Lecture 11: Hormones and Cognition Flashcards
COMPONENTS OF LEARNING AND MEMORY
- Many of us maintain vivid memories of frightening events.
- In humans, the phenomenon of vivid memories of important, stressful events has been termed flashbulb memory.
- Flashbulb memory is probably not a separate category of memory function; rather, it probably represents a class of memories that are more frequently rehearsed or more strongly encoded. –> each generation tends to have its own unique flashbulb memory
- Positive, yet stressful, events such as weddings, births of
children, or winning lotteries are also remembered with great
clarity. - Memory is not a unitary process; there are several types of memory systems, and some do not even require a nervous system.
- Males are better at visuospatial learning due to their higher levels of testosterone.
!COMPONENTS OF LEARNING AND MEMORY
- All memory systems share the ability to:
1. Enter information into storage (acquisition and consolidation)
2. Retain information
3. Retrieve information from storage
These three components of memory must operate, or learning will not occur.
Hormones can affect any of these components of memory, or they can affect learning directly and thus memory indirectly.
However, it is rare to measure learning directly; only the results of learning can be measured and quantified. Consequently, statements about the effects of hormones on learning and memory are typically based on their effects on performance of a task, or observed behavior, but there are other ways by which hormones can affect performance on a learning task.
- hard to quantify because ….
Psychological components of learning and memory
Psychological components of learning and memory:
* Motivation
* Attention
* Arousal.
These hypothetical constructs cannot be measured directly;
only performance on a test designed to assess one of these
constructs can be measured.
Learning, motivation, arousal, and attention interact and
affect one another.
Hormones are involved in arousal, motivation, and probably
also sensation, perception, attention, and emotion.
Additionally, hormones can affect the level of anxiety
independently from arousal during acquisition or memory
testing.
- Level of arousal low or very high
- U-shape is very importnant in psyc
- Hard to come up with laws in psyc but one common law is associated with the U-shape for perfromance on most test.
Definition of Learning
Learning can be defined as a process that expresses itself as an adaptive change in behavior in response to experience. The stages of learning include acquisition, consolidation, retrieval, and extinction.
- through experience you learn something
Definition of Memory
Memory—the encoding, storage, and retrieval (or forgetting) of information about past experience—is necessary if learning is to take place. Hormones can affect any one or all of these stages of learning and memory.
Definition of No Associative Learning
Learning about relationships is called associative learning (frequently called conditioning)
Definition of sensitization
Is one type of nonassociative learning in which a stimulus that originally provoked little or no response begins to evoke stronger responses after several presentations, or a single intense presentation provokes stronger responses to other stimuli.
- organism becomes more sensitive to the stimulus
Definition of Habituation
Involves learning not to respond after repeated exposure to a stimulus. So it’s a decrease in response to a stimulus after repeated exposures. Habituation results from a reduction in the amount of neurotransmitter released into the synapses.
- learns not to react to stimulus
Definition of classical conditioning
Classical conditioning: A response that was originally elicited by one stimulus can now be elicited by another stimulus that originally had no effect; in other words, learning represents the formation of an association (or pairing) between the two stimuli (Pavlovian conditioning)
Definition of operant learning
Operant learning: Occurs when an animal performs an action in the course of appetitive or searching behavior, frequently by accident, which is reinforced or rewarded. Often this single incident does not lead to a direct association of the action (the operant) with its result (reinforcement - which will make the behaviour more likely), but if the act is performed several times, by choice, and is reinforced each time, the association gradually builds
- behaviour will eventually go away if reinforcement stops
- Casinos are an example of them using this.
- Relationships also - significant others reinforcing and then not reinforcing - intermittent reinforcement
- A Skinner box is used to measure instrumental learning (aka operant conditioning). It facilitates assessment of the ability of an animal to form an association between its behavior and the outcome of that behavior.
Other forms of Associative Learning
- **Active avoidance: **Refers to a situation in which an animal must do something, that is, act, to avoid a noxious situation.
- Passive avoidance: A type of learning in which an individual must suppress some behavior that would otherwise be exhibited.
Short term memory
Short-term memory persists for seconds to minutes. Rehearsing is the best way to move items from short-term into long-term memory (mnenomic)
Semantic: learn a fact
Episodic: memory of experiencing something
Long term memory
Long-term memory lasts for days, weeks, or years. Our long-term memory appears to have no upper limit in capacity or retention
DIVIDED IN:
- declarative: episodic and semantic
- Procedural/implicit memories (conditiioning, skill learning and priming)
Memory: more definitions
Another way to categorize memory is by dividing it into working memory and reference memory.
* Working memory is similar to declarative and short-term memory in that it typically involves short-term memory for information that changes on a regular basis (effortful control/remembering of the memory).
* Reference memory, which generally refers to associations or discriminations requiring repetitious learning, as in learning the rules. ie: always putting the keys at the same spot
- could be a type of procedural memory
* Spatial memory Subcategory of memory that encodes information about the environment and its orientation. ie: knowing where in the field your keeper is
THE EFFECTS OF HORMONES ON LEARNING AND MEMORY:
EPINEPHRINE
- We don’t know exactly how epinephrine works in the brain to store memories because it does not cross the blood brain barrier - it is a polar mechanism.
- Easily assessable, it was demonstrated that it is released
when learning typically occurs. - In general, epinephrine enhances memory.
- The U-shaped function of arousal, which is known as the Yerkes-Dodson curve, responses to different concentrations of epinephrine follow an inverted U-shaped curve; that is, low and high blood levels of epinephrine impair memory, whereas moderate epinephrine levels enhance memory.
Epinephrine, when is is released?
