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LEARNING AND MEMORY
Dr. Ranadhi Das
MD PGT
ranadhi@gmail.com
LEARNING AND MEMORY
 Learning-
 Reflex Learning-
 Non Associative-
 Habituation
 Sensitization
 Associative-
 Classical Conditioning
 Operant Conditioning
 Incidental Learning
 Memory-
 Physiologically On The Basis Of How
Information Is Stored & Recalled
 Implicit Memory.
 Procedural Memory
 Priming
 Explicit Memory
 Semantic Memory
 Episodic Memory
 Depending Upon Permanency Of Storage
 Short Term.
 Intermediate Long Term.
 Long Term
 Consolidation
 Encoding
 Retrieval
 Applied Aspects
 Substances Facilitate Memory And Learning
 Addiction
 Amnesia
 Antegrade
 Retrograde
 Senile Dementia
 Alzheimer Disease
 Concept Of Dominant Hemisphere
LEARNING & MEMORY
 Learning – The ability to alter behavior on the
basis of experience.
 Memory – Acquisition , storage & retrieval of
sensory information. Ability to recall past events
at the conscious or unconscious level.
 Thought – A thought result from a pattern of
stimulation of many parts of the nervous system
at the same time & in a definite sequence,
probably involving the cerebral cortex, thalamus,
limbic system, upper reticular formation of brain
stem.
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2017
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3
LEARNING .
 Reflex learning.
 Associated with immediate
behavior change.
 Incidental learning.
 Behavior change not
immediate
 But person gets
information from
sensory inputs &
develop potential to
behave differently.
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2017
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HIGHER FUNCTIONS OF BRAIN.
REFLEX LEARNING.
 Non- associative .
Person learns about
properties of single
stimulus when repeatedly
exposed to same stimulus.
 Associative.
Person learns about
relationship between two
stimuli or a stimulus &
behavior.
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2017
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HIGHER FUNCTIONS OF BRAIN.
NON- ASSOCIATIVE .
 Habituation
Decrease in response to
benign stimulus when
stimulus presented
repeatedly.
 Sensitization.
Increase in response to
benign stimulus when
stimulus presented
repeatedly with an
pleasant or unpleasant
stimuli.
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2017
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HIGHER FUNCTIONS OF BRAIN.
First time it evokes a novel response (orientation
response or what is it response)
Evokes less & less response when repeated
Subject becomes habituated to the
stimulus & ignores it
Habituation
If a stimulus is repeated
many times
Habituation
 Example
New clock in the room.
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2017
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Cellular basis of Habituation.
 Given by KANDEL
& his colleague.
 The brain learn to ignore matter of
less important.
 This result from inhibition of the
synaptic pathway.
 Repeated stimulus.
 Gradual inactivation of Ca+2
influx at axon endings.
Decrease intracellular Ca+2
 Neurotransmitter release at
synapses.
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2017
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Sensitization
 The type of sensory
information which cause
pleasure, pain or interest are
stored in brain by facilitation of
synaptic pathway.
 Example- Spanking.
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Cellular basis of Sensitization.
 Given by KANDEL
& his colleague.
 Repeated stimulus.
 Ca+2 mediated changes in adenylyl cyclase
 Increased production of cAMP
 neurotransmitter release at synapses.
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 Due to Presynaptic Facilitation
by third interneuron ---
Facilitatory neuron.
which releases SEROTONIN.
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Sensitization
Post synaptic neuron
Pre synaptic ending
ASSOCIATIVE LEARNING.
 Classical conditioning.
 Learning relationship between
two stimuli.
 Pavlovian conditioning.
 Operant conditioning.
 Learning relationship between
special behavior with a
reinforcement event.
 Instrumental or Trial & error
conditioning.
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2017
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HIGHER FUNCTIONS OF BRAIN.
CLASSICAL CONDITIONING.
 It is a cortical phenomenon.
 These are example of higher learning.
 Conditioned reflex is Reflex response to a stimuli that previously
elicited little or no response
 Acquired by repeatedly pairing given stimulus with another
stimulus which normally produces the response.
 Thus temporal association made between neutral conditioned
stimulus (CS) & unconditioned stimulus. (US)
 It depends upon formation of new functional connections in CNS.
 Reinforcement -- CS SHOULD FOLLOWED BY US
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HIGHER FUNCTIONS OF BRAIN.
