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Neuroscience Optional Lecture
The limbic system– the emotional brainEmotion, behaviour, motivation, long-term memory, olfaction
Emotion
• 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 andmotivation.
• Cognitive process: understanding through thought, experience and senses
How are we wired?
• CNS vs Peripheral nervous system
• Somatic vs autonomous nervous system
• Motor vs sensory impulses
• Limbic system vs consciousness
* Cortex – control brain, social and environmental integration
* Limbic system – emotional brain
• „Fight or flight”• Epinephrine
• Activation of the sympathetic nervoussystem 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 thelungs- inhibits the secretions in the digestive system
The parasympathetic nervous system
• brings the body back from the emergency status
- 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 - 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 ↘
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) affectemotions and attraction
• Sensitivity to pain
- pain is an emotion; suffering
• Sexual behaviour
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.
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.
• 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
Prefronto-limbic circuitry – age-related architecture
Hippocampus
• is involved with various processes relating to cognition.
• 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 (medial hippocampus of thelimbic 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, ↘serotonin
2. Depression: - sad, reclusive
- norepinephrine↘
- use antidepressant drugs
Sleep - a brief introduction
What is sleep?• Sleep is a naturally recurring state of mind and body characterized by
altered consciousness, relatively inhibited sensory activity, inhibition of nearlyall voluntary muscles, and reduced interactions with surroundings.
Sleep studies
• The EEG is frequently used in the investigation of sleep disorders especially sleep apnoea.
• Polysomnography : EEG activity together with • heart rate,
• airflow,
• respiration,
• oxygen saturation and
• limb movement
Sleep patterns of EEG• There are two different kinds of sleep:
• Rapid eye movement sleep (REM-Sleep)
• Non-REM sleep (NREM sleep)/ slow wave sleep
• NREM sleep is again divided into 4 stages (I to IV). The EEG pattern in sleep is given in the following table:
Stage 1• Brain activation level reduced: low voltage EEG,
diminished
• alpha activity, reduced frequency activity (theta) 3-7 Hz
• EOG – Slow eye movement, low muscular activity
• EMG moderate – reduced
Stage 2
• low voltage EEG, mixed activity frequency, 12-14 Hz
• sleep spindles associated with K complexes (diphasic
• waves, > 0,5 s)
• EOG – slow, rare eye movements
• EMG moderate – reduced muscular activity
Stage 3• EEG –delta waves, 0,5-2 Hz & amplitude
• >75mV; covering around 20-50% from the
• analyzed epoch.
• EOG – rare eye movements
• EMG moderate – reduced muscular activity
Stage 4
• EEG delta activity covering >50% from the epoch
• EOG – rare eye movements
• EMG moderate - reduced
Why do we sleep?