microstimulation

Microstimulation refers to the deliberate application of small electrical currents to neural tissue through microelectrodes in order to evoke neural activity. It is used in both experimental neuroscience to probe brain function and in clinical settings to influence neural circuits. Unlike macro- or noninvasive stimulation, microstimulation targets neural populations with relatively high spatial precision.

The technique relies on implanted microelectrode arrays or depth electrodes that deliver short, charge-balanced electrical pulses. Typical pulse widths range from tens to a few hundred microseconds, with currents in the microampere range. Stimulation can be delivered as single pulses or trains at frequencies from tens to thousands of hertz, depending on the goal. Electrode geometry, impedance, and stimulation parameters determine which neurons or axons are activated, influencing the perceptual or behavioral outcome. Stimulation can evoke sensations, motor responses, or changes in neural activity that researchers use to infer causal relationships.

Applications span basic science and clinical domains. In neuroscience, microstimulation helps map cortical and subcortical circuits and test hypotheses about function. In sensory prosthetics, it underpins devices such as cochlear and visual or somatosensory prostheses, where targeted stimulation can produce percepts. Deep brain and thalamic stimulation are used clinically for movement disorders, epilepsy, and psychiatric conditions. Experimental efforts explore restoring sensation after spinal cord injury or interfacing with brain–machine systems.

Safety and limitations center on tissue response and longevity. Repeated stimulation can cause tissue heating, electrode corrosion, and gliosis, potentially reducing selectivity. Charge balance and conservative current levels are maintained to minimize damage, but chronic implants face gradual impedance changes and scarring, which can degrade performance.