All subjects underwent detailed neurological examination by a behavioural and movement disorders specialist (K.A.J.), as well as standardized testing of cognitive, behavioural, functional and motor performance. Testing of general cognitive function included the Mini-Mental State Examination (Folstein et al., 1975 (link)) and the Montreal Cognitive Assessment battery (Nasreddine et al., 2005 (link)); assessment of executive function with the Frontal Assessment Battery (Dubois et al., 2000 (link)); assessment of praxis with the Limb Apraxia subscale of the Western Aphasia Battery (Kertesz, 2007 ); assessment of calculation with the calculation subtest of the Montreal Cognitive Assessment battery (Nasreddine et al., 2005 (link)); assessment of facial recognition was performed by asking the subject to select the one famous face from a panel of three similar looking faces, for a total of 10 different panels (norms determined on 50 cognitively normal subjects); assessment of functional performance with the Clinical Dementia Rating Scale (Hughes et al., 1982 (link)); degree of behavioural dysfunction with the Frontal Behavioural Inventory (Kertesz et al., 1997 (link)); assessment of neuropsychiatric features with the brief questionnaire form of the Neuropsychiatric Inventory (Kaufer et al., 2000 (link)); assessment of motor function with the Movement Disorders Society sponsored revision of the Unified Parkinson’s Disease Rating Scale Part III (Goetz et al., 2008 (link)); assessment of eye movement abnormality with the Progressive Supranuclear Palsy Saccadic Impairment Scale (Whitwell et al., 2011b (link)); and documentation of the presence or absence of limb myoclonus, dystonia and falls. A Z-score of >2 SD below the mean on all tests with published or derived mean and standard deviation was considered abnormal.