Inputs or information are received by thousands of neurons from other neurons surrounding or around them. However, Summation is the process that makes sure whether the inputs received have the potential to elicit an action or not.
The process of Summation can be grouped into two types, temporal Summation and spatial Summation. Temporal Summation is generated from repeated inputs, and spatial Summation is calculated from simultaneously occurring multiple inputs.
A threshold voltage is achieved to get an action potential. The determination of the threshold voltage is done by the addition of the individual inputs coming from spatial Summation and temporal Summation.
Key Takeaways
- Temporal and spatial summation are two mechanisms by which neurons in the brain integrate multiple inputs to generate an output signal.
- Temporal summation refers to integrating multiple signals over time, while spatial summation refers to integrating signals from multiple neurons simultaneously.
- Temporal summation is essential for detecting changes in stimuli over time, while spatial summation is important for detecting the location of stimuli in space.
Temporal vs Spatial Summation
Spatial summation is when several weak signals from various locations are combined into a single stronger signal, where signals come from multiple simultaneous inputs. While a single source’s quick succession of weak pulses is combined into a single, big signal called temporal summation.
Temporal Summation refers to Summation in which the action potentials of many of the presynaptic neurons trigger postsynaptic action potentials.
In the case of temporal Summation, the duration of the postsynaptic action potential is higher than the interval between the action potentials.
Spatial Summation exists when an action potential is triggered by inputs and information from multiple neurons. The action potential comes mainly from the dendrites, and adding the knowledge, and the inputs gives the spatial Summation.
Comparison Table
| Parameters of Comparison | Temporal Summation | Spatial Summation |
|---|---|---|
| Definition | Temporal summation is a sensory summary incorporating single stimuli over a short period. | Spatial Summation is a kind of sensory summation, which at the same time, involves several neurons separated spatially during stimulation. |
| Presynaptic Neuron | Involves a single presynaptic neuron. | Involves multiple presynaptic neurons. |
| Mechanism | The generation of the subthreshold is done by only one presynaptic neuron. | Multiple presynaptic neurons do the generation of the subthreshold. |
| Efficiency | Temporal summation is less efficient. | Spatial Summation is more efficient. |
| Frequency | Temporal summation occurs at high frequency. | Spatial summation occurs as simultaneous stimulation. |
What is Temporal Summation?
Temporal Summation is a kind of sensory summary that involves incorporating single stimuli over a short period. This process occurs when the action potentials that summate in a high frequency elicit postsynaptic potentials.
The process of temporal Summation occurs inside the nervous system. If the time constant of the cell membrane is long enough, the span of the Summation can be increased.
To reach the threshold potential, the previous postsynaptic potential summates with the next postsynaptic potential, which produces an increasingly more significant potential.
Here, over a period, there occurs production of multiple subthreshold done by a single presynaptic neuron. Adding the subthreshold is sufficient for the postsynaptic neuron to fire an action potential or generate the action potential.
The neurotransmitters are released into the synaptic gap by the presynaptic neuron, and each subthreshold is generated. EPSPs or excitatory postsynaptic potential is another way of considering subthreshold.
What is Spatial Summation?
Spatial Summation is a kind of sensory Summation that simultaneously involves several neurons separated spatially during stimulation.
This process of spatial Summation occurs in the nervous system, in which on the postsynaptic neuron, the action potential generation is done by multiple presynaptic neurons. Spatial Summation is also a variety of simultaneous Summation.
When the chances of achieving the potential threshold increase, excitatory postsynaptic potentials also increase quantitatively to elicit an action potential.
The algebraic addition of potentials is carried from various areas of fetching information or inputs, specifically on the dendrites. Inhibitory and excitatory postsynaptic potentials can be added together during spatial Summation.
Main Differences Between Temporal and Spatial Summation
- Temporal Summation is a kind of sensory summary that involves incorporating single stimuli over a short period. In contrast, Spatial Summation is a kind of sensory Summation involving several neurons separated spatially during stimulation.
- In temporal Summation, the generation of the action potential is done by a single presynaptic neuron. In contrast, in spatial Summation, the generation of the action potential is done by multiple presynaptic neurons.
- In temporal Summation, the generation of the subthreshold is done by only one presynaptic neuron. Whereas in spatial Summation, the generation of the subthreshold is done by multiple presynaptic neurons.
- Temporal Summation requires more time to generate an action potential and, thus, is less efficient. In contrast, spatial Summation is a more efficient mechanism.
- The occurrence of temporal Summation is high. In temporal Summation, the stimulation occurs at a high frequency. In comparison, spatial Summation is a type and consequence of simultaneous stimulation.
- https://journals.physiology.org/doi/pdf/10.1152/ajplegacy.1933.106.2.365
- https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/jphysiol.1993.sp019597
Last Updated : 11 June, 2023
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
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