This content is carried over from the previous lecture on learning. ___ The engram is the hypothetical physical change that corresponds to learning something. In relation to this, it was mentioned that the corpus callosum has about 100 billion fibers connecting the two hemispheres of the brain. And if severed, it makes them function singularly, each doing their own jobs. That connection between the two is what allows the brain to work as one piece. In a patient experiencing epilepsy... if you sever the corpus callosum, you alleviate the majority of the symptoms experienced by epilepsy caused by the overwhelming electrical signals that fire in the brain. ## long-term potentiation and long term memory (relation) **Long-Term Potentiation:** The strengthening of connections (*synapses*) between neurons in the brain. It is considered a key cellular mechanism for learning and memory, as it makes it easier for signals to pass between neurons after repeated activation. [[Dendritic branching]] and new synapse formation takes place during the newborn stage. This involves the alteration of synaptic transmissions and results in changes to post-synaptic receptors. ## limbic system structures and memory ### Structures - The hippocampus (LTM consolidation) - Amygdala (conditions fear responses) - Prefrontal cortex - Brain stem - Cerebellum - Hypothalamus With the **removal of the amygdala** (or destruction), our fear responses are gone. Symptoms of anxiety are removed as well. However, this is not done due to ethical concerns of human experimentation