title: Authors' reply to the comment by Ruan.
authors.affiliation: Institute of Neuroscience, Comparative Biology Centre, The Medical School, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: J V
authors.initials: JV
authors.lastname: Roughan
authors.affiliation: Institute of Neuroscience, Comparative Biology Centre, The Medical School, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: H G M J
authors.initials: HG
authors.lastname: Bertrand
authors.affiliation: Institute of Neuroscience, Comparative Biology Centre, The Medical School, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: H M
authors.initials: HM
authors.lastname: Isles