CLASSICAL CONDITIONING.
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HIGHER FUNCTIONS OF BRAIN.
 Unconditioned reflex were present in all animal.
 Inborn reflexes
 Centre in spinal cord and medulla.
 Example- Postural reflexes for maintaining body posture, salivary reflex and sexual
reflexes.
 Conditioned reflex are acquired reflex
 Certain conditions are required to fulfill it.
 Centre- cerebral cortex
 In case of Pavlov experiment the ringing of bell is a neutral stimulus.
 It will not cause salivation in any dog, unless trained.
 For establishment of a conditioned reflex fresh connection are established in the
nervous system between the auditory center and center of salivation.
Pre-requisites for development of
conditioned reflex.
 Alertness & good health.
 Should not be harmful
 Reinforcement- once CS is established the pairing of conditioned and unconditioned
stimulus is done at intervals.
 If you go on ringing the bell and that’s not followed by giving meat, then no salivation
occurs. This abolition of reflex is known as Internal Inhibition.
 If the animal is disturbed by an external stimulus immediately after CS is applied, the CS
may not occurs, Known as External inhibition.
 CS should precede on US
 Summation- If few CS are summated the response is better.
 Discrimination- Animal can discriminate between 2 different stimuli. Eg. Change of
sound frequency of bell cause internal inhibition.
 Linking- Animal learns to associate 2 different process.
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2017
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HIGHER FUNCTIONS OF BRAIN.
 An immense number of somatic, visceral and other neural changes can be made
to occur as conditioned reflex responses.
 Conditioning of visceral responses is often called Biofeedback.
 The changes include heart rate alteration and BP changes.
 Conditioned decrease in BP has been advocated for treatment of HTN.
OPERANT CONDITIONING.
Reward conditioning.
 Naturally occurring response is
strengthened by positive
reinforcement (reward)
Adversive conditioning.
 Naturally occurring response is
Weakened by Negative
reinforcement (Punishment)
 It is to avoid an unpleasant event
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2017
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HIGHER FUNCTIONS OF BRAIN.
Experiment to demonstrate Operant
conditioning.
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2017
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HIGHER FUNCTIONS OF BRAIN.
Experiment to demonstrate Operant
conditioning.
 Positive Reinforcement – pressing a lever is associated with positive
reinforcement, reward i.e. food.
 Negative Reinforcement – pressing a lever is associated with Negative
reinforcement, punishment i.e. electric shock.
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MEMORY.
Memory –
Acquisition ,
storage &
retrieval of
sensory
information
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TYPES OF MEMORY.
 Physiologically on the basis
of how information is
stored & recalled.
 Implicit memory.
 Explicit memory.
 Depending upon
permanency of storage.
 Short term.
 Intermediate long term.
 Long term.
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TYPES OF MEMORY.
 Implicit memory.
 Non-declarative / reflexive
memory.
 How to perform
something.
 Not associated with
awareness not involve
processing in
hippocampus.
 Explicit memory.
 Declarative / Reconition
memory
 Factual knowledge of
people, places & things.
 Associated with awareness
,Involve processing in
hippocampus.
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IMPLICIT MEMORY.
 How to perform something.
 Does not depend on conscious
process.
 Includes motor skills,
 habits,
 behavioral reflexes &
 learning procedure & rules.
 Unconsciousness & automatic
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Implicit memory – reflexive learning.
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EXPLICIT MEMORY.
 Declarative / Recognition
memory
 Factual knowledge of
people, places & things.
 Associated with
awareness ,Involve
processing in
hippocampus.
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EXPLICIT MEMORY.
 SEMANTIC MEMORY
 About knowledge of
objects, facts and
concepts.
 Words & their meanings.
 EPISODIC MEMORY
 Memory of events &
personal experience.
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SEMANTIC MEMORY.
 Storage of semantic
memory
 In distributed fashion in
different association cortices.
 Visual memory
 Auditory memory
 Somatosensory memory.
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TYPES OF MEMORY
Damage to cortical area – loss of specific
information
 Associative Visual Agnosia –
posterior parietal cortex damage –
can identify but cannot name the
objects.
 Appreciative Visual Agnosia –
posterior occipital lobe damage –
can name the objects but cannot
draw
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2017
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EPISODIC MEMORY.
 Storage of Episodic Memory
 In association area of prefrontal cortex.
