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Basic ways that neurons can interact with each other when converting input to output. Summation, which includes both spatial summation and temporal summation, is the process that determines whether or not an action potential will be generated by the combined effects of excitatory and inhibitory signals, both from multiple simultaneous inputs (spatial summation), and from repeated inputs ...
Temporal summation refers to successive excitatory stimuli on the same location of the postsynaptic neuron. Both types of summation are the result of adding together many excitatory potentials; the difference being whether the multiple stimuli are coming from different locations at the same time (spatial) or at different times from the same ...
Temporal summation: When a single synapse inputs that are close together in time, their potentials are also added together. Thus, if a neuron receives an excitatory postsynaptic potential, and then the presynaptic neuron fires again, creating another EPSP, then the membrane of the postsynaptic cell is depolarized by the total sum of all the ...
Fig. 1: Spatial and temporal summation.Two EPSPs innervated in rapid succession sum to produce a larger EPSP, or an action potential in the postsynaptic cell. Coincidence detection relies on separate inputs converging on a common target.
Electrotonic potentials can sum spatially or temporally. Spatial summation is the combination of multiple sources of ion influx (multiple channels within a dendrite, or channels within multiple dendrites), whereas temporal summation is a gradual increase in overall charge due to repeated influxes in the same location. Because the ionic charge ...
Temporal summation means that the effects of impulses received at the same place can add up if the impulses are received in close temporal succession. Thus the neuron may fire when multiple impulses are received, even if each impulse on its own would not be sufficient to cause firing.
The main difference to the voltage equation of the SRM introduced above is that in the term containing the refractory kernel () there is no summation sign over past spikes: only the most recent spike (denoted as the time ^) matters. Another difference is that the threshold is constant.
The larger a time constant is, the slower the rise or fall of the potential of a neuron. A long time constant can result in temporal summation, or the algebraic summation of repeated potentials. A short time constant rather produces a coincidence detector through spatial summation.