Limbic system - Dr Rohit Bhaskar

LIMBIC SYSTEM
©2021 Dr Rohit Bhaskar PT https://www.pt-pedia.com/

OBJECTIVES.
❖ Limbic system
❖
❖
Physiological anatomy
Functions
❖ Physiology of Emotions.
❖
❖
❖
❖
Components Theories
of genesis Emotional
behavior. Neural
substrate.
❖ Physiology of Motivation.
❖ Physiological basis of psychotic disorders.

PHYSIOLOGICAL ANATOMY
■ Components of limbic
system.
■ Limbus – Ring.
■ That part of cortex &
subcortical structure that
form ring around brain
stem.
■ Earlier called –
Rhinencephalon – related
to Olfaction.

■ Limbic cortex –
Phylogenetically
older part
(allocortex)
■ Composed of
■
■
■
■
■
Orbitofrontal cortx
Subcallosal gyrus
Cingulate gyrus.
Parahippcampal gyrus.
Uncus.

■ Sub cortical structures
includes –
■ Hypothalamus
■ Septum
■ Paraolfactory area
■ Anterior nuclei of thalamus.
■ Amygdala
■ Portions of basal ganglia
■ Hippocampus.

CONNECTIONS
■ Papez circuit
■ Closed circuit formed by
connections between 4
nuclei.
■ Responsible for resting
EEG.
■ For emotions & behaviour
for preservation of species
& individuals.

EFFERENT PROJECTIONS OF LIMBIC
SYSTEM.

CHARACTERISTIC FEATURES OF
CONNECTIONS.
■ Very little connections with Neo-cortex.
■ So Emotions & Instinctual behaviour not under
voluntary control.
■ Prolonged After discharge – So emotional response
continue long after end of stimuli which produces them.

FUNCTIONS
■ Autonomic functions.
■ Regulation of feeding behavior.
■ Regulation of sexual behavior and reproduction.
■ Neural control
■ Endocrinal control.
■ Maternal behavior
■ Emotional behavior.
■ Motivational behavior.

AUTONOMIC FUNCTIONS.
■ Stimulation of mainly
– Amygdala through
Hypothalamus causes
Autonomic response.
■ During emotional
state mainly affect
■ Cardiovascular system
■ Respiratory system
■ GIT.

REGULATION OF FEEDING BEHAVIOR.
■ Hypothalamus – Regulate
food intake through feeding
centre & satiety center.
■ Amygdala – stimulation
produces movement
associated with eating
(chewing, swallowing,
licking)
■ Lesion – Produces
Hyperphagia.

REGULATION OF SEXUAL
BEHAVIOR AND REPRODUCTION.
■Basic sex drive (urge to copulate) is
instinctual behaviour as food intake.
■Function of limbic system & Hypothalamus,
influenced by sex hormones & cortex.
■Controlled by Neural & Endocrinal factors.

NEURAL CONTROL
■ Role of Neo cortex &
Limbic cortex
■ Mainly frontal region
stimulate sex
behaviour.
■ Pyriform cortex
overlying Amygdala
inhibits sex drives in
males.

NEURAL CONTROL
■ Role of Hypothalamus
■
■
Ant Hypothalamus & median
Forebrain bundle elicit sex
behaviour
Role of Encephalization –
Largely Encephalized –
perception that sexual act
produces pleasure – is a big
cause
■ Also sexual Behaviour is
strongly influenced in human
being – by social customs, rules
& social taboo.

ENDOCRINAL CONTROL
■ Role of Gonadal hormones.
■ In Males – Testosterone stimulate
■ In Females – Oestrogen raised during oestrous period.
Sexual activity slightly increased during ovulation.
■ Role of Pheromones –
■ Chemicals by their smell acts as sex attractant.

MATERNAL BEHAVIOR
■ Function of Cingulate
Gyrus & Retro splenial
portion of limbic cortex.
■ In animals mainly
Neurogenic – Depend
on olfactory, auditory,
visual & Themotactile
stimuli from younger
ones.

EMOTIONAL BEHAVIOR.
■ Most important
function of limbic
system.

MOTIVATIONAL BEHAVIOR.
■ Most important
function of Limbic
system.

