Neuronal dendrites collect excitatory synaptic inputs from presynaptic neurons and convey them to the soma. This integrative signal conversion occurs in a nonlinear manner. Most of the previous studies, however, have investigated excitatory synaptic interactions by activating synapses artificially. It remains to be elucidated how dendrites generate somatic depolarization via intrinsically emerging spatiotemporal patterns of synaptic excitation, which are usually accompanied by inhibitory activity. Thus, it is important to know the functional association of synaptic activities with somatic depolarization under physiological condition. We developed functional multi-spine calcium imaging, which could en masse visualizes activities of up to 313 individual synapses into a single neuron at 100-300 frames per second in a confocal field of approximately 150 Χ 150 μm². We discovered that synaptic inputs did not always induce somatic depolarization. Only specific combinations of synchronized synaptic inputs seemed to have the impact of soma. In addition, this decoupling of synapse and soma was alleviated by blockade of GABA_A receptors. This blockade was achieved by intracellular perfusion with a GABA_A receptor antagonist and is expected to localize the effect of the antagonist in the recorded cell. This result indicates that inhibitory synaptic inputs invalidate excitatory synaptic activities. Therefore, we suggest that dendrites filter synchronized synaptic inputs arising from specific cell assemblies, depending on whether or not inhibition is timely recruited.