1
|
Abstract
Objective: To demonstrate the effect of rhythmical auditory stimulation in a musical context for gait therapy in hemiparetic stroke patients, when the stimulation is played back measure by measure initiated by the patient's heel strikes (musical motor feedback). Does this type of musical feedback improve walking more than a less specific gait therapy? Design: The randomized controlled trial considered 23 registered stroke patients. Two groups were created by randomization: the control group received 15 sessions of conventional gait therapy and the test group received 15 therapy sessions with musical motor feedback. Setting: Inpatient rehabilitation hospital. Subjects: Median post-stroke interval was 44 days and the patients were able to walk without technical aids with a speed of approximately 0.71 m/s. Main outcome measures: Gait velocity, step duration, gait symmetry, stride length and foot rollover path length (heel-on–toe-off distance). Result: The test group showed more mean improvement than the control group: stride length increased by 18% versus 0%, symmetry deviation decreased by 58% versus 20%, walking speed increased by 27% versus 4% and rollover path length increased by 28% versus 11%. Conclusion: Musical motor feedback improves the stroke patient's walk in selected parameters more than conventional gait therapy. A fixed memory in the patient's mind about the song and its timing may stimulate the improvement of gait even without the presence of an external pacemaker.
Collapse
Affiliation(s)
- Michael Schauer
- Max-Planck-Institute of Cognitive Neuroscience, Leipzig, Germany.
| | | |
Collapse
|
2
|
Jessop RT, Horowicz C, Dibble LE. Motor Learning and Parkinson Disease: Refinement of Movement Velocity and Endpoint Excursion in a Limits of Stability Balance Task. Neurorehabil Neural Repair 2016; 20:459-67. [PMID: 17082501 DOI: 10.1177/1545968306287107] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Objective. To investigate the effects of practice on performance and retention of a balance task in persons with Parkinson disease (PD). Methods. Ten persons with PD and 10 age and gender-matched healthy control subjects were tested on an anticipatory, static base of support, limits of stability (LOS) balance task on a force plate. The motor learning paradigm utilized for all subjects included an acquisition phase and retention tests at 24 h and 1 week after acquisition. A force plate was used for testing and to collect outcome measures including movement velocity (MVL), endpoint excursion (EPE), and directional control. Data were analyzed for differences between groups and change over time. Results.Persons with PD demonstrated performance deficits relative to controls for MVL at all testing periods ( P < 0.05), and initially for EPE ( P < 0.05), but were able to maintain significant improvements through retention testing relative to baseline ( P < 0.05). Conclusions. Persons with PD demonstrated unimpaired capacity for motor learning in a LOS balance task for MVL and EPE, although performance deficits remained for MVL. The results concur with previous motor learning research of upper extremity tasks by suggesting that individuals with mild to moderate PD exhibit a preserved ability to benefit from practice as a means of improving balance task performance.
Collapse
|
3
|
Karim AA, Hinterberger T, Richter J, Mellinger J, Neumann N, Flor H, Kübler A, Birbaumer N. Neural Internet: Web Surfing with Brain Potentials for the Completely Paralyzed. Neurorehabil Neural Repair 2016; 20:508-15. [PMID: 17082507 DOI: 10.1177/1545968306290661] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neural Internet is a new technological advancement in brain-computer interface research, which enables locked-in patients to operate a Web browser directly with their brain potentials. Neural Internet was successfully tested with a locked-in patient diagnosed with amyotrophic lateral sclerosis rendering him the first paralyzed person to surf the Internet solely by regulating his electrical brain activity. The functioning of Neural Internet and its clinical implications for motor-impaired patients are highlighted.
Collapse
Affiliation(s)
- Ahmed A Karim
- Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
4
|
Abstract
Complex behavior requires a flexible system that maintains task performance in the context of specific goals, evaluating behavioral progress, adjusting behavior as needed, and adapting to changing contingencies. Generically referred to as performance monitoring, a key component concerns the identification and correction of differences between an intended and an executed response (i.e., an error). Brain mapping experiments have now identified the temporal and spatial components of a putative error-processing system in the large-scale networks of the human brain. Most of this work has focused on the medial frontal cortex and an associated electrophysiological component known as the error-related negativity (or error negativity). Although the precise role, or roles, of this region still remain unknown, investigations of error processing have identified a cluster of modules in the medial frontal cortex involved in monitoring/maintaining ongoing behavior and motivating task sets. Other regions include bilateral anterior insula/inferior operculum and lateral prefrontal cortex. Recent work has begun to uncover how individual differences might affect the modules recruited for a task, in addition to the identification of associations between pathological states and aberrant error signals, leading to insights about possible mechanisms of neuropsychiatric illness. NEUROSCIENTIST 13(2):160—172, 2007.
Collapse
Affiliation(s)
- Stephan F Taylor
- Department of Psychiatry, University of Michigan, Ann Arbor, Michigan, USA.
| | | | | |
Collapse
|
5
|
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) has a pivotal role in the mammalian circadian clock. SCN neurons generate circadian rhythms in action potential firing frequencies and neurotransmitter release, and the core oscillation is thought to be driven by “clock gene” transcription-translation feedback loops. Cytosolic Ca2+mobilization followed by stimulation of various receptors has been shown to reset the gene transcription cycles in SCN neurons, whereas contribution of steady-state cytosolic Ca2+levels to the rhythm generation is unclear. Recently, circadian rhythms in cytosolic Ca2+levels have been demonstrated in cultured SCN neurons. The circadian Ca2+rhythms are driven by the release of Ca2+from ryanodine-sensitive internal stores and resistant to the blockade of action potentials. These results raise the possibility that gene translation/transcription loops may interact with autonomous Ca2+oscillations in the production of circadian rhythms in SCN neurons.
Collapse
Affiliation(s)
- Masayuki Ikeda
- Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Suita, Osaka, Japan.
| |
Collapse
|
6
|
Abstract
On the basis of the finding that a common and homogeneous ground surface is vital for accurate egocentric distance judgments (Sinai et al, 1998 Nature395 497–500), we propose a sequential-surface-integration-process (SSIP) hypothesis to elucidate how the visual system constructs a representation of the ground-surface in the intermediate distance range. According to the SSIP hypothesis, a near ground-surface representation is formed from near depth cues, and is utilized as an anchor to integrate the more distant surfaces by using texture-gradient information as the depth cue. The SSIP hypothesis provides an explanation for the finding that egocentric distance judgment is underestimated when a texture boundary exists on the ground surface that commonly supports the observer and target. We tested the prediction that the fidelity of the visually represented ground-surface reference frame depends on how the visual system selects the surface information for integration. Specifically, if information is selected along a direct route between the observer and target where the ground surface is disrupted by an occluding object, the ground surface will be inaccurately represented. In experiments 1–3 we used a perceptual task and two different visually directed tasks to show that this leads to egocentric distance underestimation. Judgment is accurate however, when the observer selects the continuous ground information bypassing the occluding object (indirect route), as found in experiments 4 and 5 with a visually directed task. Altogether, our findings provide support for the SSIP hypothesis and reveal, surprisingly, that the phenomenal visual space is not unique but depends on how optic information is selected.
