Biology of learning and memory Flashcards
Classical Conditioning:
After repeated presentations (although a strong stimulus will work with only one pairing) of a conditioned stimulus (CS), which initially elicits no response, with an unconditioned stimulus (UCS), which automatically elicits an unconditioned response (UCR), the subject begins responding to the CS because they have come to associate it with the UCS.
- For example, Pavlov classically conditioned a dog to respond to have a salivating response to a bell after continuously pairing the bell with the dog’s food.
Instrumental Conditioning (operant conditioning):
Behavior is followed by a reinforcer (which increases the future probability of a response) or punishment (which suppresses the frequency of a response).
Engram:
Physical representation of learning.
Karl Lashley’s work on learning (using cortical lesions in varying locations within the brains of rats) led him to propose two principles about the nervous system.
c. Equipotentiality: All parts of the cortex contribute equally to complex behaviors like learning; any part of the cortex can substitute for any other.
d. Mass action: The cortex works as a whole, and the more cortex the better.
e. Lashley’s work was based on the assumption that the cerebral cortex was the best place to search for an engram and that all memories are physiologically the same. Researchers that followed found neither assumption was necessary true.
Richard F. Thompson located an engram of memory in the:
cerebellum (lateral interpositus nucleus, LIP)
Lateral interpositus nucleus (LIP):
An area essential for learning. Damage to this area of the cerebellum leads to permanent loss of a classically conditioned eyeblink response in rabbits. Temporary suppression of the area led to zero effectiveness of classical conditioning training.
Short-term memory:
Memory of events that have just occurred
- Short-term memory holds no more than seven items, while long-term memory is vast and more difficult to estimate.
- Information initially entered into short-term storage can be consolidated into long-term memory.
Long-term memory:
Memory of events from previous times.
- It was previously thought that once formed, long-term memories were permanent. However, it is now clear that consolidated memories are not always permanent. They can change, fade, and vary in detail.
reconsolidation:
If a reminder is followed by a similar experience, the memory is reconsolidated. New experiences during the reconsolidation process can modify the memory.
Working memory:
Temporary storage of memories about a task that one is attending to at the moment.
Delayed response task:
Memory task in which a subject is given a signal to which it must give a learned response after a delay. A common test for working memory.
Amnesia:
Memory loss. Damage to the hippocampus produces a powerful kind of amnesia.
retrograde amnesia:
loss of memory for events that occurred before brain damage
anterograde amnesia:
loss of long-term memories for events that happened after brain damage
episodic memories:
memories of a single event
semantic memories:
factual memory
implicit vs explicit memories in people with amnesia:
Nearly all patients with amnesia show better implicit memory (influence of a recent experience on behavior, even if one does not realize that he or she is using memory at all) than explicit memory or declarative memory (deliberate recall of information that one recognizes as a memory).
Procedural memory:
the development of motor skills and habits; a special kind of implicit memory. H.M. acquired new skills without apparent difficulty.
hippocampus and memory:
People with hippocampal damage acquire new skills but have enormous trouble learning new facts. This leads researchers to believe that the hippocampus is critical for declarative memory, especially episodic memory.
Radial Maze:
Maze with eight or more arms used to test spatial memory in animals. Damage to the hippocampus impairs performance on this task.
Morris Water Maze:
Procedure where an animal has to find a hidden platform, usually under murky water. This procedure is used to test spatial memory in animals and, like the radial maze, performance is negatively impacted by hippocampal damage.
Korsakoff’s Syndrome or Wernicke-Korsakoff’s syndrome:
Brain damage caused by prolonged thiamine deficiency (this disorder is most commonly seen in chronic alcoholics).
b. Thiamine deficiency leads to brain cell loss in the mammillary bodies of the hypothalamus and the dorsomedial nucleus of the thalamus, which projects to the prefrontal cortex.
c. Korsakoff’s patients show apathy, confusion, and have trouble reasoning about their memories. Patients with Korsakoff’s syndrome also have both anterograde and retrograde amnesia but intact implicit memory.
Confabulation:
Making up an answer to a question and accepting the invented answer as if it were true (a common symptom of Korsakoff’s syndrome). They do not confabulate for semantic memory but do confabulate for episodic memory
Alzheimer’s disease:
A dementia that becomes more prevalent with advancing age. Symptoms include short-term and long-term memory loss, confusion, restlessness, hallucinations, and disturbances of eating and sleeping.
ii. People with Alzheimer’s disease have better procedural than declarative memory and better implicit than explicit memory.
iv. Abnormal genes located on several different chromosomes can lead to an accumulation of amyloid- deposits in the brain. Deposits of amyloid cause neuronal degeneration in the brain, and the dying axons and dendrites form plaques in many areas of the cerebral cortex and hippocampus, as well as other brain areas.
v. The tau protein also accumulates and produces tangles, structures formed from degeneration within neurons
The basal ganglia is responsible for:
implicit learning or habit learning, which is gradual.
- This suggests that the hippocampus is more important for declarative memory and the basal ganglia is more important for procedural memory. Psychologists no longer believe in a strict separation between the tasks of the two structures as nearly all tasks activate both areas.
Other Brain Areas and Memory
- Almost all cortical and subcortical structures are involved in some aspect of memory.
- The amygdala is important for fear learning.
- Parietal lobe damage affects the ability to associate one type of information with another.
- Damage to the anterior and inferior temporal lobes results in semantic dementia, in which semantic memories are impaired.
- Damage to the prefrontal cortex impairs the ability to learn about rewards and punishments.
Hebbian synapse:
A synapse that increases in effectiveness because of simultaneous activity in the presynaptic and postsynaptic neurons (cells that fire together wire together)
Habituation:
A decrease in response to a stimulus that is presented repeatedly and is accompanied by no change in other stimuli. Habituation in Aplysia reflects a change in the synapse between the sensory neuron and a motor neuron.
Sensitization:
An increase in response to a mild stimulus after an intense stimulus has been presented. Sensitization in Aplysia depends on the release of serotonin by a facilitating interneuron onto the synapses of many presynaptic sensory neurons; this process ultimately blocks potassium channels and thereby prolongs the release of transmitter from that neuron.
Long-term potentiation (LTP):
Increased responsiveness to axonal input as a result of a previous period of rapidly repeated stimulation. LTP has three properties that make it an attractive candidate for the cellular basis of learning and memory:
a. Specificity: Only activated synapses become strengthened.
b. Cooperativity: Nearly simultaneous stimulation by two or more axons produces LTP; stimulation by just one axon produces it weakly.
c. Associativity: Pairing a weak input with a strong input enhances later responses to the weak input.
Long-term depression (LTD):
A prolonged decrease in responsiveness to synaptic input after repeated pairing with some previous input that is generally of low frequency. LTD occurs in the cerebellum and hippocampus.
LTP causes presynaptic changes through the release of a:
retrograde neurotransmitter from the postsynaptic cell. These changes include reduced threshold for producing action potentials, increased neurotransmitter release, expanded size of the presynaptic axonal membrane, and release of neurotransmitter from more sites on the axon.
