The ethic of primate research in the UK are getting tough. Interesting read - demonstrates how wuch of the lobbying against primate research is based on spurious claims, like this one:
"...animal species, even monkeys, are physiologically so different from us that animal experimentation will lead to misleading results."
For neuro research, primates are about as close as you can get to humans, for obvious reasons: computer simulations don't do the trick (at all), and lower mammals aren't capable of as complex behaviour. That's not to say that we should inflict senseless pain on an infinite number of monkeys.