What Happens When Neurons Are Stimulated Simultaneously?

Is simultaneous stimulation of several presynaptic neurons considered as spatial summation or temporal summation?

Spatial summation

When several presynaptic neurons are stimulated simultaneously, it is considered as spatial summation. This means that the activity of multiple inputs to a neuron are associated with each other, leading to a combined effect on the neuron's membrane potential.

Spatial summation is different from temporal summation, which occurs when multiple action potentials from a single cell result in a significant change in the membrane potential. In spatial summation, the inputs are coming from different presynaptic neurons.

Both spatial and temporal summation can play a role in determining whether a neuron will reach its threshold for firing an action potential. When these two types of summation act together, they can have a synergistic effect on the neuron's excitability.