Spatial summation at a synapse refers to:

• A Sequential EPSPs from a single presynaptic neuron adding up over time
• B Increasing amplitude of EPSPs with repeated stimulation
• C Inhibition of a synapse by a neighboring GABA-ergic neuron
• D Simultaneous EPSPs from multiple presynaptic neurons summing at a postsynaptic neuron ✓

Explanation

Spatial summation occurs when EPSPs from multiple different presynaptic neurons arrive simultaneously at a single postsynaptic neuron. The depolarizations from each synaptic input add together at the axon hillock, and if the sum exceeds the threshold, an action potential fires. Temporal summation, in contrast, involves repeated EPSPs from a single presynaptic neuron arriving in rapid succession before the previous EPSP decays.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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