You talk a lot about neurological difference but our brains are plastic and neurons are constantly laid down, pruned and rebuilt in different patterns according to our environment and actions. Even if a certain category of people have particular neurological or brainwave patterns, that can be because of what they DO with their brains, rather than what their brain does with them. The most famous example of this is the London taxi drivers in whom the area of the brain responsible for spatial awareness develops as they learn the street map of London. So if you take a step by step approach to modifying your actions, this will modify your feelings, making it easier to modify your actions, and so on. Bio-feedback. However, there may be some early neurological damage that is very hard to repair unless one is very motivated or starts very early.My Answer:
What you say is true for the most part. But in order to create new synapses you need corresponding synapses to trigger such growth. To f.x. expect someone with Down Syndrome to develop an intelligence like that of someone with an IQ of 150 is impossible because the neurological foundation required to do so simply is not there.
Take the example of the Structural Changes in the Hippocampi of London Taxi Drivers. If we imagine one of these drivers had deficiencies in their Hippocampus in conjunction with deficiencies in other parts of the brain to begin with, they would never get the chance to enhance their Spatial Awareness, because they would not have the ability to navigate well enough to drive a car.
If for a moment we imagine the cap driver's car is a person's love for another, and spatial awareness is how well they perform in situations associated with loving... If the person is a psychopath this experiment will never begin, because psychopaths don't have cars. Some have tanks, but more have war planes and can be highly skilled in airspace warfare - most psychopaths can experience aggression and enjoy the excitement related to various forms of aggressive behavior and life styles - and they can learn to drive them very efficiently. But that doesn't help them if they're required to navigate London city in peace time.
This is a crude example, of course, and in reality it is not a question about deficits in one part of the brain, but a combination of differences (I don't like to call it deficits, since lacking in one area often make room for excellence in others) which in combination produces a person with the characteristics that in modern society are poorly understood and accordingly given a stigmatizing label: Psychopath.
To imagine that a psychopathic individual might grow the synaptic network that is required for someone to feel empathy or remorse would be like imagining that someone without a visual cortex might learn to see anyway. They may have eyes like the rest of us, and they may have the blink reflexes, the tear canal may produce fluids under the appropriate circumstances, and they may even learn to turn their eyes in the direction of sound and touch like the rest of us, but they do not have the physical neurological matter required to develop the synaptic network, and that remains a fact no matter how much transmitter is fired in the appropriate area.
That said, psychopathy is a spectrum like everything else, and emotional 'deficiencies' vary. Some psychopaths have some ability to feel some level of empathy (for a short time), and in those cases the question would be whether and how much using the little empathy capacity which is there will be encouraged by experience.
Conclusion: Whereas in principle it may be possible for a psychopath to learn to access some kind of empathic emotion - or remorse (which of the two are more important is matter for debate) - my question remains: Why do we strive to make everybody alike? Why not use the differences that the human race exhibits and benefit from what we can make of it? Again, I am convinced all the differences are here for a reason.
This is in fact part of my argument when I spoke about the problems related to psychopathic children and upbringing here and here.