Learning & Memory

Learning

• According to Eric Kandel “Learning is a process by which we acquire knowledge about the world”

• Kimble “Learning refers to more or less permanent change in behaviour which occurs as a result of practice”

• Further definition says, “Learning is either a case of differential strengthening of one from a number of responses evoked by a situation of need or formation of receptor evoked connections”

What is Memory ?

• According to Kandel “Memory is a process by which that knowledge of the world is encoded, stored and later retrieved”

Types of Memory

Explicit

Episodic Semantic

Implicit

Associative Classica

leg:

pavlov’s experiment

OperantEg:

Pigeon pecks a key

Non- associative Hab

ituationEg: Dog arouse

d by tone

played

Sensitizatio

nEg: dog reacts to

less tone

NEUROSCIENCE OF LEARNING AND MEMORY

Explicit Memory

• Different forms of learning are affected differentially by lesions in different locations

Defects in memory storage for object recognition

• Hippocampal system does initial steps in long term memory storage

• Memories of single event can be stored in multiple locations

• Each new explicit memory is formed by 4 sequential processes

a) Encoding b) Consolidation c) Storage d) Retrieval

Implicit Memory

• They are stored differently on how they are acquired

• Operant conditioning involves the straitum and cerebellum

• Classical, sensitization and habituation involves sensory and motor systems

Processes of Learning

• Donald Hebb stated, “when a axon of cell A excites cell B and repeatedly or persistently takes part in firing it, some growth process of metabolic changes take place in one or both cells so that A’s efficiency as one of the cells firing B is increased”

Habituation

•What happens in nervous system to produce habituation? •Experiments performed in Aplysia californica, the sea slug, were designed to address this problem

Sensitization

1 •Axonic syanpse occurs •Serotonin (5 hydroxytryptamine) is released by pre and post synaptic axon• Activates G protein •Adenyl cyclase

2 •cAMP Produced •Activates cAMP dependent kinase•Close k channels•Opens ca channels

3 •Activation of 5HT pathway by tail stimulation , therefore causes more substance to be released by siphon stimulation •Leads to response by gills

• Short term tail stimulation • Long term tail stimulation • Structural changes occur in pre synaptic

terminals

Long term potentiation

• Hippocampus is important storage for declarative memory

• High frequency train of stimuli applied to fibers afferent to hippocampus increase amplitude of EPSPs in target neuron

• Pre and post synaptic cells both be active at same time

Experimental set up for demonstrating LTP

Made

Stimuli applied

Amplitudes Of post synaptic Potentials

For single stimulus

Hebbs rule at work

Glutamate binds to metabotropic receptor, activating PLC and to NMDA receptors NMDA can bind glutamate but no current will flow through the channels unless Mg++ Is displaced

High frequency stimulation opens glutamate Non NMDA channels leading to hypopolarization.This dislodges Mg++ , Ca++ enters the cell. Calcium triggers activity of Ca dependent kinases.Calcium calmodulin kinase phosphorylates non NMDA channels increasing their sensitivityTo glutamate and a messenger is sent to presyanptic terminal to increase the release of transmitter substance

References • Learning and Memory http://michaeldmann.net/mann18.html• Neurobiology linster http://www.nbb.cornell.edu/• Learning and Memory by John H. Byrne, Ph.D.,

Department of Neurobiology and Anatomy, The UT Medical School at Houston http://neuroscience.uth.tmc.edu/s4/chapter07.html

THANK YOU