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Higher CNS - functions

Peter Århem

Department of Neuroscience

Brain theories

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Pneuma-teorier Pneuma-theories

Hydrodynamic theories

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Electric theories

Galvani (1737-1798)

Organisation of the human brain

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Three anatomical levels Neocortex – limbic system - basal ganglia

Three evolutionary levels • Neocortex – advanced mammals • Limbic system – primitive mammals • Basal ganglia - reptiles

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Three levels of behaviour Instincts - emotions – abstract thinking

Emotions - the limbic system

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Papez circuit

• Olfactory

cortex

• Gyrus cinguli

• Amygdala

• Hippocampus

• N. accumbens

Increasing complexity – the limbic system

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Amygdala – fear and aggressiveness Connected to gyrus cinguli, thalamus, hypothalamus

Thalamus

Hippocampus – consolidation of memories

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• Activity in n. accumbens associated with pleasure – the reward system of the brain

• Release of dopamine increased at reward

Nucleus accumbens – pleasure and reward

Nucleus accumbens and drug addiction

• Nucleus accumbens is the addiction center of the brain

• Dopamine, but also noradrenalin and serotonin, are key transmitters

• Drugs as nicotine, opiates and cocaine increase release av dopamine

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• Vital process – from fruitfly to man

• Different EEG rhythms

• Regulated by reticular activating system

Sleep

Slow wave sleep and REM-sleep

• Slow wave sleep - 80% of sleep time; lowered metabolism, respiration, muscle tonus, heart frequency, bodytemperature

• REM-sleep (dream sleep) - 20% of total sleep time, 10-40 min periods, rapid eye movements

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Sleep and wakefulness

Beta waves 15-30 Hz Alpha waves 8-15 Hz Theta waves 4-7 Hz Delta waves 1-4 Hz

Gamma waves 40-50 Hz

Wakefulness regulated by reticular activating system (part of formatio reticularis in brain stem)

via thalamus

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Problems with concentration, learning and memory. Increased

frequency of infections and depressions. Increased appetite.

Suggested hypotheses: Consolidation of memory? Adaptation

to day-life.

Why do we need sleep?

Cognition – neocortical association areas

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Cognition

Set of mental abilities and processes related to

• knowledge,

• attention,

• memory,

• judgement and evaluation,

• reasoning and computation,

• problem solving and decision making,

• comprehension and production of language,.…

Association areas

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Speech and language

Aphasias • Wernickes area (sensory aphasia) Fluent speech; nonsense words • Brocas area (motor aphasia) Fragmented speech; well-preserved comprehension

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Personality and lateralization

The prefrontal association area and personality

• Moral, intelligence, self- discipline, social competence, ”right & wrong”

• Controls basic instincts

• Left side: optimistic

• Right side: pessimistic

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The different functions of the hemispheres Roger Sperry

Relation between hemispheres

• Contralaterality

– Right hemisphere controls left body half

– Left hemisphere controls right body half

• Corpus callosum

– Connects left with right hemisphere

– Enables communication between left and right hemispheres

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Hemispheric specializations

Left side:

• Speech and language

• Analytic, arithmetic

• Perception of time

Right side:

• Patterns

• Spatial perception

• Context

Consciousness

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Consciousness – the greatest problem of biology

Francis Crick

Test

1. Mention two rhythms (name and frequency) in a normal EEG from a person that is awake (with either closed or open eyes). 2. Which nucleus is central in the reward system of the brain? 3. What is the system, comprising the evolutionary older part of cortex and some underlying nuclei, involved in emotional reactions, called? 4. Mention a nucleus in this system that is activated at emotions of fear. 5. Almost all sensory information from the body passes through a group of nuclei in diencephalon on its way up to cortex. What is this group called? 7. In which hemisphere do we ususally find the speech areas (Broca’s and Wernicke’s areas)? 8. Which hemisphere handles spatial information best? 9. Mention some functions that are related to activity in the frontal lobe.