It summarizes in a concise and informative way recent concepts about the limbic system

1. LIMBIC SYSTEM & BEHAVIORAL PHYSIOLOGY:
LEARNING OBJECTIVES:
 Functional anatomy
 Functions
 Physiology of Emotions.
 Emotional behavior.
 Physiology of Motivation.
 Physiological basis of psychotic disorders.

2. Functional Anatomy:
Components of limbic system.
Limbus : border Ring.
i.e., part of cortex & subcortical structure that form ring
around brain stem.
related to Olfaction.
Limbic cortex –Composed of these cortical structures:
 Orbitofrontal cortex
 Subcallosal gyrus
 Cingulate gyrus.
 Parahippcampal gyrus.

3.  Uncus.
Subcortical structures:
 Hypothalamus
 Septal nuclei
 Anterior nuclei of thalamus.
 Amygdala
 Portions of basal ganglia
 Hippocampus.

4. CHARACTERISTIC FEATURES OF LIMBIC SYSTEM:
 Emotions & Instinctual behavior are not under
voluntary control.
 Prolonged After discharge – So emotional
responses continue long after end of stimuli which
produces them.

5. FUNCTIONS OF THE LIMBIC SYSTEM:
 Autonomic functions.
 Regulation of feeding behavior.
 Regulation of sexual behavior and reproduction.
 Neural control
 Endocrinal control.
 Maternal behavior
 Emotional behavior.

6.  AUTONOMIC FUNCTIONS.
 Stimulation of mainly – Amygdala through
Hypothalamus causes autonomic response.
 During emotional states they mainly affect:
 Cardiovascular system
 Respiratory system
 GIT.

7.  REGULATION OF FEEDING BEHAVIOR.
 Hypothalamus – Regulate food intake through
feeding center & satiety center.
 Amygdala – stimulation produces movement
associated with eating (chewing, swallowing, licking)
 Lesion in the amygdala– Produces Hyperphagia.
 REGULATION OF SEXUAL BEHAVIOR AND
REPRODUCTION.
 Basic sex drive is an instinctual behavior as food
intake.

8.  This function of limbic system & hypothalamus is
influenced by sex hormones, cerebral cortex,
pheromones.
 NEURAL CONTROL OF SEX DRIVE:
It is the role of both parts of cerebral cortex
(neocortex & limbic cortex). Mainly:
- frontal region stimulates sex behavior.
- Pyriform cortex overlying Amygdala inhibits
sex drives in males.

9.  ENDOCRINAL CONTROL OF SEX DRIVE:
i. Role of Gonadal hormones.
 In Males – Testosterone increases sex drive
 In Females – Estrogen increases sex drive, it rises
during estrous period. Sexual activity in females is
slightly increased during ovulation for the purpose of
ovum fertilization.
ii. Role of Pheromones:
–Chemicals produce by the animal, their smells act as
attractants of the opposite sex for copulation.

10.  MATERNAL BEHAVIOR:
 It is a function of Cingulate Gyrus & Retro-splenial
portion of limbic cortex:
 In animals the attachment of the mothers to the
“babies” is mainly neurogenic in nature – i.e., it
depends on olfactory, auditory, visual, thermal,and
tactile stimuli from the baby to the mother.

11.  EMOTIONAL BEHAVIOR:
(the most important function of limbic system).
PHYSIOLOGY OF EMOTIONS:
Emotions – Aroused state having an intense feeling,
autonomic activation & related behavior (physical &
mental reaction to the stimulus)

12. Example: Response of individual to sudden very loud
sound)
MENTAL (SENSORY) COMPONENT:
Composed of 3 phases:
1. Cognition – by which one becomes aware &
recognizes the sound.
2. Affect – German word means the development of
feeling. (The development of fear and becoming
frightened).
3. Conation – the internal force or drive that directs
the body to take some action in response to a very
loud sound (the force/drive to run away)

13. PHYSICAL ( EXPRESSIVE OR PERIPHERAL)
COMPONENT:
It is the motor component of the emotional behavioral
response. It is also has 2 components:
1. Somatic – changes in skeletal muscle, running
away is somatic.
2. Autonomic – includes the coordinated activity of
sympathetic & parasympathetic: HR, BP, and RR

14. Behavior – is the expression of emotions such as:
 Rage, fear and Placidity.
 Feeling of Reward and Punishment.
 Reward – Feeling of reward, tranquility &
pleasure.
 Punishment – Feeling of punishment, fearing &
aversion.
NEURAL MECHANISM OF EMOTIONS:
i. Role of cerebral cortex.
ii. Role of Hypothalamus.