Collapse
Affiliation(s)
- Zijiang J He
- Department of Psychological and Brain Sciences, University of Louisville, Louisville, KY 40292, USA.
| | | | | | | | | |
Collapse
|
7
|
Zhang D, Zhu K. COMPUTER SIMULATION STUDY ON CENTRAL PATTERN GENERATOR: FROM BIOLOGY TO ENGINEERING. Int J Neural Syst 2011; 16:405-22. [PMID: 17285687 DOI: 10.1142/s0129065706000810] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2006] [Revised: 08/21/2006] [Accepted: 10/18/2006] [Indexed: 11/18/2022]
Abstract
Central pattern generator (CPG) is a neuronal circuit in the nervous system that can generate oscillatory patterns for the rhythmic movements. Its simplified format, neural oscillator, is wildly adopted in engineering application. This paper explores the CPG from an integral view that combines biology and engineering together. Biological CPG and simplified CPG are both studied. Computer simulation reveals the mechanism of CPG. Some properties, such as effect of tonic input and sensory feedback, stable oscillation, robustness, entrainment etc., are further studied. The promising results provide foundation for the potential engineering application in future.
Collapse
Affiliation(s)
- Dingguo Zhang
- Biomedical Instrumentation Lab, S2.1-B4-02, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
| | | |
Collapse
|
8
|
Verdaasdonk BW, Koopman HFJM, van der Helm FCT. Energy efficient walking with central pattern generators: from passive dynamic walking to biologically inspired control. Biol Cybern 2009; 101:49-61. [PMID: 19504121 DOI: 10.1007/s00422-009-0316-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Accepted: 04/27/2009] [Indexed: 05/12/2023]
Abstract
Like human walking, passive dynamic walking-i.e. walking down a slope with no actuation except gravity-is energy efficient by exploiting the natural dynamics. In the animal world, neural oscillators termed central pattern generators (CPGs) provide the basic rhythm for muscular activity in locomotion. We present a CPG model, which automatically tunes into the resonance frequency of the passive dynamics of a bipedal walker, i.e. the CPG model exhibits resonance tuning behavior. Each leg is coupled to its own CPG, controlling the hip moment of force. Resonance tuning above the endogenous frequency of the CPG-i.e. the CPG's eigenfrequency-is achieved by feedback of both limb angles to their corresponding CPG, while integration of the limb angles provides resonance tuning at and below the endogenous frequency of the CPG. Feedback of the angular velocity of both limbs to their corresponding CPG compensates for the time delay in the loop coupling each limb to its CPG. The resonance tuning behavior of the CPG model allows the gait velocity to be controlled by a single parameter, while retaining the energy efficiency of passive dynamic walking.
Collapse
Affiliation(s)
- B W Verdaasdonk
- Department of Bio-mechanical Engineering, Faculty of Engineering Technology, University of Twente, 7500 AE, Enschede, The Netherlands.
| | | | | |
Collapse
|
9
|
Samu D, Eros P, Ujfalussy B, Kiss T. Robust path integration in the entorhinal grid cell system with hippocampal feed-back. Biol Cybern 2009; 101:19-34. [PMID: 19381679 DOI: 10.1007/s00422-009-0311-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 04/01/2009] [Indexed: 05/27/2023]
Abstract
Animals are able to update their knowledge about their current position solely by integrating the speed and the direction of their movement, which is known as path integration. Recent discoveries suggest that grid cells in the medial entorhinal cortex might perform some of the essential underlying computations of path integration. However, a major concern over path integration is that as the measurement of speed and direction is inaccurate, the representation of the position will become increasingly unreliable. In this paper, we study how allothetic inputs can be used to continually correct the accumulating error in the path integrator system. We set up the model of a mobile agent equipped with the entorhinal representation of idiothetic (grid cell) and allothetic (visual cells) information and simulated its place learning in a virtual environment. Due to competitive learning, a robust hippocampal place code emerges rapidly in the model. At the same time, the hippocampo-entorhinal feed-back connections are modified via Hebbian learning in order to allow hippocampal place cells to influence the attractor dynamics in the entorhinal cortex. We show that the continuous feed-back from the integrated hippocampal place representation is able to stabilize the grid cell code.
Collapse
Affiliation(s)
- Dávid Samu
- Department of Biophysics, KFKI Research Institute for Particle and Nuclear Physics, Hungarian Academy of Sciences, 1121 Budapest, Hungary
| | | | | | | |
Collapse
|
10
|
Christ SE, Van Essen DC, Watson JM, Brubaker LE, McDermott KB. The contributions of prefrontal cortex and executive control to deception: evidence from activation likelihood estimate meta-analyses. Cereb Cortex 2009; 19:1557-66. [PMID: 18980948 PMCID: PMC2693617 DOI: 10.1093/cercor/bhn189] [Citation(s) in RCA: 217] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previous neuroimaging studies have implicated the prefrontal cortex (PFC) and nearby brain regions in deception. This is consistent with the hypothesis that lying involves the executive control system. To date, the nature of the contribution of different aspects of executive control to deception, however, remains unclear. In the present study, we utilized an activation likelihood estimate (ALE) method of meta-analysis to quantitatively identify brain regions that are consistently more active for deceptive responses relative to truthful responses across past studies. We then contrasted the results with additional ALE maps generated for 3 different aspects of executive control: working memory, inhibitory control, and task switching. Deception-related regions in dorsolateral PFC and posterior parietal cortex were selectively associated with working memory. Additional deception regions in ventrolateral PFC, anterior insula, and anterior cingulate cortex were associated with multiple aspects of executive control. In contrast, deception-related regions in bilateral inferior parietal lobule were not associated with any of the 3 executive control constructs. Our findings support the notion that executive control processes, particularly working memory, and their associated neural substrates play an integral role in deception. This work provides a foundation for future research on the neurocognitive basis of deception.
Collapse
Affiliation(s)
- Shawn E Christ
- Department of Psychological Sciences, University of Missouri, Columbia, MO 65203, USA.
| | | | | | | | | |
Collapse
|
11
|
Just A, Kurtz L, de Wit C, Wagner C, Kurtz A, Arendshorst WJ. Connexin 40 mediates the tubuloglomerular feedback contribution to renal blood flow autoregulation. J Am Soc Nephrol 2009; 20:1577-85. [PMID: 19443640 PMCID: PMC2709687 DOI: 10.1681/asn.2008090943] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2008] [Accepted: 03/05/2009] [Indexed: 12/30/2022] Open
Abstract
Connexins are important in vascular development and function. Connexin 40 (Cx40), which plays a predominant role in the formation of gap junctions in the vasculature, participates in the autoregulation of renal blood flow (RBF), but the underlying mechanisms are unknown. Here, Cx40-deficient mice (Cx40-ko) had impaired steady-state autoregulation to a sudden step increase in renal perfusion pressure. Analysis of the mechanisms underlying this derangement suggested that a marked reduction in tubuloglomerular feedback (TGF) in Cx40-ko mice was responsible. In transgenic mice with Cx40 replaced by Cx45, steady-state autoregulation and TGF were weaker than those in wild-type mice but stronger than those in Cx40-ko mice. N omega-Nitro-L-arginine-methyl-ester (L-NAME) augmented the myogenic response similarly in all genotypes, leaving autoregulation impaired in transgenic animals. The responses of renovascular resistance and arterial pressure to norepinephrine and acetylcholine were similar in all groups before or after L-NAME inhibition. Systemic and renal vasoconstrictor responses to L-NAME were also similar in all genotypes. We conclude that Cx40 contributes to RBF autoregulation by transducing TGF-mediated signals to the afferent arteriole, a function that is independent of nitric oxide (NO). However, Cx40 is not required for the modulation of the renal myogenic response by NO, norepinephrine-induced renal vasoconstriction, and acetylcholine- or NO-induced vasodilation.
