Neurosurgery notes/Anatomy/Higher function/Memory

Memory

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Higher function

Summary

---
config:
  layout: dagre
---
graph LR
    A[Memory] --> B[Short-term memory]
    A --> C[Long-term memory]
    A --> D[Sensory memory]
    D --> E[Haptic memory]
    D --> F[Echoic memory]
    D --> G[Iconic memory]
    B --> H[Working memory]
    C --> I[Declarative/Explicit memory]
    C --> J[Non-declarative/Implicit memory]
    I --> K[Episodic memory]
    K --> K1[Autobiographical episodic memory]
    K --> K2[Experimental episodic memory]
    K2 --> K3[Flashbulb memory]
    I --> L[Semantic memory]
    J --> M[Procedural memory]
    J --> N[Associative memory]
    J --> O[Non-associative memory]
    J --> P[Priming]

    %% Define classes with specific styles
    classDef memory fill:Black,stroke:#333,stroke-width:2px,font-size:30;
    classDef SensoryMemory fill:Green,stroke:#333,stroke-width:2px;
    classDef shortTerm fill:#ff6161,stroke:#333,stroke-width:2px;
    classDef longTerm fill:#000080,stroke:#333,stroke-width:2px; 
    classDef declarative fill:#00BFFF,stroke:#333,stroke-width:2px;
    classDef nonDeclarative fill:#4682B4,stroke:#333,stroke-width:2px;

    %% Apply classes to nodes
    class A memory;
    class D,E,F,G SensoryMemory;
    class B,H shortTerm;
    class I,K,K1,K2,K3,L declarative;
    class C longTerm;
    class J,M,N,O,P nonDeclarative;

Long-term memory:

  • Unlimited, continuing memory store that can hold information over lengthy periods of time, even for an entire lifetime.
  • Long-term memory is mainly preconscious and unconscious.
  • Information in long-term memory is to a great extent outside of our awareness, but can be called into working memory to be used when needed.
  • Some of this information is easy to recall, but some is much more difficult to access”

Explicit/declarative memory:

  • Conscious memories of previously stored experiences, facts and concepts that are verifiable through a verbal reporting of them.

Episodic memory:

  • Involves the ability to learn, store, and retrieve information about unique personal experiences that occur in daily life.
  • Time related
  • These memories typically include information about the time and place of an event, as well as detailed information about the event itself
  • Eg:
    • When you went to the zoo with a friend last week.
  • Can be split further into
    • Autobiographical episodic memory
      • Memories of specific episodes of one’s life
      • Flashbulb memories are detailed autobiographical episodic memories that are stored permanently when they are first learned, often because they were of emotional or historical importance in that person’s life (e.g. a birth or a death).
    • Experimental episodic memory
      • Learning a fact [a semantic memory] has been associated with memory of the specific life episode when it was learned).
  • Anatomy
    • Cortical structures involved
      • Medial temporal (i.e. parahippocampal cortex and hippocampus)
      • Diencephalic (i.e. thalamus) structures
      • Interactions between the parietal cortex and the medial temporal structures may be required when attention is needed during a mnemonic activity
      • Parietal cortex
        • Dorsal aspect of the posterior parietal cortex: used when attention is directed by retrieval goals,
        • Ventral aspect of the posterior parietal cortex: used when attention is captured by relevant memory cues or recovered memory
    • Sub cortical structures involved
      • Medial temporal structures, especially the
        • Fornix
          • Direct connectivity between the hippocampus and the diencephalic structures
          • Damaged: Severe anterograde amnesia
        • Cingulum
          • Uncertain yet its role
        • Uncinate fasciculus.
          • Funtion:
            • Associative learning

Semantic memory:

  • Memory of meanings, interpretations and concepts related to facts, information and general knowledge about the world.
  • Concepts and meanings
  • Semantic memory gives meaning to words and phrases that would otherwise be meaningless and allows for learning based on past experience.
  • However, the conscious recall here is of facts that have meaning, as opposed to the recall of past life events associated with episodic memory.