 With other areas of neo-cortex for collection of information
 Damage – Amnesia.
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MECHANISM OF MEMORY.
 Explicit memory.
 Short term memory.
Neural substrate for encoding of memory.
 Intermediate long term.
 Long term.
Consolidation of memory.
Storage of memory.
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MECHANISM OF SHORT TERM MEMORY
 Theory of reverberating neurons-
 Caused by continual neural activity resulting from nerve signals that travel round and round in
a temporary trace through a circuit of reverberating neurons.
 Presynaptic facilitation or inhibition-
 Occurs at synapses that lie on the presynaptic terminals, not on the subsequent
neuron. The neurotransmitter secreted at such terminals frequently cause prolonged
facilitation or inhibition.
 Synaptic Potentiation-
 It can enhance synaptic conduction.
 Accumulation of large amount of Ca in presynaptic terminals due to train of impulses
passing through.
 When amount of Ca become greater than the mitochondria can absorb  causes
prolonged presynaptic release of NT.
Working memory.
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MECHANISM OF INTERMEDIATE LONG
TERM MEMORY
 Intermediate Memory
due to temporary physical
or chemical change in pre
or post synaptic
membrane.
 Still labile until becomes
long term by process
called – Consolidation.
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2017
HIGHER FUNCTIONS OF BRAIN.
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Mechanism of intermediate Long term memory
Post synaptic neuron
Pre synaptic ending
C
B
A
Mechanism of intermediate Long term memory
 Mechanism for Habituation-
 Results from progressive closure of Ca+2 channel of presynaptic terminal membrane
 Very small entry of Ca+2  very Little amount of NT released.
 Mechanism for Facilitation-
 Stimulation of facilitator terminal B at the same time of sensory terminal A
 Serotonin released by the sensory terminal B
 It acts on the serotonin receptor in sensory terminal A membrane
 Receptor activate enzyme Adenylyl cyclase at membrane
 Formation of cAMP inside A
 cAMP activates Protein Kinase
 Protein kinase cause phosphorylation of a protein that is a part of K+ channel at
sensory terminal A
 This blocks the channel for K+ conductance (mins to Wks)
 Lack of K+ conductance cause greatly prolonged AP in terminal A (Outflux of K+ is
necessary for transmission of AP)
 Prolonged AP causes prolonged activation of Ca+2 channel
 Tremendous quantity of Ca+2 enter into the sensory terminal A
 Ca+2 result in increased NT release, thereby greatly facilitating synaptic transmission.
LONG TERM MEMORY
 The difference is only in degree
 Result in actual structural changes ( physical restructuring of synapses) , instead of
chemical changes only
 Changes due to DNA which replicate the protein in presynaptic neurons
 Also responsible for development of memory trace.
 The changes are-
1. Increase in no. of vescicles release sites for secretion of NT  increase NT release by
exocytosis
2. Increase in no. of transmitter vescicles
3. Increase in no. of presynaptic terminals
 In contrast to working memory long term memory was improved with exposure of the
subject to an enriched environment.
 This induce dramatic anatomical changes in cerebral cortex, hippocampus and
cerebellum of brain.
 The ability of a neural tissue to change because of its activation is known as plasticity.
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2017
HIGHER FUNCTIONS OF BRAIN.
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MECHANISM OF LONG TERM MEMORY
 Consolidation of Memory
 Rehearsal of the same information
again and again in the mind
accelerate and potentiate the
degree of transfer of short term
memory to long term memory.
 For mild – 5-10 min
 For strong – 1 or more hour.
 If this time not given – retrograde
amnesia
 E.g. – Precise time of sleep
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PROCESS OF CONSOLIDATION
 Expression of genes
 Synthesis of new proteins
 Structural changes.
 Increase in no of vesicle release sites
 No of vesicles
 No of synaptic terminals
 Change in shape or no of postsynaptic spines
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CODYFYING THE MEMORIES DURING CONSOLIDATION
 Similar information is recalled from the memory storage bin and used to help
process the new information.
 Parts involved-
 Hippocampus
 Thalamus
 Prefrontal cortex
 Amygdala
 neocortex
RETRIEVAL OF MEMORY.
 Components.
 Attentional control system.
 Rehearsal system.
 Articulatory loop.
 Visuospatial sketch pad.
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HIGHER FUNCTIONS OF BRAIN.
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Neural substrate for encoding of memory.