Collapse
Affiliation(s)
- Armin Just
- Department of Cell & Molecular Physiology, Carolina Cardiovascular Biology Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
| | | | | | | | | | | |
Collapse
|
12
|
Nagengast AJ, Braun DA, Wolpert DM. Optimal control predicts human performance on objects with internal degrees of freedom. PLoS Comput Biol 2009; 5:e1000419. [PMID: 19557193 PMCID: PMC2694986 DOI: 10.1371/journal.pcbi.1000419] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 05/19/2009] [Indexed: 11/18/2022] Open
Abstract
On a daily basis, humans interact with a vast range of objects and tools. A class of tasks, which can pose a serious challenge to our motor skills, are those that involve manipulating objects with internal degrees of freedom, such as when folding laundry or using a lasso. Here, we use the framework of optimal feedback control to make predictions of how humans should interact with such objects. We confirm the predictions experimentally in a two-dimensional object manipulation task, in which subjects learned to control six different objects with complex dynamics. We show that the non-intuitive behavior observed when controlling objects with internal degrees of freedom can be accounted for by a simple cost function representing a trade-off between effort and accuracy. In addition to using a simple linear, point-mass optimal control model, we also used an optimal control model, which considers the non-linear dynamics of the human arm. We find that the more realistic optimal control model captures aspects of the data that cannot be accounted for by the linear model or other previous theories of motor control. The results suggest that our everyday interactions with objects can be understood by optimality principles and advocate the use of more realistic optimal control models for the study of human motor neuroscience. Humans are highly skilled at tool use. Simple tools have no internal degrees of freedom. For example, knowing the position and orientation of a hammer allows us to, in theory, predict the forces it will generate on our hand when we wield it and the consequences our actions will have on the hammer. In contrast, more complex tools can have internal degrees of freedom, such as a glass of water in which the motion of the fluid (the internal degree of freedom) is not fully determined by the current position and orientation of the glass. Such objects can be difficult to control. Here we use a robotic interface to simulate complex objects with internal degrees of freedom and find that subjects are able to learn to control the objects and that the pattern of movement found across subjects is similar. We develop an optimal feedback control model and explain complex object interactions as a simple trade-off between effort and task accuracy.
Collapse
Affiliation(s)
- Arne J Nagengast
- Department of Engineering, Computational and Biological Learning Lab, University of Cambridge, Cambridge, United Kingdom.
| | | | | |
Collapse
|
13
|
Sutherland C, Doiron B, Longtin A. Feedback-induced gain control in stochastic spiking networks. Biol Cybern 2009; 100:475-489. [PMID: 19259695 DOI: 10.1007/s00422-009-0298-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 02/05/2009] [Indexed: 05/27/2023]
Abstract
The joint influence of recurrent feedback and noise on gain control in a network of globally coupled spiking leaky integrate-and-fire neurons is studied theoretically and numerically. The context of our work is the origin of divisive versus subtractive gain control, as mixtures of these effects are seen in a variety of experimental systems. We focus on changes in the slope of the mean firing frequency-versus-input bias (f-I) curve when the gain control signal to the cells comes from the cells' output spikes. Feedback spikes are modeled as alpha functions that produce an additive current in the current balance equation. For generality, they occur after a fixed minimum delay. We show that purely divisive gain control, i.e. changes in the slope of the f-I curve, arises naturally with this additive negative or positive feedback, due to a linearizing actions of feedback. Negative feedback alone lowers the gain, accounting in particular for gain changes in weakly electric fish upon pharmacological opening of the feedback loop as reported by Bastian (J Neurosci 6:553-562, 1986). When negative feedback is sufficiently strong it further causes oscillatory firing patterns which produce irregularities in the f-I curve. Small positive feedback alone increases the gain, but larger amounts cause abrupt jumps to higher firing frequencies. On the other hand, noise alone in open loop linearizes the f-I curve around threshold, and produces mixtures of divisive and subtractive gain control. With both noise and feedback, the combined gain control schemes produce a primarily divisive gain control shift, indicating the robustness of feedback gain control in stochastic networks. Similar results are found when the "input" parameter is the contrast of a time-varying signal rather than the bias current. Theoretical results are derived relating the slope of the f-I curve to feedback gain and noise strength. Good agreement with simulation results are found for inhibitory and excitatory feedback. Finally, divisive feedback is also found for conductance-based feedback (shunting or excitatory) with and without noise.
Collapse
Affiliation(s)
- Connie Sutherland
- Center for Neural Dynamics, University of Ottawa, 150 Louis Pasteur, Ottawa, K1N 6N5, Canada
| | | | | |
Collapse
|
14
|
Welch TDJ, Ting LH. A feedback model explains the differential scaling of human postural responses to perturbation acceleration and velocity. J Neurophysiol 2009; 101:3294-309. [PMID: 19357335 PMCID: PMC2694108 DOI: 10.1152/jn.90775.2008] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Accepted: 04/01/2009] [Indexed: 11/22/2022] Open
Abstract
Although the neural basis of balance control remains unknown, recent studies suggest that a feedback law on center-of-mass (CoM) kinematics determines the temporal patterning of muscle activity during human postural responses. We hypothesized that the same feedback law would also explain variations in muscle activity to support-surface translation as perturbation characteristics vary. Subject CoM motion was experimentally modulated using 34 different anterior-posterior support-surface translations of varying peak acceleration and velocity but the same total displacement. Electromyographic (EMG) recordings from several muscles of the lower limbs and trunk were compared to predicted EMG patterns from an inverted pendulum model under delayed feedback control. In both recorded and predicted EMG patterns, the initial burst of muscle activity scaled linearly with peak acceleration, whereas the tonic "plateau" region scaled with peak velocity. The relatively invariant duration of the initial burst was modeled by incorporating a transient, time-limited encoding of CoM acceleration inspired by muscle spindle primary afferent dynamic responses. The entire time course of recorded and predicted muscle activity compared favorably across all conditions, suggesting that the initial burst of muscle activity is not generated by feedforward neural mechanisms. Perturbation conditions were presented randomly and subjects maintained relatively constant feedback gains across all conditions. In contrast, an optimal feedback solution based on a trade-off between CoM stabilization and energy expenditure predicted that feedback gains should change with perturbation characteristics. These results suggest that an invariant feedback law was used to generate the entire time course of muscle activity across a variety of postural disturbances.
Collapse
Affiliation(s)
- Torrence D J Welch
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332-0535, USA
| | | |
Collapse
|
15
|
Sun SY, Xu Y, Wang D. Regulation of environmental factors on the expression of a solid-state specific lipase (Lip1) with Rhizopus chinensis by western blot and indirect Elisa. Bioresour Technol 2009; 100:3152-3156. [PMID: 19269167 DOI: 10.1016/j.biortech.2009.01.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 05/27/2023]
Abstract
To identify which solid-state typical environmental factors are involved in the induction of a solid-state special lipase (Lip1), western blot and Elisa based on Lip1 antibody were used. A low water activity played a significant role in the induction of Lip1, as evidenced by the increased expression level (20-46 microg/g dry cell) along with the decrease of water activity (0.927-0.969). Physical barrier against hyphal extension was found to be another required factor, since the expression of Lip1 was significantly enhanced by 3-fold using a membrane with smaller pore size (0.45 and 0.22 microm) covered on top of surface culture.
