Memory

• Amnesia


  Loss of memory
• Anterograde amnesia


  • Inability to form new long-term memories
• Formal assessment of H.M.'s anterograde amnesia

  1. Digit span test

  2. Block-tapping memory-span test

  3. Mirror-drawing test

  4. Incomplete-picture test

  5. Pavlovian conditioning
• H.M.'s case


  • Medial temporal lobe plays an important role in memory
  • Memory functions are diffusely and equivalently distributed throughout the brain
  • Renewed efforts to relate individual brain structures to specific mnemonic (memory-related) processes
  • Bilateral medial temporal lobectomy affects ability to form certain kinds of long-term memories
  • Supported the theory that there are different modes of storage for short-term, long-term, and remote memory
  • First to reveal that an amnesic patient might claim no recollection of a previous experience while demonstrating memory for it by improved performance
• Explicit memories/declarative


  Conscious long-term memories, flexible use of information
• Implicit memories


  Long-term memories demonstrated by improved test performance without conscious awareness
• Medial temporal lobe amnesia


  • Difficulty in forming explicit long-term memories while retaining ability to form implicit long-term memories
• Semantic memories


  Explicit memories for general facts or information
• Episodic memories


  Explicit memories for particular events of one's life
• Hippocampus and memory


  • Global cerebral ischemia can cause medial temporal lobe amnesia
  • Selective hippocampal damage can produce medial temporal lobe amnesia
• Transient global amnesia


  • Severe anterograde amnesia and moderate retrograde amnesia for explicit episodic memories, but transient, typically lasting only 4 to 6 hours
• Amnesia of Alzheimer's disease


  • Memory deficits are more general than those associated with medial temporal lobe damage, medial diencephalic damage, or Korsakoff's syndrome
  • Implicit memory for verbal and perceptual material is often deficient, whereas implicit memory for sensorimotor learning is not
  • Degeneration of the basal forebrain, the main source of acetylcholine, results in reduced acetylcholine level in the brain
  • Brain damage is extremely diffuse, involving many areas including the medial temporal lobes and the prefrontal cortex
• Amnesia after concussion


  • Post-traumatic amnesia following a nonpenetrating head injury
  • Memory consolidation and gradients of retrograde amnesia
  • Electroconvulsive shock can erase memories that have not yet been consolidated
  • Hippocampus plays a special role in temporarily storing memories until they can be transferred to a more stable cortical storage system
• Hippocampal place cells and entorhinal grid cells

  • Hippocampal place cells obtain their spatial information from grid cells in the entorhinal cortex
  • Entorhinal grid cells produce a pattern of graph paper and are essential for hippocampal place cell function
• Amnesia


  Any pathological loss of memory
• Bilateral medial temporal lobectomy


  The removal of media portions of both temporal lobes, including most of the hippocampus, amygdala, and adjacent cortex
• Lobectomy


  An operation in which a lobe, or a major part of one, is removed from the brain
• Lobotomy


  An operation in which a lobe, or a major part of one, is separated from the rest of the brain by a large cut but is not removed
• Retrograde amnesia


  Backward-acting amnesia
• Anterograde amnesia


  Forward-acting amnesia
• Short-term memory


  Storage of new information for brief periods while a person attends to it
• Long-term memory


  Storage of new information once the person stops attending to it
• Global amnesia


  Amnesia for information presented in sensory modalities
• Learning


  Deals with how experience changes the brain
• Memory


  Deals with how these changes are stored and subsequently reactivated
• H.M. tests


  1. Digit span + 1 test

  2. Block tapping memory-span test

  3. Mirror-drawing test

  4. Incomplete pictures test
• Remote memory


  Memory for experiences in the distant past
• Memory consolidation


  The translation of short-term memories into long-term memories
• Explicit memories (declarative memories)


  Conscious long-term memories
• Implicit memories


  Long-term memories without conscious awareness
• Medial temporal lobe amnesia


  Neuropsychological patients with a profile of mnemonic deficits similar to those of H.M., with preserved intellectual functioning, and with evidence of medial temporal lobe damage
• Repetition priming tests


  Tests that assess implicit memory
• Semantic memories


  Explicit memories for general facts or information
• Episodic memories


  Explicit memories for the particular events (i.e., episodes) of one's life
• Global cerebral ischemia


  Patients who have experienced an interruption of blood supply to their entire brains
• CA1 subfield


  Part of the hippocampus
• Transient global amnesia


  Sudden onset of severe anterograde amnesia and moderate retrograde amnesia for explicit episodic memories, typically lasting only 4 to 6 hours
• Korsakoff's syndrome


  A disorder of memory common in people who have consumed large amounts of alcohol, characterized by a variety of sensory and motor problems, extreme confusion, personality changes, and a risk of death
• Medial diencephalic amnesia


  Amnesia, such as Korsakoff amnesia, associated with damage to the medial diencephalon
• Alzheimer's disease


  A major cause of amnesia, characterized by a progressive deterioration of memory and dementia