1. LIMBIC SYSTEM
LECTURE 12
DR.ZAHOOR

2. LIMBIC SYSTEM Limbic System works for 1. Emotion 2. Behavior
3. Motivation
4. Memory (we will discuss in next lecture).

3. LIMBIC SYSTEM We will study Limbic System under the heading 1) History
2) Functional Anatomy
3) Functions
4) Experiments done in animals
5) Chemical transmitters
6) Clinical applications.

4. LIMBIC SYSTEM 1- History - Rhincephlon in RATS was first identified.
Why it was named Rhincephalon?
Because Rats are led by Olfactory stimuli.
Than name was changed to LIMBIC SYSTEM because all animals are not guided by olfactory stimuli.

5. 2. Functional Anatomy WHAT IS LIMBIC SYSTEM?
It is ring of Fore brain structures that surround the brain stem
2. Functional Anatomy
Limbic System includes
i). Amgdala
ii). Hippocampus
iii). Cingulate gyrus
iv). Portions of hypothalamus
v). Portions of thalamus
Vi) Portions of basal nuclei
vi). Portions of lobes of cerebral cortex [limbic
association cortex]

6. Schematic of the Limbic System Components

8. Location of the Limbic System
Figure 58-4; Guyton & Hall

9. LIMBIC SYSTEM Limbic System nuclei are connected by neuron pathway
3. We will discuss the functions of Limbic System
1. Emotion
2. Behavior
3. Motivation

10. Functions 1. Emotions
Emotion means feelings, mood, anger, happiness, fear, and physical responses associated with these feeling e.g. laughing, crying
Important – Input processed and giving rise to sensation of FEAR is in Amygdala, it lies in temporal lobe

11. Functions 2. Behavior
Control of behavior is under the limbic system and higher cortex
e.g. behavior of survival – search for food, attack, socio-sexual behavior response

12. Functions 3. Motivation
It is well known that person reinforces behavior that has proved gratifying and suppresses that behavior which are associated with unpleasant experience
Areas in limbic system are named as
- Reward center
- Punishment center

13. Functions 3. Motivation [cont..]
Why we call reward and punishment center?
Because stimulation in these areas give rise to pleasant and unpleasant sensations
Reward center – are found in regions of behavior activities of eating, drinking
Punishment center – are found in regions of pain

14. LIMBIC SYSTEM – Different areas Cingulate Gyrus
Cingulate Gyrus – situated above corpus callosum
Functions
- Sociable adaptable
- Maternal behavior – care of offspring ( Animal who eat offspring has no cingulate gyrus)
- Emotional behavior
Dysfunction causes
- Addictions to drugs– seeking pleasure

15. LIMBIC SYSTEM AMGDALA AMGDALA Functions
- Sociability – more social, more friends
- Fear response
- Pleasure
- Post traumatic stress
- Aggression
- Memory

16. LIMBIC SYSTEM Hippocampus
Hippocampus – (Sea horse) Located in Temporal
lobe
Functions
- Memory – Short term and Long term memory. If damage to hippocampus, patient cannot make long term memory.
- damage causes anterograde amnesia

17. Hippocampus IMPORTANT
FUNCTIONS [CONT..]
reward and punishment determine whether or not information will be stored as memory
If no reward or punishment, it is hardly remembered but a person learns any sensory experience that causes pain or pleasure and makes strong memory trace
hippocampus provides the drive to rehearse and consolidate these sensory experiences
IMPORTANT
First area to show damage in ALZEHIMER DISEASE is Hippocampus

18. Limbic Cortex FUNCTIONS
cerebral association area functions for control of behavior
stimulation of various portions of this area can elicit almost all types of behavior in an animal

19. LIMBIC SYSTEM HYPOTHALAMUS
Major part of Limbic system, it plays role in
- Behavioral control , body temperature, osmolality of body fluids, control of body weight ( eating and drinking )
- These internal functions are called VEGETATIVE functions of brain and are closely related to Behavior.

20. Hypothalamus major output pathway of the limbic system
vegetative functions:
neurogenic control of arterial pressure
regulation of body temperature
regulation of fluid volume
regulation of endocrine gland secretion
growth hormone, thyroid hormone, glucocorticoid secretion, sex hormones

21. Behavioral Functions of the Hypothalamus and Related Areas
lateral hypothalamus
eating, thirst, general level of activity, rage
ventromedial nucleus
satiety, tranquillity
periventricular nucleus
fear, punishment reactions
anterior and posterior hypothalamus
sexual drive

22. Functional Areas of the Hypothalamus
Figure 58-6; Guyton & Hall

23. Behavior and its Control
Reward and punishment causes the Limbic system so that we can learn. If no reward or punishment we ignore.
Several limbic structures are concerned with sensory experience–is it pleasant or unpleasant?
Reward center - the lateral and ventromedial hypothalamus, thalamus certain areas, Amygdala,
Punishment center - located in hypothalamus and thalamus, Amygdala and Hippocampus
Punishment always takes precedent over reward.
Punishment can frequently inhibit reward center.

26. 4. Experiments done in rats
- Experiments done in animals to see behavioral response to Reward and Punishment.
- What was found ?
- It was found if electrical stimulus is rewarding, animal presses the button more often , positive reinforcement.
- But if electrical stimulus causes pain , animal decreases the rate of pressing the bar. So if punishment , we do not do the things again.

28. Emotional Behavior
Cerebral cortex plays major role in directing many motor responses during emotional behavior e.g. to do or avoid situation, or modulation, or inhibition of emotional behavior.

29. 5. NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR
These are
1. Norepinephrine
2. Dopamine
3. Serotonin

30. NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR
Norepinephrine and dopamine are catecholamines, that are present in regions that elicit highest rate of self stimulation –
DO IT YOURSELF
That is why amphatamine [stimulant] is used in depression. It causes increased release of dopamine from dopamine secreting neurons

31. OTHER EFFECT OF DOPAMINE
Many drugs increase dopamine in pleasure pathways in limbic system, therefore, cause intense sensation of pleasure e.g. cocaine
Cocaine blocks re-uptake of dopamine at synapses

32. 6. Clinical Application Limbic System defects 1- Depression
It is psychiatric disorder associated with defect in limbic system neurotransmitters
In depression, neurotransmitter is decreased which is Norepinephrine or serotonin or both
NOTE – Depression is not neurological disorder i.e.
there is no lesion in the brain

33. DEPRESSION Symptoms in depression are - Loss of interest
- Negative mood
- Inability to experience pleasure
- Suicidal tendency

34. TREATMENT FOR DEPRESSION
Anti-depressant drugs are used - Prozac – blocks re-uptake of released serotonin, therefore, there is increased serotonin at synapses - Amphetamine – causes increase release of Dopamine .

35. Clinical Application Alzheimer disease
Memory loss- recent memory can not be converted to long term memory ( Ante grade Amnesia)

36. THANK YOU