Neuroscience LTP and Memory Quiz

Intro to Memory & Learning

• Hermann Ebbinghaus's contribution to memory study involved developing the first scientific methods, specifically the nonsense syllable method
• He invented nonsense syllables (random letter sequences) to measure "pure memory," excluding prior knowledge interference
• Ebbinghaus's work was significant in demonstrating the need for nonsense material to isolate the pure effects of memory
• His work led to a better understanding of memory processes

Forgetting Curve

• The forgetting curve visually represents the decline of memory retention over time, showing an initial rapid decline followed by a slower rate.
• This highlights the crucial role of repetition and reinforcement in strengthening memory.
• Memory retention is heavily influenced by initial encoding and continued practice after initial memory formation

Single-Trace vs. Dual-Trace Theory

• Single-trace theory suggests memory strength diminishes steadily over time.
• Dual-trace theory proposes two memory traces: a short-term trace that fades quickly and a more enduring long-term trace that decays more slowly.

Ribot's Law

• Ribot's Law posits that older memories are more resistant to brain damage compared to newer memories. This explains why individuals with brain damage often forget recent events first.

Korsakoff's Syndrome

• Korsakoff's Syndrome is caused by thiamine deficiency, often resulting from chronic alcoholism.
• Characteristic symptoms include anterograde amnesia (inability to form new memories), retrograde amnesia (loss of past memories), and confabulation (filling memory gaps with false information).

William James's Stages of Memory

• James conceptualized memory stages involving immediate sensory memory (after-imade), followed by a short-term memory stage (primary), and finally, a long-term memory stage (secondary), that requires cues for retrieval.

Neuron Doctrine

• The Neuron Doctrine asserts that the brain comprises individual nerve cells (neurons) separated by a membrane.
• This theory contrasts with the older reticulum theory, which proposed that neurons were physically interconnected.

Synaptic Plasticity Hypothesis

• The Synaptic Plasticity Hypothesis, proposed by Cajal, states that synaptic connections strengthen with experience.
• This concept is fundamental to understanding learning and memory formation because it explains how experiences lead to changes in the brain.

Rosenzweig and Bennett Experiment

• The Rosenzweig and Bennett experiment demonstrated that enriched environments increase synaptic connections in brains.
• This supports the Synaptic Plasticity Hypothesis, showcasing that experiences can physically alter the brain structure.

Classical Conditioning (Pavlov)

• Ivan Pavlov's work on classical conditioning involved associating a neutral stimulus (like a bell) with an unconditioned stimulus (like food) to elicit a conditioned response (like salivation).
• This demonstrates how learning involves associating stimuli to create new associations, thereby altering behaviors.

Instrumental Conditioning (Thorndike)

• Edward Thorndike's Law of Effect states that behaviors followed by positive outcomes are reinforced, while those followed by negative outcomes are weakened.
• Practical use can be seen in the use of puzzle boxes to study learning in animals.

Skinner's Contributions to Behaviorism

• B.F. Skinner expanded on Thorndike's work by developing operant conditioning.
• He used the Skinner box to study how reinforcement (positive or negative) influences behavior and learning.

Positive and Negative Reinforcement

• Positive reinforcement involves adding a desirable stimulus to increase a behavior (e.g., giving a reward).
• Negative reinforcement involves removing an undesirable stimulus to increase a behavior (e.g., turning off a noisy alarm).

Memory Applications in Education

• Spaced repetition and active recall techniques (like flashcards) enhance learning and memory retention.

Memory Applications in Law

• Memory research aids in understanding eyewitness testimony reliability, false memories, and jury decision-making.

Long-Term Potentiation (LTP)

• LTP, defined as strengthening of synaptic connections, is a key mechanism for learning and memory.
• LTP is induced experimentally by applying high-frequency stimulation to a synapse.
• LTP can be recorded by observing the enhanced synaptic responses after stimulation which lasts in minutes to hours

Neuronal Activity Recording

• Field potentials are measured during neuronal activity using electrodes placed near neuronal populations.
• The amplitude of recorded electrical signals reflects the strength of synaptic connections.

