Intermuscular Coherence as a Biomarker for ALS

Inclusion Criteria: * AIM 1: Patients with arm or leg weakness, spastic gait, muscle wasting and/or fasciculations (muscle twitching), dysphagia (difficulty swallowing), dysarthria (difficulty speaking), shortness of breath, hyperreflexia or pathological reflexes, or findings of muscle denervation in previous needle electromyography (EMG) studies. * AIM 2: Subjects between 20 and 90 years of age. * AIM 3: Subjects will be selected from among Aim 1 patients who carry an Awaji (without IMC) category of Possible, Probable, or Definite ALS. Exclusion Criteria: * AIM 1: 1. Classified as probable or definite ALS by Awaji criteria prior to initial study evaluation 2. Have significant sensory loss in the weak or spastic limbs 3. Have significant musculoskeletal or neuropathic pain 4. Have an inability or are unwilling to provide informed consent 5. Are unable to perform the study-related task 6. Are taking baclofen or benzodiazepines 7. Have a known non-ALS cause for symptoms * AIM 2: 1. Have a history of neurological disorders such as stroke, neuropathy, or myopathy 2. Have significant pain or sensory loss 3. Are taking baclofen or sedatives such as benzodiazepines 4. Lack of cognitive ability or willingness to provide informed consent * AIM 3: 1. Were unclassified according to the Awaji category or had a defined ALS mimic 2. Are taking baclofen, sedatives or benzodiazepines. NOTE: Participation in a therapeutic clinical trial is NOT an exclusion criterion since this study would not interfere with any potential interventions.