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Soft Computing
Published in Vivek Kale, Digital Transformation of Enterprise Architecture, 2019
A neuron’s dendritic tree is connected to a thousand neighboring neurons. When one of those neurons fires; a positive or negative charge is received by one of the dendrites. The strengths of all the received charges are added together through the processes of: Spatial summation occurs when several weak signals are converted into a single large one, whereasTemporal summation converts a rapid series of weak pulses from one source into one large signal
Biological Responses in Context
Published in Arthur T. Johnson, Biology for Engineers, 2019
Biological control responses are rarely simple. There is often a great deal of processing that takes place in the nervous systems of animals. At the very least, for complex animals, there is a spatial summation of inputs from many of the same type of receptors at different locations around the body. There may also be added the effects of additional inputs. For example, hemorrhage can decrease blood pressure, which is sensed and at least partially corrected by increasing the resistance of peripheral blood vessels. This response can be influenced also by information about the partial pressures of oxygen and carbon dioxide in the blood.
Artificial neural networks
Published in A. W. Jayawardena, Environmental and Hydrological Systems Modelling, 2013
The brain is a biological neural network with over 10 billion neurons and over 60 trillion synapses. Each neuron (sometimes called neurone or nerve cell) is a cell that receives, processes, and transmits information through biochemical processes. A biological neuron has a cell body, which is the central part, of typical sizes ranging from about 10 to 80 μm; dendtrites, which are root-like extensions from the cell body with typical size a few micrometers; and an axon, which is a single tubular fibre projecting from the cell body with typical diameters a few micrometers and lengths ranging from about 0.1 mm to 1 m. The dendrites act as receptors for signals from nearby neurons, whereas the axons transmit the generated neuron activity to other neurons or muscle fibres. When a neuron fires, an electric charge is received by a dendrite. Such charges are summed spatially and temporally and passed onto the cell body. Spatial summation takes place when several weak signals are converted into a single strong signal, whereas temporal summation takes place when a series of weak signals from one source is converted into a single strong signal. If the strength of the summed signal is greater than the threshold value of the axon, then the neuron fires and an output is transmitted via the axon. Otherwise, the neuron does not fire and there is no output transmitted. The strength of the output is constant regardless of the strength of the input signal as long as it is above the threshold value. The axon has several terminal buttons, which are, in turn, connected to other neurons across a small gap called the synapse whose characteristics determine the strength and polarity of the new input signal. Over a period, the strengths of the synapses are adjusted through experience or exposure to various signals, such as vision, hearing, emotions, etc.
Biological function simulation in neuromorphic devices: from synapse and neuron to behavior
Published in Science and Technology of Advanced Materials, 2023
Hui Chen, Huilin Li, Ting Ma, Shuangshuang Han, Qiuping Zhao
In the nervous system, when the stimuli signal is transmitted in the neurons, the continuous and variable action potential are integrated as an excitatory or inhibitory information to the postsynaptic neuron from different presynaptic neurons. The neuronal integration is an important step of this transformation, which mainly includes spatial summation and temporal summation [106,107]. Spatial summation involves events that occur simultaneously in different synapses, while temporal summation is taken over non-simultaneous events. Spatial and temporal summation can coexist in one neuron to display the spatiotemporal information processing in the nervous system. Therefore, it is a vital significance for computation and memory in neuromorphic hardware to emulate this function using the artificial neurons. In order to emulate this function, an additional resistor was added into the circuit of I&F neuron in Figure 7(a-i) to form the new circuit in Figure 7(a-iii). The spatial integration has been observed by applied simultaneously stimulus on the two load resistors, and also relies on the pulse voltage and frequency (Figure 7(a-iv,v)). Interestingly, the firing frequency of the artificial neuron is a function of the time interval (∆t) between the two pulse trains, in which different time intervals generate different firing states (Figure 7(a-vi)) [99].