Psychology of Memory

Memory

Short-term Memory

• Limited capacity (7 ± 2 chunks of information)
• Information is stored for a short period ( seconds to minutes)
• Information is readily available for recall, but easily forgotten
• Primarily auditory and visual information

Long-term Memory

• Large capacity ( potentially unlimited)
• Information is stored for an extended period (hours to years)
• Information is not readily available for recall, but can be retrieved with effort
• Primarily semantic and episodic information

Sensory Memory

• Brief storage of sensory information ( milliseconds to seconds)
• Information is stored in its original sensory form (e.g., visual, auditory)
• Primarily automatic and unconscious processing
• Examples: iconic memory (visual), echoic memory (auditory)

Working Memory

• A system that temporarily holds and manipulates information
• Involved in tasks such as mental arithmetic, following instructions, and learning
• Comprises:
  • Phonological loop (verbal information)
  • Visuospatial sketchpad (visual and spatial information)
  • Central executive (attention, control, and manipulation)

Amnesias

• Types:
  • Anterograde amnesia: inability to form new memories
  • Retrograde amnesia: inability to recall past memories
  • Transient global amnesia: sudden, temporary loss of all memories
• Causes:
  • Brain damage (e.g., head injury, stroke)
  • Neurodegenerative diseases (e.g., Alzheimer's)
  • Infections (e.g., encephalitis)
  • Psychological trauma

Memory

Short-term Memory

• Has a limited capacity of 7 ± 2 chunks of information
• Stores information for a short period, ranging from seconds to minutes
• Primarily stores auditory and visual information
• Information is readily available for recall, but easily forgotten

Long-term Memory

• Has a large, potentially unlimited capacity
• Stores information for an extended period, ranging from hours to years
• Primarily stores semantic and episodic information
• Information is not readily available for recall, but can be retrieved with effort

Sensory Memory

• Briefly stores sensory information, lasting from milliseconds to seconds
• Stores information in its original sensory form (e.g., visual, auditory)
• Primarily involves automatic and unconscious processing
• Examples include iconic memory (visual) and echoic memory (auditory)

Working Memory

• Temporarily holds and manipulates information
• Involved in tasks such as mental arithmetic, following instructions, and learning
• Comprises three components:
  • Phonological loop (verbal information)
  • Visuospatial sketchpad (visual and spatial information)
  • Central executive (attention, control, and manipulation)

Amnesias

• Types of amnesia include:
  • Anterograde amnesia: inability to form new memories
  • Retrograde amnesia: inability to recall past memories
  • Transient global amnesia: sudden, temporary loss of all memories
• Causes of amnesia include:
  • Brain damage (e.g., head injury, stroke)
  • Neurodegenerative diseases (e.g., Alzheimer's)
  • Infections (e.g., encephalitis)
  • Psychological trauma

Memory

Short-term Memory

• Holds information for a brief period of time (seconds to minutes)
• Limited capacity (7 ± 2 chunks of information)
• Information is either forgotten or transferred to long-term memory
• Example use: remembering a phone number long enough to dial it

Long-term Memory

• Stores information for an extended period of time (hours to years)
• Large capacity, can store vast amounts of information
• Information can be retrieved through recall or recognition
• Types of long-term memory:
  • Episodic: specific events and experiences
  • Semantic: general knowledge and facts
  • Implicit: skills and habits

Working Memory

• Temporary holding and manipulation of information for cognitive tasks
• Involves attention, reasoning, and decision-making
• Components of working memory:
  • Phonological loop: verbal information
  • Visuospatial sketchpad: visual and spatial information
  • Central executive: attention and control

Sensory Memory

• Brief storage of sensory information in the brain
• Information is stored in a raw, unprocessed form
• Types of sensory memory:
  • Iconic memory: visual information
  • Echoic memory: auditory information
  • Haptic memory: tactile information