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MECHANISM OF LONG TERM
POTENTIATION(LTP)
 It involves protein synthesis and growth of presynaptic and postsynaptic neurons and
their connections.
 LTP occurs in many parts of the brain.
 Studied on synapses of hippocampus, connection of pyramidal cell in CA 3 and CA 1
region via Schaffer Collateral.
 At the membrane potential, Glutamate release from presynaptic nu.
 Bind both NMDA and Non-NMDA (AMPA) receptors on postsynaptic nu
 Mg+ blocks NMDA receptor so Na+, K+ can flow only through AMPA receptors
 Mg+ expel from NMDA due to high frequency tetanic stimulation of presynaptic nu.
 Ca+2 influx at postsynaptic neuron
 Activation of Ca+2/calmodulin Kinase, Pr. Kinase C, Tyrosin Kinase (Together induce LTP)
 Ca+2/calmodulin complex phosphorylate AMPA receptors
 Increased conductance, more and more of these receptors move to synaptic cell membrane from
cytoplasmic storage site
 When LTP induced, chemical signal NO released by postsynaptic nu and pass retrograde to presynaptic
neur. And produce long term increase in Glutamate release
MECHANISM OF LONG TERM POTENTIATION
Pre synaptic
ending
Post synaptic
neuron
APPLIED ASPECT.
 Drugs facilitating learning & memory.
 Common CNS stimulant
 Caffeine,
 amphetamine,
 Physostigmine ( Inhibit acetylcholinesterase,
prevent breakdown of Ach)
 Nicotine ( stimulate nicotinic cholinergic
receptors)
 Pemoline ( stimulate RNA synthesis)
 Mechanism of action.
 By facilitating consolidation of energy.
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ADDICTION
 Morphine
 Amphetamine
 Cocaine
 Heroin
 Nicotine
 Alcohol
 All these produces Dopamine on the limbic system on nu. Accumbens
 All stimulate reward area.
AMNESIA.
 Antegrade.
 Inability to establish new long term
memories
 Mostly in lesions involving
hippocampus.
 Retrograde –
 Inability to recall past memories.
 Amnesia greater for recent past than
remote past.
 Lesions involving temporal lobe
(Temporal lobe syndrome)
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2017
HIGHER FUNCTIONS OF BRAIN.
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SENILE DEMENTIA.
 Syndrome in elderly people
characterized by progressive
impairment of memory &
cognitive capacity.
 Causes –
 Alzheimer’s disease,
 Cerebrovascular disease,
Parkinsonism,
 Lewy body dementia,
 Prion disease
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2017
HIGHER FUNCTIONS OF BRAIN.
54
Alzheimer’s disease.
 Senile dementia
 Prototypical neurodegenerative disease.
 Degeneration of pathways from septal region
of the forebrain to the hippocampus.
 Affecting 15-25% people over 65
 Cholinergic neurons cease functions.
 Associated with decrease release of Ach in
some area of brain.
 Loss of postsynaptic neurons.
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2017
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CHARACTERISTIC FEATURES.
 Loss of recent memory.
 Impairment in other areas of
cognition –
 language,
 problem solving,
 judgment,
 calculation,
 attention.
 Psychiatric symptoms
 Loss of spatial orientation.
Saturday, July 29,
2017
HIGHER FUNCTIONS OF BRAIN.
56
CONCEPT OF DOMINANT HEMISPHERE.
 Interpretive
functions of
Wernicke’s area,
Angular gyrus &
Frontal motor
speech area – more
developed in
Dominant
hemisphere.
Saturday, July 29,
2017
57
HIGHER FUNCTIONS OF BRAIN.
CONCEPT OF DOMINANT HEMISPHERE
 95% left hemisphere is dominant.
 Wernicke’s area in Non-dominant
is concerned with
 emotional content,
 intonation of spoken language,
 understanding & interpreting
non-verbal, visual & auditory
experiences as interpretation of
Music.
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2017
HIGHER FUNCTIONS OF BRAIN.
58
CONCEPT OF CATEGORICAL &
REPRESENTATIONAL HEMISPHERE.
 Functions allotted to left
hemisphere in right handed person.
 Right hand control.
 Spoken language.
 Written language.
 Mathematical skills.
 Scientific skills.
 Reasoning.
 Functions allotted to right
hemisphere in right handed person.
 Left hand control.
 Music awareness.
