As a result of my growing interest in neuroscience, I have begun to try and understand the functioning of the brain. However, I am always confronted by the following questions:
The brain is a highly specialized organ with innumerable nuclei and pathways, and yet the brain of one individual is surprisingly similar to that of another. Hence, it must be the case that the structure of the brain must, in part, be determined by our genes. If this assessment is correct, how much is our brain structure dependent on our genes?
Now consider the case of a newborn and suppose his/her brain structure has been established somehow. As he/she grows, the brain starts taking sensory input and learns to process it better through neuroplasticity. If so, then why does everyone's, say amygdala only process fear, anxiety, etc. What prevents it from maintaining autonomous functions? Are the functions of different parts also determined by our genetics? (Is neuroplasticity the only force dictating learning?)
In other words, why are all human brains so similar in brain structure, specialization of their parts and functioning?