Collapse
Affiliation(s)
- Shu Yang Sun
- Key Laboratory of Industrial Biotechnology of Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi 214122, PR China
| | | | | |
Collapse
|
16
|
Smith RJ, Tenore F, Huberdeau D, Etienne-Cummings R, Thakor NV. Continuous decoding of finger position from surface EMG signals for the control of powered prostheses. Annu Int Conf IEEE Eng Med Biol Soc 2009; 2008:197-200. [PMID: 19162627 DOI: 10.1109/iembs.2008.4649124] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
As development toward multi-fingered dexterous prosthetic hands continues, there is a growing need for more flexible and intuitive control schemes. Through the use of generalized electrode placement and well-established methods of pattern recognition, we have developed a basis for asynchronous decoding of finger positions. With the present method, correlations as large as 0.91 and mean overall decoding errors of approximately 11% have been achieved with average decoding errors of between decoded and actual conformation of the metacarpophalangeal joints of individual fingers. It is hoped that these results will serve as a foundation from which to encourage further investigation into more intuitive methods of myoelectric control of powered upper limb prostheses.
Collapse
Affiliation(s)
- Ryan J Smith
- Biomedical Engineering department, The Johns Hopkins University, Baltimore, MD, USA.
| | | | | | | | | |
Collapse
|
17
|
Guo D, Li C. Stochastic and coherence resonance in feed-forward-loop neuronal network motifs. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:051921. [PMID: 19518494 DOI: 10.1103/physreve.79.051921] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Indexed: 05/27/2023]
Abstract
The relationships between noise and complex dynamic behaviors of neuronal ensembles are key questions in computational neuroscience, particularly in understanding some basic signal transmission mechanisms of the brain. Here we systemically investigate both the stochastic resonance (SR) and coherence resonance (CR) in the triple-neuron feed-forward-loop (FFL) network motifs by computational modeling. We use the Izhikevich neuron model as well as the chemical coupling to build the FFL motifs, and consider all possible motif types. The simulation results demonstrate that these motifs can exploit noise to enrich its dynamic performance. With a proper choice of noise intensities, both the SR and CR can be exhibited in many types of the FFLs. On the other hand, our results also indicate that the coupling strength serves as a control parameter, which has great impacts on the stochastic dynamics of the FFL motifs. Additionally, biological implications of presented results in the field of neuroscience are outlined.
Collapse
Affiliation(s)
- Daqing Guo
- Centre for Nonlinear and Complex Systems, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | | |
Collapse
|
18
|
Chang W, Jin DZ. Spike propagation in driven chain networks with dominant global inhibition. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:051917. [PMID: 19518490 DOI: 10.1103/physreve.79.051917] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Indexed: 05/27/2023]
Abstract
Spike propagation in chain networks is usually studied in the synfire regime, in which successive groups of neurons are synaptically activated sequentially through the unidirectional excitatory connections. Here we study the dynamics of chain networks with dominant global feedback inhibition that prevents the synfire activity. Neural activity is driven by suprathreshold external inputs. We analytically and numerically demonstrate that spike propagation along the chain is a unique dynamical attractor in a wide parameter regime. The strong inhibition permits a robust winner-take-all propagation in the case of multiple chains competing via the inhibition.
Collapse
Affiliation(s)
- Wonil Chang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | | |
Collapse
|
19
|
Roudi Y, Tyrcha J, Hertz J. Ising model for neural data: model quality and approximate methods for extracting functional connectivity. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:051915. [PMID: 19518488 DOI: 10.1103/physreve.79.051915] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 04/03/2009] [Indexed: 05/24/2023]
Abstract
We study pairwise Ising models for describing the statistics of multineuron spike trains, using data from a simulated cortical network. We explore efficient ways of finding the optimal couplings in these models and examine their statistical properties. To do this, we extract the optimal couplings for subsets of size up to 200 neurons, essentially exactly, using Boltzmann learning. We then study the quality of several approximate methods for finding the couplings by comparing their results with those found from Boltzmann learning. Two of these methods--inversion of the Thouless-Anderson-Palmer equations and an approximation proposed by Sessak and Monasson--are remarkably accurate. Using these approximations for larger subsets of neurons, we find that extracting couplings using data from a subset smaller than the full network tends systematically to overestimate their magnitude. This effect is described qualitatively by infinite-range spin-glass theory for the normal phase. We also show that a globally correlated input to the neurons in the network leads to a small increase in the average coupling. However, the pair-to-pair variation in the couplings is much larger than this and reflects intrinsic properties of the network. Finally, we study the quality of these models by comparing their entropies with that of the data. We find that they perform well for small subsets of the neurons in the network, but the fit quality starts to deteriorate as the subset size grows, signaling the need to include higher-order correlations to describe the statistics of large networks.
Collapse
Affiliation(s)
- Yasser Roudi
- NORDITA, Roslagstullsbacken 23, 10691 Stockholm, Sweden
| | | | | |
Collapse
|
20
|
Takahashi YK, Kori H, Masuda N. Self-organization of feed-forward structure and entrainment in excitatory neural networks with spike-timing-dependent plasticity. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:051904. [PMID: 19518477 DOI: 10.1103/physreve.79.051904] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Indexed: 05/27/2023]
Abstract
Spike-timing dependent plasticity (STDP) is an organizing principle of biological neural networks. While synchronous firing of neurons is considered to be an important functional block in the brain, how STDP shapes neural networks possibly toward synchrony is not entirely clear. We examine relations between STDP and synchronous firing in spontaneously firing neural populations. Using coupled heterogeneous phase oscillators placed on initial networks, we show numerically that STDP prunes some synapses and promotes formation of a feedforward network. Eventually a pacemaker, which is the neuron with the fastest inherent frequency in our numerical simulations, emerges at the root of the feedforward network. In each oscillatory cycle, a packet of neural activity is propagated from the pacemaker to downstream neurons along layers of the feedforward network. This event occurs above a clear-cut threshold value of the initial synaptic weight. Below the threshold, neurons are self-organized into separate clusters each of which is a feedforward network.
Collapse
Affiliation(s)
- Yuko K Takahashi
- Faculty of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | | | | |
Collapse
|
21
|
Chow AY, Dickerson CR. Shoulder strength of females while sitting and standing as a function of hand location and force direction. Appl Ergon 2009; 40:303-308. [PMID: 19162258 DOI: 10.1016/j.apergo.2008.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 12/11/2008] [Accepted: 12/14/2008] [Indexed: 05/27/2023]
Abstract
This study evaluated single-handed isometric push strength capabilities of females working at or above-shoulder level. We examined the influence of force exertion direction (vertical, horizontal and lateral), angle of shoulder flexion from horizontal (0 degrees, 30 degrees, 60 degrees and 90 degrees) and gross body posture (standing and sitting), on maximal volitional shoulder strength. Force exertion direction had the greatest affect on shoulder strength (p<0.0001). Strength was greatest in the vertical axis pushing downwards and weakest in the horizontal plane pushing forwards. Angle influenced shoulder strength when considered together with direction (p<0.0001). However, these effects were dominated by direction results. Marginal differences in strength existed between sitting and standing (p>0.05). These results can be used to design workspaces that consider individual strength limitations and their dependence on force direction, work orientation, and gross body posture.
