chapter24.txt

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eibrahim
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chapter24.txt
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2010-12-16 18:24:51
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ch24
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  1. How do we know there are different types of memories?
    Brain lesions
  2. Give examples of the following memory types:
    • Declarative
    • Procedural
    • Associations
    • Emotional responses
    • Declarative: facts, events
    • Procedural: skills/habits
    • Associations: food associated with saliva
    • Emotional responses: fear
  3. What are the basic differences between declarative and non-declarative memories?
    • Declarative: conscious recollection, easily formed and forgotten
    • Non-declarative: unconscious knowledge, long-term experience, less forgetting
  4. What are the differences between working memory, short-term memory, long-term memory? How do we know these are different types?
    • Working: temporary info storage
    • Short term: lasts seconds to hours and are vulnerable to disruption
    • Long term: you can recall days, months, years after they were stored, requires rehearsal
    • We know the different types because the memories last different amounts of time.
  5. What is consolidation?
    The process of storing new info into long term memory
  6. Where is sensory information stored in the brain for short-term memories?
    Wherever the information is processed in (ie. Visual information stored in visual cortex)
  7. Define retrograde and anterograde amnesias.
    • Retrograde: forget things you already knew
    • Anterograde: inability to form new memories
  8. What is one piece of evidence that memory storage changes over time?
    Memory loss
  9. Explain Hebb�s model of short-term memory.
    Whatever cells you use to remember a stimulus are the same cells you used to perceive the stimulus with.
  10. What was Hebb�s proposal for the relationship between neurons that perceive or respond to a stimulus and neurons that are active during a memory of that stimulus?
    The internal representation of an object/event consists of all the cortical cells that are activated by that stimulus. (ie. The neurons that perceive/respond to a stimulus are the same as the ones that are active during a memory of that stimulus)
  11. What is a cell assembly? How does a cell assembly encode a short-term memory?
    • Cell assembly: group of simultaneously active neurons
    • As long as activity reverberated through the connections of the cell assembly, the stimulus is held in short term memory.
  12. How does Hebb describe consolidation?
    Consolidation is by a �growth process� that made the reciprocal connections more effective�if activation of the cell assembly persisted long enough, consolidation would occur�neurons that fired together would wire together.
  13. If a memory is based on a single sensory modality, where would it be stored?
    Within that sensory cortex
  14. Describe an experiment with monkeys that supports the idea that visual information is stored in a higher-order visual cortex.
    • Monkey is given a circle and then later is given a triangle in which he does not recognize the circle as his legion gets bigger.
    • Be able to locate the inferotemporal cortex on a diagram. What does this region do?
  15. a-Be able to describe the experiment shown in Figure 24.6. b-How does the experiment support the idea that visual information is stored as a memory in the inferotemporal cortex? c- Is this neuron showing that it is �learning� and remembering a face?
    • a-Responses to faces in inferotemporal cortex: suggests IT neurons may encode memories of faces. Experiment: monkeys are alert and an electrode is used to record from an IT neuron. Initially, the response of the neuron to multiple presentations of familiar faces�other monkeys the subject frequently sees�is recorded. The face cell responds more to some faces than to others. When new faces unfamiliar to the monkey are introduced for the first time, the cell responds at about the same moderate level to all of them. However, with a couple of additional exposures, the response changes, such that some faces evoke a significantly greater response than others. The cell is becoming selevtive in its response to these new stimuli. With continued presentation of the same group of faces, the response of the neuron to each patter becomes more stable.
    • b- memory for association stored in high-order visual cortex
    • c- inferotemoral cortex is both a visual area and memory area
  16. What is the point of Figure 24.7
    Functional MRI recordings of brain activity in bird and car experts. Bird experts showed greater activity in extrastriate visual areas in response to birds than other objects. Extrastriate cortex in car experts was more activated by images of cars.�reflects highly developed specialized processing of visual features needed to classify particular examples.
  17. a-What happens in humans when the temporal lobe is stimulated by slight electrical stimulation? b-Does this indicate that memories are stored in the temporal lobe in humans? c-Why is this not a straight-forward finding?
    • a-elicits complex sensory experiences -- voices, images, sensations, hallucination-like
    • b-not known because it is unknown if these are past experiences (all patients may have abnormal cortex associated with epilepsy)
    • c- Contradictory evidence: When these �memory� regions of the temporal lobe are removed surgically, the memory could be evoked by stimulating other areas
  18. a-What part of H.M.�s brain was removed? b-What were his symptoms of memory loss? c-What memory types were intact?