❑ Because epinephrine is released in response to stressful (traumatic/negative quality) events, a reasonable possibility is that epinephrine potentiates the effects of the noxious stimuli used to train animals in active avoidance tasks.
* The memory-enhancing effects of epinephrine are both dose- and time-dependent.
* For example, animals perform better in avoidance situations after receiving a moderate rather than a mild foot shock thus. A stronger shock is better because the milder shock does not elicit epinephrine release. Stronger stressor will ellicit the resposne but too strong = start to see u shape curve
Optimal level of epinephrine for avoidance memory
- The optimal level of epinephrine for avoidance memory enhancement in rats is 1500 (pg/ml) in blood. This level is typically observed in rats that show optimal performance in avoidance tasks.
- If a mild foot shock produces blood epinephrine levels of 1000 pg/ml and this shock is paired with an injection that raises epinephrine levels another 500 pg/ml, then the exogenous and endogenous epinephrine sum together, and the animal exhibits optimal learning. Complementary use were able to have the rats reach optimal learning
- The best time to administer epinephrine is immediately after training; treatment either before training or after a substantial period of time has elapsed since training is not effective in enhancing memory These temporal constraints are consistent with the hypothesis that epinephrine influences memory by potentiating the effects of noxious events
How does epinephrine enhance memory? Epinephrine activates peripheral receptors that directly influence brain function hypothesis
- Epinephrine modulates memory by activating peripheral receptors that communicate with the central nervous system.
- Many experiments indicate that epinephrine effects on memory consolidation are initiated by activation of peripheral βadrenoceptors located on vagal afferents that project to the nucleus of the solitary tract (NTS) in the brain stem.
- Noradrenergic projections originating in the NTS innervate forebrain structures involved in learning and memory, including the amygdala
- Although the amygdala has been considered for years to be involved in emotions, this of the limbic forebrain is also involved in learning and memory, both directly and indirectly via its close association with the hippocampus.
- Electrical stimulation of the amygdala can also increase memory retention
How does epinephrine enhance memory?
Epinephrine + human memory
- In humans, individuals that read either an emotionally charged story or a similar story that was judged by other people to be more emotionally neutral, and treated with propranolol, a potent βadrenergic antagonist, had significantly impaired memory of the emotionally arousing stories but did not affect memory of the neutral ones
- The researchers who conducted this study were able to rule out the possibility that the drug had nonspecific effects on attention or motivation. These results support the hypothesis that highly charged emotional memories require activation of β-adrenergic receptors.
How does epinephrine enhance memory? Epinephrine affects memory via its effect on blood glucose levels hypothesis
❖ The glucose and peripheral receptor hypotheses of how epinephrine affects memory are not incompatible. Epinephrine elevates blood glucose concentrations, which increases the amount of glucose that enters neurons in the brain.
❖ In general, glucose enhances memory for avoidance learning.
❖ As with epinephrine, the effects of glucose are time-dependent; injections of glucose delayed by 1 hour after training have no effect on retention and performance.
These two pathways seem to be complimentary and not dependent.
How does glucose enhance memory? Epinephrine affects memory via its effect on blood glucose levels hypothesis
❑ The brain requires a constant supply of glucose in order to function.
❑ Elevated blood glucose levels permit more glucose to enter
neurons, which in turn stimulates an increase in the release of the neurotransmitter acetylcholine (excitatory) from neurons in the brain.
❑ Increases in acetylcholine levels in the brain synapses are
characteristic of all known cognitive enhancers
- acetylcholine increases cognition.
❑The severe memory deficits observed in patients with advanced Alzheimer’s disease or AIDS are correlated with a marked reduction in neurons that secrete acetylcholine.
THE EFFECTS OF HORMONES ON LEARNING AND
MEMORY: INSULIN
INSULIN
If unregulated blood glucose levels interfere with learning,
then diabetic animals and humans should display learning
difficulties. This is something that we actually see.
❑ Although the relationship between glucose regulation and
cognitive impairment is well established the association with
insulin-dependent diabetes is not.
- several cognitive deficits associated with diabetes.
Diabetes effect on Cognition
❑ Both types of Diabetes negatively affect measures of verbal and numerical reasoning, attention, concentration, verbal and visual memory, and verbal fluency.
❑ Diabetes may also increase the risk of dementia
❑ Impaired insulin signaling has been proposed as important in the development of Alzheimer’s disease, what sometimes are referred as Type-3 diabetes.- not necessarily are diabetic…
Not super clear what insulin does in the brain…some modulatory effects.
- purple regions = observe reduced utilization of glucose.
- Brain alterations also regions that show reduction in glucose utilization.
- plaques are also regions associated with glucose level alteration
- Type 3 diabetes = early marker for alzeihmers.
GLUCOCORTICOIDS
Impairments in learning and memory
- They dye the water
- which group preformed worse if you think about cortisol release? cortisol is released in long term response so the animals in the 30 mins group showed impaired spatial memory in this task.
- if the shock was too much, it would impair their ability due to too much release of cortisol.
GLUCOCORTICOIDS
Improvements in learning and memory
Amygdala is also involved:
❖ The memory-enhancing effects of glucocorticoids appear to involvethe amygdala, which modulates the memory consolidation process that probably occurs elsewhere in the brain.
❖ The basolateral amygdala appears to integrate hormonal
information that signals the hippocampus and other brain regions involved in memory consolidation.
❖ Specific lesions of the basolateral amygdala block the memory facilitating effects of glucocorticoids, and infusions of GR-blocking drugs directly into this region impair memory consolidation.
We have GR in amygdala and hippocampus. Depending on the levels of these we can have impairement or learning.
