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Information processing streams in rodent barrel cortex: The differential functions of barrel and septal circuits

CEREBRAL CORTEX 2008年第5期18卷 979-989页

作者： Alloway, Kevin D. Penn State Univ Dept Neural & Behav Sci Coll Med Hershey Med Ctr Hershey PA 17033 USA

Rodent somatosensory cortex contains an isomorphic map of the mystacial whiskers in which each whisker is represented by neuronal populations, or barrels, that are separated from each other by intervening septa. Separate afferent pathways convey somatosensory information to the barrels and septa that represent the input stages for 2 partially segregated circuits that extend throughout the other layers of barrel cortex. Whereas the barrel-related circuits process spatiotemporal information generated by whisker contact with external objects, the septa-related circuits encode the frequency and other kinetic features of active whisker movements. The projection patterns from barrel cortex indicate that information processed by the septa-related circuits is used both separately and in combination with information from the barrel-related circuits to mediate specific functions. According to this theory, outputs from the septal processing stream modulate the brain regions that regulate whisking behavior, whereas both processing streams cooperate with each other to identify external stimuli encountered by passive or active whisker movements. This theoretical view prompts several testable hypotheses about the coordination of neuronal activity during whisking behavior. Foremost among these, motor brain regions that control whisker movements are more strongly coordinated with the septa-related circuits than with the barrel-related circuits.

关键词： columnar organization rate coding sensorimotor integration spatial coding temporal coding whisking behavior

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Neural coding of temporal information and its topography in the auditory cortex

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JOURNAL OF BIOSCIENCES 2010年第4期35卷 499-500页

作者： Terleph, Thomas A. Pinaud, Raphael Sacred Heart Univ Dept Biol Fairfield CT 06825 USA Univ Oklahoma Hlth Sci Ctr Dept Physiol Oklahoma City OK 73104 USA Univ Oklahoma Hlth Sci Ctr Dept Geriatr Med Oklahoma City OK 73104 USA Univ Oklahoma Hlth Sci Ctr Reynolds Oklahoma Ctr Aging Oklahoma City OK 73104 USA

A significant challenge for auditory neuroscience lies in the quest for a thorough understanding of how highly complex stimuli, such as human speech and other animal vocal signals, are encoded. Speech has components that vary on a timescale from the relatively slow (< 40 Hz), as with the rhythm of phonemes, to more rapid features (>100 Hz) that potentially provide the cues needed to identify a speakers voice (Rosen 1992). The auditory cortex is involved in the processing of these complex sounds (Heffner and Heffner 1984; Fitch et al. 1997; Mesgarani et al. 2008; Woolley et al. 2009) and most cortical neuron responses are timing-locked to the lower range of modulation (Joris et al. 2004).

关键词： Auditory cortex rate coding temporal coding tessellation map topography

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Human motor unit recordings: Origins and insight into the integrated motor system

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BRAIN RESEARCH 2011年 1409卷 42-61页

作者： Duchateau, Jacques Enoka, Roger M. Univ Libre Bruxelles Fac Motor Sci Lab Appl Biol B-1070 Brussels Belgium Univ Colorado Dept Integrat Physiol Boulder CO 80309 USA

Soon after Edward Liddell [1895-1981] and Charles Sherrington [1857-1952] introduced the concept of a motor unit in 1925 and the necessary technology was developed, the recording of single motor unit activity became feasible in humans. It was quickly discovered by Edgar Adrian [1889-1977] and Detlev Bronk [1897-1975] that the force exerted by muscle during voluntary contractions was the result of the concurrent recruitment of motor units and modulation of the rate at which they discharged action potentials. Subsequent studies found that the relation between discharge frequency and motor unit force was characterized by a sigmoidal function. Based on observations on experimental animals, Elwood Henneman [1915-1996] proposed a "size principle" in 1957 and most studies in humans focussed on validating this concept during various types of muscle contractions. By the end of the 20th C, the experimental evidence indicated that the recruitment order of human motor units was determined primarily by motoneuron size and that the occasional changes in recruitment order were not an intended strategy of the central nervous system. Fundamental knowledge on the function of Sherrington's "common final pathway" was expanded with observations on motor unit rotation, minimal and maximal discharge rates, discharge variability, and self-sustained firing. Despite the great amount of work on characterizing motor unit activity during the first century of inquiry, however, many basic questions remain unanswered and these limit the extent to which findings on humans and experimental animals can be integrated and generalized to all movements. (C) 2011 Elsevier B.V. All rights reserved.