Collapse
Affiliation(s)
- Amy Y Chow
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1
| | | |
Collapse
|
22
|
Sakaguchi H. Ratio control in a cascade model of cell differentiation. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:051916. [PMID: 19518489 DOI: 10.1103/physreve.79.051916] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 03/16/2009] [Indexed: 05/27/2023]
Abstract
We propose a kind of reaction-diffusion equations for cell differentiation, which exhibits the Turing instability. If the diffusivity of some variables is set to be infinity, we get coupled competitive reaction-diffusion equations with a global feedback term. The size ratio of each cell type is controlled by a system parameter in the model. Finally, we extend the model to a cascade model of cell differentiation. A hierarchical spatial structure appears as a result of the cell differentiation. The size ratio of each cell type is also controlled by the system parameter.
Collapse
Affiliation(s)
- Hidetsugu Sakaguchi
- Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
| |
Collapse
|
23
|
Beloussov LV, Luchinskaya NN, Ermakov AS, Glagoleva NS. Gastrulation in amphibian embryos, regarded as a succession of biomechanical feedback events. Int J Dev Biol 2009; 50:113-22. [PMID: 16479480 DOI: 10.1387/ijdb.052057lb] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Gastrulation in amphibian embryos is a composition of several differently located morphogenetic movements which are perfectly coordinated with each other both in space and time. We hypothesize that this coordination is mediated by biomechanical interactions between different parts of a gastrulating embryo based upon the tendency of each part to hyper-restore the value of its mechanical stress. The entire process of gastrulation in amphibian embryos is considered as a chain of these mutually coupled reactions, which are largely dependent upon the geometry of a given embryo part. We divide gastrulation into several partly overlapped steps, give a theoretical interpretation for each of them, formulate the experiments for testing our interpretation and describe the experimental results which confirm our point of view. Among the predicted experimental results are: inhibition of radial cell intercalation by relaxation of tensile stresses at the blastula stage; inversion of convergent intercalation movements by relaxation of circumferential stresses at the early gastrula stage; stress-promoted reorientation of axial rudiments, and others. We also show that gastrulation is going on under a more or less constant average value of tensile stresses which may play a role as rate-limiting factors. A macro-morphological biomechanical approach developed in this paper is regarded as complementary to exploring the molecular machinery of gastrulation.
Collapse
Affiliation(s)
- Lev V Beloussov
- Faculty of Biology, Moscow State University, Moscow, Russia.
| | | | | | | |
Collapse
|
24
|
de Graaf JB, Frolov A, Fiocchi M, Nazarian B, Anton JL, Pailhous J, Bonnard M. Preparing for a motor perturbation: early implication of primary motor and somatosensory cortices. Hum Brain Mapp 2009; 30:575-87. [PMID: 18172849 DOI: 10.1002/hbm.20526] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Although preparation of voluntary movement has been extensively studied, very few human neuroimaging studies have examined preparation of an intentional reaction to a motor perturbation. This latter type of preparation is fundamental for adaptive motor capabilities in everyday life because it allows a desired motor output to be maintained despite changes in external forces. Using fMRI, we studied how the sensorimotor cortical network is implicated in preparing to react to a mechanical motor perturbation. While maintaining a given wrist angle against a small force, subjects were instructed to prepare a reaction to a subsequent wrist angle displacement. This reaction consisted of, either resisting the imposed movement, or remaining passive. During the preparation of both reactions we found an early implication of M1 and S1 but no implication at all of the higher order motor area preSMA. This is clearly different from what has been found for voluntary movement preparation. These results show that the sensorimotor network activation during preparation of voluntary motor acts depends on whether one expects a motor perturbation to occur: when external forces can interfere with ongoing motor acts, the primary sensorimotor areas must be ready to react as quickly as possible to perturbations that could prevent the goal of the ongoing motor act from being achieved.
Collapse
Affiliation(s)
- Jozina B de Graaf
- Mediterranean Institute of Cognitive Neuroscience, UMR 6193, CNRS-University of Aix-Marseille, Marseille, Cedex 20, France.
| | | | | | | | | | | | | |
Collapse
|
25
|
Stepp CE, Heaton JT, Rolland RG, Hillman RE. Neck and face surface electromyography for prosthetic voice control after total laryngectomy. IEEE Trans Neural Syst Rehabil Eng 2009; 17:146-55. [PMID: 19304494 PMCID: PMC3392649 DOI: 10.1109/tnsre.2009.2017805] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The electrolarynx (EL) is a common rehabilitative speech aid for individuals who have undergone total laryngectomy, but they typically lack pitch control and require the exclusive use of one hand. The viability of using neck and face surface electromyography (sEMG) to control the onset, offset, and pitch of an EMG-controlled EL (EMG-EL) was studied. Eight individuals who had undergone total laryngectomy produced serial and running speech using a typical handheld EL and the EMG-EL while attending to real-time visual sEMG biofeedback. Running speech tokens produced with the EMG-EL were examined for naturalness by 10 listeners relative to those produced with a typical EL using a visual analog scale. Serial speech performance was assessed as the percentage of words that were fully voiced and pauses that were successfully produced. Results of the visual analog scale assessment indicated that individuals were able to use the EMG-EL without training to produce running speech perceived as natural as that produced with a typical handheld EL. All participants were able to produce running and serial speech with the EMG-EL controlled by sEMG from multiple recording locations, with the superior ventral neck or submental surface locations providing at least one of the two best control locations.
Collapse
Affiliation(s)
- Cara E Stepp
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA.
| | | | | | | |
Collapse
|
26
|
Cowan SM, Crossley KM. Does gender influence neuromotor control of the knee and hip? J Electromyogr Kinesiol 2009; 19:276-82. [PMID: 17904864 DOI: 10.1016/j.jelekin.2007.07.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 04/27/2007] [Accepted: 07/19/2007] [Indexed: 11/21/2022] Open
Abstract
Patellofemoral pain (PFP) is a common condition that occurs more frequently in females. Anatomical, hormonal and neuromuscular factors have been proposed to contribute to the increased incidence of PFP in females, with neuromuscular factors considered to be of particular importance. This cross-sectional study aimed to evaluate differences in the neuromotor control of the knee and hip muscles between genders and to investigate whether clinical measures of hip rotation range and strength were associated with EMG measures of hip and thigh motor control. Twenty-nine (16 female and 13 male) asymptomatic participants completed a visual choice reaction-time stair stepping task. EMG activity was recorded from vastus medialis oblique, vastus lateralis, anterior and posterior gluteus medius muscles. In addition hip rotation range of motion and hip external rotation, abduction and trunk strength were assessed. There were no differences in the timing or peak of EMG activation of the vasti or gluteus medius muscle between genders during the stepping task. There were however significant associations between EMG measures of motor control of the vasti and hip strength in both females and males. These findings are suggestive of a link between hip muscle control and vasti neuromotor control.
Collapse
Affiliation(s)
- Sallie M Cowan
- Centre Health Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Victoria 3010, Australia.
| | | |
Collapse
|
27
|
Gregson RAM. Conceptual problems in cardiological prediction. Nonlinear Dynamics Psychol Life Sci 2009; 13:209-223. [PMID: 19327255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The internal dynamics of cardiac activity are complex and can vary significantly over time, individuals may exhibit chaos, singularities, and nonstationarity at various time scales. The heart is one of the most studied psychobiological nonlinear systems, at various levels of mathematical and statistical sophistication. Some of its properties can be associated with morbidity or mortality. Prediction of when activity will terminate without acute clinical intervention is only possible at a statistical level over homogeneous groups of subjects under known conditions. Various consequent problems with data analysis at both individual and group levels are reviewed; the two related inferential issues, from individual dynamics to epidemiology, and from epidemiology to individual treatment issues, are critically examined.