    • a-temporal lobe: amygdala, hippocampus, cortex
    • b-severe anterograde amnesia, partial retrograde amnesia for several years, cannot form new declarative memories
    • c- long term, working, procedural
  19. Which memory types are processed in these regions (declarative, procedural, working memory, short-term, long-term)? 1) Medial temporal lobes (specifically the perirhinal cortex and entorhinal cortex) 2) The hippocampus 3) The diencephalon: fornix, mammillary bodies of the hypothalamus, thalamus 4) The prefrontal and frontal cortex 5) The striatum
    • Medial temporal: declarative, short term
    • Hippocampus: declarative, working, spatial, relational
    • Diencephalon: working
    • Stiatum: procedural
    • Prefrontal cortex: working memory
  20. Describe the delayed-non-match to sample task and explain how this series of experiments showed us that the medial temporal lobe plays a role in short term memory. Which part of the medial temporal lobe seems to contribute the most to short term memory.
    • --Monkey first displaces a sample object to obtain a food reward. After a delay, two objects are shown, and recognition memory is tested by having the animal choose the object that does not match the sample.with delays between the two stimulus presentations of anywhere from a few seconds to 10 minutes, the monkey correctly displaces the non-matching stimulus about 90% of the time.
    • --with a medial temporal lesion, the percentage of trials that were correct decreased significantly, indicating that medial temporal lobe plays a role in short term memory.
    • --perirhinal cortex
  21. a-What part of N.A.�s brain was damaged? b-What were his symptoms? c-What did this case study tell us about memory storage?
    • a-dorsomedial thalamus
    • b-antegrade amnesia, retrograde amnesia for about 2 years, working memory, long-term, procedural memory intact.
    • c-Medial temporal and diencephalic areas interconnected system serving similar type of memory consolidation
  22. a-What part of the brain associated with memory is damaged in Korsakoff�s syndrome? b-How does Korsakoff�s syndrome develop? c-What type of memory impairments are associated with Korsakoff�s syndrome? d-What does Korsakoff�s syndrome tell us about brain regions underlying memory?
    • a-dorsomedial thalamus and mammillary bodies
    • b-thiamin deficiency
    • c-devere anterograde amnesia and severe retrograde amnesia
    • d-diencephalon regions affect memory
  23. What 3 memory functions seem to be associated with the hippocampus?
    Spatial, working, and relational memory
  24. How does a rat with a hippocampal lesion respond to: 1) retrieving food in a radial arm maze? 2) finding a platform in a Morris Water maze? What kind of memory do these studies suggest is processed by the hippocampus?
    • 1) hippocampal lesion affected retrieving food
    • 2) hippocampal lesion did not affect Morris water maze
    • spatial memory
  25. What are place cells? When do they fire? Where in the brain are they located?
    Place cells are certain neurons in the hippocampus that fire when they are stimulated when the person is at a particular object.
  26. What is known in humans about the kind of memory that is processed in the hippocampus? What is the evidence for this?
    Spatial; in PET scans human hippocampus is activated in situations involving virtual or imagined navigation (requires learning, not following arrows)
  27. What is the Relational Memory hypothesis of hippocampal function?
    Highly processed sensory information comes into the hippocampus and nearby cortex --> a memory is formed linking all events happening at a given time.
  28. Describe 2 studies which demonstrate that the striatum plays a role in procedural memory. (One experiment in rats, one in humans)
    • 1) Rats: train rats on new radial maze task to test prodecural memory: lights illuminate arms that contain food, the goal is to retrieve food from lit arms and avoid unlit arms�learned association between light and food�when striatum was damaged this task was affected
    • 2) humans: present 1, 2, or 3 card cues, guess whether associated with a prediction of sun or rain, different probabilities that cues associated with sun or rain, correct or error feedback to the patient, learn a stimulus�response habit
  29. Describe 2 studies which demonstrate that the prefrontal cortex plays a role in working memory. (One experiment in monkeys, one in humans)
    • 1) Humans: Wisconsin card sorting test
    • Cards can be sorted by color, shape, number
    • Subject not told which sorting criteria to use
    • Starts sorting cards, and is told when errors are made
    • Sorting criteria is then switched after 10 correct trials (learned sorting rule)
    • Must have memory for previous cards and errors in order to plan next card placement
    • Prefrontal cortex lesions: difficulty changing sorting category criteria � don�t use data
    • in working memory to change behavior
    • 2) Monkeys: 1) Fixate on a point on a computer screen, Target presented briefly in periphery, Delay, Fixation point disappears and the subject makes a saccadic movement
    • Cell fires throughout the delay in which there is no stimulus

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