WEEK 8- Memory Systems and Neural Anatomy

Memory is a complex system, not a singular entity. It operates through various types and divisions, enabling individuals to encode, store, and retrieve information.

Multi-Store Model (Atkinson and Shiffrin, 1968)

Proposed that memory is divided into two main systems:

Short-Term Memory (STM):
- Holds a limited amount of information for a brief duration, approximately 20 seconds without rehearsal.
- Capacity is often described as 7±2 items (George Miller), meaning most people can hold between 5 to 9 distinct items in their STM at any one time.
- Strategies like chunking—grouping information into larger, meaningful units—can enhance memory retention and increase effective capacity.
Long-Term Memory (LTM):
- Exhibits a seemingly unlimited capacity and can store information over extensive periods, sometimes for an entire lifetime.
- Long-term memory can be further categorized into:
- Declarative Memory:
  - Explicit memory that can be consciously recalled, essential for learning and education.
  - Includes:
  - Episodic Memory:
    - Personal experiences and specific events, allowing individuals to recall past events, such as a birthday party or a wedding.
  - Semantic Memory:
    - General knowledge and facts about the world, such as understanding the concept of a democracy or knowing the capital of France.
- Nondeclarative Memory:
  - Implicit memory that does not require conscious recall, often used in learning tasks that involve skills.
  - Includes:
  - Procedural Memory:
    - Skills and habits, such as riding a bike or playing a musical instrument, which can be performed without consciously thinking about them.

Sensory Memory

The initial stage of memory that captures information through the senses and holds it briefly for processing.
Types of sensory memory include:
- Iconic Memory (Visual):
- Stores visual information for about 0.5 to 1 second.
- Echoic Memory (Auditory):
- Retains auditory information for approximately 3 to 4 seconds.

Information Processing Stages

Memory involves several key processes:

Encoding:
- This is the transformation of sensory input into a cognitive format that can be stored in the brain.
- Semantic encoding, where the meaning of the information is processed, tends to lead to better retention than just superficial characteristics.
Storage:
- The maintenance of encoded information over time.
- Can be thought of as the ‘warehouse’ of information, where memories are kept until they are needed.
Retrieval:
- The process of accessing and bringing stored information into consciousness when needed, which can sometimes be influenced by cues and context.

Working Memory

Working Memory:
- Involves active processing and manipulation of information, crucial for tasks that require reasoning, comprehension, and learning.
- Subdivided into several components as per Baddeley and Hitch’s Multi-Component Model:
- Central Executive:
  - Directs attention and coordinates the elements of working memory.
- Phonological Loop:
  - Manages verbal and auditory information.
- Visuospatial Sketchpad:
  - Handles visual and spatial information.
- Episodic Buffer:
  - Integrates information from different sources to form a cohesive memory.

Brain Regions Involved in Memory

Different regions of the brain are responsible for various aspects of memory:
- Central Executive:
- Located in the dorsolateral prefrontal cortex; crucial for planning and executing tasks related to memory.
- Visual Sketchpad & Phonological Loop:
- Responsible for processing visual and auditory information, respectively.
- Episodic Buffer:
- Combines information from multiple sources.
- Hippocampus:
- Plays a central role in forming, consolidating, and retrieving both episodic and semantic memories, acting as a storage area for memories before they are transferred to other regions.
- Amygdala:
- Impacts emotional memory retention; enhances the encoding of emotional experiences, working in conjunction with the hippocampus to create strong memories of highly emotional events.

Autobiographical Memory

Integrates both episodic and semantic details regarding self-relevant experiences.
Essential for the formation of personal identity and continuity across time, shaping how individuals perceive themselves and their past.

Impacts of Damage and Disturbances

Damage to different brain regions can result in specific types of amnesia:
- Hippocampal Damage:
- Typically leads to difficulties forming new memories (anterograde amnesia) and retrieving old ones (retrograde amnesia).
Memory Reconsolidation:
- The process by which memories can be altered upon retrieval, indicating that memory is not static but rather dynamic, influenced by new information or experiences.

Memory Disorders

Various conditions can impact memory function:
- Alzheimer's Disease:
- Causes gradual memory loss, impacting both short and long-term memory.
- Traumatic Brain Injury:
- Can lead to memory deficits depending on the severity and location of brain damage.
- Wernicke-Korsakoff Syndrome:
- Often associated with thiamine deficiency, affecting memory encoding and retrieval, leading to profound memory impairments, particularly in forming new memories.