Collapse
Affiliation(s)
- Robert A M Gregson
- Department of Psychology, Australian National University, Canberra, ACT, 0200, Australia.
| |
Collapse
|
28
|
Xu J, Shang HL, Huang Y. Effects of delays on the basin boundary of attraction in a hopfield network of two delay-connecting neurons. Nonlinear Dynamics Psychol Life Sci 2009; 13:161-180. [PMID: 19327253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A continuous-time Hopfield neural network with two delay-connecting neurons is considered in this paper. Some sufficient conditions for the number and delay-independent stability of the equilibria in the network are given analytically. It is necessary to classify the attraction domains since multiple attractors coexist when the sufficient conditions are satisfied. Thus, effects of the delays on the boundary separating the basins of attraction of the stable equilibria are investigated analytically and numerically. The results show that the evolution of the boundary depends on the delays and is neither simple nor intuitive even if the delays do not affect the stability of attractors. The results provide also the possibility to design the network according to the memory pattern and storage.
Collapse
Affiliation(s)
- Jian Xu
- xuSchool of Aerospace Engineering and Applied Mechanics,Tongji University, Shanghai, 200092, China.
| | | | | |
Collapse
|
29
|
Milton J, Townsend JL, King MA, Ohira T. Balancing with positive feedback: the case for discontinuous control. Philos Trans A Math Phys Eng Sci 2009; 367:1181-1193. [PMID: 19218158 DOI: 10.1098/rsta.2008.0257] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Experimental observations indicate that positive feedback plays an important role for maintaining human balance in the upright position. This observation is used to motivate an investigation of a simple switch-like controller for postural sway in which corrective movements are made only when the vertical displacement angle exceeds a certain threshold. This mechanism is shown to be consistent with the experimentally observed variations in the two-point correlation for human postural sway. Analysis of first-passage times for this model suggests that this control strategy may slow escape by taking advantage of two intrinsic properties of a stochastic unstable first-order delay differential equation: (i) time delay and (ii) the possibility that the dynamics can be 'temporarily confined' near the origin.
Collapse
Affiliation(s)
- John Milton
- W. M. Keck Science Center, The Claremont Colleges, Claremont, CA 91711, USA.
| | | | | | | |
Collapse
|
30
|
Abstract
Neural delays are a general property of computations carried out by neural circuits. Delays are a natural consequence of temporal summation and coding used by the nervous system to integrate information from multiple resources. For adaptive behaviour, however, these delays must be compensated. In order to sense and interact with moving objects, for example, the visual system must predict the future position of the object to compensate for delays. In this paper, we address two critical questions concerning the implementation of the compensation mechanisms in the brain, namely, where does compensation occur and how is it realized. We present evidence showing that compensation can happen in both the motor and sensory systems, and that compensation using 'diagonal neural pathways' is a suitable strategy for implementing compensation in the visual system. In this strategy, neural signals in the early stage of information processing are sent to the future cortical positions that correspond to the distance the object will travel in the period of transmission delay. We propose a computational model to elucidate this using the retinal visual information pathway.
Collapse
Affiliation(s)
- Romi Nijhawan
- Department of Psychology, University of Sussex, Falmer, East Sussex BN1 9QH, UK.
| | | |
Collapse
|
31
|
Abstract
The influence of time delay in systems of two coupled excitable neurons is studied in the framework of the FitzHugh-Nagumo model. A time delay can occur in the coupling between neurons or in a self-feedback loop. The stochastic synchronization of instantaneously coupled neurons under the influence of white noise can be deliberately controlled by local time-delayed feedback. By appropriate choice of the delay time, synchronization can be either enhanced or suppressed. In delay-coupled neurons, antiphase oscillations can be induced for sufficiently large delay and coupling strength. The additional application of time-delayed self-feedback leads to complex scenarios of synchronized in-phase or antiphase oscillations, bursting patterns or amplitude death.
Collapse
Affiliation(s)
- Eckehard Schöll
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
| | | | | | | |
Collapse
|
32
|
Morgan SW, Plank G, Biktasheva IV, Biktashev VN. Low energy defibrillation in human cardiac tissue: a simulation study. Biophys J 2009; 96:1364-73. [PMID: 19217854 DOI: 10.1016/j.bpj.2008.11.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 11/21/2008] [Indexed: 11/19/2022] Open
Abstract
We aim to assess the effectiveness of feedback-controlled resonant drift pacing as a method for low energy defibrillation. Antitachycardia pacing is the only low energy defibrillation approach to have gained clinical significance, but it is still suboptimal. Low energy defibrillation would avoid adverse side effects associated with high voltage shocks and allow the application of implantable cardioverter defibrillator (ICD) therapy, in cases where such therapy is not tolerated today. We present results of computer simulations of a bidomain model of cardiac tissue with human atrial ionic kinetics. Reentry was initiated and low energy shocks were applied with the same period as the reentry, using feedback to maintain resonance. We demonstrate that such stimulation can move the core of reentrant patterns, in the direction that depends on the location of the electrodes and the time delay in the feedback. Termination of reentry is achieved with shock strength one-order-of-magnitude weaker than in conventional single-shock defibrillation. We conclude that resonant drift pacing can terminate reentry at a fraction of the shock strength currently used for defibrillation and can potentially work where antitachycardia pacing fails, due to the feedback mechanisms. Success depends on a number of details that these numerical simulations have uncovered.
Collapse
Affiliation(s)
- Stuart W Morgan
- Department of Mathematical Sciences, University of Liverpool, Liverpool, United Kingdom
| | | | | | | |
Collapse
|
33
|
Abstract
Eukaryotic cells can move spontaneously without being guided by external cues. For such spontaneous movements, a variety of different modes have been observed, including the amoeboid-like locomotion with protrusion of multiple pseudopods, the keratocyte-like locomotion with a widely spread lamellipodium, cell division with two daughter cells crawling in opposite directions, and fragmentations of a cell to multiple pieces. Mutagenesis studies have revealed that cells exhibit these modes depending on which genes are deficient, suggesting that seemingly different modes are the manifestation of a common mechanism to regulate cell motion. In this paper, we propose a hypothesis that the positive feedback mechanism working through the inhomogeneous distribution of regulatory proteins underlies this variety of cell locomotion and cytofission. In this hypothesis, a set of regulatory proteins, which we call cortical factors, suppress actin polymerization. These suppressing factors are diluted at the extending front and accumulated at the retracting rear of cell, which establishes a cellular polarity and enhances the cell motility, leading to the further accumulation of cortical factors at the rear. Stochastic simulation of cell movement shows that the positive feedback mechanism of cortical factors stabilizes or destabilizes modes of movement and determines the cell migration pattern. The model predicts that the pattern is selected by changing the rate of formation of the actin-filament network or the threshold to initiate the network formation.
