L11 addiction Flashcards
Which parts are modulated by dopaminergic input?
Motor (frontal) cortex, prefrontal brain structures which are involved in ‘cognitive’ and ‘limbic’ processing (select actions) or motor intentions, forming analogous (feedback) loops through basal ganglia
Which part do the rats like to self stimulate?
Septal region
Why septal region is an effective self-stimulation site?
It will activate dopaminergic fibres of the medial forebrain bundle which travel from the ventral tegmental area to the nucleus accumbens
Nucleus accumbens is considered as part of the…
Ventral striatum, a limbic extension of putamen and caudate
What is Pavlov’s Dog used to describe?
Conditioned reflexes
What can produce automatic responses?
Unconditioned stimuli
How can conditioned stimuli produce the same responses as unconditioned stimuli does?
After a period of reinforcement learning
What is phasic dopamine?
A reward prediction error signal
What will happen to the action potentials’ firing rate when doesn’t receive the perceived reward?
Decrease
Where did the stimulating electrode implant to remote control the rat?
Each somatosensory cortex
What does the stimulating electrode stimulate except the somatosensory cortex?
The medial forebrain bundle which contains dopaminergic output fibres from the ventral tegmental area
What does the somatosensory cortex electrode do?
Tells the direction
What does the medial forebrain bundle do?
Tells the animal to predict a reward if it follows the instructions form the somatosensory electrodes
For human, when they win a gamble, which parts of the brain will have increasing activity?
Substantia nigra/ Ventral tegmental area and the ventral striatum
What synapses are highly plastic, and what can they undergo?
Cortico-striatal glutamatergic synapses and undergo long term depression/ potentiation
What can regulate the synaptic plasticity?
Dopaminergic input
What makes learning faster?
L-DOPA
What makes learning slower?
Halperidol
Which parts’ activity levels reflect reward prediction errors?
Ventral striatum and posterior putamen
Which part of the brain learn new association quicker than cortex? after decoding the neural activities in…
Caudate neurons; caudate and prefrontal cortex
If the animals predicted there is a reward, where will the burst of action potentials be?
At the trigger
If the animals receive an instruction cue preceding the reward predicting trigger stimulus, where will the burst of action potentials be?
At the instruction cue
When reward is unpredictable, dopamine neurons will…
increase more than ones expected
Cortex-basal ganglia circuits are designed to…
engrain habits of action selection which increase our chances of ‘rewarding’ outcomes
What will rats self-inject to nucleus accumbens in drug self-administration experiments?
Amphetamine
How does D-amphetamine stimulates dopamine release in self-administration experiments?
By messing with transporter proteins in dopaminergic terminals of afferents from the ventral tegmental area
What does cocaine do?
Potentiates dopaminergic action by blocking dopamine reuptakes
What does amphetamine do?
speed up and derivatives releases dopamine and noradrenaline by interfering with cell internal catecholamine transporters
Where are the opiate receptors?
Dopaminergic neurons in the brainstem and midbrain
What does nicotine activate?
Cholinergic receptors carried by striatal neurons
What does cocaine, amphetamine, opiate and nicotine all do in common?
Activate dopamine sensitive neurons in the striatum
What do very rapidly absorbed drugs give?
A phasic DA strike
Why does smoking cocaine bring much greater addiction risk than drinking cocaine in tea?
Faster absorption than drinking it
Name some addiction-like side effects that may be faced by Parkinson patients receiving prolonged courses of dopamine-enhancing medication.
Craving Gambling Hypersexuality Hypomania Punding (stereotypic behaviours)
What do rats need to do if they need to be trained to self-administer virtually all addictive drugs?
Repeated exposure/ prolonged access to intravenous drugs
How are addictions marked?
Escalation in dose
Habituation/ tolerance
Resistance to extinction
What is resistance to extinction?
Behaviours continue even if they are no longer given drugs
Why tolerance happens?
A homeostatic mechanism: prolonged exposure to dopaminergic inputs makes the brain less sensitive to such inputs. Greater doses are needed. Healthy, positive reinforcers may become less effective
What is withdrawal/ cravings?
Not having access to drugs is perceived as stressful. Stress hormone levels rise in response to withdrawal
Name the stages in addiction.
Explorative drug taking is pleasurable
Positive reinforcement learning encourages repeated drug taking
Habituation/ tolerance develops
Withdrawal causes stress
Which stages in addiction is evitable?
Third and fourth
What is amygdala?
A major component of the limbic system
What does the amygdala known to be doing?
Involved in fear conditioning responses, and mediate positive emotional responses
What is the major sources of input to the VTA?
Amygdala
What is the stress hormone that the amygdala contains?
Corticotropin releasing factor
What will trigger CRF release?
Abrupt withdrawal of addictive substances
Addicts are no longer pleasure seeking when taking drugs, what will they become?
Negative reinforcer
What do impulsive rats have?
Less effective D2/3 receptors in the ventral striatum
What makes it possible to learn which actions are more likely to be rewarded many steps into the future?
Temporal difference learning