Implicit/non-declarative memory:

  • This encompasses all unconscious memories, as well as certain abilities or skills.
  • There are four types of implicit memory:
      • Procedural memory
      • A memory area involved in remembering executive and motor skills necessary to perform a task.
      • It is an executive system that guides activity
      • Usually works on an unconscious level.
      • When necessary, procedural memories are automatically retrieved for use in the implementation of integrated procedures related to motor and intellectual skills
      • Comprises of
        • Motor skills
        • Executive skills
      • Eg: riding a bike –you might struggle to consciously recall how to manage the task, but we can [unconsciously] perform it with relative ease
      Associative memory
      • Refers to the storage and retrieval of information resulting from an association (i.e., resulting from an association with other information).
      • Two types of conditioning are involved in its acquisition:
        • Classical conditioning
          • A kind of associative learning between stimuli and behaviour
        • Operant conditioning
          • A form of learning in which new behaviours develop in terms of their consequences.
      Non-associative memory
      • Newly learned behaviour due to repeated exposure to a single stimulus.
      • The new behaviour can be classified into two processes:
        • Sensitization
        • Habituation
      Priming memory
      • An effect whereby exposure to certain stimuli influences the response to subsequently presented stimuli.
      • Smelling gas and thinking of durian or could be gas

Visual memory:

  • Constituted by iconic memory, visual short-term and long-term memory.
  • Visual short-term memory/visuospatial sketchpad:
    • Sketchpad’s main function is to create and maintain a visuospatial representation that persists through the irregular form found in eye movement and that characterises our exploration of the visual world
    • Eg Seeing a new car shape

Perceptual memory:

  • Memory acquired through the senses.
  • It includes a lot of individual experience
  • It ranges from the simplest forms of sensory memory to the most abstract knowledge

Sensory memory:

  • Sensory memory refers to the retention of information coming from the senses.
  • Sensory memory is the capacity for briefly retaining the large amounts of information that people encounter daily.
  • Echoic memory:
    • Sensory memory that receives and processes auditory information.
  • Haptic memory:
    • Sensory memory that receives and processes information from the sense of touch.
  • Iconic memory:
    • Visual-sensory memory that receives and processes visual stimuli.

Short-term memory:

  • Is the ability to keep a small amount of information available for a short period of time.
  • Short-term memory should be distinguished from working memory, which refers to structures and processes used for temporarily storing and manipulating information.
    • The notion of working memory is broader and more general because it refers to structures and processes used for temporarily stored and manipulated information
  • The relationship between short-term memory and working memory is presented variously by different theories.

Working memory:

  • A brain system that provides temporary storage and manipulation of the information necessary for such complex cognitive tasks as language comprehension, learning and reasoning
  • Performs processing of short term memory
  • Anatomy
    • Formed by
      • Network of fronto-parietal cortical areas
        • Posterior parietal cortex and
        • Inferior and middle prefrontal gyri
    • Interconnected by SLF layer III
  • Damage
    • Impairs span task performance
  • Consists of four elements that process information:
      • Central executive
      • Attention control
      Visuospatial sketchpad
      • Creates and maintains a visuospatial representation)
      • Conceptual short-term memory/episodic buffer:
        • This is a temporary storage system capable of integrating information from different sources that is probably controlled by the central executive.
        • It is episodic in that it has episodes in which information is integrated through space and, potentially, extended through time.
      Phonological buffer
      • Stores and consolidates new words
      • Phonological working memory is divided into
        • Phonological store
          • Located at left supramarginal gyrus
        • Articulatory rehearsal mechanism
          • That can revitalized the transiently stored information
          • Located at
            • Left inferior frontal gyrus
            • Left the ventral premotor cortex
      Episodic buffer
      • Stores and integrates information from different sources.