Concept
Impedance
What a circuit presents to a signal at a given frequency — the quantity that decides whether an electrode can hear a neuron, or a coil can reach one.
From the EE side
From the neuro side
Every interface between metal and tissue is an impedance, and almost every constraint on recording or stimulating something in the body turns out to be a statement about it.
Nearby concepts
All topics under Impedance
- Cochlear implants 1991 An electrode array in the cochlea driven by a filter bank, which restores speech understanding using a couple of dozen channels where the ear has thousands.
- Deep brain stimulation 1987 Chronically implanted electrodes delivering continuous high-frequency pulses, which treat Parkinsonian symptoms effectively while nobody fully agrees on why.
- Transcranial magnetic stimulation 1985 Discharging a capacitor bank through a coil induces enough electric field inside the skull to fire cortical neurons, making non-invasive stimulation of a chosen region possible.
- The patch clamp 1976 A glass pipette sealed against a membrane made the current through single ion channels measurable, turning channels from inference into instrument readings.
- Microelectrode arrays 1972 Photolithographed electrode grids traded single-channel resolution for many cells at once, which is what turned single-unit recording into population dynamics.
- Cable theory 1959 Treating a dendrite as a leaky transmission line, borrowed from nineteenth-century telegraph engineering, which showed that dendrites compute rather than merely collect.
- The Hodgkin–Huxley model 1952 Circuit theory borrowed to explain the axon as a capacitor with voltage-dependent conductances — then handed back decades later as the template for analog silicon neurons.
- The voltage clamp 1949 A feedback amplifier that holds membrane potential at a commanded value and reports the current needed to do it, which is what turned excitability into a measurable quantity.
- Electroencephalography 1929 Microvolt potentials measured at the scalp, which established that the brain has continuous electrical rhythms and states rather than only responses to stimuli.