Collapse
Affiliation(s)
- Shin I Nishimura
- Department of Computational Science and Engineering, Nagoya University, Nagoya, Japan.
| | | | | |
Collapse
|
34
|
Hu K, Peng CK, Czosnyka M, Zhao P, Novak V. Nonlinear assessment of cerebral autoregulation from spontaneous blood pressure and cerebral blood flow fluctuations. ACTA ACUST UNITED AC 2009; 8:60-71. [PMID: 18080758 DOI: 10.1007/s10558-007-9045-5] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cerebral autoregulation (CA) is an most important mechanism responsible for the relatively constant blood flow supply to brain when cerebral perfusion pressure varies. Its assessment in nonacute cases has been relied on the quantification of the relationship between noninvasive beat-to-beat blood pressure (BP) and blood flow velocity (BFV). To overcome the nonstationary nature of physiological signals such as BP and BFV, a computational method called multimodal pressure-flow (MMPF) analysis was recently developed to study the nonlinear BP-BFV relationship during the Valsalva maneuver (VM). The present study aimed to determine (i) whether this method can estimate autoregulation from spontaneous BP and BFV fluctuations during baseline rest conditions; (ii) whether there is any difference between the MMPF measures of autoregulation based on intra-arterial BP (ABP) and based on cerebral perfusion pressure (CPP); and (iii) whether the MMPF method provides reproducible and reliable measure for noninvasive assessment of autoregulation. To achieve these aims, we analyzed data from existing databases including: (i) ABP and BFV of 12 healthy control, 10 hypertensive, and 10 stroke subjects during baseline resting conditions and during the Valsalva maneuver, and (ii) ABP, CPP, and BFV of 30 patients with traumatic brain injury (TBI) who were being paralyzed, sedated, and ventilated. We showed that autoregulation in healthy control subjects can be characterized by specific phase shifts between BP and BFV oscillations during the Valsalva maneuver, and the BP-BFV phase shifts were reduced in hypertensive and stroke subjects (P < 0.01), indicating impaired autoregulation. Similar results were found during baseline condition from spontaneous BP and BFV oscillations. The BP-BFV phase shifts obtained during baseline and during VM were highly correlated (R > 0.8, P < 0.0001), showing no statistical difference (paired-t test P > 0.47). In TBI patients there were strong correlations between phases of ABP and CPP oscillations (R = 0.99, P < 0.0001) and, thus, between ABP-BFV and CPP-BFV phase shifts (P < 0.0001, R = 0.76). By repeating the MMPF 4 times on data of TBI subjects, each time on a selected cycle of spontaneous BP and BFV oscillations, we showed that MMPF had better reproducibility than traditional autoregulation index. These results indicate that the MMPF method, based on instantaneous phase relationships between cerebral blood flow velocity and peripheral blood pressure, has better performance than the traditional standard method, and can reliably assess cerebral autoregulation dynamics from ambulatory blood pressure and cerebral blood flow during supine rest conditions.
Collapse
Affiliation(s)
- Kun Hu
- Division of Gerontology, Beth Israel Deaconess Medical Center, Harvard Medical School, 812 Stoneman Bldg, 330 Brookline Avenue, Boston, MA 02115, USA.
| | | | | | | | | |
Collapse
|
35
|
Batzel JJ, Novak V, Kappel F, Olufsen MS, Tran HT. Introduction to the special issues: Short-term cardiovascular-respiratory control mechanisms. ACTA ACUST UNITED AC 2009; 8:1-4. [PMID: 18196456 DOI: 10.1007/s10558-007-9053-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
36
|
Schneider FM, Schöll E, Dahlem MA. Controlling the onset of traveling pulses in excitable media by nonlocal spatial coupling and time-delayed feedback. Chaos 2009; 19:015110. [PMID: 19335014 DOI: 10.1063/1.3096411] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The onset of pulse propagation is studied in a reaction-diffusion (RD) model with control by augmented transmission capability that is provided either along nonlocal spatial coupling or by time-delayed feedback. We show that traveling pulses occur primarily as solutions to the RD equations, while augmented transmission changes excitability. For certain ranges of the parameter settings, defined as weak susceptibility and moderate control, respectively, the hybrid model can be mapped to the original RD model. This results in an effective change in RD parameters controlled by augmented transmission. Outside moderate control parameter settings new patterns are obtained, for example, stepwise propagation due to delay-induced oscillations. Augmented transmission constitutes a signaling system complementary to the classical RD mechanism of pattern formation. Our hybrid model combines the two major signaling systems in the brain, namely, volume transmission and synaptic transmission. Our results provide insights into the spread and control of pathological pulses in the brain.
Collapse
Affiliation(s)
- Felix M Schneider
- Institut fur Theoretische Physik, Technische Universitat Berlin, Berlin, Germany
| | | | | |
Collapse
|
37
|
Mujica-Parodi LR, Korgaonkar M, Ravindranath B, Greenberg T, Tomasi D, Wagshul M, Ardekani B, Guilfoyle D, Khan S, Zhong Y, Chon K, Malaspina D. Limbic dysregulation is associated with lowered heart rate variability and increased trait anxiety in healthy adults. Hum Brain Mapp 2009; 30:47-58. [PMID: 18041716 DOI: 10.1002/hbm.20483] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVES We tested whether dynamic interaction between limbic regions supports a control systems model of excitatory and inhibitory components of a negative feedback loop, and whether dysregulation of those dynamics might correlate with trait differences in anxiety and their cardiac characteristics among healthy adults. EXPERIMENTAL DESIGN Sixty-five subjects received fMRI scans while passively viewing angry, fearful, happy, and neutral facial stimuli. Subjects also completed a trait anxiety inventory, and were monitored using ambulatory wake ECG. The ECG data were analyzed for heart rate variability, a measure of autonomic regulation. The fMRI data were analyzed with respect to six limbic regions (bilateral amygdala, bilateral hippocampus, Brodmann Areas 9, 45) using limbic time-series cross-correlations, maximum BOLD amplitude, and BOLD amplitude at each point in the time-series. PRINCIPAL OBSERVATIONS Diminished coupling between limbic time-series in response to the neutral, fearful, and happy faces was associated with greater trait anxiety, greater sympathetic activation, and lowered heart rate variability. Individuals with greater levels of trait anxiety showed delayed activation of Brodmann Area 45 in response to the fearful and happy faces, and lowered Brodmann Area 45 activation with prolonged left amygdala activation in response to the neutral faces. CONCLUSIONS The dynamics support limbic regulation as a control system, in which dysregulation, as assessed by diminished coupling between limbic time-series, is associated with increased trait anxiety and excitatory autonomic outputs. Trait-anxious individuals showed delayed inhibitory activation in response to overt-affect stimuli and diminished inhibitory activation with delayed extinction of excitatory activation in response to ambiguous-affect stimuli.
Collapse
Affiliation(s)
- Lilianne R Mujica-Parodi
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794-8181, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Hon N, Thompson R, Sigala N, Duncan J. Evidence for long-range feedback in target detection: Detection of semantic targets modulates activity in early visual areas. Neuropsychologia 2009; 47:1721-7. [PMID: 19397867 DOI: 10.1016/j.neuropsychologia.2009.02.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 01/29/2009] [Accepted: 02/06/2009] [Indexed: 11/18/2022]
Abstract
In a variety of attention and search tasks, single-cell recordings of the primate brain have frequently shown an enhancement of responses in early visual areas to selected target stimuli. This enhancement is observed only at longer latencies, suggesting the possibility that it reflects the action of feedback or return signals from upstream processing areas. However, in typical studies, targets are specified on the basis of elementary visual features; as these are coded at multiple levels of the visual system, it is impossible to determine where enhanced target processing begins. Using human functional magnetic resonance imaging (fMRI), we demonstrate enhancement of activity in early visual areas even when low-level visual information is insufficient for target detection to occur. We found enhanced activity in early visual areas to targets defined purely by semantic category, suggesting that feedback signals returning from at least as far forward as temporal lobe semantic processing can influence visual responses. These findings also suggest feedback signaling as a mechanism by which early and late brain systems coding for different properties of a target object can integrate their activity, allowing for the target object to dominate overall processing.
