Memory Disorders Study Guide

Memory Disorders

Amnesia

  • Definition: Pathological loss of memory, often due to brain damage or dysfunction.
  • Onset: Usually sudden, possibly due to events like hypoxia, injury, surgery, infection, or medications.
  • Memory Impairment: Severe memory impairment occurs, while other cognitive functions (language, intelligence, attention) are relatively spared.
  • Functioning: Daily functioning is moderately preserved with support and external aids.

Dementia

  • Definition: A symptom of a disorder or disease, not a diagnosis on its own.
  • Cognitive Decline: Gradual and acquired cognitive decline.
  • Multi-domain Cognitive Deficits: Includes deficits beyond memory, such as language, attention, executive function, visuospatial abilities, and social cognition.
  • Independence Loss: Results in progressive loss of independence in everyday activities.

Amnesia in Popular Media

  • Films:
    • 50 First Dates: Features themes of daily memory loss in romantic contexts (Adam Sandler, Drew Barrymore).
    • Memento: Explores the concept of memory loss with the tagline "Some memories are best forgotten" (Guy Pearce, Carrie-Anne Moss).

Anatomy of Memory

Medial Temporal Lobe Structures
  • Hippocampus
  • Entorhinal Cortex
  • Perirhinal Cortex
  • Parahippocampal Cortex
  • Amygdala

Amnesic Syndrome and Memory Loss

Types of Amnesia
  • Anterograde Amnesia: Inability to form NEW memories following brain damage.
  • Retrograde Amnesia: Inability to retrieve OLD memories prior to brain damage.
Time Frame of Memory Loss
  • Retrograde Memory Loss:
    • Remote past
    • Recent past
  • Anterograde Memory Loss:
  • Brain Injury Examination:
    • Hippocampus-dependent amnesia vs. hippocampus-independent memory storage.
Recovery from Amnesia
  • Study by Barbizet (1970): Repeated assessments of an individual with traumatic brain injury.
    • Time 1: 2 years retrograde
    • Time 2: 1 year retrograde
    • Time 3: 2 weeks retrograde.
    • New Encoding: Normal new memory encoding achieved 5 months after injury.

Long-Term Memory Organization in the Brain

  • Squire et al. (1986; 2004): Findings on amnesic syndrome include
    • Intact working memory.
    • Intact implicit memory.
    • Intact procedural memory.
    • Impaired episodic memory.
    • Impaired semantic memory.

Medial Temporal Lobe and Declarative Memory

Contribution to Memory
  • Theory: All medial temporal lobe structures contribute to declarative memory, thus damage can lead to a declarative memory deficit.
  • Role of Hippocampus: Involved in episodic memory consolidation, which is time-limited as memories are eventually stored in the cortex.
  • Independence: The medial temporal lobe functions independent of other cognitive aspects like perception and working memory.
Division of Memory Functions
  • Episodic vs Semantic Memory
    • Focus on the differentiation between episodic and semantic memory, based on neuroanatomical and functional perspectives.
    • Concepts including recollection vs. familiarity, and recall vs. recognition are critical in understanding memory types.

Effects of Medial Temporal Lobe Damage

Patient HM Case Study
  • HM was unable to form new episodic and semantic memories.
  • Gabrieli et al. (1988) attempted to teach HM new words.
    • Example words include quotidian, manumit, hegira, anchorite, minatory, egress, welkin, and tyro.
Developmental Amnesia
  • Early damage to MTL and its effects on children.
  • Vargha-Khadem et al. (1997) studied three individuals with selective hippocampal lesions early in life.
    • Beth: Birth complications and hypoxia, memory problems noticed around age 5.
    • Jon: Born prematurely with seizures, memory issues apparent by age 6.
    • Kate: Toxic medication dose leading to seizures and memory issues on recovery.

Memory Assessment in Developmental Amnesia

  • Logical Memory Test: e.g., recall details from a story.
  • Delayed Drawing Test: Test for immediate and delayed recall of geometric figures and stories.
Findings of Vargha-Khadem et al.
  • Their semantic memory abilities are within the normal range despite profound episodic memory deficits.
  • Indicates a division of cognitive labor, with hippocampus not necessary for all declarative memory forms.

A Revised Account of Medial Temporal Lobe Contributions

  • The medial temporal lobe's contributions suggest that the structures within play varying roles in declarative memory functions, complicating the notion of a unified memory system.

Distinctions in Memory Types

Recollection vs. Familiarity
  • Recollection: Retrieval of contextual details from an episode, characterized by conscious awareness.
  • Familiarity: Recognition based on the stimulus without recalling the context, leading to feelings of knowing.
Empirical Studies on Memory Types
  • Yonelinas et al. (2002): MTL damage affects both familiarity and recollection, with specific lesions having differentiated impacts.
  • Eldridge et al. (2000): fMRI study highlights that hippocampal activity correlates with recollective tasks compared to familiarity tasks.

Memory Systems and Patient Impairments

Memory Tests and Patient Y.R.
  • Findings show selective hippocampal damage leading to deficits in free recall and intact recognition tasks, implying different processing mechanisms for recall versus recognition.

Neuropathology of Alzheimer’s Disease

Key Features of Alzheimer’s Disease
  • Amyloid Plaques: Accumulation of proteins disrupting neuronal communication.
  • Neurofibrillary Tangles: Tau proteins collapse leading to cell death.
Neuropathological Stages
  • Changes in the transentorhinal cortex precede more widespread changes, typically starting 20 years before clinical diagnosis.

Dementia Types and Alzheimer’s Disease Statistics

  • Alzheimer’s Disease: Most common form of dementia, with projections of increasing prevalence and economic burden.
  • Korsakoff’s Syndrome: Severe amnesia due to vitamin B1 deficiency, primarily impacting thalamic nuclei and mammillary bodies.

Capgras Syndrome

Description and Mechanism
  • Capgras Syndrome: Delusional misidentification where an individual believes loved ones have been replaced.
  • Underlying Mechanisms: Disruption of associative processes in face processing leading to altered emotional responses upon recognition, typically without autonomic arousal.