Memory: Flashbulb Memory & Hormones

• Memory involves encoding, storing, and retrieving information.
• The human brain categorizes memories based on importance.
• Emotional events often create stronger and clearer memories.

Flashbulb Memory

• Emotionally charged events are remembered vividly and in detail.
• Flashbulb memory examples: 9/11 attacks, the Challenger explosion, weddings, or the birth of children.
• These memories are more stable and long-lasting than others.
• Flashbulb memories are stronger due to emotional arousal during an event.

Hormones in Memory

• The brain "tags" memories using stress hormones released during intense emotional or physical events.
• Stress hormones help encode memories more strongly, making them easier to retrieve later.
• Stress hormones, such as cortisol, enhance the encoding process during stressful experiences.

Memory Stages

• Acquisition is the process of receiving and encoding information.
• Consolidation involves stabilizing and storing memories in long-term memory.
• Retrieval means accessing stored memories when needed.
• Hormones influence all stages of memory.
• Cortisol can enhance the encoding and consolidation of emotional memories.

Types of Memory Systems

• Memory isn't unique to humans; immune systems in vertebrates also have memory, which allows them to identify and respond to previous infections.
• Computers and smartphones possess memory systems to enter, store, and retrieve information.

Types of Memory

• Short-term memory (working memory) temporarily stores information.
• Long-term memory permanently stores information.
• Procedural memory stores skills like riding a bike.
• Declarative memory stores facts and events.
• Stress hormones influence the conversion of short-term memories into long-term ones, which enhances recall and memory stability.

Yerkes-Dodson Law

• Learning performance is affected by the level of arousal.
• The relationship is inverted-U-shaped, moderate arousal is best for performance, while too low or too high arousal impairs learning.
• Moderate anxiety can help with exam performance, but extreme stress hinders it.
• Hormones like adrenaline affect arousal, the right level of arousal improves focus and memory consolidation.

Nonassociative Learning

• Involves learning in response to a single stimulus.
• Sensitization: Increased response to a stimulus after repeated exposure or a strong initial stimulus.
• Habituation: Decreased response after repeated exposure to a harmless stimulus.
• Stress hormones like cortisol can enhance sensitization or prevent habituation.

Associative Learning: Classical Conditioning (Pavlov)

• Learning occurs through association when a neutral stimulus (bell) is paired with an unconditioned stimulus (food) to elicit a conditioned response (salivation).
• Pavlov's dogs learned to salivate at the sound of a bell after repeated pairing with food.
• Stress hormones can strengthen associations in classical conditioning.

Operant Conditioning (B.F. Skinner)

• Learning occurs when behaviors are reinforced.
• Dopamine reinforces behaviors by increasing the reward value of a stimulus
• Hormones such as cortisol, adrenaline, and dopamine affect the brain's ability to encode, consolidate, and retrieve memories, affecting everything from acquisition to retrieval.

Active Avoidance

• The animal engages in a behavior to avoid an unpleasant stimulus.
• An animal in a test box learns to move compartments to avoid a foot shock after hearing a bell.
• Memory strength is gauged by the duration the memory is retained even after delays and weaker electric shocks.

Passive Avoidance

• An animal inhibits a behavior to avoid an unpleasant stimulus.
• A mouse learns to stay in the illuminated compartment to avoid a shock, going against its natural inclination to seek the dark.
• Memory strength is gauged by how long the mouse stays in the light.

Fear Conditioning and Aversive Conditioning

• An animal learns to associate a neutral stimulus with an aversive one, leading to a freeze in response to a warning even without shock.
• Stress from the shock alters glucocorticoids and other hormones affecting memory.

Memory Systems

• Necessary for adaptive behavior, comparing current situations to past events.
• Memory is categorized to understand its mechanisms.

Short-term Memory

• Lasts seconds to minutes, retaining a phone number briefly.
• Rehearsal is needed to move information to long-term memory.

Long-term Memory

• Lasts days, weeks, or years, remembering facts for exams.
• There is no maximum capacity.

