Learning and Memory VITHUSS SRIRAJASINGAM ☻ & PAVITHIRAN SIVABALAN

Behaviour  There are two main types of behaviours - Innate - Learned  Behaviour is: 1. The total activities of a living organism ranging from a simple movement to complex patterns involved with courtship, threat, camouflage, etc.. 2. The observable response of an organism to stimuli from the environment.

Innate  Also known as species-characteristic  Not learned and observed within all members of the species  Genetically determined response to a particular stimulus  Specific nerve pathways laid down/formed in the embryo form the DNA  The response for a stimulus will always be the same response, which has been selected over generations for its survival value.  Responses can vary from simple avoidance reflexes to highly complex courtship/ territorial displays.

Imprinting  This is distinguished by a sensitive period- limited phase in an animal’s development that is only time when certain behaviours can be learned.  A rapid learning process, where a new-born/ young established behaviour patterns of recognition and attraction to another animal of its own kind, or to a substitute or an object identified as a parent.  This includes both learning and innate components and is generally irreversible. –Closely associated with instict

Learned  Also known as Individual-characteristic behaviour  This is an adaptive change in the behaviour of an individual which occurs as the result of experience.  An individual learns from an experience and modifies their behaviour accordingly.  This learning experience will vary from individual to individual. -Some require one experience, whilst other will require multiple learning opportunities to modify their behaviour.  Some may even not need to experience, as they see another individual react and therefore learn from it.

Example of Learned behaviour  Scarecrows for crows/ birds  Birds associate through experience that by coming near to the scarecrow, nothing happens. This leads to their behaviour being modified.  The bird will then learn from experience that the crow wont do anything and continue eating the vegetables

Habituation  A permanent change in the response for a stimulus.  This occurs when a stimulus is repeated, and nothing happens. “there is neither punishment nor reward”.  The subject then ignores stimulus and makes no response.  Once the response is habituated or lost, it does no return unless the subject is specifically sensitized.  This is particularly important in the development of young animals, as they learn not to react to the neutral elements in the world around them.  Habituation is generally short term, however it may become long term, so that a response is lost permanently.

More on habituation YAY  Most research and work regarding habituation has been conducted on invertebrates (worms and giant sea slugs YUM)  EXAMPLE: Aplysia (giant sea slug) breathes through its gills (found in cavity on upper body). With water passing through and being expelled through a siphon tube at one end. IF you touch the siphon, the whole gill is withdrawn into the body as a defence mechanism. The sea slug lives in the sea, so the movement of water constantly stimulates the siphon. Via habituation, the sea slug learns to not retract its gills every time a wave hits

Difference between Habituation and Sensitisation?  Habituation and sensitisation work in different ways neurologically. In neural communication, a neurotransmitter is released from the axon of one neuron, crosses a synapse, and is then picked up by the dendrites of an adjacent neuron.  During habituation, fewer neurotransmitters are released at the synapse.  In sensitisation, however, there are more pre-synaptic neurotransmitters, and the neuron itself is more excitable.

Conditioning  Conditioned reflexes are result of subjects learning to associate new stimuli with an existing unconditioned reflex.  Example: Pavlov’s dogs

Operant Learning (trial and error)  Reward and Punishment system.  When a trial behaviour is either rewarded or punished.  The subject would naturally associate each outcome with their actions and repeat the outcome that they would desire the most. Therefore, the outcome that is least desired is repeated fewer times.

Latent (Exploratory) Learning  Also known as exploratory learning  This takes place when an animal explores new surroundings and learns them without any immediate reward or punishment.  This becomes useful at another later time.

Insight Learning  Based on the thought of reasoning.  This type of learning is mainly seen within mammals and particularly primates, and is regarded as the highest sort of learning.  Solving a problem is the main part of this learning variation, however the solution to the problem is then remembered.

Nerve Accommodation  The ability of a nerve tissue to adjust to a constant source and intensity of stimulation so that some change in either intensity or duration of stimulus is necessary to elicit a response beyond the initial reaction.  This is probably caused by reduced sodium ion permeability, which results in an increased threshold intensity and subsequent stabilisation of the resting membrane potential.

Memory

Mr Davis’s Snails ♪♫♪  Eric Kandel was one of the many research to use animals to study the nervous system and he performed some classic experiments.  He stimulated the siphon on an aplysia with a jet of water, which made it withdraw its gills.  The stimulation was applied repeatedly.  The response of the animal became less and less until eventually water squirted at the siphon had no effect- no gills withdrawing  The animal had habituated! - learned to ignore the stimulus  This was retained over time showing it was not a simple case of accommodation.

Mr Davis’ Snails ♫♪♫ What Kandel discovered was that:  The Calcium channels in the presynaptic membrane become less responsive with repeated stimulation  With fewer calcium channels open fewer calcium ions cross into the presynaptic knob.  Therefore, fewer vesicles move to the presynaptic membrane, fuse and discharge their neurotransmitter.  Less neurotransmitter available to bind to post- synaptic membrane, the post-synaptic excitatory potential is not high enough to trigger an action potential  And SO there is no response !