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Principal Investigator: JESSE C. DEAN
Organization: RALPH H JOHNSON VA MEDICAL CENTER
Fiscal Year: 2024
Funding agency: Veterans Affairs
After a stroke, deficits in the control of standing balance contribute to a decreased quality of life, decreased
functional mobility, and an increased risk of falls. Unfortunately, rehabilitation methods that have successfully
reduced fall incidence in older adults (e.g., targeted strengthening exercises, perturbation training) have not yet
shown the same benefits among people with chronic stroke (PwCS). This lack of success is likely due in part to
these interventions not including a component that targets the somatosensory deficits that contribute to losses
of balance and are quite common among PwCS.
The objective of this proposal is to design a novel multisensory augmentation approach to improve the control
of standing balance in PwCS. With sensory augmentation, artificial feedback provides the nervous system with
information about the dynamic state of the body, which can be used to prevent losses of balance. Such
methods have been used to improve balance among individuals with vestibular deficits, primarily by applying
vibratory stimuli to the trunk that provide information about body sway. However, three primary barriers have
prevented the effective use of this approach among PwCS. First, these methods rely on cognitive processing
to interpret and respond to the novel source of feedback, while many PwCS have cognitive deficits. Second,
the focus on a single source of augmented feedback does not account for the extensive variability in how
PwCS respond to sensory stimulation. Finally, it is presently unclear whether sensory augmentation would be
more effectively applied among PwCS as a training tool (i.e., used temporarily during rehabilitation) or as an
assistive tool (i.e., a device worn during daily activities in the community). The proposed study will address
each of these barriers, centered around the hypothesis that targeting somatosensory augmentation toward the
feedback sources that are most useful for an individual patient will improve post-stroke balance performance.
This hypothesis will be addressed through three Specific Aims.
The first Specific Aim is to characterize changes in balance performance with augmented sensory feedback
among PwCS. Four distinct sources of somatosensory feedback will be augmented (trunk tactile sense, hip
proprioception, ankle proprioception, foot sole cutaneous sense), each of which can contribute to the control of
mediolateral balance. The relative effectiveness of each type of augmentation will be quantified for individual
participants, as will the ability to predict this effectiveness from brief sensory perturbations – which would be of
great value in quickly identifying an appropriate augmentation approach. The second Specific Aim is to assess
the feasibility and effectiveness of human-in-the-loop optimization of multisensory augmentation. Given the
many sources of sensory feedback that can contribute to balance control, this use of novel optimization
methods to identify the best stimulation paradigm to improve an individual’s balance would increase the
likelihood of sensory augmentation having an important clinical impact. The third Specific Aim is to determine
whether multisensory augmentation produces sustained balance improvements when applied as either a
training device or as an assistive device. Here, both training effects (e.g., improved balance when
augmentation is not applied) and assistive effects (e.g., continuously improved balance over long periods of
augmentation) will be assessed over the course of a 10-week intervention.
The proposed project has a foundation in the neurophysiology of sensorimotor balance control, applying
sensory augmentation methods that are based on prior rigorous basic science research. This approach will
thus further the field’s understanding of the relationship between sensory feedback and balance, while
simultaneously increasing the probability of providing clinically relevant insight into the important problem of
post-stroke balance deficits.
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