Basic Outline with Notes
CHAPTER 12
Learning and Memory
Basic Outline with notes
I. The Nature of Learning
Definition: The process by which experiences change our nervous system and hence our behavior. We refer to these changes as memory. Experiences change the way we perceive, perform, think and plan.
A. Learning can take 4 basic forms:
1. Perceptual Learning – The identification of objects and things. Changes in the perceptual systems that make it possible for us to recognize stimuli so that we can respond to them appropriately. Each of the sensory systems is capable of perceptual learning. Is it the establishment of changes within the sensory systems of the brain. Example: smell, sight hearing touch and taste.
2. Stimulus-Response learning - The ability to learn to perform a particular behavior when a particular stimulus is present... It is the establishment of connections between sensory systems and motor systems.
a. Classical Conditioning –Association between two stimuli. (An unimportant stimulus becomes important.) A stimulus that previously had little effect on behavior becomes able to evoke a reflexive, species-typical behavior. Ex. Species-typical response – fear becomes paired with an unimportant stimulus – peanut butter. Ex. Species-typical response – salivation becomes paired with unimportant stimulus - red arches-
1. Hebb’s 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.
2. Central nucleus of amygdale plays an important role in organizing a pattern of emotional responses that are provoked by aversive stimuli, both learned and unlearned.
3. Most stimuli that cause an aversive emotional response are not intrinsically aversive; we have to learn to fear them. – Ex. CER’s –conditioned emotional response.
b. Instrumental Conditioning – While classical conditioning involves species-typical responses, instrumental conditioning involves behaviors that have been learned. It is the means by which we profit from experience.
Classical conditioning involves an association between two stimuli. Instrumental conditioning involves an association between a response and a stimulus. It is a more flexible form of learning. It permits an organism to adjust its behavior according to the consequences of that behavior.
Role of the Basal Ganglia – When learned behaviors become automatic and routine, they are transferred to the basal ganglia.
Ex. Walking, getting in and out of a chair, chewing, brushing our teeth. Parkinson’s disease can be seen as failures of automated memories.
Reinforcement – The best and most reliable location is the medial forebrain bundle (MFB) or the ventral tegmental area which passes through the lateral hypothalamus. This contains dopaminergic, noradrenergic, and serotonergic axons on their way from the brain stem to their projection areas in the forebrain.
Dopaminergic neurons play a particularly important role in reinforcement. The nucleus accumbens is where natural reinforcers, i.e. water, food or a sex partner, are stimulated by the release of dopamine.
Three inputs that probably pay the most important role in reinforcement are the amygdale, the lateral hypothalamus, and the prefrontal cortex.
3. Motor Learning – A complex form of stimulus-response learning occurs in the cerebellum. It differs from other forms of learning. The more novel the behavior, the more the neural circuits in the motor system of the brain must be modified. Ex. Riding a bicycle vs. getting out of a chair. Or brushing your teeth vs. extreme skiing.
4. Relational Learning – The most complex form of learning.
a. Episodic learning – remembering a sequence of events.
b. Observational learning – modeling – learning by watching others
c. Spatial learning – knowing where you are in relationship with the things around you.
Human Anterograde Amnesia - Failure of relational learning. Failure to establish new declarative memories... similar to episodic memories. Can be caused by damage to the temporal lobes.
Human Retrograde Amnesia – The inability to remember events that happened before the brain damage occurred.
Korsakoff’s syndrome is a severe anterograde amnesia – usually (but not always) due to chronic alcoholism the disorder actually results from a thiamine (vitamin B1) deficiency caused by alcoholism.
Declarative Memories – Ex. What you had for breakfast. Or the time and date of your doctor’s appointment.
Nondeclarative Memories – how to make coffee or
Role of the Hippocampal Formation in Spatial Memory – circuit of neurons passes through the hippocampal formation, from the entorhinal cortex to the detate gyrus to field CA3 to field CA1.
- It is not the location of long-term memories; not necessary for the retrieval of long-term memories.
- The hippocampus is not the location of immediate (short-term) memories
- The hippocampus is involved in converting immediate (short-term) memories into long term memories.
II. Learning and Synaptic Plasticity
A. Induction of Long-Term Potentiation (LTP) – Hebb’s rule states that if a synapse is active at about the same time the postsynaptic neuron is active, that synapse will be strengthened. Induction of LTP “ to strengthen, to make more potent”. The hippocampal formation is a specialized region of the limbic cortex located in the temporal lobe. It includes the hippocampus proper (ammon’s horn), dentate gyrus, and subiculum.
Role of NMDA Receptors - Located in field CA 1 and in the dentate gyrus. These receptors, sensitive to glutamate, control calcium channels but can open them only if the membrane is already depolarized. Thus the combination of membrane depolarization and activation of a NMDA receptor cause the entry of calcium ion. The increase in calcium activates several calcium-dependent enzymes.
LTP requires two events: Activation of synapses and depolarization of the postsynaptic neuron.
First – electrical
Second – chemical
Before priming: If a molecule of glutamate binds with an NMDA receptor, calcium channel cannot open, because magnesium ion blocks channel.
Priming – An EPSP arrives from nearby synapses; depolarization evicts magnesium ion. (Electrical event)
Activation – Molecule of glutamate binds with NMDA receptor opens calcium channel. Because membrane is still depolarized, magnesium ion is still gone; calcium ion enter cell, initiates changes responsible for LTP (long-term potentiation)
Changes in the cell occur (Plasticity)
1. New AMPA receptors appear.
2. Dendritic spies change in shape.
3. Long-lasting long-term potentiation involves protein synthesis in the postsynaptic neuron.
(All references in these notes are from Carlson, Neil R., Foundations of Physiological Psychology, Fifth ed. Allyn and Bacon, c. 2002).