Synapse Components

• Synapses consist of a presynaptic terminal that releases neurotransmitters, the synaptic cleft which is the physical space where neurotransmitters travel, and a postsynaptic membrane that contains receptors to receive signals.
• Postsynaptic densities (PSDs) are the main components of postsynaptic membranes containing receptors like AMPA and NMDA, scaffolding proteins to organize receptors and signaling molecules, plus signaling proteins like kinases and phosphatases.

Role of Scaffolding Proteins

• Scaffolding proteins play a significant role in synaptic transmission by organizing receptors and signaling molecules in the postsynaptic density, creating higher synaptic strength and elasticity.
• These proteins ensure proper functioning and adaptation of synaptic structures.

Cellular Signaling Cascades

• First messengers are external signals (e.g., neurotransmitters), while second messengers are intracellular molecules (e.g., calcium, cAMP) that amplify signal strength, amplifying the initial signal from a first messenger.

Kinases and Signal Transduction

• Protein kinases phosphorylate proteins, altering their functions in signal transduction pathways.
• The example of CaMKII strengthening synaptic connections during LTP illustrates the role of kinases.

Intensity and Duration of LTP

• Stronger stimulation duration leads to more sustained changes in synaptic transmission, creating a lasting LTP.
• Greater calcium influx results in more significant synaptic modifications.

General Processes in LTP

• LTP involves three general processes: Induction (initial stimulation like tetanus), Expression (enhanced synaptic strength), and Maintenance (long-term structural changes).

NMDA vs. AMPA Receptors

• NMDA receptors require glutamate and depolarization to activate, while AMPA receptors are activated by glutamate alone.
• NMDA receptors regulate calcium influx, impacting plasticity, whereas AMPA receptors are involved in fast synaptic transmission.

Actin Filaments and LTP

• Actin filaments stabilize and reshape synapses, enhancing dendritic spine strength, thereby increasing synaptic strength and long-term memory storage capacity.

Calcium's Role in LTP

• Calcium plays a crucial role in triggering second messengers (e.g., CaMKII) and activating protein kinases to enhance synaptic strength.
• Calcium is essential for various forms of memory formation within the brain.

Cellular & Molecular Mechanisms of Memory

• Memory types are characterized by their duration and capacity, differentiating in terms of function.
• Sensory memory offers fleeting and detailed storage. Short-term memory (STM) has limitations on capacity and duration, while long-term memory (LTM) has seemingly limitless capacity and duration.

Short-Term Memory (STM)

• STM capacity is approximately 7 +/- 2 items, as defined by Miller's Law.
• Chunking improves STM capacity by grouping information.

Explicit vs. Implicit Memory

• Explicit memory (declarative) involves conscious recall of facts and events.
• Implicit memory (non-declarative) involves unconscious skills and learned behaviors.

Hippocampus and Memory

• The hippocampus is crucial for consolidating short-term memories into long-term memories.
• In the case study of H.M., hippocampal removal led to significant anterograde amnesia.

Episodic vs. Semantic Memory

• Episodic memory relates to personal experiences and events.
• Semantic memory relates to general facts and knowledge.

Procedural Memory

• Procedural memory involves implicit memories for motor skills and learned behaviors.

Types of Non-Associative Learning

• Habituation involves a decrease in response after repeated stimuli.
• Sensitization involves an increased response after repeated stimuli.
• Latent learning involves learning without using the learned information immediately.
• Insight learning involves a sudden realization to learning or problem solving.

Multiple Memory Systems Theory

• This theory posits that different types of memory rely on distinct brain structures emphasizing the different types of memory systems and the physical structures in the brain that store and process it.
• Evidence for this theory comes from case studies of patients with brain damage (like H.M.) as well as more general brain imaging research.

Test your knowledge on the critical roles of AMPA and NMDA receptors in long-term potentiation (LTP) and memory. This quiz covers various aspects of sensory and short-term memory, as well as the mechanisms involved in neuronal signaling and LTP induction. Challenge yourself with questions on characteristics, functions, and relationships in neurobiology.