
With repeated exposure of a drug, positive reinforcement occurs via DA stimulation, eventually circuits change, stimuli aren’t what they used to be and the brain is increasingly more sensitive to environmental stimuli
Mesocorticolimbic dopamine system
DA neurons in the VTA project to the NAc, amygdala, hippocampus, PFC and other forebrain regions.
Part of the brain involved in arousal and consciousness
ARAS in the reticular formation
DA receptors most involved in reward from drugs
Where is DA produced?
Substantia nigra and VTA
Region of the mesocorticolimbic dopamine system involved with motivation, cognition and addiction
Why are adolescents more impulsive?
Their orbital frontal cortex is not fully developed.
Why are there so many comorbidities with drug addiction such as gambling, shop lifting and over eating?
Stimulation of the NAc with dopamine from the VTA results in stimulation of the substantia nigra.
Parts of the nucleus accumbens
Shell: repetitive stimulation by DA in the shell strengthens the association of the drug with the stimulus. There are also more 5HT synapses in the shell, which may be the site of LSD. Core: spatial learning.
Comorbidities in the limbic system associated with TBIs
Amygdala damage = loss of ability to forget negative memories. Orbital frontal cortex = impulsivity.
Brain damage to this area of the brain reduces cravings for nicotine
Insula, note that auricular acupuncture stimulates this area and may explain why it is helpful in tobacco cessation.