Types of Learning

TYPES OF LEARNING

1) Perceptual learning - ability to learn to recognize stimuli that have been seen before

* Primary function is to identify and categorize objects and situations

* Changes within the sensory systems of the brain

2) Stimulus-response learning - ability to learn to perform a particular behavior when a certain stimulus is present

* Establishment of connections between sensory systems and motor systems

* Classical conditioning - association between two stimuli

o Unconditioned Stimulus (US), Unconditioned Response (UR), Conditioned Stimulus (CS), Conditioned Response (CR)

o Hebb rule - if a synapse repeatedly becomes active at about the same time that the postsynaptic neuron fires, changes will take place in the structure or chemistry of the synapse that will strengthen it (see Figure 14.1)

o Rabbit experiment - tone paired with puff of air

* Instrumental conditioning - association between a response and a stimulus; allows an organism to adjust its behavior according to the consequences of that behavior

o Reinforcement - positive and negative

o Punishment

3) Motor learning - establishment of changes within the motor system

4) Relational learning - involves connections between different areas of the association cortex

5) Spatial learning - involves learning about the relations among many stimuli

6) Episodic learning - remembering sequences of events that we witness

7) Observational learning - learning by watching and imitation other people

LONG-TERM POTENTIATION

* long-term increase in the excitability of a neuron to a particular synaptic input caused by repeated high-frequency activity of that input

* hippocampal formation - specialized region of the limbic cortex located in the temporal lobe. It contains:

o entorhinal cortex whose axons grow toward the dentate gyrus, forming the perforant path

o dentate gyrus projects to pyramidal cells in CA3

o pyramidal cells project both to CA1 and to basal forebrain

* associative long-term potentiation - produced by association in time between 2 sets of synapses; weaker strengthens after being paired with stronger synapse

* series of pulses delivered at a high rate all in one burst will produce long-term potentiation, but not the same number of pulses given at a slow rate

o there are aftereffects which serve to prime future pulses by depolarizing the postsynaptic membrane

o long-term potentiation requires two events:

1. activation of synapses

1. depolarization of the postsynaptic neuron

* NMDA receptors - type of glutamate receptor, critical in long-term potentiation

o found in hippocampus, mostly CA1

o controls a calcium ion channel which normally is blocked by a magnesium ion

o even the channel is stimulated by glutamate, calcium ions can't get past the magnesium

o but, if the membrane is depolarized, then the magnesium is ejected and the channel can admit calcium ions

o therefore, need both glutamate and depolarization to admit calcium

o calcium is critical for long-term potentiation - both necessary and sufficient

+ entry of calcium activates some calcium dependent enzymes

1) protein kinase C (PKC) - normally in cytoplasm, activated by calcium to increase synaptic transmission

2) CaM-KII - when activated by calcium it remains active even after calcium is gone, until deactivated by another enzyme

3) tyrosine kinase - also plays a role in long-term potentiation

o nitric oxide - soluble gas used as a messenger in various parts of the body

+ produced by nitric oxide synthase in postsynaptic cell, communicates with presynaptic terminal buttons - retrograde effect

o dendritic "spikes" - what are they? How do they happen? Why are they significant?

AMPA receptors - control sodium channels - involved once long-term potentiation has occurred

Long-term depression - low-frequency stimulation of the synaptic inputs to a cell can decrease their strength; opposite of Hebb rule - weak synapses not associated with strong ones become weaker

PERCEPTUAL LEARNING

* Involves learning about things, not what to do when they are present

* Simple perceptual learning, recognizing stimuli, takes place in appropriate regions of sensory association cortex

1) Visual Learning

* inferior temporal cortex - necessary for visual pattern discrimination, receives info from visual cortex

* ventral/dorsal streams - what and where

* delayed matching-to-sample task - requires that stimulus be remembered for a period of time

o "remembering" the stimulus involves a neuronal circuit; it is the circuits, not the individual neurons that recognize