Historical Perspectives

(A Century's Research on Biology of Learning and Memory)

Part 1, Pre-1960s period

  1. The origin of experimental psychology:
    1. Fechner & Weber: psychophysics
    2. Wilhelm Wundt, 1879, opened a formal laboratory of experimental psychology at Univ of Leipzig, founder of psychology as a science
    3. Hermann Ebbinghaus 1850-1909, performed dozens of experiments
      1. Study-test method: memorized lists of nonsense syllables and tested himself
      2. excluded the influence of extraneous factors on the outcome of experiments (he realized that a major contaminating factor could be the prior knowledge that subjects bring to an experiment).
      3. novel and successful attempt to test memory experimentally
  2. William James 1890, Principles of Psychology, separate chapters to habit, association and memory, Harvard lab (teaching)
    1. Habit, memory, and other aspects of behaviour are based on physiological properties of the brain, even though not be able to specify
    2. Separate chapters on habit and memory, a precursor to nondeclarative and declarative memory
    3. The idea that conscious experience requires memory
    4. Memory systems include
      1. consciousness primary memory,
      2. secondary memory, which comprises our permanent record of the past.
      3. later came to be called short term and long term memory
    5. His ideas about memory did not start to influence experimental psychology until the 1960s. This extraordinary delay can be attributed to the direct influence of behaviourism.
  3. Edward Thorndike (1874-1949), one of the first psychologists to perform systematic experiments on the learning process
    1. Extended the research to animals
    2. Instrumental conditioning (operant conditioning), See Fig. 1-1
  4. Pavlov, the turn of 19 century, 1904 Nobel price,
    1. The concept of conditioning from observations on salivary responses
    2. the first one to demonstrate that salivation could be evoked by a previously neutral stimulus after this has been paired with an effective stimulus, See Fig. 1-1
  5. "Search for the engram" (engram is the term to describe the memory trace that is presumably present in the brain after something has been learned) -- debate over whether specific engrams are localized in discrete areas of the brain or interwoven throughout the entire brain
  6. Pavlov believed that during classical conditioning new connections were formed among neurons in cerebral cortex of the brain. But he did not provide any evidence.
  7. Karl Lashley (1929) tried in vain to provide evidence that specific cortical connections are formed during conditioning procedures.
    1. He found no evidence that destruction or removal of any specific area of the cerebral cortex could either erase the engram or cause learning to be prevented from occurring.
    2. His results suggested that the amount of cortical tissue destroyed was far more important than the location of the damage.
    3. The results forced him to reject the localizationist position, instead, he came to champion the view that specific memories were diffusely distributed throughout the cerebral cortex and that all parts of the cortex were equally involved in learning.
    4. "This series of experiments has yielded a good bit of information about what and where the memory trace is not. It has discovered nothing directly on the real nature of the engram. I sometimes feel, in reviewing the evidence on the localization of the memory trace, that the necessary conclusion is that learning is just not possible." -- Lashley, 1950
  8. Durup and Fessard (1935)
    1. Electrophysiological observations (EEG) of learning effect
    2. But, precise localization of EEG activity in the human cortex is difficult

Part 2, Multiple memory systems (Neuropsychology and cognitive psychology)

  1. Challenge to the early assumption that memory is a unitary or monolithic entity in early 19th century
    1. Franz Joseph Gall, founder of the phrenological movement, each specialized faculty of the mind is concerned with particular contents (e.g. music, mathematics) and maintains its own memory
    2. Maine de Biran
      1. representative memory: recollection of ideas and events
      2. mechanical memory: acquisition of habits and skills
      3. sensitive memory: memory for feelings
  2. After the promising beginning, this ideas disappeared during first half of the century
  3. 1960s, 1970s, converging evidence from cognitive neuropsychology, psychology, neurobiology support the view of Multiple memory systems, efforts to experimentally dissociate memory systems emerged as a central research direction
  4. Famous amnesic patient H.M.
    1. "frankly experimental" brain surgery
      1. a complete bilateral resection of medial temporal lobes (incl. hippocampus and amygdala) for relief of intractable epilepsy.
    2. Symptoms
    3. Psychological testing
      1. Probe digit task (Waugh and Norman, 1965). Subject listened to a sequence of 16 digits which was then followed by a probe digit. The subject's task was to name the digit that occurred after the probe. Example: 5824972537196435, and 6 is probe (See Fig.1-2)
        1. as the number of items occurring after the probe digit increased, performance on the probe task became poorer, declining at a steeper rate with five or fewer intervening items.
        2. The change in the gradient was taken as indicating the transition from primary to secondary memory, and its occurrence at the five-item point provided the first empirical demonstration of separate primary and secondary memories and the first estimate of primary memory capacity.
        3. Easier version of the probe digit task, test of HM (Wicklegen, 1968)
      2. Digit span task also showed normal primary memory in HM, 7 plus or minus2
        1. digit span task measures the ability to repeat a random series of numbers in the correct order immediately after seeing or hearing them
      3. HM's extremely poor ability on tests requiring the retention of verbal information over longer periods of time
      4. Conclusion: primary memory exists independently of secondary memory
      5. Mirror-tracing task (Brenda Miller, 1965)
      6. HM did not show deficit on motor learning. (See Fig. 1-3)
  5. Declarative vs. Procedural memory
    1. HM's memory problem could not be attributed solely to difficulties with verbal materials
      1. he had difficult reproducing or recognizing pictures and spatial designs
      2. could learn some kinds of information about the verbal materials
        1. e.g. could learn to read works printed mirror-reversed (requiring the ability to deal with abstract rules or procedures)
    2. the important distinction is probably not between verbal and motor performance, rather between declarative and procedural memory
    3. Declarative memory
      1. Concept
        1. facts and information acquired through learning
        2. memory that we are aware of accessing
      2. including:
        1. episodic memory: autobiographical, personal history
        2. semantic memory: generalized memory, e.g. knowing the meaning of the words
    4. Nondeclarative memory (procedural memory)
      1. Shown by performance rather than by conscious recollection.
      2. including:
        1. skill learning
        2. priming, a change in the processing of a stimulus as a result of prior exposure
        3. conditioning
    5. cognitive psychologist Tulving's contribution on episodic memory and semantic memory and the work of "Toronto school" (the work of theorist: Craik, Schacter, Tulving).
  6. Logic underlying the use of the evidence from neuropsychology (rationale for cognitive neuropsychology)
    1. K. Craik (1943) writes: 'In any well-made machine one is ignorant of the working of most of the parts - the better they work, the less we are conscious of them... it is only a fault which draws attention to the existence of a mechanism at all.' - from Ellis and Young's influential book Human Cognitive Neuropsychology (1988).
    2. The concept of modular system
      1. Cognitive neuropsychology assumes that the various components of cognition, including memory, are spatially distributed within the brain and that, furthermore, each of these mental functions is modular.
      2. A modular system is one in which several components interact to perform a function, but each component, or module, is functionally autonomous - i.e. it can continue to operate if other modules cease to work for any reason.
      3. When the brain is damaged, either by accident or by illness, it is assumed that modules may become dissociated from each other in a meaningful way and thereby reveal something about the underlying organization of the system.
    3. Double dissociation and one-way dissociation. (See Fig. 1-4)