The purpose of this study is to capture sensorimotor ankle function in a chronic stroke population through validation of novel, experimental metrics and their comparison with established, clinical measures of function. For this purpose, the researchers will evaluate various single-joint, impairment-level measures such as visuomotor tracking performance and proprioception as well as functional-level measures including spatiotemporal gait (e.g., gait speed and stride length/time) and standardized clinical scales. This study will be carried out in chronic stroke patients as well as age-matched healthy controls. Results will help the researchers identify more quantitative metrics that can be used to monitor and rehabilitate sensorimotor function following stroke.

The purpose of this study is to capture sensorimotor ankle function in a chronic stroke population through validation of novel, experimental metrics and their comparison with established, clinical measures of function. Target populations will perform various single-joint ankle tasks (i.e., dorsiflexion and plantarflexion), assessing the quality of their movements during visuomotor tracking, goal-directed movements and unilateral/bilateral tests of joint position and force sense. Collecting these data will delineate which measures of ankle function are specific to chronic stroke, as well as sensitivity to the severity of stroke, assessed via the Fugl-Meyer Assessment for the Lower Extremity. In addition, the investigators will determine the relationship between deficits in proprioception and assessments which integrate multiple feedback modalities (i.e., proprioception, motor control and vision) to assess the role of peripheral sensory feedback in performing ankle movements post-stroke. The investigators will correlate measures of ankle impairment to clinical scales commonly used in physical therapy. As a first step, the investigators will directly compare these ankle measures to clinical tests of ankle sensation and motor control to demonstrate improvements in assessment sensitivity with this method. Furthermore, the investigators will correlate these ankle measures with clinical measures of lower-limb function during ambulatory and balance tasks, to better understand the contribution of ankle impairments to dynamic, multi-joint activities in chronic stroke.

Inclusion criteria

• 40 - 80 years of age, inclusive
• Normal hearing and vision, can be corrected
• No skin allergies to adhesive material, conductive paste, or silver
• Ability to walk >10m independently on level ground without an assistive device or bracing
• Able to understand and give informed consent
• Able to understand and speak English

Inclusion criteria specific for healthy participants:

• No neurological disorders
• Absence of pathology that could cause abnormal movements of extremities (e.g., epilepsy, stroke, marked arthritis, chronic pain, musculoskeletal injuries)

Inclusion criteria specific for participants post-stroke:

• Unilateral, supratentorial ischemic or hemorrhagic stroke ≥ six months prior
• Minimum activation against gravity for dorsiflexion and plantarflexion, equivalent to a Manual Muscle Test (MMT) score of ≥ +2
• Self-selected walking speed is less than 1.2 m/s

Exclusion criteria

• Cognitive limitations that would prevent playing games
• Adults unable to consent, pregnant women, children, or prisoners
• Infection, wounds, or graft sites on lower limbs
• History of sustained non-prescribed drug use or substance abuse (as reported by subject; current nicotine use is allowed)
• History of peripheral nerve injury
• Severe hip, knee, or ankle arthritis
• Recent fracture or osteoporosis (as reported by subject)
• Bone or joint instability in the lower limb
• Severe pain syndromes affecting any part of the lower limbs
• Fixed contractures affecting the lower limbs
• Medical (cardiac, renal, hepatic, oncological) or psychiatric disease that would interfere with study procedures
• Inability or unwillingness to perform study-required activities
• Prior neurosurgical procedures

Exclusion criteria specific for healthy participants:

- Any neurological diseases (e.g., stroke, Parkinson's disease or other neurodegenerative disorder, severe dementia, brain injury, spinal cord injury, multiple sclerosis, or cancer of the central nervous system)

Exclusion criteria specific for participants post-stroke:

• Co-existence of other neurological diseases (e.g., Parkinson's disease or other neurodegenerative disorder, severe dementia, brain injury, spinal cord injury, multiple sclerosis, or cancer of the central nervous system)
• Botox (botulinum toxin) injection to lower limbs within the prior 3 months
• Significant spasticity or contracture in the lower limbs (Modified Ashworth Scale score of 4)
• Severe aphasia
• Significant loss of sensation in the lower limbs

Chronic patients post-stroke and healthy individuals as controls