Neuroscience 210

- biopsychosocial model

• - control--loss of control of use of the drug
• - compulsive use--feel compelled to keep using the drug
• - consequences--keep using despite consequences
• - cravings
• - chronic--long term use

• 1. Europhoria (taking the drug and feeling great afterwards because of it)
• 2. Adaptation (after initial phase, same amount of drug doesn't do as much, early withdrawal)
• 3. Exposure to cues and stress--cause you to have 4. Cravings
• 5. Loss of control--go back to 6. drug seeking behaviour
• taking the drugs leads to more feelings of euphoria, which starts the cycle over again

• Causes:
• positive reinforcement
• impulsive use, want the high again

• activates subcortical reward pathways
• - ventral tegmental area to nucleus accumbens= pleasure pathway (reward pathway, involved in more than just drugs)
• - involves dopamine

food deprived rats with intracranial pipettes, were given food and then the dopamine levels were measured. The food caused a spike in dopamine

drugs work on the same architecture of reward as other things like good. Dopamine levels also increased after cocain admistration, but increased a higher amount.

Involves:

• - tolerance--need more substance to get same effect
• - withdrawal--both physical and psychological
• - homeostasis-->allostasis --a change in the set point of homeostasis

there is usually equilibrium in what is important, e.g. between food, sex, drugs, but this changes with repeated drug seeking

with repeated stimulation of dopamine pathway, there gets to be fewer receptor available, to try and reinstate homeostatis from the overstimulation---results in less activation and less binding

Orbitofrontal cortex is involved in motivation, in saying what behaviours are important, and it attaches a preference to the drug behaviour

negative reinforcement-- when you are craving and then you take the drug, you are rewarded by the removal of the craving feelings

compulsive use--feeling like they have to use to take away withdrawl feelings

dysregulated reward pathways involving-neurotransmitters and transcription factors (genetic codes

• limbic activation--remembering good and bad times
• - emotion and memory--drug users remember the high and cues related to the high

sensory cues---people and places

stress--makes you want to go back to what you always did

study where cocain addicts were shown vidoes of nature and animals and then cocain cues, the amygdala light up, and the people reported cravings as well.

• denial
• impaired decision making
• hypofrontality--reduced activity, in the frontal lobes where you make decisions

• PFC--involved in decision making, tells you what not to do
• damage causes impulsivity

brain glucose metabolism in cocain abusers and controls--decreased glucose levels in the frontal lobes in abusers, decreased activation of frontal lobes

• result of:
• - drug seeking behaviour
• - failed impulse suppression

• VTA--NA= pleasure pathway mediated by dopamine
• amygdala and hippocampus involved in memory for high and cues
• Orbitofrontal --motivation involved in setting preferences
• PFC--breaks on behaviour have failed

All these systems working together causes addiction

Regeneration of dopamine receptors can occur, with time and treatment

but: imprinting is so strong inthe brain, a person could be clean for a while and then a cue could trigger a relapse.