Inclusion criteria:  Age >18 years and able to give informed written or verbal (in the presence of two witnesses) consent.  In the case of non-control subjects, a clinical diagnosis of:  (i) Probable frontotemporal dementia (FTD) including behavioural variant FTD, semantic dementia or primary progressive aphasia) with supportive brain imaging or known FTD causing genetic mutation (ii) Multiple sclerosis (MS) according to the McDonald criteria (Polman et al., 2011) or (iii) Possible, probable or definite amyotrophic lateral sclerosis (ALS) according to the El Escorial Criteria Revised (Brooks et al. 2000)  Exclusion criteria:  Any diagnosed neurological/muscular disease other than ALS, MS or FTD Use of neuro- or myo-modulatory medications except riluzole Inability to participate due to disease-related motor symptoms (e.g. inability to sit for the required time or click the mouse to respond) Upper body metallic implants History of seizure disorders in the participant or immediate family members Anxiety-induced fainting Regular migraine Evidence of significant respiratory insufficiency Sleep time >2 hours below normal and/or alcohol consumption the night before data collection (in which case, recording session will be rescheduled).