The release of serotonin leads to a transient strengthening of the connection between the sensory and motor neuron (fig. 4.5, center). When repeated shocks and repeated release of serotonin are paired with the firing of the sensory neuron in associative learning, a signal is sent to the nucleus of the sensory neuron. This signal activates a gene, CREB-1, which leads to the growth of new connections between the sensory and motor neuron (fig. 4.5, right) (Bailey and Chen 1983; Kandel 2001). These connections are what enable a memory to persist. So if you remember anything of what you have read
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