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Power efficiency of the dendritic arbor has a high impact on the overall power efficiency of a neuromorphic design. We deploy a sub-threshold switched-capacitor mechanism and power gating to carry out summation of post synaptic potentials (PSPs) as well as capturing passive properties of dendrites through sampling PSPs on the capacitors and serializing them to perform summation rather than providing...
A neuromorphic model of C. elegans undulating motion and simulation results are presented. The model contains 72 neurons and ancillary timing circuits that model the worm's motion due to a gentle touch. Analog CMOS circuits model sensory neurons, interneurons, and motor neurons, including synapses.
In neurons, the essence of nonlinear dendritic computations cannot be neglected as some neural behaviors depend heavily on these functions. In this paper, a power-efficient biomimetic intra-branch dendritic adder is introduced to emulate dendritic computations within the branches of the dendritic arbor. The proposed adder is implemented using 45nm CMOS technology. While exhibiting nonlinear behavior...
Noise can play beneficial roles in neural network systems from biology to neuromorphic computing through stochastic resonance, averaging signals, and other mechanisms. To achieve the benefits of noise in neuromorphic circuits, we propose a random pulse generator(RPG) as a source of noise and describe its implementation in neuromorphic circuits. The RPG includes three components: an LED, a wave guide,...
Learning in the human brain is mediated by different forms of plasticity. The circuit processing spatiotemporal inputs we demonstrate here highlights the mechanisms and role of structural plasticity. In many neuromorphic systems, synaptic plasticity is used for learning, memory and information processing. In these systems, neurons are fully or sparsely connected and synaptic connections between neurons...
We have designed a fully-connected neural network implemented as an analog circuit consisting of 8 neurons and 64 synapses that can learn rules of 2-by-2 Sudoku or Sudoku-like puzzles and then can solve them. In this circuit, learning is mediated by giving a dopamine reward signal to correct actions, which has a biological basis and is known as reinforcement learning [1]. Regular architecture of the...
Astrocytes, a type of glial cell, have been shown to actively modulate neural activity in the central nervous system. One way in which astrocytes can be stimulated is through receptors of retrograde messengers that are located on the astrocyte processes. Retrograde messengers are released by a neuron's postsynaptic dendrite in response to neural activity, and retrograde signaling can potentiate heteroneuronal...
The CORTICO-STRIATAL-THALAMO-CORTICAL (CSTC) circuit in the brain has an important role in controlling movement and thought. As a consequence, any dysfunction in this circuit may cause movement and psychological disorders. For example, one hypothesis to explain Obsessive Compulsive Disorder (OCD) is that alteration in this circuit causes a positive feedback loop (direct pathway) to become strengthened...
Research shows that the way we remember things for a few seconds is a different mechanism from the way we remember things for a longer time. Short-term memory is based on persistently firing neurons, whereas storing information for a longer time is based on strengthening the synapses or even forming new neural connections. Information about location and appearance of an object is segregated and processed...
We have designed a neuromorphic circuit that models directional selectivity in the visual cortex, where selected neurons fire depending on the direction of object motion, along with the size and orientation of the object. The neuromorphic circuit is biomimetic. It consists of neurons and synapses, and models biological mechanisms. Neurons (including the Axon Hillock and the Dendritic Arbor) are designed...
The neural system in the human brain can identify regularities in received stimuli and, based on that, predict future stimuli [1]. Neural prediction circuits reduce responses to predictable and thus possibly redundant events. Failures in predictions that result in erroneous responses may cause positive and negative symptoms in people who suffer from schizophrenia [2]. Here, we have designed a bio-inspired,...
In this paper, We demonstrate biomimetic neural circuits (CMOS circuits) responsible for touch induced-locomotion in the nematode Caenorhabditis elegans (C. elegans). Our circuits model the neural network responsible for touch-induced locomotion of C. elegans worm (Chalfie and Sulston, 1985 [1]). Most animals use action potentials (spikes) for information transfer across neurons. Our initial touch-sensitive...
We present an electronic cortical neuron incorporating dynamic spike threshold and active dendritic properties. The circuit is simulated using a carbon nanotube field-effect transistor SPICE model. We demonstrate that our neuron has lower spike threshold for coincident synaptic inputs; however when the synaptic inputs are not in synchrony, it requires larger depolarization to evoke the neuron to fire...
We present an electronic cortical neuron with nonlinear dendritic computations that performs border-ownership assignment. The circuit is simulated using a carbon nanotube field-effect transistor SPICE model. We demonstrate that our neuron can distinguish convex and concave contours, selectively respond to a figure based on the contour and/or disparity cues, and transform this neural information into...
We present an electronic cortical neuron incorporating both active and passive dendritic properties. The circuit is simulated using a carbon nanotube field-effect transistor SPICE model. We demonstrate that our neuron can detect coincident spatiotemporal input, and transform this neural information into a precisely-timed output spike. We also demonstrate that a dendritic spike is key to enhance precisely-timed...
CMOS neuromorphic circuits are proposed to emulate the role of astrocytes in phase synchronization of neuronal activity. We emulate, to a first order, the ability of slow inwards currents (SICs) evoked by the astrocyte, acting on extrasynaptic N-methyl-D-aspartate receptors (NMDAR) of adjacent neurons, as a mechanism for phase synchronization. We do an experiment incorporating two small networks of...
Sensory pathways in the brain attain large dynamic ranges and novelty detection through adaptive mechanisms. We present a CMOS neuromorphic circuit emulating the adaptation dynamics of short-term depressing synapses for both transient and steady state. The circuit detects abrupt changes in the input firing rate following the Weber-Fechner relation, where the transient response is proportional to the...
This paper presents a novel biomimetic CMOS two-input non-linear adder circuit to fully emulate computations within dendritic branches of pyramidal neurons. It automatically and dynamically adjusts neuron responses based on the input magnitudes of EPSP potentials. The design is based on CMOS 180nm technology with dual power supplies.
A first-order neuromorphic implementation of structural plasticity is shown. Our circuit models spiking behavior of somatosensory neurons and neuronal receptive fields in the upper layers of the rodent barrel (somatosensory) cortex while replicating biological observations of experience-dependent changes in receptive field organization, network topology and synaptic connectivity in silico. Anatomical...
A CMOS neuromorphic circuit is proposed with two main features. First, we emulate the uptake of neurotransmitters by astrocytes, a type of glial cell, that plays an active role in the coordination of information between neurons. Second, we propose a synapse inactivation mechanism, which prevents the saturation of postsynaptic neurons in the absence of an astrocytic process. We show the influence of...
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