scholarly journals Neural Readout of a Latency Code in the Active Electrosensory System

2021 ◽  
Author(s):  
Nathaniel B Sawtell ◽  
Krista Perks
Keyword(s):  
Sensory Information ◽  
Granular Cell ◽  
Nerve Fibers ◽  
Spike Count ◽  
Stimulus Amplitude ◽  
Electrosensory System ◽  
Afferent Nerve Fibers ◽  
Mormyrid Fish ◽  
Sensory Responses ◽  
Spike Latency

The latency of spikes relative to a stimulus conveys sensory information across modalities. However, in most cases it remains unclear whether and how such latency codes are utilized by postsynaptic neurons. In the active electrosensory system of mormyrid fish, a latency code for stimulus amplitude in electroreceptor afferent nerve fibers (EAs) is hypothesized to be read out by a central reference provided by motor corollary discharge (CD). Here we demonstrate that CD enhances sensory responses in postsynaptic granular cells of the electrosensory lobe, but is not required for reading out EA input. Instead, diverse latency and spike count tuning across the EA population gives rise to graded information about stimulus amplitude that can be read out by standard integration of converging excitatory synaptic inputs. Inhibitory control over the temporal window of integration renders two granular cell subclasses differentially sensitive to information derived from relative spike latency versus spike count.

scholarly journals Effects of Divalent Ions and Drugs on Synaptic Transmission in Phasic Electroreceptors in a Mormyrid Fish

1971 ◽  
Vol 58 (5) ◽  
pp. 580-598 ◽  
Author(s):  
A. B. Steinbach ◽  
M. V. L. Bennett
Keyword(s):  
Synaptic Transmission ◽  
Sensory Nerve ◽  
Nerve Fibers ◽  
Sensory Nerves ◽  
Block Transmission ◽  
Afferent Nerve Fibers ◽  
Similar Chemical ◽  
Mormyrid Fish ◽  
Nerve Synapse ◽  
Skin Receptors

We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg+2 depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg+2 and Ca+2 masks divalent ion dependence of transmission, but a large excess of Mg+2 cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces a sequence of excitation and depression of medium receptor response which indicates that a similar chemical is the transmitter in the afferent synapse.

scholarly journals Neural feedback strategies to improve grasping coordination in neuromusculoskeletal prostheses

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Enzo Mastinu ◽  
Leonard F. Engels ◽  
Francesco Clemente ◽  
Mariama Dione ◽  
Paolo Sassu ◽  
...  
Keyword(s):  
Motor Coordination ◽  
Sensory Information ◽  
Nerve Fibers ◽  
Tactile Feedback ◽  
Somatosensory Feedback ◽  
Afferent Nerve Fibers ◽  
Feedback Strategies ◽  
Neural Feedback ◽  
Novel Concept ◽  
Implant System

Abstract Conventional prosthetic arms suffer from poor controllability and lack of sensory feedback. Owing to the absence of tactile sensory information, prosthetic users must rely on incidental visual and auditory cues. In this study, we investigated the effect of providing tactile perception on motor coordination during routine grasping and grasping under uncertainty. Three transhumeral amputees were implanted with an osseointegrated percutaneous implant system for direct skeletal attachment and bidirectional communication with implanted neuromuscular electrodes. This neuromusculoskeletal prosthesis is a novel concept of artificial limb replacement that allows to extract control signals from electrodes implanted on viable muscle tissue, and to stimulate severed afferent nerve fibers to provide somatosensory feedback. Subjects received tactile feedback using three biologically inspired stimulation paradigms while performing a pick and lift test. The grasped object was instrumented to record grasping and lifting forces and its weight was either constant or unexpectedly changed in between trials. The results were also compared to the no-feedback control condition. Our findings confirm, in line with the neuroscientific literature, that somatosensory feedback is necessary for motor coordination during grasping. Our results also indicate that feedback is more relevant under uncertainty, and its effectiveness can be influenced by the selected neuromodulation paradigm and arguably also the prior experience of the prosthesis user.

Spontaneous action potential generation due to persistent sodium channel currents in simulated carotid body afferent fibers

2008 ◽  
Vol 104 (5) ◽  
pp. 1394-1401 ◽  
Author(s):  
David F. Donnelly
Keyword(s):  
Carotid Body ◽  
High Sensitivity ◽  
Nerve Fibers ◽  
Afferent Nerve ◽  
Random Pattern ◽  
Nerve Terminals ◽  
Discharge Rates ◽  
Afferent Nerve Fibers ◽  
Axonal Diameter ◽  
Spontaneous Action

The mechanism by which action potentials (APs) are generated in afferent nerve fibers in the carotid body is unknown, but it is generally speculated to be release of an excitatory transmitter and synaptic depolarizing events. However, previous results suggested that Na+ channels in the afferent nerve fibers play an important role in this process. To better understand the potential mechanism by which Na+ channels may generate APs, a mathematical model of chemoreceptor nerve fibers that incorporated Hodgkin-Huxley-type Na+ channels with kinetics of activation and inactivation, as determined previously from recordings of petrosal chemoreceptor neurons, was constructed. While the density of Na+ channels was kept constant, spontaneous APs arose in nerve terminals as the axonal diameter was reduced to that in rat carotid body. AP excitability and pattern were similar to those observed in chemoreceptor recordings: 1) a random pattern at low- and high-frequency discharge rates, 2) a high sensitivity to reductions in extracellular Na+ concentration, and 3) a variation in excitability that increased with AP generation rate. Taken together, the results suggest that an endogenous process in chemoreceptor nerve terminals may underlie AP generation, a process independent of synaptic depolarizing events.

