CCC impulse control Flashcards
What happened to Phineas Gage?
American railway worker
Accident- tamping iron exploded.
Gage- returned to “full” health after accident- except for a few personality changes.
Intellectual manifestations- feeble
fitful, irreverent (lack of respect for people)
Indulging in the grossest profanity (irreligious behaviour)
Impatient of restraint- or advice when conflicts with his desires.
From this- researchers learnt lots about the frontal lobes roles in behavior & psychology
What did researchers learn due to the case with Phineas Gage?
Learnt lots about the frontal lobes roles in behavior & psychology
Who was the birth of psychosurgery by?
Moniz
What did Moniz come up with?
Birth of orbitofrontal lobotomy. (surgical procedure)
Technique- used for conditions prevalent in those days- people suffered from psychological psychiatric conditions.
E.g. schizophrenia, depression - those days there weren’t any treatments. Psychiatry was seen as a discipline without tools.
Moniz- came up with a radical idea- of surgery- to help various conditions- on frontal lobes.
It was applied widely in USA- 40,000 frontal lobotomies performed.
UK- around 17,000
Majority performed on females & used for various clinical conditions.
When were labotomies performed?
1936- 1960s/70s
Not used anymore!
What marked the end of lobotomies as a treatment for mental illness?
Introduction of antipsychotic Thorazine by GSK
Were labotomies effective?
Variability in results- some people became better & others became impulsive & childish.
Now we know the frontal cortex is very complex.
When is the frontal cortex used?
If you have a choice between something harder (better decision) and something easier- the frontal cortex is what makes you do the harder decision.
Mynopic Discounting Of future rewards after medial orbitofrontal damage.
What were the results for subjects with:
Damage to prefrontal cortex
Damage to other areas of brain
Healthy controls?
As the delay increases for a certain amount of money..
Can see classic discounting curves for:
Healthy controls- prefer the easier option
Damage to other areas- also prefer easier option
HOWEVER
Damage to prefrontal cortex- the change is more dramatic- line much steeper, the patients switch to the easier option much quicker- not willing to wait.
What is the lowa gambling task?
Who were the subjects?
Subjects choose from 4 decks of cards.
Total of 100 choices from the decks.
Two decks- large short term gain, long term loss (non advantageous)
Two decks- smaller short term gain, long term gain (advantageous)
Subjects:
Patients with sustained unilateral focal damage to the frontal lobes & healthy controls.
Subjects didn’t know what the rules were- had to figure it out.
Healthy controls will figure it out pretty quickly.
What were the results on the lowa gambling task?
Frontal lesion subjects showed impaired decision making compared to control subjects, and persist with disadvantageous decks- despite obvious failure.
What are the main substances of abuse?
Alcohol
Nicotine
Heroin, morphine, codeine & other opioid agonists
Cocaine, cathinone, amphetamine & other psycho-stimulants
THC (cannabis)
Hallucinogens
Inhalants
Why do people take drugs?
Experimentation: novelty seeking, exploring
Pleasure: Drugs as desired rewards (liking/ desire)
Medication: To relieve unpleasant states (anxiety, depression, pain)
Peer pressure: to be seen as cool.
What is not addiction?
Experimental use
Recreational (casual) use
Circumstantial use
If people suffer with mental disorders- are they more/ less likely to take drugs?
More likely- to relieve them
What are the characteristics of addiction?
Compulsive drug seeking & taking
Inability to stop & high rates of relapse cessation
Why drugs become more wanted & less liked.
What percentage of people try illicit drugs
What does the percentage change to when alcohol is included?
What percentage of people actually obtain an addiction?
60% try/ use illicit drugs
90% if include legal drugs (i.e. alcohol)
Only 5-10% develop an addiction
What percentage of people actually develop an addiction?
5-10%
Who decides the classification of addicts?
DSM- Diagnostic and statistical manuals of mental disorders.
What does the DSM state is the diagnostic criteria for substance use disorders?
A problematic substance use, leading to clinically significant impairment or distress, as manifested by at least two of the following, occurring within a 12 month period.
Examples include:
Craving/ strong desire to use the substance.
