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ch 13 the biology of learning and memory

Terms in this set (68)

- The "weather task" involves both declarative and
implicit memory, the typical example for
demonstrating the role of both hippocampus and
basal ganglia in learning and memory.
-The task is done by giving you 3-4 pieces of information, like pictures on which you predict the weather to be either sunny or rainy.
-. This task resembles the actual task of weather forecasting that estimates the weather by analyzing a few of feature images.
-Perhaps when the first picture is a light bulb instead of a candle, it usually rains. But other two might also indicate probable rain.
-Most normal people quickly adopt a strategy of responding based on one of the pictures, and therefore getting the correct answer most of the time but not always. This is done based on declarative (explicit) memory.
-The fact is that none of the pictures is completely accurate, but each is partly accurate. By attending to all three, you could increase your accuracy.
-After many repetitions, gradually people start doing better, eventually approaching 100% correct. This is the process of implicit memory.
-People with amnesia from hippocampal damage perform randomly on the weather task for many trials, because they form no declarative memories and they cannot keep the memory that any particular symbol is usually a signal for one type of weather or the other. However, if they continue for long enough, they show gradual improvement based on habits supported by the basal ganglia
-This suggests that the hippocampus is more important for declarative (explicit) memory and the basal ganglia is more important for procedural (implicit) memory. Nearly all tasks activate both areas, and it is possible to shift from one type of memory to the other, even on the same task.
Neurobiochemical mechanisms of LTP are known to depend on changes at glutamate and GABA primarily in the postsynaptic neuron (Refer to chapter 3).
1. In a few cases, LTP depends on changes at GABA synapses.
2. Most cases of LTP depend on changes at glutamate receptors. This occurs at several types of receptor sites including the ionotropic receptors:
AMPA receptors;
NMDA receptors.
-. The AMPA receptor and the NMDA receptor are both usually excited by the neurotransmitter glutamate, but can respond to drugs abbreviated AMPA and NMDA respectively.
-Both are ionotropic receptors. That is, when they are stimulated by glutamte, they open a channel to let ions enter the postsynaptic cell.
-The AMPA receptor is a typical ionotropic receptor that opens sodium channels after bound by glutamate.
-The NMDA receptor, however, is different: Its response to the transmitter glutamate depends on the degree of polarization across the membrane.
-. When glutamate attaches to an NMDA receptor while the membrane is at its resting potential, the ion channel is usually blocked by magnesium ions. (Mg2+ ions, positively charged, are attracted to the negative charge inside the cells but do not fit through the NMDA channel.)
-About the only way to activate NMDA receptors is first to repeatedly stimulate nearby AMPA glutamate receptors, thereby depolarizing the dendrite. Depolarization repels the magnesium ions and allows glutamate to open NMDA channels so that both sodium and calcium ions can enter the cell.
-Suppose an axon releases glutamate repeatedly. And more, let's say to activate two axons repeatedly, side by side on the same dendrite. So many sodium ions enter through the AMPA channels that the dendrite becomes strongly depolarized, which causes to repel the magnesium ions, enabling glutamate to open the
NMDA channel.