关键词： History Electrophysiology Motoneuron rate coding Recruitment Spinal cord

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Neural control of the healthy pectoralis major from low-to-moderate isometric contractions

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JOURNAL OF NEUROPHYSIOLOGY 2021年第1期126卷 213-226页

作者： Lulic-Kuryllo, Tea Thompson, Christopher K. Jiang, Ning Negro, Francesco Dickerson, Clark R. Univ Waterloo Dept Kinesiol Waterloo ON Canada Temple Univ Dept Hlth & Rehabil Sci Philadelphia PA 19122 USA Univ Waterloo Dept Syst Design Engn Waterloo ON Canada Univ Brescia Dept Clin & Expt Sci Brescia Italy

The pectoralis major critically enables arm movement in several directions. However, its neural control remains unknown. High-density electromyography (HD-sEMG) was acquired from the pectoralis major in two sets of experiments in healthy young adults. Participants performed ramp-and-hold isometric contractions in: adduction, internal rotation, flexion, and horizontal adduction at three force levels: 15%, 25%, and 50% scaled to task-specific maximal voluntary force (MVF). HD-sEMG signals were decomposed into motor unit spike trains using a convolutive blind source separation algorithm and matched across force levels using a motor unit matching algorithm. The mean discharge rate and coefficient of variation were quantified across the hold and compared between 15% and 25% MVF across all tasks, whereas comparisons between 25% and 50% MVF were made where available. Mean motor unit discharge rate was not significantly different between 15% and 25% MVF (all P > 0.05) across all tasks or between 25% and 50% MVF in horizontal adduction (P = 0.11), indicating an apparent saturation across force levels and the absence of rate coding. These findings suggest that the pectoralis major likely relies on motor unit recruitment to increase force, providing first-line evidence of motor unit recruitment in this muscle and paving the way for more deliberate investigations of the pectoralis major involvement in shoulder function. NEW & NOTEWORTHY This work is the first to investigate the relative contribution of rate coding and motor unit recruitment in the pectoralis major muscle in several functionally relevant tasks and across varying force levels in healthy adults. Our results demonstrate the absence of motor unit rate coding with an increase in EMG amplitude with increases in force level in all tasks examined, indicating that the pectoralis major relies on motor unit recruitment to increase force.

关键词： motor unit motor unit decomposition motor unit recruitment shoulder rate coding

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Motor unit firing rates of the gastrocnemii during maximal brief steady-state contractions in humans

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JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY 2016年 26卷 82-87页

作者： Graham, Mitchell T. Rice, Charles L. Dalton, Brian H. Univ Western Ontario Fac Hlth Sci Sch Kinesiol Canadian Ctr Act & Aging London ON Canada Univ Western Ontario Schulich Sch Med & Dent Dept Anat & Cell Biol London ON Canada Univ Oregon Dept Human Physiol 1240 Univ Oregon122C Esslinger Hall Eugene OR 97403 USA

