What Are Some of the Challenges in Linking Correlation of Changes

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The Answer is There are many different answers to this question. It has been difficult to show causation between synaptic changes and learning in mammals. To show that changes in synaptic strength result in learning it is necessary to identify which neurons are activated and measure how their synaptic weight changes with a task. However, the neurons in the hippocampus that are activated during a task are distributed and therefore it is difficult to know exactly which neurons are involved. It is also difficult to show that blocking those specific synapses block learning, or that activating specific synapses trigger a memory. In addition, as discussed in the next section of the textbook, memories are not stored in the hippocampus for long periods of time and there are many ways to access those circuits. This makes tracing the memory even more difficult.
There are a couple of experiments discussed that link changes in synaptic strength to learning and memory. One experiment used multi-electrode arrays in the hippocampus to identify some of the CA1 neurons that were potentiated after training. After training, the input fibers to the CA1 neurons were activated with high frequency stimulation to induce LTP and it was found that LTP was occluded from these neurons. Therefore these synapses could no longer be potentiated after they had already been potentiated in one learning task. In a second experiment investigators artificially induced LTP in many synapses in the hippocampus. These rats did not perform well on the Morris water maze suggesting their synapses could not undergo further LTP and the rat could therefore not learn well.

What Are Some of the Challenges in Linking Correlation of Changes

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