Neuroscience Optional Lecture The limbic system- the emotional brain - Fiziologie

Neuroscience Optional Lecture
The limbic system– the emotional brain

The limbic system

                    • Emotion, behaviour, motivation,
                      long-term memory, olfaction

                    • System - Network of neurons
                      associated with many different
                      anatomic parts of the brain

                    • It involves a collection of various
                      structes that interact to relate to
                      our emotions

Emotion
• Subjective conscious experience – intense mental activity and a certain degree of
  pleasure and displeasure
• Arousal
• Can change metabolic and organ functions → change in behavior
• Often intertwined with mood, temperament, personality, disposition and
  motivation.
• Cognitive process: understanding through thought, experience and senses

Thoughts can depend on our mood!

How are we wired?

• Limbic system vs consciousness
* Limbic system – emotional brain
* Cortex – control brain, social and environmental integration

• Somatic vs autonomous nervous system, which control reaction to stress
 → Sympathetic and parasympathetic nervous system (with contrary effects)

• „Freeze - Fight - Flight”
• Epinephrine

• Activation of the sympathetic nervous
  system has the following effects:

- opens the eyelids
- stimulates the sweat glands
- dilates the blood vessels in large muscles
- constricts the blood vessels in the rest of the
body
- increases the heart rate
- opens up the bronchial tubes of the lungs
- inhibits the secretions in the digestive system

The parasympathetic nervous system
Roles:
• Maintains the internal equilibrium
• Brings the body back from the emergency status

Acetylcoline:
- pupil constriction
- activation of the salivary glands
- stimulating the secretions of the stomach
- stimulating the activity of the intestines
- stimulating secretions in the lungs
- constricting the bronchial tubes
- decreasing heart rate

The limbic system

The limbic system - functions
• Generation of emotions:
      - hapiness, joy and euphoria
      - anger and rage
      - anxiety, fear and terror
      - sadness and depression

• Emotional state can affect the general level of alertness (via thalamus)
       - anxiety, fear, excitement, anger → level of alertness ↗
       - depresion, sadness → level of alertness ↘

Thalamus activates the prefrontal cortex and   Prefrontal cortex: the top-down regulation
            increases alertness

The limbic system - functions
• Motivation

     - Passion!

• Short-term memory and learning (hippocampus)

     - Motivation and passion are needed for learning

The limbic system - functions
• Sense of smell
      - odors (like perfumes and aftershaves) affect
emotions and attraction
• Sexual behaviour

• Sensitivity to pain
      - pain is an emotion; suffering

The limbic system -
Components

• Subcortical areas:

• Septal nuclei, a set of structures that lie in front of the lamina terminalis,
  considered a pleasure zone.
• Amygdala, located deep within the temporal lobes and related with a number of
  emotional processes. It represents the main site of neural plasticity linked to fear.
• Nucleus accumbens: involved in reward, pleasure and addiction.

Prefronto-limbic circuitry – age-related architecture

• The case of Phineas Gage – damage of the frontal
  lobe during a work-related accident

→ irritable, aggresive and violent attitude
→ low emotional regulation
→ changes in behavior and personality
→ decreased self-reflective awareness
→ impaired social behavior

Components
• Cortical areas:
• Limbic lobe (parahippocampal gyrus)
• Orbitofrontal cortex, a region in the frontal lobe
  involved in the process of decision-making.
• Piriform cortex, part of the olfactory system.
• Entorhinal cortex, related with memory and
  associative components.

• Subcortical areas:
• Hippocampus and associated structures, which play a central role in the
  consolidation of new memories.
• Fornix, a white matter structure connecting the hippocampus with other brain structures,
  particularly the mammillary bodies and septal nuclei

Hippocampus
• is involved with various processes relating to cognition.
• Main roles:
• Spatial memory
        - an important component for the generation
 of new neurons, called adult-born granules (GC), in
 adolescence and adulthood
        - formation (dorsal hippocampus) and
recall of the spatial memories (left hippocampus)

• Learning

Components

• Diencephalic structures:

   • Hypothalamus: a center for the limbic system, connected with the frontal
     lobes, septal nuclei and the brain stem reticular formation, with the
     hippocampus and with the thalamus. It regulates a great number of
     autonomic processes: body temperature, blood sugar level, osmolarity.
   • Mammillary bodies, part of the hypothalamus that receives signals from
     the hippocampus via the fornix and projects them to the thalamus.
   • Anterior nuclei of thalamus receive input from the mammillary bodies.
     Involved in memory processing

Papez circuit

Clinical considerations
• Rabies: viral infection that affects the limbic system (especially the amygdaloid
  nucleus and the medial hippocampus of the limbic system) → anger/violence,
  fear/anxiety, Kluver – Bucy syndrome
• Charles Whitman (murderer)
- Murdered his mother and wife
- Shot 38 people
- Autopsy: tumour (the amydaloid
nucleus of the limbic system)

Clinical considerations
• Schizofrenia: „antisocial behaviour”
       - ↗ dopamine
       - familial (genetic)
• Mania and depression
       1. Mania: - „high”, impulsive, agressive
                    - ↗ norepinephrine
       2. Depression: - sad, social isolation
                          - low self-esteem
                          - norepinephrine, dopamine↘
                          - serotonine ↘
                          - use antidepressant drugs