Limbic System

Locations of Amygdala and basal ganglia

Amygdala: at the end of hippocampus

Basal Ganglia: contains nucleus accumbens + is anterior to the amygdala

TEMPORAL LOBE

Left hemisphere: behavioral activation system - low to moderate autonomic arousal and a tendency to approach: HAPPINESS OR ANGER

Right hemisphere: behavioral inhibition system - increases attention and arousal, inhibits action, and stimulates emotions such as fear and disgust

• Enhanced in people with low levels of MAOa, which breaks down DA, norepinephrine, and serotonin

Testosterone increases violent behaviors slightly

Tryptophan hydroxzylase (converts tryptophan into serotonin) 

people with less active forms of this enzyme are more likely than average to report frequent anger and aggression

What are the two neurochemical messengers released from axons leaving the amygdala? 

What are their effects on anxiety?

  How can the release of each be used to induce or reduce anxiety?  

Benzodiazepenes - bind to GABAa receptors as an agonist. mimic neurotransmitters, more sensitive to GABA + increase responsiveness and transmission of GABA

Barbituates - bind to GABA receptors to increase anxiety. more addictive than benzodiazepenes 

Where are GABA_A receptors located?

GABAa is located in the...

•  amygdala
• hypothalamus
• thalamus
• cortex
• midbrain

Name a few common benzodiazepines

valium

xanax

Librium

 What are the effects of benzodiazepines when acting on GABA_A receptors in the A) amygdala and B) thalamus and cortex? (lecture) 

Amygdala: emotions (fear, aggression, and anxiety) - if increased GABAa activity, then decreases fear and anxiety

Thalamus + cortex: increase GABAa -> causes sleepiness, impairs memory, and reduces seizures

1. Alarm: increased activity of the sympathetic nervous system, readying the body for brief emergency activity

2. Resistance: sympathetic response declines, but the adrenal cortex secretes cortisol and other hormones to enable body to maintain prolonged alertness, heal wounds, etc.

3. Exhaustion: tired, inactive, and vulnerable because the nervous system and immune system no longer have energy to sustain heightened responses

sympathetic nervous system: fight or flight, prepares body for brief emergency responses

HPA axis: hypothalamus, pituitary gland, adrenal cortex

occurs in people that have endured terrifying experiences 

symptoms: freq. distressing recollections, exaggerated arousal responses

vulnerability: smaller than avg. hippocampus, lower than normal cortisol levels after event + AMYGDALA DAMAGE

conscious

recalling events, etc

procedural, unconscious

conditioning, etc. 

Prefrontal cortex: working memory/ STM

What is a delayed non-match to sample task? 

What neurotransmitter is released in the prefrontal cortex during the retention phase of this task?

Which receptor in the prefrontal cortex is important for working memory?

Delayed nonmatch to sample: radial arm maze – food in arms, go to ones with food.

Arms open, find food, go to prev location after delay. Use working memory to remember last arms visited to find food.

OR

Delayed nonmatch to position: operant chamber – 2 levers, press top one for food. Delay. Arms disappear. Press other arms for food. Bottom ones

During retention phase: use working memory.

The cerebral cortex of the Alzheimer’s patient shows clear signs of neural degeneration.  Evidence for this can be found in the form of plaques and tangles. 

What are plaques and tangles?  

plaques: form before alzheimer's symptoms appear, clusters of damaged axons and dendrites due to high lvls of amyloid-beta protein 

tangles: formed from degenerating structures within neuronal cell bodies

a synapse that increases in effectiveness because of simultaneous activity in the presynaptic + postsynaptic neurons

critical for associative learning 

Important for: speech comprehension

 What is the most common side effect of ECT?

 What biological effect might be shared between ECT and antidepressants?