Why is Nibbanna unconditioned if it's dependent on mind & brain Often it is said that nibbana is unconditioned, but nibbana is definitely dependent on other conditions. Also, according to modern psychology nothing can be 'eliminated' (greed, hatred and delusion in this case). Once learned, never able to unlearn. A skill, therefore zu can become either more efficient or less efficient, so why is it in Religion that something can be absolutely eliminated, whereas psychology tells us differently?
Often it is said that nibbana is unconditioned


True, Nibbana is unconditioned


  but nibbana is definitely dependent on other conditions


False. This statement cannot be backed-up by any reference from Pali canon.


  Also, according to modern psychology........


You cannot explain Dhamma with modern Sciences.

WHY??

There is a true nature in this world. That is the nature of causes and effects. An effect is made by many causes and that effect will cause many other effects in several ways. (This is a very complex, hard to understand, hard to see, and very deep truth which has been taught in the "Book of Causal Relationships or Patthana Pakarana" in Pali canon. There have been mentioned 24 modes of conditionality). Only a lord Buddha can see this ultimate truth with his own wisdom without the guidance of a teacher. No other can.

Scientific method is the foundation for all modern sciences. In scientific method you carefully observe something or a pattern in the world.

Observation:


  Once learned, never able to unlearn.


Then a hypothesis is developed upon that observation. 

Hypothesis:


  nothing can be 'eliminated' (greed, hatred and delusion,...)


Then a prediction is developed and carried out an experiment to prove the hypothesis.
At the end a conclusion has been made whether the hypothesis can be rejected or cannot be rejected. There lies the limitation of scientific method. An experiment can only support a hypothesis but cannot prove the hypothesis. So, a hypothesis can be true only under the conditions which the experiments carried out to support it. This is the reason one hypothesis is criticized and proved false by another over the time. 

Scientists may explain a natural phenomenon with theories well supported by extensive amount of researches. And yes, that would have been true for a while until they find another behavior within that phenomenon which cannot be explained with the same theory. For example some phenomenon cannot be explained with Newtonian Physics but they can be well explained with Quantum Physics.

Dhamma cannot be criticized or argued. It is true for all the time.