 Three dimensional awareness.
 Art awareness.
 Insight.
 Imagination.
Saturday, July 29,
2017
59
HIGHER FUNCTIONS OF BRAIN.
Saturday, July 29,
2017
60
HIGHER FUNCTIONS OF BRAIN.
Thank You

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Learning and Memory

  • 1. LEARNING AND MEMORY Dr. Ranadhi Das MD PGT ranadhi@gmail.com
  • 2. LEARNING AND MEMORY  Learning-  Reflex Learning-  Non Associative-  Habituation  Sensitization  Associative-  Classical Conditioning  Operant Conditioning  Incidental Learning  Memory-  Physiologically On The Basis Of How Information Is Stored & Recalled  Implicit Memory.  Procedural Memory  Priming  Explicit Memory  Semantic Memory  Episodic Memory  Depending Upon Permanency Of Storage  Short Term.  Intermediate Long Term.  Long Term  Consolidation  Encoding  Retrieval  Applied Aspects  Substances Facilitate Memory And Learning  Addiction  Amnesia  Antegrade  Retrograde  Senile Dementia  Alzheimer Disease  Concept Of Dominant Hemisphere
  • 3. LEARNING & MEMORY  Learning – The ability to alter behavior on the basis of experience.  Memory – Acquisition , storage & retrieval of sensory information. Ability to recall past events at the conscious or unconscious level.  Thought – A thought result from a pattern of stimulation of many parts of the nervous system at the same time & in a definite sequence, probably involving the cerebral cortex, thalamus, limbic system, upper reticular formation of brain stem. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 3
  • 4. LEARNING .  Reflex learning.  Associated with immediate behavior change.  Incidental learning.  Behavior change not immediate  But person gets information from sensory inputs & develop potential to behave differently. Saturday, July 29, 2017 4 HIGHER FUNCTIONS OF BRAIN.
  • 5. REFLEX LEARNING.  Non- associative . Person learns about properties of single stimulus when repeatedly exposed to same stimulus.  Associative. Person learns about relationship between two stimuli or a stimulus & behavior. Saturday, July 29, 2017 5 HIGHER FUNCTIONS OF BRAIN.
  • 6. NON- ASSOCIATIVE .  Habituation Decrease in response to benign stimulus when stimulus presented repeatedly.  Sensitization. Increase in response to benign stimulus when stimulus presented repeatedly with an pleasant or unpleasant stimuli. Saturday, July 29, 2017 6 HIGHER FUNCTIONS OF BRAIN.
  • 7. First time it evokes a novel response (orientation response or what is it response) Evokes less & less response when repeated Subject becomes habituated to the stimulus & ignores it Habituation If a stimulus is repeated many times
  • 8. Habituation  Example New clock in the room. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 8
  • 9. Cellular basis of Habituation.  Given by KANDEL & his colleague.  The brain learn to ignore matter of less important.  This result from inhibition of the synaptic pathway.  Repeated stimulus.  Gradual inactivation of Ca+2 influx at axon endings. Decrease intracellular Ca+2  Neurotransmitter release at synapses. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 9
  • 10. Sensitization  The type of sensory information which cause pleasure, pain or interest are stored in brain by facilitation of synaptic pathway.  Example- Spanking. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 10
  • 11. Cellular basis of Sensitization.  Given by KANDEL & his colleague.  Repeated stimulus.  Ca+2 mediated changes in adenylyl cyclase  Increased production of cAMP  neurotransmitter release at synapses. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 11
  • 12.  Due to Presynaptic Facilitation by third interneuron --- Facilitatory neuron. which releases SEROTONIN. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 12 Sensitization Post synaptic neuron Pre synaptic ending
  • 13. ASSOCIATIVE LEARNING.  Classical conditioning.  Learning relationship between two stimuli.  Pavlovian conditioning.  Operant conditioning.  Learning relationship between special behavior with a reinforcement event.  Instrumental or Trial & error conditioning. Saturday, July 29, 2017 13 HIGHER FUNCTIONS OF BRAIN.
  • 14. CLASSICAL CONDITIONING.  It is a cortical phenomenon.  These are example of higher learning.  Conditioned reflex is Reflex response to a stimuli that previously elicited little or no response  Acquired by repeatedly pairing given stimulus with another stimulus which normally produces the response.  Thus temporal association made between neutral conditioned stimulus (CS) & unconditioned stimulus. (US)  It depends upon formation of new functional connections in CNS.  Reinforcement -- CS SHOULD FOLLOWED BY US Saturday, July 29, 2017 14 HIGHER FUNCTIONS OF BRAIN.
