31 – Behavior, Emotions, Learning and Memory

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Behavior and emotions
Our limbic system play an important role in emotions and behavior. Limbic system is often referred to the emotional brain, where it has a role in a range of emotions (fear-pleasure).
Limbic system
Cortical structures (medial part of cerebral hemisphere)
-Cingulate gyrus
-Parahippocampal gyrus
-Entorhinal cortex

Subcortical structure (diencephalon, brainstem, RF)
-Mammilary bodies
-Ant. thalamic nuclei
-Habenular nuclei

All these structures and more have interconnections and play an important role in memory, emotions and behavior.

Papez circuit
Papez circuit
One of several ways how structures of limbic system communicate. It is very important for our i emotions.
Its involved in cortical control of emotions and storage of memories.
It starts and ends in hippocampus.

1) Signals from hippocampus are transferred via fornix to mammilary bodies (hypothalamus)
2) Fibers run from mam. bodies to the anterior thalamic nuclei (mammilothalamic tract)
3) From thalamus, signals are transmitted to cingulate gyrus and via cingulum it goes to parahippocampal gyrus -> entorhinal cortex (28)
4) Fibers from entorhinal cortex will enter subiculum og hippocampus

Papez circuit lesions
Leads to abnormality in emotional expression.
-shaped like a sea-horse
-located in the temporal lobe
-huge impact on memories
-formation of new memories
-connect hippocampus with other structures – mam-bod.
-commisure of fownix is where the R+L fornix connects
-center for emotions and emotional behavior
-stimulation of amygdala can cause fear.
-patients with post-traumatic-stress disorder have large amygdala

-Amygdala communicates with other structures:

-amygdala-fugal pathway (to brainstem, thal, hypothal)

-stria terminalis (to hypothalamus) – direct pathway
-> autonomic response to emotions (inc. HR, BP)

-connection to hippocampus
-> create memories regarding a fearful experience
-> can explain why we remember scary, sad things

-connections to trigeminal nuclei: facial expression
-several connections to prefrontal area (behavior)

Amygdala lesion
Kluver-bucy syndrome:
-less fear, more restless, emotional instability
Association areas
Association areas of cortex are incolved in complex functions such as memory, behavior, emotion etc.
-Prefrontal cortex (9,10,11,12)
= personality
*Phineas Gage got a metal rod penetrated through his prefrontal cortex -changed personality and behavior
Endorphins, Enkephalins
Neuropeptides have influence on memory and learning. Improves it!
Emotional feelings like euphora, pleasure.
Nucleus accumbens
Nucleus accumbens
Involved in feelings of reward, pleasure, addiction
The ability to aquire new information or skills.
Process where information aquired through learning is stored and retrieved/recalled.
Memory – 3 phases
2) Storage
3) Retrieval
1 – Encoding
One important process involved in the first phase of memory is synaptic plasticity.
When our body brings sensory info to our brain, the stimulus causes transmission via synapses and neurotransmitters.
When there is increased synaptic transmission, the synapses has the ability to strengthen.
So we say that synaptic plasticity is the ability of synapses to strengthen or weaken in response to increase or decrease in their activity.

Increased plasticity: stronger response to stimuli.
The act of glutamate on NMDA receptors are especially important.

2- Storage of memory
Storage of memory can either be as short-term memory or long-term memory.

Short term memory: look up phone number, remember and dial. We forget it within seconds.
-Hippocampus, mammilary bodies, ant&med thalamic ncl

Long term memory: permanent type of memory-days/years
-we see a phone number several times and it becomes a part of LTM, where info can be retrieved when needed.
-only 1% of conscious info is stored as LTM

LTM is divided into 2 parts
1) Declarative memory: events, things, people etc

2) Non-declarative memory: you recall specific skills or procedures. – how to use a pencil, ride a bike.

Circuit for declarative memory
Circuit for declarative memory
Neocortex -> Entorhinal cortex -> Hippocampus -> Entorhinal cortex -> Neocortex
Circuit for non-declarative memory
Dentate nucleus -> Red nucleus -> Inf.olivary complex -> Dentate nucleus
3 – Retrieval
Memory that is stored and can be used when needed (Recall)
Testing retrieval
1) Free recall
-if a person is given a list of items to remember and is tested if he could recall them in any given order.

2) Cued recall
-some numbers are paired with items and he is tested if he can recall the numbers with associated items.

3) Serie recall
-the person has the ability to recall the items in the correct order.

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