The human triceps surae (soleus, medial (MG) and lateral (LG) gastrocnemii) is complex and important for posture and gait. The soleus exhibits markedly lower motor unit firing rates (MUFRs;similar to 16 Hz) during maximal voluntary isometric contraction (MVC) than other limb muscles, but this information is unknown for the MG and LG. During multiple visits, subjects performed a series of 5-7, similar to 7-s plantar flexor MVCs with tungsten microelectrodes inserted into the MG and LG. During a separate testing session, another group of subjects performed submaximal isometric contractions at 25%, 50%, and 75% MVC with inserted fine-wires in the MG, LG and soleus. Maximum steady-state MUFRs for MG and LG (similar to 23 Hz) were not different, but faster than prior reports for the soleus. No differences between the three triceps surae components were detected for 25% or 50% MVC, but at 75% MVC, the MG MUFRs were 31% greater than soleus. The triceps surae exhibit similar torque modulation strategies at <75% MVC, but to achieve higher contraction intensities (>75% MVC) the gastrocnemii rely on faster rates to generate maximal torque than the soleus. Therefore, the MG and LG exhibit a larger range of MUFR capacities. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Triceps surae Isometric Motor neuron rate coding

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Time and frequency domain responses of the mechanomyogram and electromyogram during isometric ramp contractions: A comparison of the short-time Fourier and continuous wavelet transforms

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JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY 2008年第1期18卷 54-67页

作者： Ryan, Eric D. Cramer, Joel T. Egan, Alison D. Hartman, Michael J. Herda, Trent J. Univ Oklahoma Dept Hlth & Exercise Sci Norman OK 73019 USA

The purposes of this study were to examine the mechanomyographic (MMG) and electromyographic (EMG) time and frequency domain responses of the vastus lateralis (VL) and rectus femoris (RF) muscles during isometric ramp contractions and compare the time-frequency of the MMG and EMG signals generated by the short-time Fourier transform (STFT) and continuous wavelet transform (CWT). Nineteen healthy subjects (mean +/- SD age = 24 +/- 4 years) performed two isometric maximal voluntary contractions (MVCs) before and after completing 2-3, 6-s isometric ramp contractions from 5% to 100% MVC with the right leg extensors. MMG and surface EMG signals were recorded from the VL and RF muscles. Time domains were represented as root mean squared amplitude values, and time-frequency representations were generated using the STFT and CWT. Polynomial regression analyses indicated cubic increases in MMG amplitude, MMG frequency, and EMG frequency, whereas EMG amplitude increased quadratically. From 5% to 24-28% MVC, MMG amplitude remained stable while MMG frequency increased. From 24-28% to 76-78% MVC, MMG amplitude increased rapidly while MMG frequency plateaued. From 76-78% to 100% MVC, MMG amplitude plateaued (VL) or decreased (RF) while MMG frequency increased. EMG amplitude increased while EMG frequency changed only marginally across the force spectrum with no clear deflection points. Overall, these findings suggested that MMG may offer more unique information regarding the interactions between motor unit recruitment and firing rate that control muscle force production during ramp contractions than traditional surface EMG. In addition, although the STFT frequency patterns were more pronounced than the CWT, both algorithms produced similar time-frequency representations for tracking changes in MMG or EMG frequency. (C) 2006 Elsevier Ltd. All rights reserved.

关键词： MMG EMG motor unit recruitment motor unit firing rate rate coding

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Motor unit discharge rate following twitch potentiation in human triceps brachii muscle

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NEUROSCIENCE LETTERS 2001年第3期316卷 153-156页

作者： Klein, CS Ivanova, TD Rice, CL Garland, SJ Univ Western Ontario Sch Phys Therapy London ON N6G 1H1 Canada Univ Western Ontario Sch Kinesiol London ON N6G 1H1 Canada Univ Western Ontario Dept Anat & Cell Biol London ON N6G 1H1 Canada Univ Western Ontario Dept Physiol London ON N6G 1H1 Canada