Amnesias

• Types of memory impairments or disorders
• Causes of amnesia:
  • Brain damage or injury
  • Neurodegenerative diseases (e.g. Alzheimer's)
  • Psychological trauma
• Examples of amnesias:
  • Anterograde amnesia: inability to form new memories
  • Retrograde amnesia: inability to recall past memories
  • Infantile amnesia: inability to recall early childhood memories

Memory

Long-term Memory

• Permanent storage and retrieval of information over an extended period (hours, days, years, or a lifetime)
• Vast storage capacity, potentially unlimited
• Information stored in a permanent and stable form, resistant to interference or forgetting
• Retrieval of information is slower and more effortful compared to short-term memory

Declarative Memory

• Stores factual information, including:
  • Episodic memory: personal experiences and events
  • Semantic memory: general knowledge and facts
• Divided into:
  • Implicit memory: unconscious recall of skills and habits
  • Explicit memory: conscious recall of facts and events

Non-Declarative Memory

• Stores skills, habits, and conditioned responses
• Also known as implicit memory or procedural memory
• Characteristics:
  • Unconscious learning process
  • Automatic retrieval, no conscious effort required
  • Long-lasting, skills and habits retained over time
  • Difficult to verbalize, hard to put into words

Examples of Non-Declarative Memory

• Riding a bike
• Playing a musical instrument
• Tying shoelaces
• Habits like nail biting or smoking

Memory Loss

• Types of Memory Loss:
  • Transient Global Amnesia (TGA): sudden, temporary loss of all memories, often triggered by physical or emotional stress
  • Anterograde Amnesia: inability to form new memories, while retaining old ones
  • Retrograde Amnesia: inability to recall past events, while forming new memories normally

Causes of Memory Loss:

• Physical Factors:
  • Head trauma
  • Infections (e.g., encephalitis)
• Neurological Factors:
  • Neurodegenerative diseases (e.g., Alzheimer's)
• Nutritional Factors:
  • Nutritional deficiencies (e.g., thiamine deficiency)
• Pharmacological Factors:
  • Medications (e.g., benzodiazepines)

Henry Molaison (H.M.)

Case Study:

• Background:
  • Suffered from severe epilepsy
  • Underwent surgery to remove medial temporal lobe (including hippocampus) to alleviate symptoms
• Findings:
  • Developed anterograde amnesia, unable to form new memories
  • Demonstrated intact short-term memory, but unable to consolidate new information into long-term memory
  • Showed normal learning and memory for skills and habits, but no episodic memory
• Significance:
  • Provided valuable insights into the role of the hippocampus in memory formation
  • Contributed significantly to our understanding of the neural basis of memory
  • Case study led by Brenda Milner and Wilder Penfield

Henry Molaison (H.M.)

Overview

• H.M. was a patient who suffered from severe anterograde amnesia, unable to form new memories
• His case has been extensively studied in neuroscience and psychology

Background

• H.M. was born in 1926 and suffered from intractable epilepsy
• He underwent bilateral medial temporal lobe resection in 1953 to remove the seizure focus
• The surgery resulted in the removal of his hippocampus and surrounding structures, leading to his amnesia

Characteristics of H.M.'s Amnesia

• H.M. had anterograde amnesia, unable to form new memories after the surgery
• He had some difficulty recalling events from the past, but this was less severe (retrograde amnesia)
• H.M. could learn new skills and habits, but had no conscious memory of doing so (implicit memory)
• His short-term memory was intact, but he could not consolidate information into long-term memory

Insights from H.M.'s Case

• The hippocampus is crucial for forming new memories
• H.M.'s case demonstrated the distinction between declarative (facts and events) and procedural (skills and habits) memory
• Despite his amnesia, H.M.'s brain was able to adapt and learn new skills through repetition and practice (neuroplasticity)

Legacy of H.M.'s Case

• H.M.'s case has been the subject of over 100 research papers, contributing significantly to our understanding of memory and the brain
• His case has informed the development of treatments for memory disorders, such as Alzheimer's disease and traumatic brain injury