WK11 Reading: Memory, Memory Loss & Unlearning

• Learning


  The process of acquiring factual knowledge about some subject area
• Memory


  The knowledge acquired and stored in the brain
• Memory trace


  The stored representation of a memory
• Autobiographical memory


  Memories of things that we did or that happened to us
• There are cases where learning takes place but does not result in the formation of memories that can be recalled and verbalized
• Declarative memory


  A form of memory that involves the (conscious) recollection of experiences and facts. These recollections can be communicated to someone else either verbally or by some other means (they can be declared).
• Non-declarative memory


  A form of memory that does not involve conscious recollection and that cannot be described or expressed verbally (cannot be declared). The existence of the memory is demonstrated through performance (i.e. by doing something).
• Explicit memory refers to memory that involves the "conscious recollection of previous experiences" and is often used as a synonym for declarative memory
• Implicit memory is used as a synonym for non-declarative memory
• Experts spend years acquiring knowledge about their skill, which they use very effectively to support their performance, but they have little explicit access to that knowledge
• Lane changing


  1. Phase 1: Steering wheel movement to the right and back to the centre

  2. Phase 2: Steering wheel movement to the left and back to the centre
• Most people are unaware that lane-changing involves a two-phase (biphasic) movement of the steering wheel, though they are quite capable of executing the manoeuvre in a skillful fashion
• When participants could not see the road, they did not execute both phases of the lane change manoeuvre. Only the first phase was executed and the second was absent
• Initiation of the second phase of the lane change manoeuvre requires feedback from execution of the first phase
• Anterograde amnesia


  A serious impairment of the ability to form memories of things that occurred after the brain was damaged
• Anterograde amnesia is not a loss of existing memory, it is a loss an ability to form memories
• The public showed that most people (83%) believe that amnesia involves loss of identity (Simons & Chabris, 2011)
• See the paper by Baxendale (2004), the link is on this week's Moodle page
• In the real world, amnesia due to brain injury is rather different. There is often partial inability to recall events that occurred prior to the damage (termed retrograde amnesia), but loss of identity and associated personality changes are very rare indeed
• Anterograde amnesia is not a loss of existing memory, it is a loss an ability to form memories, the term itself means (roughly) amnesia going forward
• Anterograde amnesic


  • Can remember facts acquired prior to the damage and can recall life events that occurred prior to the damage, but cannot remember anything experienced after the damage
  • Can hold some things in mind for a few seconds, but usually for no more than a minute or so
  • Has an intact short term memory that allows them to hold a limited number of things in mind, but a severely impaired ability to form new long term memories
• Henry Molaison (known as HM in published studies) suffered from very severe epilepsy for which he received brain surgery when he was twenty seven years old (in 1953). The surgery was drastic and involved removing the medial parts of the temporal lobe (including the hippocampus) on both sides of the brain
• HM's surgery successfully dealt his epilepsy and had little or no detectable effect on his personality, perceptual ability or intelligence. However, it left him unable to form new memories of events in his life and of new facts
• HM was able to develop skill in a variety of motor tasks and to retain what he had learned for many months or years
• Mirror tracing task


  • Move a pen around a star shape, keeping the pen within the gap between the inner and outer stars
  • Performed when the star, the pen and the hand could only be seen in a mirror
• Mirror tracing task performance

  1. HM attempted to draw around the star without crossing the lines ten times using his right (dominant) hand on each of three consecutive days

  2. On the first attempt on day 1, he made 29 errors; by day 3 he made no more than four errors on any of his ten attempts
• Findings of the sort just described are not unique to HM—they have been replicated in many other patients who suffer from anterograde amnesia
• Pursuit rotor task


  • Keep a stylus in continuous contact with a metal disc attached to a turntable that made thirty complete revolutions every minute
• Pursuit rotor task performance


  1. Initial training phase consisted of five trials of thirty seconds each

  2. Two retention tests were administered, one twenty minutes after the training phase and one two years later
• Boswell, an amnesic patient, performed slightly better than the average of the controls in the retention tests, showing clear evidence of retaining the skill acquired during the training phase over a period of two years
• Declarative memory


  Memory of facts and events that can be consciously recalled
• Non-declarative memory


  Memory underlying the acquisition of skills and habits, which cannot be consciously recalled
• The results from patients HM and Boswell show a clear dissociation of the effects of brain damage on declarative memory and non-declarative memory
• The structures damaged or removed in patients who show this dissociation implicate the medial temporal lobe of the cerebral cortex (that includes the hippocampus and nearby regions such as the entorhinal cortex and perirhinal cortex) in the process of forming long term declarative memories
• These structures are not necessary for the formation of non-declarative memories underlying the acquisition of motor skill
• Delay conditioning procedure


  CS-US pairings with a delay interval between the CS and US
• Delay conditioning experiment


  1. Training took place while participants watched a silent movie

  2. Immediately after the training sessions, participants completed a questionnaire about their awareness of the CS-US relationship

  3. Participants were classified as aware or unaware based on their questionnaire responses

  
• All the amnesic patients were classified as unaware as they could not remember the stimuli, let alone the relationship between them
• Neither an intact hippocampus nor having conscious knowledge of the CS-US relationship is necessary for learning conditional eye-blinks in the delay conditioning procedure


  All three groups (amnesics, normal aware, normal unaware) gradually acquired CRs during training
• Trace conditioning procedure


  CS-US pairings with a trace interval between the CS and US