Coding of temporal parameters of complex sounds by frog auditory nerve fibers

1991 ◽  
Vol 65 (3) ◽  
pp. 424-445 ◽  
Author(s):  
A. S. Feng ◽  
J. C. Hall ◽  
S. Siddique
Keyword(s):  
Auditory Nerve ◽  
Transfer Functions ◽  
Nerve Fibers ◽  
Spike Count ◽  
Complex Sounds ◽  
Temporal Parameters ◽  
Low Pass ◽  
The Mean ◽  
Auditory Nerve Fibers ◽  
High Pass

1. Physiological recordings were made from single auditory fibers in the frog eighth nerve to determine quantitatively how the different behaviorally relevant temporal parameters (the signal rise-fall time, duration, and rate of amplitude modulation) of complex sounds are encoded in the auditory periphery. Individual temporal parameters were varied. Response functions (RFs) were constructed with respect to each of these parameters using each unit's best excitatory frequency (BF) as the carrier. 2. In response to a change in signal rise-fall time, auditory nerve fibers showed little change in the mean spike count or firing rate, i.e., all fibers displayed ALL-PASS RFrfts. But the transient components, particularly the early phasic component, of responses varied with rise-fall times; these components were more pronounced in the responses to stimuli with shorter rise-fall times. 3. In response to an increase in signal duration, auditory nerve fibers showed a corresponding increase in firing duration and thus in the mean spike count, giving rise to HIGH-PASS RFdurs. The shape of response curves differed among fibers; the difference appeared to be related to the fiber's temporal adaptation characteristic. When the firing rate was measured, all fibers displayed higher mean firing rates in response to shorter duration stimuli than they did to longer duration stimuli, thus giving rise to LOW-PASS response functions. 4. To determine the response transfer functions to modulation rate, pulsed (PAM) and sinusoidally (SAM) amplitude-modulated signals were used. These signals differed substantially in terms of their envelopes and how they varied with AM rate. Data were analyzed by 1) plotting spike counts against the AM rate to derive modulation transfer functions (MTFspks) and 2) plotting synchronization coefficients (SCs) against the AM rate to generate MTFscs. 5. In response to PAM stimuli, all fibers showed an increase in mean spike count with modulation frequency over the range examined, giving rise to HIGH-PASS MTFspks. 6. For SAM stimuli, the average energy and duty cycle are independent of AM rate. Most (79%) auditory fibers showed little selectivity for AM rate over a range of 5-400 Hz, giving rise to ALL-PASS MTFspks. The remaining auditory fibers displayed LOW-PASS MTFspks, i.e., there was a distinct decline in the mean spike count with increasing AM rate. 7. In response to PAM stimuli, most fibers showed good response synchrony at low AM rates but the SC declined with an increase in the AM rate (i.e., LOW-PASS MTFscs). The cut-off frequency was typically very high, averaging 90 pulses/s.(ABSTRACT TRUNCATED AT 400 WORDS)

Lung inflation: effects on heart rate, respiration, and vagal afferent activity in seals

1981 ◽  
Vol 240 (2) ◽  
pp. H190-H198 ◽  
Author(s):  
J. E. Angell-James ◽  
R. Elsner ◽  
M. De Burgh Daly
Keyword(s):  
Transpulmonary Pressure ◽  
Harbor Seal ◽  
Nerve Fibers ◽  
Cardiac Response ◽  
Impulse Frequency ◽  
Lung Inflation ◽  
Afferent Nerve Fibers ◽  
Close Relationship ◽  
Vagal Afferent ◽  
Carotid Body Chemoreceptors

In the anesthetized harbor seal, Phoca vitulina, the Hering-Breuer inflation reflex was weak and comparable to that in humans. Single inflations of the lungs from a syringe during the expiratory phase of normal breathing caused temporary inhibition of breathing and an immediate tachycardia dependent on the integrity of the cervical vagosympathetic nerves. A similar cardiac response occurred when the lungs were artificially inflated during an experimental dive and under conditions in which apnea and bradycardia were reflexly induced by a combination of stimulation of the carotid body chemoreceptors and of the trigeminal or laryngeal input. Recordings from single vagal afferent nerve fibers innervating presumptive pulmonary stretch receptors showed a close relationship between the increase in impulse frequency and increase in lung volume or transpulmonary pressure. It appears that in diving the decrease in pulmonary stretch receptor activity during apnea, combined with cessation of central inspiratory neuronal drive, is an important integrative mechanism that helps development of the reflex bradycardia of trigeminal, carotid, chemoreceptor, and baroreceptor origin.

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