"I have a question about free-will. An atheist objected that we don't have free will because neurology has demonstrated that specific neurons fire before we are under the impression that we are making a free choice. Do you know where he is going with this, and what a response to this would be?"

      The objection here is a double-edged sword and need not entail that
free will does not exist.  The other end of the blade is that the notion of
determinism is not true.  In other words, the argument given here does not
warrant the conclusion that free will does not exist.  Rather, what this
suggests, given the apparent intuition that free will is an authentic
property of human free creatures, is that the mind is not merely a set of
specific neurons firing in the brain.  Indeed, many Christian dualists use
the reality of free will in their apologetic to show why there must be
something beyond the mere physical.  Secular philosophers who oppose
determinism go on to show how moral culpability, value, and ethics are all
meaningless if determinism is true.
     But precisely how should we respond to this atheist friend of yours?
I think I would emphasize what I started out by saying - that all we know
from neurophysiology is that there is a close correspondence between the
choices we make and certain neurons in the brain.  Even one of the greatest
materialists defending reductionism over dualism admits that dualism can
possibly account for this correspondence (see Paul Churchland, A
Neurocomputational Perspective, p. 72).  What the materialist would have to
show is that only neurons are in play and there is nothing else contributing
to the decision-making in human creatures.  This, of course, is quite the
tall order!
     You could also deflect this attack if you are addressing other, more
pressing issues by noting that some Christians are in fact materialists too
(think of Lynne Rudder Baker and Peter van Inwagen).  As Professor John Hick
has rightly pointed out in his small Philosophy of Religion text, the
Christian hope is ultimately not to be disembodied but to be resurrected in
physical form.  Belief in an intermediate state of disembodiment is an
optional component to Christian theology - for better or worse.