Learning & Memory

Learning & Memory

1. Stimulus-Response Learning

   • Classical Conditioning
     • Pavlov - Form of learning, association between 2 stimuli
       • Unconditioned Stimulus (US)
         • Food
       • Unconditioned Response (UR)
         • Dog Salivates
       • Conditioned Stimulus (CS)
         • Bell
       • Conditioned Response (CR)
         • Dog Salivates to Bell
   • Instrumental/Operant Conditioning
     • The process by which experiences alters the probability that an animal will perform a given behavior.
     • Punishment
       • Positive
         • Caned for bad behavior
       • Negative
         • Less TV Time for bad behavior
       • Suppresses frequency of response
     • Reinforcement
       • Positive
         • Given sweets for good behavior
       • Negative
         • Taking painkillers to rid headache
       • + Future probability of response

2. Basis of Reinforcement

   • Neural
     • Medial Forebrain Bundle (MFB)
       • Goes from midbrain > basal forebrain
         • Passes through lateral hypothalamus
           • Reward & Pleasure
     • Dopaminergic Systems
       • Nigrostriatal system
       • Mesolimbic system
         • Begins in ventral tegmental area (VTA) > forebrain
       • Mesocortical system
         • Begins in VTA > Prefrontal cortex, Limbic cortex, Hippocampus
     • Nucleus Accumbens
       • Electrical stimulation, Pharmacological stimulation
         • Microdialysis (measures release of neurotransmitters via electric probe)
           • DA is released after MFB/VTA administration; water, food, sex causes release of DA in accumbens
   • Cellular Basis of Learning
     • Hebb's Rule
       • when an axon successfully stimulates a cell it will be stronger in the future
     • Aplysia (marine invertebrate) popular experimental animal
       • Habituation
         • Repetition = no more AP
       • Sensitization
         • Intense stimulus = facilitates serotonin release

3. Long-Term Potentiation

   • long-term increase in the excitability of a neuron to a particular synaptic input caused by repeated high-frequency activity of that input.
     • Mechanism
       • Frequency > 10Hz = LTP
       • Frequency < 10Hz = LTD
       • AP5 blocks NMDA receptors
         • AP5 prevents LTP in field CA1 & dentate gyrus
           • AP5 has no effect on LTP once it has been established
         • NMDA receptor = ionotropic glutamate receptor that controls a calcium channel that is normally blocked by Mg2+
       • Drugs that block the AMPA receptor block LTP after a single stimulus.

4. Perceptual Learning

   • Involves learning to recognize things, not what to do when they are present
     • involves changes in synaptic connections in the visual association cortex that establish new neural circuit
   • Lesion to inferior temporal cortex
     • disrupt the ability to discriminate among visual stimuli.
   • Short-Term Memory
     • Delayed-Matching-To-Sample Task
       • indicate which of several stimuli has just been perceived

5. Relational Learning

   • Anterograde Amnesia
     • Amnesia for events that occur after some disturbance
       • Korsakoff's Syndrome
         • Permanent anterograde amnesia caused by brain damage resulting from chronic alcoholism or malnutrition
           • thiamine (B1) deficiency results in damage to neurons
           • Better implicit than explicit memory
   • Retrograde Amnesia
     • Amnesia for events that preceded some disturbance to the brain
   • Morris Water Maze

6. Case Study of H.M

   • Brain surgery for severe epilepsy - bilateral removal of medial temporal lobe
     • Epilepsy was cured but resulted in complete Anterograde Amnesia
     • Surgery damaged part of hippocampus
       • Hippocampal lesions disrupt navigation in homing pigeons
   • Conclusions
     • 3. Hippocampus is not the location of LTM & is not required for the retrieval of LTM
       • H.M retained past memories
     • 2. Hippocampus is not the location of STM
       • H.M able to carry out conversation
     • 1. Hippocampus is involved in converting STM > LTM
       • when presented with new info, H. M. understood & rememberd it as long as he thought about it but a permanent record of the info was never made
       • (Consolidation)
   • Still capable of perceptual learning, stimulus-response learning, and motor learning
     • Per: Broken lines, Faces & memories
     • SR: Classical conditioned eyeblink response
       • Morris Water Maze
     • Motor: Trace a star in mirror, Pushing button
   • Intact procedural & implicit memory, Poor explicit memory, No declarative memory

7. Declarative Memory

   • Memory that can be consciously/verbally expressed, such as memory for events in a person’s past.

8. Non-Declarative Memory

   • instances of perceptual, stimulus-response, and motor learning that we are not necessarily conscious of
     • does not depend on the hippocampal formation

9. Alzheimer's Disease

   • Severe memory loss associated w aging
     • Strikes 50% over age 85
     • Brain proteins fold abnormally, clump together and interfere with normal neuronal activity
       • amyloid protein produces Aß42 plaques between neurons
       • tau protein produce tangles in cell bodies
   • Better procedural than declarative memory
     • Able to acquire new skills but doesn't remember learning
   • Treatment
     • Drugs that + ACH
     • Rich antioxidant diet
     • block Aß42 production, inoculate with small amounts of Aß42