1. Research aims of animal models
    1. Neuropsychological aim
      1. Permits the investigator to maintain very strong control of the learning experiences of the subjects and,
      2. permits systematic studies to be performed to delineate precisely the critical structures
    2. Comparative aim
      1. Search for cross-species commonalities and differences in the functional role of the structures
      2. Inquire about the kinds of mechanisms that have evolved to support memory in the species with different environmental challenges and behavioural demands.
    3. Neurobiological mechanisms
      1. Allow systematic exploration of these structures' physiological properties and functional organization with methods not amenable for use with humans
        1. Single unit recording
        2. Neuroanatomical and neurochemical studies
  2. Limitations and special challenges associated with the study of declarative memory in animals
    1. Lack of verbal declaration
    2. Distinctions between episodic vs. semantic, explicit vs. implicit memory is not immediately clear
  3. Visual recognition memory in nonhuman primates
    1. The set of behavioural tests
      1. delayed non-match-sample task (DNMS), see Fig. 2-15
        1. Ss are exposed to an object once and then,
        2. after a delay,
        3. asked to recognize the object by indicating the unfamiliar one in a two-choice presentation
    2. Monkeys with experimental lesions of the entire medial temporal area (see Fig. 2-14)
      1. intact STM but impaired LTM, see Fig. 2-16
      2. Retrograde amnesia
      3. intact capacities for skill acquisition task
    3. Structures of the medial temporal lobe critical to supporting declarative memory
      1. amygdala is not important
      2. damage limited to the hippocampus has only modest effect in monkeys (but bigger effect in humans)
      3. damage to the perirhinal and parahippocampal region can produce the full pattern of the amnesic deficit, see Fig. 2-17, 2-18, 2-19, 2-20, 2-21.
  4. Cognitive processing in rodents (see: Memory, amnesia, and the hippocampal system, written by Cohen, N. J. and Eichenbaum, H. B. Cambridge, MA: MIT Press, 1993. On reserve in Health Sciences Library WL 102 .C6785m 1993, pp.154-160; pp.109-126 )
    1. O'Keefe and Nadel's (1978): hippocampus mediates cognitive map (the establishment of an organized neural representation of the physical environment)
      1. Rats with hippocampal system damage are severely impaired in many form of spatial exploration and learning.
    2. Place learning: Morris water-maze task, see Fig. 22
      1. rats are trained to find a hidden escape platform submerged just below the surface in a pool of cloudy water
      2. Hippocampal system damage (see Fig. 2-14) impair the ability to lean the location of the escape platform
    3. Place learning (a detailed description)
      1. Water maze, developed by Morris (1981), see Fig. 2-22
        1. Tank
        2. water
        3. platform
        4. extra maze cues
      2. Experiment 1
        1. Demand of the task
          1. The animal swims around until it to find the platform to escape
          2. standard version of the task, variable-start-location
        2. Results, escape latency
          1. Across the trial, normal rats come to locate the platform increasingly rapidly, and eventually swim directly to the platform, produce very short latency.
          2. Hippocampal system damage
            1. Impaired ability to learn, not able to swim directly to the platform, maintain long escape latency
            2. but demonstrate the ability to learn and retain the procedures of the task, and to generate and use adaptive strategies
      3. Experiment 2
        1. Demand of the task for task version 2
          1. Constant starting location
        2. Results
          1. H damage did not prevent rats from learning
      4. Interpretation
        1. Variable-start-location
          1. The need of animals to build a representation of the position of the platform in relation to the various visual cues arrayed in the room, independent of particular swimming routes,
          2. and to flexibly express this stored information regardless the start location.
          3. The characteristics of the hippocampal-dependent declarative memory system: representational flexibility and relationality
        2. Constant-start-location
          1. Lack of the demand for flexibility and relationality in the standard test
          2. Emphasis on the representation of spatial relations among the distal cues is eliminated
          3. learning a rigid approach trajectory guided toward a particular cue or cue complex
          4. Procedural memory systems
    4. Hippocampus place cells
      1. These neurons fire only when the rat is in a particular location in its environment and firing is independent of the rat's orientation or ongoing behaviour.
      2. Several lines of evidence indicate that place cell activity reflects an encoding of the spatial relationships between physical stimuli in the environment
        1. place fields move in concert with rotation of salient visual cues, see Fig. 2-23
        2. they scale with enlargement of all features of the environment, see Fig. 2-24
        3. they are altered when the spatial arrangement of cues is disrupted
        4. Place cell activity can be related to the rat's memory about its spatial location, see Fig. 2-25
      3. Relational processing is not exclusively spatial, see Fig. 2-26