Important activities given up/ reduced due to substance use.
A great deal of time is spent on the activites.
What are the effects people experience from most drugs?
Euphoria
What are the effects of cocaine?
Euphoria
self confidence
arousal
cognitive enhancement
Study- 1997- looked at the structural changes in the brains of alcoholics.
In severe & less severe alcoholics.
What did the results show?
There is reduced cortical grey matter volume in alcoholics.
Very dramatic changes in the front part of the structures.
Atrophy- shrinkage of the brain tissue in the cortex.
When we get to the frontal & prefrontal cortex- the older alcoholics-we see a reduction in the structural mass.
Study- on poly-substance abusers
What are the results?
Can see- with increase in the substance use- the volume in the prefrontal cortex reduces. There is lots of variability in results.
Frontal function in drug users
What did the PET scan show when comparing a cocaine abusers brain & a control?
Was a PET scan of the glucose metabolism in controls & drug abusers.
Cells need glucose when active to function.
The brighter the area- the more activity.
Found reduced OFC function is cocaine abusers compared to control subjects during protracted withdrawal. Basil neuronal activity is reduced & reduced structural volume.
Frontal function in drug users.
When do the areas such as the OFC become hyperactive?
What study shows this?
When presented to certain stimuli.
Study- Childress (2000)
Looks at functional activity using an fMRI- cocaine addicts.
Watching various videos e.g. including videos/ pictures of cocaine/ smoking it- compared to nature pictures/ or pornographic images.
Found the OFC- becomes hyperactive to drug associated cues.
Substance users
Lowa gambling task- how do substance users do?
Like subjects with frontal lesions- substance dependent subjects show impaired decision making (persistence with disadvantageous deck on lowa gambling sort task)- in spite of obvious failure.
Delay discounting in Meth (methamphetamine) subjects.
How did they do in the task?
Subjects asked to choose which option they would/ wouldn’t want.
Meth users more quickly choose the smaller- immediate reward.
Delay discounting effect
What was the difference between controls & opioid using & recovering participants (Methadone maintained)?
Steeper discounting rates in opioid using & recovering subjects.
Their brain would have been permanently changed.
They are taking methadone as a treatment for the opioid
addiction- however methadone is another form of an opioid.
Why can we not experiment on humans?
There are severe ethical implications- especially when dealing with drug-naive subjects.
Problem of causality- we don’t know where the effect goes.
For example- individual may already have changes in the brain- which is why they are more vulnerable to develop addiction.
As we can’t experiment on humans for drugs- what do we resort to instead?
Non- humans- animals
Do experiments with rats.
Can make them take drugs in skinner boxes & see the effects on the brain.
When studying animals- what are you able to look at?
Individual cells
Medium spiny neuron- which is found in the nucleus accumbens.
Can look at the number of spines that come off the processes (spines are how neurons communicate)- each spine is a communication point.
If see changes in spine- this is important.
Drugs change you brain
When rats were given amphetamine- how did results compare to controls?
For rats taking amphetamine for a month - the number of spines increased significantly.
However- in the frontal cortex- when you take lots of amphetamine- you reduce the number of spines.
Therefore- drugs change the brain & neurons in fundamental ways.
Summary of drug use?
Long term drug use- may lead to increased impulsive behaviour/ loss inhibitory control due to changes in the prefrontal cortex.
But the relationship may also work in the opposite direction.
individual differences in “trait” impulsivity may be a risk factor for drug taking.
What occured in the 5 choice serial reaction time task?
Jeffery W. Dalley 2007
Rats have choice of 5 holes- to stick their nose in.
If stick in right whole- receive a reward.
when get the right answer- the light turns on.
Findings
Some rats can’t wait.
Some rats more impulsive- make more mistakes.
Question is- are more impulsive rats more likely to take drugs?
Are more impulsive rats more/ less likely to take drugs?
More likely!
What model is there ?
Prefrontal model on addiction (Jentsch & Taylor 1999)
What is in the prefrontal model on addiction?
As impulse control decreases- there is an increase likelihood of taking drugs (drug intake increases)
As you take more drugs- there are drug induced structural & functional changes in prefrontal regions.
