About the Authors

Boyd C. P. Ghosh

boydghosh@doctors.org.uk

Affiliations Wessex Neuroscience Centre, Southampton University Hospital NHS Trust, Southampton, Hampshire, United Kingdom, Department of Clinical Neurosciences, Cambridge University, Cambridge, Cambridgeshire, United Kingdom

Roger H. S. Carpenter

Affiliation Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom

James B. Rowe

Affiliations Department of Clinical Neurosciences, Cambridge University, Cambridge, Cambridgeshire, United Kingdom, MRC Cognition and Brain Sciences Unit, Cambridge, Cambridgeshire, United Kingdom, Behavioural and Clinical Neuroscience Institute, Cambridge, Cambridgeshire, United Kingdom

Competing Interests

I have read the journal's policy and Boyd Ghosh has the following conflicts: I have received grants to attend movement disorders meetings in Paris and Toronto from the Fearnside scholarship and the ABN travel grant respectively. I have received payment for lectures related to the differential diagnosis and management of Parkinson's plus disorders from the PSP Association and GlaxoSmithKline. I also serve on the PSP Association advisory panel. James Rowe declares the following: He has received an honorarium for lectures to the Copenhagen University Hospitals and fees for examination of PhD's. He also sits on the PSP association advisory board. Roger Carpenter was an unpaid director of Advanced Clinical Instrumentation that acted as a distributor for the saccadometer, but ceased that role in 2011. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: BCPG JBR. Performed the experiments: BCPG JBR. Analyzed the data: BCPG RHSC JBR. Contributed reagents/materials/analysis tools: RHSC JBR. Wrote the manuscript: BCPG RHSC JBR.