Epinephrine (Adrenaline)

• A hormone and neurotransmitter involved in the body's response to stress
• Secreted by the adrenal glands in response to stressors.
• Plays a key role in physiological arousal, cognitive functions, particularly memory.
• Exposure to stress increases secretion of epinephrine, assisting the body to adapt to stress.
• Aversive conditioning studies in animals revealed links between epinephrine and learning/memory.

Yerkes-Dodson Curve

• Epinephrine's effect on memory exhibits an inverted U-shaped curve; low and high levels impair memory, while moderate levels enhance it.

Epinephrine Effects

• Epinephrine's effect on memory is time-dependent and most effective when administered immediately after training; delayed administration reduces effectiveness.
• Optimal epinephrine level for avoidance memory in rats is 1500 pg/ml.
• Epinephrine enhances memory by influencing encoding, storage, and retrieval.
• Epinephrine activates peripheral adrenergic receptors, communicating with the central nervous system (CNS).

Amygdala

• Crucial for emotionally charged memory formation.
• Electrical stimulation can enhance memory retention.
• Epinephrine acts via β-noradrenergic receptors, activating neurons in the vagus nerve → nucleus of the solitary tract (NTS) → amygdala.
• Blocking this pathway prevents memory enhancement.

fMRI & PET Studies

• Higher amygdala activation correlates with better recall of emotionally intense stimuli.
• Women show greater left amygdala activation; men show greater right amygdala activation;

Salivary α-Amylase (sAA)

• Serves as a biomarker for adrenergic activity.
• Increased sAA after emotional image viewing is linked to improved emotional memory recall.
• Women show a stronger sAA response.

Epinephrine mechanisms

• Elevates blood glucose levels and enhances memory, while improving synaptic function by direct action on neurons.

Glucose

• Increases neuronal glucose entry, enhancing acetylcholine release.
• Optimal memory enhancement occurs at 100 mg/kg glucose.
• Effective timing of glucose intake is crucial for memory enhancement.

Insulin's Role

• Regulates glucose metabolism and influences memory, with brain receptors particularly in the hippocampus.

Glucose in Elderly Individuals

• Improves memory
• Memory is diminished when glucose regulation is impaired
• Streptozotocin induces Cognitive Impairment

Streptozotocin In Rodents

• Induces diabetes and cognitive impairment in rodents
• Memory is impaired with Passive avoidance learning
• Enhances memory performance in diabetic rats.

Effects of Diabetes on Spatial Memory

• It can be induced via streptozotocin which affects spatial learning
• Insulin treatment at the onset prevents learning deficits
• Diabetes impairs hippocampal LTP but can be treated with insulin.
• The best memory can be acquired with the combination of glucose and insulin

Long-Term Potentiation (LTP) in Diabetic Rats

• Diabetic rats show impaired hippocampal LTP; insulin treatment from the onset prevents these impairments.
• Fructose enhances memory despite not being metabolized by neurons.

Stress and Memory: Enhancement

• Acute stress and glucocorticoids promote lasting memory formation, with short-term exposure improving learning and memory.
• Treatment with stress hormones improves recall before learning.

Stress and Memory: Impairment

• Chronic stress and/or long-term stress hormone treatment impairs memory.
• Chronic exposure to stress hormones facilitates forgetfulness.

The Amygdala's Role in Memory

• The basolateral amygdala (BLA) mediates the memory-enhancing effects of stress hormones; lesions in the BLA disrupt these effects.
• Cortisol interferes with the extinction of fear memories, allowing them to persist.
• Stressful conditions and unpredictable food supply lead to higher corticosterone levels.

Spatial Memory

• Is impaired by Chronic Stress
• High-arousal conditions mitigate stress's effects.
• High stress hormone levels correlate with increased errors in spatial tasks; blocking stress hormone receptors can improve task performance.

Sex Differences in Learning and Memory Performance

• Female rats excel earlier with fast active avoidance tasks. Males excel in passive avoidance tasks.

Sex Differences: Activity Levels

• The differences depend on activity levels rather than variances in learnings
• High estrogen can improve learning and vice versa for low testestorone