How does spatial summation work?

Spatial summation refers to the process by which postsynaptic neurons integrate excitatory and inhibitory signals from multiple presynaptic neurons across different locations at the same time. When several presynaptic neurons release neurotransmitters and generate excitatory postsynaptic potentials (EPSPs) on the same postsynaptic neuron, these potentials can combine to reach the threshold needed to trigger an action potential.

In the context of this question, the correct option highlights that spatial summation specifically involves combining graded potentials—signals that can vary in magnitude—from different excitatory neurons. This is a fundamental mechanism by which neurons process information and decide whether to fire an action potential based on the sum of inputs they receive from various sources. This ability to integrate signals from multiple neurons is crucial in ensuring the proper functioning of neural circuits and is pivotal for processes such as sensation and motor control.

Understanding spatial summation is essential in neurobiology since it illustrates how neurons can work together to influence behavior and physiological responses in the nervous system.