For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the

The given condition of an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the hyperpolarization of the neuron.

Hyperpolarization is a change in a cell's membrane potential becomes more negative at a particular spot on the neuron's membrane

Thus, the correct answer would be the hyperpolarization of the neuron.

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The potassium ions are positively charged(cations) if the charge is -70mV the outflow of cations will cause a decrease in the potential. The potential will become lower than -70mV.

your answer is "the 1950's"