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Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Neural reflexes could be somatic, affecting skeletal muscles, or autonomic, involving internal organs. The pathway from the receptor that normally initiates the reflex to the effector that executes the reflex action is the reflex arc. Depending on the type of neural reflex, the effector could be muscle – skeletal, smooth, or cardiac – or a gland. An example of an autonomic reflex is the control of blood pressure. When this falls, the pressure receptors in the aorta and carotid arteries cause the sympathetic system to increase the heart rate and the cardiac output so as to restore the blood pressure to its normal level. Neural reflexes are “wired” in the neuronal circuitry, but can be influenced by the action of inputs from other parts of the nervous system on various neurons in the reflex arc. Reflexes are thus modifiable, and almost all somatic reflexes can be overridden by voluntary control. The eyeblink reflex and the flexion reflex discussed below are examples of protective reflexes, whereas other reflexes, such as the aforementioned blood pressure and blood glucose level serve a regulatory function through negative feedback control.
Vestibulo-ocular reflex characteristics during unidirectional translational whole-body vibration without head restriction
Published in Ergonomics, 2020
Tomoko Sugawara, Hiroyuki Sakai, Yutaka Hirata
Comparing these data with our findings (Table 1), the latencies for head angular-velocity components are relatively short (6.4 ms for pitch velocity and 0.82 ms for yaw velocity), while the latencies for head linear-acceleration components are relatively long (68 ms for z acceleration and 87 ms for y acceleration). Although these discrepancies may also be attributed to differences in experimental conditions (e.g., multidirectional and multiband vibration stimulation), the latencies reported for head angular velocity may be too short when considering the VOR neuronal pathway as a typical three-neuron reflex arc (Kandel et al. 2012). Predictive (phase advancing) mechanisms for the control of eye movements might underlie such short latencies in response to head angular-velocity components (Sprenger et al. 2006). Indeed, evidence from animal studies suggests that the VOR in response to more predictable motion stimuli (i.e., sinusoidal yaw rotation) is nearly in phase with head movements (Huterer and Cullen 2002; Minor et al. 1999).
Emerging electrolyte-gated transistors for neuromorphic perception
Published in Science and Technology of Advanced Materials, 2023
Cui Sun, Xuerong Liu, Qian Jiang, Xiaoyu Ye, Xiaojian Zhu, Run-Wei Li
Recent years have witnessed booming enthusiasm for building intelligent tactile perception system for electronic skin and intelligent prosthetics applications [127,128], inspiring the exploration of combining pressure sensors with neuromorphic devices. Wan et al. [129] reported a neuromorphic tactile sensory device (NeuTap) that mimics the tactile sensory neurons for perceptual learning. As shown in Figure 6(a), the system consists of a resistive pressure sensor, a flexible ionic cable, and a EGT-based artificial synapse, which are in analogous to the biological sensory receptors, axons, and synapses. The pressure sensor converts the pressure stimulus into electrical signals, which are transmitted to the synaptic transistor through the ion/electron interface coupling. The synaptic transistor can discriminate the difference in the temporal features of the stimulation pattern using the inherent short-term dynamics. Figure 6(b,c) shows the dynamic responses of the device to different spatiotemporally correlated haptic patterns for identification. After training, the error rate of NeuTap in pattern recognition could be reduced from ~44% to ~0.4%. Notably, the sensors in NeuTap are directly wired with the EGT, where the pressure signals are fed to the synaptic transistor without executing spiking coding. Kim et al. [130] designed an artificial afferent nerve with spike frequency coding ability by incorporating a ring oscillator, where external tactile stimuli are collected and converted into action potentials by pressure sensors and ring oscillators (Figure 6(d)). The magnitude and duration of stimulus from pressure sensors are well demonstrated by the different peaks of EPSC, i.e. from 2.5 to 83 kPa and from 2 to 6 sec, respectively. A detached cockroach leg serving as the actuator was further connected with the synaptic transistors to form a hybrid reflex arc, aiming to showcase the response of the intelligent perception system to the tactile stimuli (Figure 6(e)). It was shown that increasing the intensity and duration of the tactile stimulus accordingly enhances the isometric contraction force of the cockroach leg (Figure 6(f)).