15. iii. Role of Amygdala.
iv. Role of Hippocampus.
v. Role of peripheral Nervous system.
a) Autonomic
b) Somatic motor.
ROLE OF CEREBRAL CORTEX.
 Frontal cortex play imp. role in generation of
mental component of emotions:
 Provide the mechanism by which Memory and
imagination generate emotional feelings.

16.  Directs physical (peripheral component) of
emotional responses by sending neuronal signals
(from the primary and secondary motor areas in the
precentral gyrus of the frontal lobe) to skeletal
muscles in response to external stimuli/events.
 It also helps in modulation, direction,
understanding or inhibition of the expected
emotional behavior.

17. LIMBIC CORTEX:
 Ant. temporal cortex:
Gustatory & Olfactory association areas.
 Parahippocampal Gyrus:
Auditory association area.
 Post. cingulate cortex:
Sensory & motor association areas

18. ROLE OF HYPOTHALAMUS.
Lat hypothalamic area – Thirst, hunger, rage & fighting
center
Ant. hypothalamic areas – Stimulate parasympathetic
System
Post. Hypothalamic nucleus – Stimulate sympathetic
system
Mamillary bodies – Feeding reflexes center
Dorso-medial nucleus – GI stimulation center
Ventro-medial & paraventricular nuclei – Satiety &
tranquility center opposite to lat. Hypothalamic area

19. Peri-ventricular nuclei zone – fear and punishment
reactions
Peri-fornical nucleus – Rage & hunger center
Post. Pre-optic nucleus – Body temperature & sweating
Center
Suprachiasmatic nucleus – Circadian rhythm (Master
biological clock) center
Most ant. area and most post portions – Stimulate sexual
drive

20. ROLE OF AMYGDALAS.
 Amygdalas – multiple small cell nuclei located
beneath medial anterior pole of both temporal lobes
 2 sub-divisions:
1. Cortico-medial (concerned with olfactory stimuli
and their relations to the limbic cortex)
2. Basolateral (play imp. roles in Behavioral activities)
 Afferents to amygdala – from neocortex (esp.
auditory and visual association areas) & Limbic
cortex – Therefore it has been called the “WINDOW”
through which limbic system sees the place of
person in the world.

21.  Efferents – to some cortical areas, Hippocampus,
septal nuclei, thalamus & Hypothalamus.
In general stimulation of the amygdalae can cause
all effects caused by direct stimulation of the
hypothalamus.
Stimulation of certain amygdaloid nuclei can cause
rage and punishment reactions
Other amygdaloid nuclei stimulation can cause
reward and pleasure reactions.
Amygdalas are considered behavioral awareness
areas, operate at semi-conscious levels, and make the

22. individual behavioral response appropriate to both
thoughts and surroundings for each occasion.
ROLE OF HIPPOCAMPUS.
 Has connections to and from –cerebral cortex and
the basal parts of limbic system: hypothalamus,
amygdalas, septal nuclei, mammillary bodies.
 Stimulation of different areas can evoke different
reactions such as: pleasure, rage, passivity &
excessive sexual drive.

23. Functions of the hippocampi:
i. Additional channel that incoming stimulus sensory
signals can initiate different reactions for different
purposes.
ii. Provide signal for memory consolidation, i.e.,
Transformation from short term memory to long term
memory).
PHYSIOLOGY OF MOTIVATION.
Neural mechanism of Motivation is based on the
Concept of Reward & Punishment.

24. ROLE OF NEUROTRANSMITTERS:
Drugs that increase stimulation of reward center:
 Amphetamine
 Nicotine & Alcohol
 Cocaine
Drugs that decrease stimulation of both reward &
punishment center.
 Chlorpromazine
 Haloperidol

25. PHYSIOLOGICAL BASIS OF PSYCHATRIC DISORDERS:
 DEPRESSION:
 When Mood chronically remains down without any
specific reason
 Signs & symptoms – lack of interest, suicidal
tendency, excessive sleep & overeating.
 Causes – decreased activity of noradrenergic or
serotonergic activity.
 Treatment – Antidepressants.

26.  MANIA:
 Mood remains chronically Elated without any reason.
 Due to over activity of nor-adrenergic & serotonergic
neuronal activity.
 Treatment: drugs that stabilize noradrenergic &
serotonergic neurons (Mood stabilizers)
 SCHIZOPHRENIA.
 There is false perception of sensation (Hallucination)
without any anatomical lesions in sensory pathways.
 Cause – excessive activity of Dopaminergic
mesolimbic pathway.

27.  Characteristic features:
 Hallucinations – Auditory & Visual
 Grandeur or persecutory delusions,
 intense fear,
 paranoia
 Withdrawal from society
 Treatment –Drugs decreasing Dopamine conc. in
brain