Political correctness.  Many topics are off limits because we do not want to address the findings.

Among others,  ethical concerns and the lack of a comprehensive and reliable framework in which cognitive affective, and psychomotor abilities are integrated to each other in terms of their neurological and functional basis more or less restrict the further developemtn of brain science. I think the technological developments are only a matter of time. However, these two issues that I have mentioned are the prominent obstacles. Nevertheless, I should also mention that current neurobological and neuropsychological scientific research begins to  examine the topics regarding human brain and its functions in a holistic manner, which is highly promising. 

Anthony, that is an interesting answer.  Could you please give some examples?

"Could you please give some examples?"

I am an Independent Scholar interested in many topics.  This scope is very useful since there are numerous ares of research where it would be inadvisable or even dangerous to proceed, in which case I can switch to a less contentious topic.  Subject areas where I hesitate to write freely include:

• IQ differences between countries and ethnic groups
• Disadvantages of prolonged breastfeeding
• Seduction of adults by minors
• Alcohol and rape
• Criminal responsibility and mental illness
• Safe cycling (the prime responsible agent is the cyclist)
• High infant mortality is attributable to maternal behavior
• Education is an ideological evidence-free area 
• Mental illness has an otological, not neurological, foundation
• Concussion is not due to brain injury

    There are plenty more examples which I can't think of at present.

The last two are not politically incorrect topics, although they do seem scientifically implausible.  It is not evident why the topic of criminal responsibility and mental illness  should be considered politically incorrect either.

"It is not evident why the topic of criminal responsibility and mental illness should be considered politically incorrect either."

   Perhaps not, in the sense that I have written about this on RG and elsewhere, and I have had no hesitation in stating that the US legal system is barbaric and uncivilised.   However, how far would candidates for office in the USA get if they said it was disgraceful that psychotic murderers were kept on Death Row for decades, then executed? 

"The last two are not politically incorrect topics, although they do seem scientifically implausible."

Yes, you are right.   However, were I applying for an academic or mental health position, I really would be mad to mention these theories, so it is more a question of self-censorship..

I suppose that one obstacle is the fact that we cannot directly examine the human neurogenesis, synaptogenesis, and other structural changes at the brain cell level. Perhaps the scientific-technological progress should resolve this problem in the future.  

Neurogenesis in development has been closely examined, and I believe that neurogenesis in adult organisms has been tracked from the genesis of the cells to their migration and even integration into new memory circuits in the hippocampus.  And much has been written about the growth of gray matter in the brain, mostly from the growth of synapses.  MRI gives us global pictures, and post-morten examination of rodent brains can give us microscopic detail.  An article on memory in the latest issue of Scientific American indicates how to refine the observation to individual neurons in vivo.