  • 15. CLASSICAL CONDITIONING. Saturday, July 29, 2017 15 HIGHER FUNCTIONS OF BRAIN.
  • 16.  Unconditioned reflex were present in all animal.  Inborn reflexes  Centre in spinal cord and medulla.  Example- Postural reflexes for maintaining body posture, salivary reflex and sexual reflexes.  Conditioned reflex are acquired reflex  Certain conditions are required to fulfill it.  Centre- cerebral cortex  In case of Pavlov experiment the ringing of bell is a neutral stimulus.  It will not cause salivation in any dog, unless trained.  For establishment of a conditioned reflex fresh connection are established in the nervous system between the auditory center and center of salivation.
  • 17. Pre-requisites for development of conditioned reflex.  Alertness & good health.  Should not be harmful  Reinforcement- once CS is established the pairing of conditioned and unconditioned stimulus is done at intervals.  If you go on ringing the bell and that’s not followed by giving meat, then no salivation occurs. This abolition of reflex is known as Internal Inhibition.  If the animal is disturbed by an external stimulus immediately after CS is applied, the CS may not occurs, Known as External inhibition.  CS should precede on US  Summation- If few CS are summated the response is better.  Discrimination- Animal can discriminate between 2 different stimuli. Eg. Change of sound frequency of bell cause internal inhibition.  Linking- Animal learns to associate 2 different process. Saturday, July 29, 2017 17 HIGHER FUNCTIONS OF BRAIN.
  • 18.  An immense number of somatic, visceral and other neural changes can be made to occur as conditioned reflex responses.  Conditioning of visceral responses is often called Biofeedback.  The changes include heart rate alteration and BP changes.  Conditioned decrease in BP has been advocated for treatment of HTN.
  • 19. OPERANT CONDITIONING. Reward conditioning.  Naturally occurring response is strengthened by positive reinforcement (reward) Adversive conditioning.  Naturally occurring response is Weakened by Negative reinforcement (Punishment)  It is to avoid an unpleasant event Saturday, July 29, 2017 19 HIGHER FUNCTIONS OF BRAIN.
  • 20. Experiment to demonstrate Operant conditioning. Saturday, July 29, 2017 20 HIGHER FUNCTIONS OF BRAIN.
  • 21. Experiment to demonstrate Operant conditioning.  Positive Reinforcement – pressing a lever is associated with positive reinforcement, reward i.e. food.  Negative Reinforcement – pressing a lever is associated with Negative reinforcement, punishment i.e. electric shock. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 21
  • 22. MEMORY. Memory – Acquisition , storage & retrieval of sensory information Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 22
  • 23. TYPES OF MEMORY.  Physiologically on the basis of how information is stored & recalled.  Implicit memory.  Explicit memory.  Depending upon permanency of storage.  Short term.  Intermediate long term.  Long term. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 23
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  • 25. TYPES OF MEMORY.  Implicit memory.  Non-declarative / reflexive memory.  How to perform something.  Not associated with awareness not involve processing in hippocampus.  Explicit memory.  Declarative / Reconition memory  Factual knowledge of people, places & things.  Associated with awareness ,Involve processing in hippocampus. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 25
  • 26. IMPLICIT MEMORY.  How to perform something.  Does not depend on conscious process.  Includes motor skills,  habits,  behavioral reflexes &  learning procedure & rules.  Unconsciousness & automatic Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 26
  • 27. Implicit memory – reflexive learning. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 27
  • 28. EXPLICIT MEMORY.  Declarative / Recognition memory  Factual knowledge of people, places & things.  Associated with awareness ,Involve processing in hippocampus. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 28
  • 29. EXPLICIT MEMORY.  SEMANTIC MEMORY  About knowledge of objects, facts and concepts.  Words & their meanings.  EPISODIC MEMORY  Memory of events & personal experience. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 29
  • 30. SEMANTIC MEMORY.  Storage of semantic memory  In distributed fashion in different association cortices.  Visual memory  Auditory memory  Somatosensory memory. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 30
  • 32. Damage to cortical area – loss of specific information  Associative Visual Agnosia – posterior parietal cortex damage – can identify but cannot name the objects.  Appreciative Visual Agnosia – posterior occipital lobe damage – can name the objects but cannot draw Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 32
  • 33. EPISODIC MEMORY.  Storage of Episodic Memory  In association area of prefrontal cortex.  With other areas of neo-cortex for collection of information  Damage – Amnesia. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 33
  • 34. MECHANISM OF MEMORY.  Explicit memory.  Short term memory. Neural substrate for encoding of memory.  Intermediate long term.  Long term. Consolidation of memory. Storage of memory. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 34
  • 35. MECHANISM OF SHORT TERM MEMORY  Theory of reverberating neurons-  Caused by continual neural activity resulting from nerve signals that travel round and round in a temporary trace through a circuit of reverberating neurons.  Presynaptic facilitation or inhibition-  Occurs at synapses that lie on the presynaptic terminals, not on the subsequent neuron. The neurotransmitter secreted at such terminals frequently cause prolonged facilitation or inhibition.  Synaptic Potentiation-  It can enhance synaptic conduction.  Accumulation of large amount of Ca in presynaptic terminals due to train of impulses passing through.  When amount of Ca become greater than the mitochondria can absorb  causes prolonged presynaptic release of NT.
