Electrochemical activation and inhibition of neuromuscular systems through modulation of ion concentrations with ion-selective membranes

Conventional functional electrical stimulation aims to restore functional motor activity of patients with disabilities resulting from spinal cord injury or neurological disorders. However, intervention with functional electrical stimulation in neurological diseases lacks an effective implantable method that suppresses unwanted nerve signals. We have developed an electrochemical method to activate and inhibit a nerve by electrically modulating ion concentrations in situ along the nerve. Using ion-selective membranes to achieve different excitability states of the nerve, we observe either a reduction of the electrical threshold for stimulation by up to approximately 40%, or voluntary, reversible inhibition of nerve signal propagation. This low-threshold electrochemical stimulation method is applicable in current implantable neuroprosthetic devices, whereas the on-demand nerve-blocking mechanism could offer effective clinical intervention in disease states caused by uncontrolled nerve activation, such as epilepsy and chronic pain syndromes.Massachusetts Institute of Technology. Faculty Discretionary Research FundNational Institutes of Health (U.S.) (Award UL1 RR 025758)Harvard Catalyst (Grant

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In bound volumes: Copyright Deposits 1820-186

Coin Configuration Spaces

A coin configuration is a collection of coins (closed disks) in a plane such that the union of all coins is connected while the interiors are disjoint, giving the property that each coin is tangent to at least one other coin. The configuration space C(r1,...,rn) includes all coin configurations with n coins having radii r1,..., rn. Each coin configuration has an associated tangency graph which records the tangent relationships between coins. By studying when the tangency graphs change we get a partition of the configuration space into smaller pieces, which are the flexible spaces. A flexible space then consists of all configurations with the same tangency graph. Building on previous work, we determined the flexible spaces within the configuration space of coins of varying size. We studied how the sizes of the coins affects which tangency graphs are possible and also the boundary relationships between flexible spaces. We use information about boundaries of flexible spaces together with the tools of homology to piece together this configuration space