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?