Chapter13_PPT Learning and Memory

LEARNING & MEMORY OVERVIEW

• Core Concepts

  • Learning: The process of acquiring information.

  • Memory: The ability to store and retrieve information.

CASE STUDY: PATIENT H.M.

• Background: Henry Gustav Molaison suffered from severe epilepsy due to a bicycle accident. At age 27, he underwent surgery to remove parts of his brain.

  • Surgery: Bilateral medial temporal lobectomy, removing medial portions of both temporal lobes, including the hippocampus, amygdala, and surrounding cortex.

SURGERY RESULTS

• Immediate Effects:

  • General convulsions eliminated.

  • Reduced frequency of partial seizures.

  • Decreased use of anti-convulsant medication.

  • No change in perceptual or motor abilities; slight intelligence increase.

AMNESIA AND MEMORY IMPAIRMENT

• Consequences of Surgery: Severe memory impairment with both retrograde and anterograde amnesia.

  • Retrograde Amnesia: Loss of memories formed before the injury. Mild retrograde amnesia noted; limited memory of events from 2 years prior to surgery.

  • Anterograde Amnesia: Inability to form new memories post-injury. Short-term memory remains intact; can hold new info momentarily if attended to (e.g., digit-span task).

MEMORY TYPES

• Declarative Memory (Explicit): Memory of facts and autobiographical information. Classified into:

  • Episodic Memory: Personal experiences.

  • Semantic Memory: General knowledge and facts.

• Non-declarative Memory (Implicit): Skills and conditioned responses, can operate without awareness.

  • Procedural Memory: Skill learning, doesn’t require the medial temporal lobe; relies on basal ganglia, cerebellum, and motor cortex.

  • Priming: Changes in perception influenced by previous exposure to similar stimuli, linked to reduced activation in specialized brain areas such as the occipitotemporal cortex.

  • Associative Learning: Learning relationships between events; includes classical and instrumental conditioning.

NON-DECLARATIVE MEMORY EXAMPLES

• Classical Conditioning: Requires cerebellum, not hippocampus.

  • Involves unconditioned (US, UR) and conditioned stimuli (CS) with responses (CR).

• Instrumental Conditioning: Learning actions yield certain consequences, not tied to specific brain regions.

MEMORY TESTING AND IMPLICATIONS

• Various memory tests, such as the mirror drawing task and incomplete pictures task, show patient H.M.’s preserved implicit memory despite declarative memory deficits.

• Important: Ensuring awareness of sensory modalities in memory tests is crucial. Some patients display global amnesia, while others do not.

SCIENTIFIC INSIGHTS FROM H.M.

• Findings illustrate that memory functions are not uniformly distributed in the brain. The medial temporal lobe plays a vital role in memory consolidation, with distinct processes for short-term vs. long-term memory.

ANIMAL MODELS OF MEMORY

• Studying animal models like monkeys and rats has shown that damage to the hippocampus and related areas disrupts recognition memory, informing our understanding of memory processing in humans.

COMPONENTS OF MEMORY

• Memory Stages:

  • Sensory Buffers: Brief glimpses of memory.

  • Short-Term Memory (STM): Active attention span temporarily holding information (working memory).

  • Long-Term Memory (LTM): Durable storage of information post-attention.

MEMORY PROCESSES

• Encoding: Inputting information into STM.

• Consolidation: Transferring information from STM to LTM.

• Retrieval: Accessing stored information back into working memory.

NEUROPLASTICITY

• Changes in synapse structure and function underpin learning and memory. This includes mechanisms for enhancing or diminishing synaptic responses.

  • Neuroplasticity involves structural alterations like synapse formation, increased dendritic branches, and cellular changes due to experiences.

SYNAPTIC PLASTICITY & MEMORY

• Long-Term Potentiation (LTP): A stable, long-lasting enhancement in synaptic transmission linked to memory formation, showing parallels with memory retention processes.

  • Role of Glutamate: Acts as a neurotransmitter crucial for LTP, highlighting importance in synaptic enhancements during memory formation.

MEMORY STORAGE STRATEGIES

• Memories stored across various brain regions participate in the original experience, making them resilient to localized brain damage. Key Brain Areas:

  • Inferotemporal Cortex: Visual patterns.

  • Amygdala: Emotional significance.

  • Prefrontal Cortex: Tasks with sequential responses.

  • Cerebellum: Motor skills.

  • Striatum: Stimuli-response relationships.

This overview synthesizes key insights on learning and memory processes, particularly through the lens of H.M.'s case study and broader neuropsychological research on memory systems and mechanisms.