Lecture7_revised

Lecture7_revised - Psychology 110: Biological Psychology...

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1 Psychology 110: Biological Psychology Lecture 7: Cellular mechanisms of learning and memory
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2 Recap of Lecture 6 we looked at the development of the nervous system from the embryo to adulthood areas of the cortex are able to expand, contract or subsume another function entirely during the course of development there are ‘sensitive periods’ where experience has a much more dramatic effect on the nervous system
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3 Outline of Lecture 7 in order to study learning and memory, neuroscientists require a ‘model’ system. We will look at some of these systems and the learning that they are capable of. we will explore the cellular and molecular mechanisms that underpin these simple forms of learning
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4 Sherrington Nobel Prize “The nerve cell directs its pent-up energy towards amplifying its connections with its fellow, in response to the events which stir it up. Hence it is capable of an education unknown to other tissues.”
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5 A model system of learning Kandel Nobel Prize SEA SLUG Aplysia californica HEAD
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6 Aplysia: the behavior During normal locomotion the aplysia’s siphon is fully extended. A mild touch causes the aplysia to contract its gill which retracts the siphon. A stronger touch causes the animal to release a cloud of ink.
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7 Aplysia: the circuit and the learning SIPHON 24 SENSORY NEURONS 6 MOTOR NEURONS GILL This circuit exhibits both short-term and long-term learning: 1. Short term habituation – if the siphon is repeatedly stimulated over the course of an hour the animal gradually stops contracting its gill. 2. Long term habituation – if the animal undergoes repeated habituation sessions the habituation takes place more and more rapidly. Habituation is one of the simplest forms of learning that is taking place all the time. For example, you don’t notice the feel of the clothes on your back, even though that sensory stimulation is present throughout the day.
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8 Aplysia: cellular mechanisms Short-term habituation arises due to a decrease in the release of neurotransmitter from the sensory neuron. Fewer vesicles are released per action potential, which in turn arises due to a decrease in Ca 2+ influx.
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9 Aplysia: cellular mechanisms Active zones are areas of the synaptic membrane where vesicles collect ready to be released. In the synapse that has undergone long-term habituation there is a decease in the number of these active zones, their size, and the number of vesicles associated with each zone.
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10 Aplysia: cellular mechanisms Long-term habituation arises due to structural changes in the synapse. For example: decrease in the number of active zones per synapse decrease in the total number of synapses per neuron and the extent of axonal branching
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Lecture7_revised - Psychology 110: Biological Psychology...

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