Lecture 4 - Food & Drugs Flashcards
Explain the (in)activation of neurotransmitters
- Blocking release of neurotransmitters
- Reuptake by axon terminals or glial cells for reuse
- Deactivated by enzymes
- Diffusion via blood
What 2 processes are part of ‘Blocking release of neurotransmitters’?
- Botulinium toxin (ACh) –> muscle paralysis
- Clozapine in Schizophrenia (lowers DA/dopamine)
What 3 processes are part of ‘reuptake by axon terminals or gliall cells for reuse’?
- Cocaine and speed delay reuptake norepinephrine (increases pleasure)
- Anti-depressants (prozac) block reuptake of Serotonin
- Lithium speeds reuptake (lowers dopamine)
What 2 processes are part of ‘deactivated by enzymes’?
- COMT-gene encodes an enzyme that modulates DA in the PFC
- Nerve gas (VX) destroys AChE
Why are neurotransmitters diffused by the blood?
So neurotransmitters can diffuse out of the synaptic cleft
What is dopamine associated with?
- Reward (ice-cream, promotions)
- Goal proximity (to-do lists, video games)
- Motivation (trouble in Parkinson’s)
What role does dopamine play in ADHD and Schizophrenia?
- ADHD: High Dopamine Transporter Density
* Impulsive, increased cravings
* Reduced inhibition - Schizophrenia: Overactive dopamine
* DA-antagonists (blockers) reduce hallucinations
What are the executive functions?
- Updating/Monitoring
- Switching/Shifting
- Inhibition
Wisconsin Card Sorting Task
A neuropsychological instrument used to measure the executive functions, reportedly sensitive to brain dysfunction affecting the frontal lobes
N-back task
Participants are presented with a sequence of stimuli (e.g., letters) one at a time and asked to compare the current stimulus to one presented n items prior in the sequence.
What 5 functions does Updating/Monitoring have
- Primarily -> Working memory
- Encode relevant incoming information
- Update/revise existing representations
- Manipulate representations
- Monitor for changes
Task Switching Paradigm
Performance in task switching is an important measure of cognitive flexibility. In task switching, participants randomly alternate between performances of two (or more) tasks, with an advance cue specifying the task to perform on the upcoming trial.
What 3 functions does Switching/Shifting have
- Engagement of a new/relevant task
- Disengagement from an old/irrelevant task
- Suppress proactive interference
Stop Signal Task
Participants are presented with an imperative stimulus and are asked to respond as fast as possible.
On a subset of trials, the imperative stimulus is followed by a second stimulus (the stop signal) that instructs participants to abort the response already initiated.
What function does Inhibition have
Supress irrelevant but dominant actions
What are dominant actions
- Learned habits
- Practiced actions or overlearned skills
- Personality traits or tendencies
2 traits of the Nigrostriatal pathway
- Motor control
- Death of neurons in this pathway can result in Parkinson’s disease
5 functions of the mesolimbic and mesocortical pathways
- Memory
- Motivation & emotional response
- Reward and desire
- Addiction
- Can cause hallucinations and schizophrenia if not functioning properly
4 functions of tuberoinfundibular pathway
- hormonal regulation
- Maternal behavior
- pregnancy
- sensory processes
High prefrontal DA leads to:
Cognitive stability
* Goal maintenancy
* Focussing
* Suppressing distraction
* Inflexible/insensitive
Low prefrontal DA leads to:
Cognitive flexibility
* Flexibility - inhibition and switching
* Prone to distraction and interference
What is associated with low cognitive performance?
High and low DA levels
Which two types of medications can optimise our baseline dopamine levels?
- Stimulants
- Depressants
What do the effect of drugs depend on?
- Type and difficulty of task
- Genetics predisposition
- Type of drug
- Dosage, consumption history
- Age, gender, disease, infection, immunity
How does the COMT gene regulate dopamine in the PFC
Enzymes in the COMT gene inactivate released dopamine, thereby regulating its flux in the PFC.
What 2 flavors of alleles does the COMT gene have?
- Val-Val (low DA)
- Met-Met (high DA)
What are traits of Valine amino acid people
- Warriors
- Resilient to stress, relax quicker
What are traits of Methionine people
- More DA is not necessarily a good thing
- worriers
- Neurotic, less resilient to stress
- Higher IQ, do well at school, creative
WCST and Amphetamine
- Val-carriers are worse in sustained attention task
- Val improves with AMP
- Met-carriers show decline with AMP
N-back task and Amphetamine
Val-Val
* No difference in accuracy with AMP
* Better PFC efficiency in AMP vs Placebo at all levels of load
Met-Met
* No difference in accuracy or efficiency with AMP at low load
* Low accuracy and low PFC efficiency in AMP vs Placebo at high load
What is said about Inhibition and Dosage of Dopamine
- “… facilitating effects of stimulant drugs on inhibitory control are limited to a range of intermediate doses, above which improvement is no longer evident and impairing effects could possibly emerge”
- “Acute impairments of inhibitory mechanisms could compromise the ability to terminate drug-acquisition behavior leading to continued self-administration”
What is Tyrosine?
- Precursor of Dopamine (and NE - Norepinephrine), naturally produced in body
- Source: apples, soy, chicke, fish, milk, spinach
- 1 hr after intake, DA levels go up. Half life = 2 hrs
- Can reverse mental decline and improve cognition in short-term
- Low TyrH expression in Parkinson’s
- Very difficult to overdose on TYR due to limited TyrH
- Safe to use as compared to performance enhancing supplements like ritalin
What is serotonin?
‘Happy’ neurotransmitter
Associated with:
* OCD (reduced information processing)
* Sleep and mood
* Agression
* Lowers depression, autism and OCD
* High = serotonin syndrome
What happens if you decrease serotonin?
- Less affiliative behavior (social/emotional bonding)
- Increased aggression
- Stronger response to unfairness
- Bias towards negative stimuli
Tryptophan
- Alternative to serotonin drugs
- Precursor to serotonin and melatonin
- Not produced naturally in the body
- Source: salmon, poultry, eggs, spinach, nuts
- Half life = 2 hours
- Used for treating depression, anxiety and as a sleep aid
- Increase recall of positive material
- Decreases recognition of negative faces
What does tryptophan induce?
A positive emotional bias
