On 2013 Dec 10, Lorene M Nelson commented:

From the senior author of the original article: Please note that a reply to this letter by Hill-Burns et al. was published in the European Journal of Neurology; however, PubMed failed to index the reply letter. For those who are interested, here is the citation for the reply letter: Popat RA et al., Eur J Neurol 2011;18:e109.

On 2013 Dec 10, Lorene M Nelson commented:

From the senior author of the original article: Please note that a reply to this letter by Hill-Burns et al. was published in the European Journal of Neurology; however, PubMed failed to index the reply letter. For those who are interested, here is the citation for the reply letter: Popat RA et al., Eur J Neurol 2011;18:e109.