Applied Cognitive Psychology - Leiden University (2019)

Lecture 6:Food and Drugs

Effect of food on cognition

-Source of energy

-Maintain cognitive function

-Adapting for food acquisition has affected evolution of the modern brain and cognitive skills

-Omega 3 linked to brain development

-Fish based diet decreased, saturated/trans fatty acids increase --> depression also increases

-Gut bacteria can influence mood, prevent depression

Neurotransmitters

Acetycholine (Ach):

-involved in muscle action, memory and attention

-Malfunction: associated with AD

Dopamine (DA):

-Movement, learning, attention, emotion. Mediates effects of natural rewards and drugs

-Malfunction: Reduced – Parkinson’s, ADHD, Excess – Schizophrenia

Seratonin:

-Affects mood, hunger, sleep, arousal, and social behavior

-Malfunction: low – depression, high - autism

Norepinephrine:

-Helps control mood, alertness, and arousal

-Malfunction: low- depression, high – anxiety

GABA:

-Major inhibitory neurotransmitter

-Malfunction: low – Huntington’s disease and personality changes, high – sleeping and eating disorders

Glutamate:

-Major excitatory neurotransmitter, involved in memory formation

-Malfunction: low – depression, schizophrenia, high – migraines, seizures

Inactivation of Neurotransmitters

Neurotransmitters are released from the presynaptic cell into the synapse, to be absorbed in the postsynaptic cell

Some drugs block the release of neurotransmitters:

-Botulinium toxin (Ach) --> muscle paralysis (like botox)

-Clozapine in Schizophrenia --> to decrease dopamine

Reuptake by axon terminals or glial cells for reuse: released dopamine gets reabsorbed

-Cocaine and Speed delay reuptake of Norepinephrine ( more pleasure)

-Anti-depressants (Prozac) block reuptake of Serotonin

-Lithium speeds reuptake (increases depression)

Neurotransmitters deactivated by enzymes:

-Nerve gas (VX) destroys AChE

-COMT-gene encodes an enzyme that destroys DA in the pre-frontal cortex

Neurotransmitters can also be diffused via blood

Dopamine level

-Low: Poor performance – Parkinson’s disease, ADHD

-Moderate: Maximum performance

-High: Poor performance – Schizophrenia, drug overdosing

-Optimise baseline by either CNS stimulants (e.g.coffee) or depressants (e.g. alcohol) or both

-Effects of a drug depends on the dose and baseline DA levels

Baseline DA level correlates with working memory capacity

High listening span: higher activity of caudate and plutamen (in Basal ganglia)

Genetics and dopamine:

-Enzymes in the COMT gene inactivate released dopamine, thereby regulating its flux in the PFC

-COMT knockout mice show increased DA in the PFC and COMT inhibitors shows to improve WM in humans

-COMT gene has 2 alleles: Val-Val, Val-Met, Met-Met

-->e.g.: we get Val from our mother, Met from our father (rare genotype)

Val amino acid: Fast DA degradation (“warriors”)

Met: Slow DA degradation (“worriers”)

Wisconsin card sorting test and N-Back tasks:

Effect of amphetamine on participants who do the tasks:

N-back task:

-Val allele people: Because of amphetamine, their performance increases – maximum performance – Less PFC activity, less RT, same/higher accuracy

-Met allele people: From maximum performance --> poor performance due to amphetamine (too high dopamine level) – More PFC activity, higher RT, less accuracy

WCST:

-Val +AMP: less preservation errors

-Met+ AMP: high preservation error

Consumption History & dopamine

Chronic use of cocaine is associates with deficiencies in cognitive control

-Reduces functioning of dopamine receptors (delay reuptake)

-Dysfunction in PFC and ACC (necessary for WM, goal-direction action, decision-making)

Threats in recreational users (1-4gm/w)

Measurement:

-Go-signal RT (latency in responding to targets) for speed of goal-directed action

-Stop-Signal RT (SSRT, latency to inhibit a prepotent response) for delay and inhibiting goal-directed action

-SSRT measures degree of cognitive control

Recreational users show no difference in goal-execution times

But: significant difference in the time taken to inhibit goal execution

Inhibitory deficits could compromise ability to terminate drug addiction

Tyrosine: alternative to dopamine drugs

-Precursor of dopamine and norepinephrine, naturally produced in the body

-Source: apples, soy, chicken, fish, milk, spinach etc

-1 hr after intake, DA levels go up, Half life = 2 hrs

-used for enhancing concentration, flexibility, sleep, depression

-can reverse mental decline and improve cognition in short-term (only some cases, not in PD)

-Deficiency can cause Phenylketonuria

-Very difficult to overdose on TYR due to limited TH

-Safe to use as compared to performance enhancing supplements like Ritalin

-Tyrosine only helpful when there is stress

Those with Val genotype perform better than the Met genotypes

Tryptophan: alternative to serotonin drugs

-precursor of serotonin

-not produced naturally in the body

-source: salmon, poultry, eggs, spinach, nuts

-Half life: 2 hours

- Used for treating depression

-Tryptophan induces a positive bias

-Females have more effect in the positive bias with tryptophan

-Increases interpersonal trust (or maybe risk-taking?)

-Promotes charity