  • 36. Working memory. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 36
  • 37. MECHANISM OF INTERMEDIATE LONG TERM MEMORY  Intermediate Memory due to temporary physical or chemical change in pre or post synaptic membrane.  Still labile until becomes long term by process called – Consolidation. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 37
  • 38. Mechanism of intermediate Long term memory Post synaptic neuron Pre synaptic ending C B A
  • 39. Mechanism of intermediate Long term memory  Mechanism for Habituation-  Results from progressive closure of Ca+2 channel of presynaptic terminal membrane  Very small entry of Ca+2  very Little amount of NT released.  Mechanism for Facilitation-  Stimulation of facilitator terminal B at the same time of sensory terminal A  Serotonin released by the sensory terminal B  It acts on the serotonin receptor in sensory terminal A membrane  Receptor activate enzyme Adenylyl cyclase at membrane  Formation of cAMP inside A  cAMP activates Protein Kinase
  • 40.  Protein kinase cause phosphorylation of a protein that is a part of K+ channel at sensory terminal A  This blocks the channel for K+ conductance (mins to Wks)  Lack of K+ conductance cause greatly prolonged AP in terminal A (Outflux of K+ is necessary for transmission of AP)  Prolonged AP causes prolonged activation of Ca+2 channel  Tremendous quantity of Ca+2 enter into the sensory terminal A  Ca+2 result in increased NT release, thereby greatly facilitating synaptic transmission.
  • 41. LONG TERM MEMORY  The difference is only in degree  Result in actual structural changes ( physical restructuring of synapses) , instead of chemical changes only  Changes due to DNA which replicate the protein in presynaptic neurons  Also responsible for development of memory trace.  The changes are- 1. Increase in no. of vescicles release sites for secretion of NT  increase NT release by exocytosis 2. Increase in no. of transmitter vescicles 3. Increase in no. of presynaptic terminals  In contrast to working memory long term memory was improved with exposure of the subject to an enriched environment.  This induce dramatic anatomical changes in cerebral cortex, hippocampus and cerebellum of brain.  The ability of a neural tissue to change because of its activation is known as plasticity.
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  • 43. MECHANISM OF LONG TERM MEMORY  Consolidation of Memory  Rehearsal of the same information again and again in the mind accelerate and potentiate the degree of transfer of short term memory to long term memory.  For mild – 5-10 min  For strong – 1 or more hour.  If this time not given – retrograde amnesia  E.g. – Precise time of sleep Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 43
  • 44. PROCESS OF CONSOLIDATION  Expression of genes  Synthesis of new proteins  Structural changes.  Increase in no of vesicle release sites  No of vesicles  No of synaptic terminals  Change in shape or no of postsynaptic spines Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 44
  • 45. CODYFYING THE MEMORIES DURING CONSOLIDATION  Similar information is recalled from the memory storage bin and used to help process the new information.  Parts involved-  Hippocampus  Thalamus  Prefrontal cortex  Amygdala  neocortex
  • 46. RETRIEVAL OF MEMORY.  Components.  Attentional control system.  Rehearsal system.  Articulatory loop.  Visuospatial sketch pad. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 46
  • 47. Neural substrate for encoding of memory. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 47
  • 48. MECHANISM OF LONG TERM POTENTIATION(LTP)  It involves protein synthesis and growth of presynaptic and postsynaptic neurons and their connections.  LTP occurs in many parts of the brain.  Studied on synapses of hippocampus, connection of pyramidal cell in CA 3 and CA 1 region via Schaffer Collateral.