PHYSIOLOGY OF EMOTIONS
■ Emotions – Aroused
state having intense
feeling, Autonomic
activation & related
behaviour.
■ Components
■ Mental
■ Physical (exa- Response
of individual to sudden
very loud sound)

MENTAL OR SENSORY COMPONENT
■ Cognition – by which
one become aware &
recognises the sound.
■ Affect – German word
means development of
feeling. (frightening)
■ Conation – force which
direct to take some
action (Run away)

PHYSICAL OR EXPRESSIVE OR PERIPHERAL
COMPONENTS
■
■
■
■
■
Motor side of emotional
behaviour
2 components
Somatic – changes in skeletal
muscle, running away is somatic
part.
Autonomic – includes
coordinated activity of
sympathetic & parasympathetic
HR, BP, Respiratory rate

THEORIES OF GENESIS OF EMOTIONS
■ Arnold theory.
■ By Cognition – aware &
recognition
■ By Unconcious
evaluation – Judged as
harmful or Beneficial.
■ Affect – Concious
reflection of unconscious
appraisal. (Fear, Joy,
Grief or Rage)

EMOTIONAL BEHAVIOUR
■ Behaviour – is
expression of
emotions.
■ Rage, fear and
Placidity.
■ Sexual behaviour
■ Feeling of Reward and
Punishment.

NEURAL SUBSTRATE OF EMOTIONS
■ Role of central Nervous system.
■ Role of cerebral cortex.
■ Role of Hypothalamus.
■ Role of Amygdala.
■ Role of Hippocampus.
■ Role of peripheral Nervous system.
■ Autonomic
■ Somatic motor.

ROLE OF CEREBRAL CORTEX.
■Frontal, cingulate &
parahippocampal
cortices play imp role in
Affective component.
■Provide mechanism by
which Memory and
imagination evoke
Emotional feeling.

ROLE OF CEREBRAL CORTEX.
■Also directs Motor responses to external
events.
■It also helps in Modulation, Direction,
Understanding or inhibition of emotional
behaviour.

LIMBIC CORTEX
■ Ant temporal cortex
–Gustatory &
Olfactory association.
■ Parahippocampal
Gyrus – Auditory
association.
■ Post singulate cortex
–Sensory motor
association.

ROLE OF HYPOTHALAMUS.
■ Lat hypothalamus– stimulation – Rage & Aggression
■ Ant & Post portion – Sexual arousal
■ Reward center – Feeling of reward, tranquility & pleasure.
■ Punishment center – Feeling of punishment, fearing &
aversion.

ROLE OF AMYGDALA.
■ Amygdala – cells located above inferior horn
of
2 subdivisions – Corticomedial & Basolateral
(play role in Behavioral activities)

ROLE OF AMYGDALA.
■ Afferent – from cortex & Limbic system – so called
“WINDOW” through which limbic system sees place of
person in the world.
■ Efferent – To cortex, Hippocampus, septum,
Thalamus & Hypothalamus.

KLUVER BUCY SYNDROME
■ Bilateral destruction of temporal lobe –
■ Extreme orality
■ Loss of fear
■ Decreased aggressiveness.
■ Change in eating behaviour
■ Hypersexuality
■ Psychic blindness.

ROLE OF HIPPOCAMPUS.
■ Connections – Mainly to cerebral cortex.
■ Stimulation – evoke Rage, Passivity & excessive
sexual drive.
■ Functions – Provide signal for memory
consolidation, transformation from short term to long
term memory.

ROLE OF PERIPHERAL NERVOUS SYSTEM.
■ Autonomic nervous system
■ Canon described response of ANS in emergency
■ Somatic motor nervous system
■ Involved in physical component of emotions – skeletal
muscle movements.

PHYSIOLOGY OF MOTIVATION.
■ Neural mechanism of
Motivation based on
■ Concept of reward &
Punishment.

ROLE OF NEUROTRANSMITTERS
■ Drugs that increases stimulation of reward center.
■
■
■ Amphetamine
Nicotine & Alcohol
cocaine
■ Drugs that Decreases stimulation of reward center.
■ Drugs which inhibit activity of Catecholamines – Chlorpromazine
Hydrochloride.

PHYSIOLOGICAL BASIS
OF PSYCHOTIC DISORDERS
■ Depression
■ Mania
■ Schizophrenia.

DEPRESSION
■ When Mood
chronically remains
down without any
specific reason
■ Signs & symptoms –
lack of interest,
suicidal tendency,
excessive sleep &
overeating.

DEPRESSION
■ Causes – decreased
activity of
noradrenergic or
serotonergic fibres.
■ Treatment –
■ MAO inhibitors,
tricyclic
antidepressants.

MANIA
■ Mood remain
chronically Elated
without any reason.
■ Due to over activity of
Nor-adrenergic fibre
activity.

SCHIZOPHRENIA.
■ There is false perception
of sensation
(Hallucination) without
any anatomical lesions in
sensory pathways.
■ Cause – excessive
activity of
Dopaminergic
mesolimbic pathway.

SCHIZOPHRENIA
■ Characteristic
features
■ Hallucinations –
Auditory & Visual
■ Grandeur Delusions,
intense fear, paranoia
■ Withdrawl from society
■ Treatment –
■ Drugs decreasing
Dopamine conc in brain

Limbic system - Dr Rohit Bhaskar

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