It has been proposed that during brief voluntary contractions, twitch potentiation may sustain force output despite a decline in motor unit discharge rate. This study examined the evoked twitch force and motor unit discharge rates during submaximal voluntary contractions of the triceps brachii muscle before and after a 5 s conditioning contraction (CC) at 75% of maximal voluntary force. After the CC, twitch force potentiated (similar to1.3-2-fold), and the discharge rate in 33 of 35 motor units declined significantly by 1-6 Hz. The increase in twitch force was significantly correlated with the decline in discharge rate (r = -0.74). These findings suggest that the extent of the decrease in motor unit discharge rate following a CC is associated with the magnitude of twitch potentiation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

关键词： motoneuron contractile properties rate coding recruitment

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OXYGEN AVAILABILITY AND MOTOR UNIT-ACTIVITY IN HUMANS

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EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY 1992年第6期64卷 552-556页

作者： MORITANI, T SHERMAN, WM SHIBATA, M MATSUMOTO, T SHINOHARA, M KYOTO UNIV COLL LIBERAL ARTS & SCI APPL PHYSIOL LAB SAKYO KU KYOTO 606 JAPAN KYOTO COLL ART DEPT HLTH & PHYS EDUC KYOTO 606 JAPAN OHIO STATE UNIV SCH HLTH PHYS EDUC & RECREAT COLUMBUS OH 43210 USA

Six men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.

关键词： MOTOR UNIT RECRUITMENT rate coding METABOLISM ELECTROMYOGRAM FREQUENCY POWER SPECTRA

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How the threshold of a neuron determines its capacity for coincidence detection

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BIOSYSTEMS 1998年第1-3期48卷 105-112页

作者： Kempter, R Gerstner, W van Hemmen, JL TU Munchen Dept Phys D-85747 Garching Germany Ecole Polytech Fed Lausanne Ctr Neuromimet Syst DI Swiss Fed Inst Technol CH-1015 Lausanne Switzerland

Coherent oscillatory activity of a population of neurons is thought to be a vital feature of temporal coding in the brain. We focus on the question of whether a single neuron can transform a spike code into a rate code. More precisely, how does a neuron vary its mean output firing rate, if its input changes from random to coherent? We investigate the coincidence detection properties of an integrate-and-fire neuron in dependence upon internal parameters and input statistics. In particular, we show how coincidence detection depends on the membrane time constant and the threshold. Furthermore, we demonstrate that there is an optimal threshold for coincidence detection and that there is a broad range of near-optimal threshold values. Fine-tuning is not necessary. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.

关键词： coincidence detection voltage threshold coherent activity temporal coding rate coding integrate-and-fire neuron

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Modelling the signal delivered by a population of first-order neurons in a moth olfactory system

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BRAIN RESEARCH 2012年 1434卷 123-135页

作者： Gremiaux, Alexandre Nowotny, Thomas Martinez, Dominique Lucas, Philippe Rospars, Jean-Pierre INRA UMR Physiol Insecte 1272 F-78026 Versailles France Univ Sussex Brighton E Sussex England LORIA CORTEX Team Vandoeuvre Les Nancy France

A statistical model of the population of first-order olfactory receptor neurons (ORNs) is proposed and analysed. It describes the relationship between stimulus intensity (odour concentration) and coding variables such as rate and latency of the population of several thousand sex-pheromone sensitive ORNs in male moths. Although these neurons likely express the same olfactory receptor, they exhibit, at any concentration, a relatively large heterogeneity of responses in both peak firing frequency and latency of the first action potential fired after stimulus onset. The stochastic model is defined by a multivariate distribution of six model parameters that describe the dependence of the peak firing rate and the latency on the stimulus dose. These six parameters and their mutual linear correlations were estimated from experiments in single ORNs and included in the multidimensional model distribution. The model is utilized to reconstruct the peak firing rate and latency of the message sent to the brain by the whole ORN population at different stimulus intensities and to establish their main qualitative and quantitative properties. Finally, these properties are shown to be in agreement with those found previously in a vertebrate ORN population. This article is part of a Special Issue entitled: Neural coding. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Olfactory receptor neuron Neural population rate coding Temporal coding Insect Sexual pheromone

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