  • 49.  At the membrane potential, Glutamate release from presynaptic nu.  Bind both NMDA and Non-NMDA (AMPA) receptors on postsynaptic nu  Mg+ blocks NMDA receptor so Na+, K+ can flow only through AMPA receptors  Mg+ expel from NMDA due to high frequency tetanic stimulation of presynaptic nu.  Ca+2 influx at postsynaptic neuron  Activation of Ca+2/calmodulin Kinase, Pr. Kinase C, Tyrosin Kinase (Together induce LTP)  Ca+2/calmodulin complex phosphorylate AMPA receptors  Increased conductance, more and more of these receptors move to synaptic cell membrane from cytoplasmic storage site  When LTP induced, chemical signal NO released by postsynaptic nu and pass retrograde to presynaptic neur. And produce long term increase in Glutamate release
  • 50. MECHANISM OF LONG TERM POTENTIATION Pre synaptic ending Post synaptic neuron
  • 51. APPLIED ASPECT.  Drugs facilitating learning & memory.  Common CNS stimulant  Caffeine,  amphetamine,  Physostigmine ( Inhibit acetylcholinesterase, prevent breakdown of Ach)  Nicotine ( stimulate nicotinic cholinergic receptors)  Pemoline ( stimulate RNA synthesis)  Mechanism of action.  By facilitating consolidation of energy. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 51
  • 52. ADDICTION  Morphine  Amphetamine  Cocaine  Heroin  Nicotine  Alcohol  All these produces Dopamine on the limbic system on nu. Accumbens  All stimulate reward area.
  • 53. AMNESIA.  Antegrade.  Inability to establish new long term memories  Mostly in lesions involving hippocampus.  Retrograde –  Inability to recall past memories.  Amnesia greater for recent past than remote past.  Lesions involving temporal lobe (Temporal lobe syndrome) Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 53
  • 54. SENILE DEMENTIA.  Syndrome in elderly people characterized by progressive impairment of memory & cognitive capacity.  Causes –  Alzheimer’s disease,  Cerebrovascular disease, Parkinsonism,  Lewy body dementia,  Prion disease Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 54
  • 55. Alzheimer’s disease.  Senile dementia  Prototypical neurodegenerative disease.  Degeneration of pathways from septal region of the forebrain to the hippocampus.  Affecting 15-25% people over 65  Cholinergic neurons cease functions.  Associated with decrease release of Ach in some area of brain.  Loss of postsynaptic neurons. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 55
  • 56. CHARACTERISTIC FEATURES.  Loss of recent memory.  Impairment in other areas of cognition –  language,  problem solving,  judgment,  calculation,  attention.  Psychiatric symptoms  Loss of spatial orientation. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 56
  • 57. CONCEPT OF DOMINANT HEMISPHERE.  Interpretive functions of Wernicke’s area, Angular gyrus & Frontal motor speech area – more developed in Dominant hemisphere. Saturday, July 29, 2017 57 HIGHER FUNCTIONS OF BRAIN.
  • 58. CONCEPT OF DOMINANT HEMISPHERE  95% left hemisphere is dominant.  Wernicke’s area in Non-dominant is concerned with  emotional content,  intonation of spoken language,  understanding & interpreting non-verbal, visual & auditory experiences as interpretation of Music. Saturday, July 29, 2017 HIGHER FUNCTIONS OF BRAIN. 58
  • 59. CONCEPT OF CATEGORICAL & REPRESENTATIONAL HEMISPHERE.  Functions allotted to left hemisphere in right handed person.  Right hand control.  Spoken language.  Written language.  Mathematical skills.  Scientific skills.  Reasoning.  Functions allotted to right hemisphere in right handed person.  Left hand control.  Music awareness.  Three dimensional awareness.  Art awareness.  Insight.  Imagination. Saturday, July 29, 2017 59 HIGHER FUNCTIONS OF BRAIN.
  • 60. Saturday, July 29, 2017 60 HIGHER FUNCTIONS OF BRAIN. Thank You