Collapse
Affiliation(s)
- Nicholas Hon
- Department of Psychology, National University of Singapore, Singapore.
| | | | | | | |
Collapse
|
39
|
Abstract
BACKGROUND Contraction-excitation feedback, that is, electrophysiologic changes that are caused or preceded by mechanical changes of the myocardium, has been extensively studied in the ventricles. The role of contraction-excitation feedback in the atria, and more particularly in the genesis and maintenance of atrial fibrillation, has been less adequately investigated. HYPOTHESIS The aim of the present study was to determine whether increased right atrial pressure (RAP) facilitates the induction of atrial fibrillation (AF) in patients with a history of lone AF. METHODS Sixteen patients with a history of paroxysmal AF but without structural heart disease were included in the study. All patients underwent electrophysiologic study at both a lower (3.1 +/- 2.0 mmHg) and (in 13 cases) a higher (6.4 +/- 2.5 mmHg) RAP. "Higher" was considered the pressure following rapid (in about 30 min) intravenous administration of normal saline or before the administration of a diuretic. RESULTS Rapid atrial pacing induced AF in 19 of 29 attempts. At a lower pressure, rapid pacing induced brief (3 s to 3 min) AF in 3 of 16 patients, long-lasting (> 3 min) AF in 3 of 16 patients, and no AF in 10 of 16 patients. At a higher pressure, brief AF was induced in 3 of 10 patients in whom no AF could be induced at a lower pressure, and long-lasting AF in 10 patients in whom either brief AF (3 cases) or no AF (7 cases) was induced at a lower pressure. In 11 patients, in whom Wenckebach periodicity was determined at both higher and lower pressure, the critical cycle length at which atrioventricular block appeared was significantly (p < 0.001, paired t-test) longer (349.1 +/- 44.4 ms, i.e., +15.5 +/- 11.3 ms) at higher than at lower atrial pressure (333.6 +/- 41.0 ms). In nine patients, in whom Wenckebach periodicity was determined and two rhythms occurred at different pressures, the critical cycle length was 332.2 +/- 45.8 ms when associated with sinus rhythm, and significantly (p < 0.01) longer (344.4 +/- 48.0 ms, i.e., +12.2 +/- 8.3 ms) when associated with induction of AF. CONCLUSION In patients with lone atrial fibrillation, modest increases in atrial pressure may facilitate the induction of atrial fibrillation.
Collapse
Affiliation(s)
- A Antoniou
- Department of Clinical Therapeutics, Medical School of Athens University, Greece
| | | | | | | | | |
Collapse
|
40
|
Zou X, Hang HF, Chu J, Zhuang YP, Zhang SL. Oxygen uptake rate optimization with nitrogen regulation for erythromycin production and scale-up from 50 L to 372 m3 scale. Bioresour Technol 2009; 100:1406-1412. [PMID: 18929481 DOI: 10.1016/j.biortech.2008.09.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 09/02/2008] [Accepted: 09/03/2008] [Indexed: 05/26/2023]
Abstract
Effects of different nitrogen sources on the erythromycin production were investigated in 50 l fermenter with multi-parameter monitoring system firstly. With the increase of soybean flour concentration from 27 g/l to 37 g/l to the culture medium, the erythromycin production had no obvious increase. Whereas adding corn steep liquor 15 g/l in the medium was beneficial for the production of erythromycin, the maximum erythromycin production was 22.2% higher than that of the control. It was found that corn steep liquor can regulate and enhance the oxygen uptake rate (OUR) which characterizes the activity of the microbial metabolism by inter-scale observation and data association. Both Intracellular and extracellular organic acids of central metabolism were analyzed, and it was found that the whole levels of lactic acid, pyruvic acid, citric acid, and propionic acid were higher than those of control before 64th h. The consumption amount of amino acids, which could be transformed into the precursors for erythromycin synthesis (i.e. threonine, serine, alanine, glycine and phenylalanine), were elevated compared with the control in erythromycin biosynthesis phase. The results indicated that corn steep liquor can regulate OUR to certain level in the early phase of fermentation, and enhance the metabolic flux of erythromycin biosynthesis. Erythromycin production was successfully scaled up from a laboratory scale (50 l fermenter) to an industrial scale (132 m(3) and 372 m(3)) using OUR as the scale-up parameter. Erythromycin production on industrial scale was similar to that at laboratory scale.
Collapse
Affiliation(s)
- Xiang Zou
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China
| | | | | | | | | |
Collapse
|
41
|
Carlsen AN, Chua R, Inglis JT, Sanderson DJ, Franks IM. Differential effects of startle on reaction time for finger and arm movements. J Neurophysiol 2009; 101:306-14. [PMID: 19005006 PMCID: PMC2637008 DOI: 10.1152/jn.00878.2007] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Accepted: 11/03/2008] [Indexed: 11/22/2022] Open
Abstract
Recent studies using a reaction time (RT) task have reported that a preprogrammed response could be triggered directly by a startling acoustic stimulus (115-124 dB) presented along with the usual "go" signal. It has been suggested that details of the upcoming response could be stored subcortically and are accessible by the startle volley, directly eliciting the correct movement. However, certain muscles (e.g., intrinsic hand) are heavily dependent on cortico-motoneuronal connections and thus would not be directly subject to the subcortical startle volley in a similar way to muscles whose innervations include extensive reticular connections. In this study, 14 participants performed 75 trials in each of two tasks within a RT paradigm: an arm extension task and an index finger abduction task. In 12 trials within each task, the regular go stimulus (82 dB) was replaced with a 115-dB startling stimulus. Results showed that, in the arm task, the presence of a startle reaction led to significantly shorter latency arm movements compared with the effect of the increased stimulus intensity alone. In contrast, for the finger task, no additional decrease in RT caused by startle was observed. Taken together, these results suggest that only movements that involve muscles more strongly innervated by subcortical pathways are susceptible to response advancement by startle.
Collapse
Affiliation(s)
- Anthony N Carlsen
- School of Human Kinetics, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
| | | | | | | | | |
Collapse
|
42
|
Murphy RB, Young BR, Kecman V. Optimising operation of a biological wastewater treatment application. ISA Trans 2009; 48:93-97. [PMID: 18762295 DOI: 10.1016/j.isatra.2008.07.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 07/22/2008] [Accepted: 07/29/2008] [Indexed: 05/26/2023]
Abstract
The objective of this work was to optimize (minimize) the compressed air required to control the rate of ammonia removal in a commercially operated wastewater bioreactor, while still maintaining operation within environmental consent limits. In order to do this, a nonlinear dynamic model based on the International Association on Water Quality (IAWQ) activated sludge model No. 3 was developed, expressing the nitrification kinetics and hydraulic dynamics of the system. From this model a steady state representation of the plant was derived, and simulated for various load characteristics experienced at the facility, and as a result an optimal load profile was developed for the compressed air distribution to the four aerobic zones. The optimal load profile will ensure that the amount of compressed air required to control the rate of ammonia removal is optimized.
Collapse
Affiliation(s)
- R B Murphy
- Department of Mechanical Engineering, The University of Auckland, New Zealand
| | | | | |
Collapse
|
43
|
Chow JY, Davids K, Button C, Rein R, Hristovski R, Koh M. Dynamics of multi-articular coordination in neurobiological systems. Nonlinear Dynamics Psychol Life Sci 2009; 13:27-55. [PMID: 19061544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Although previous work in nonlinear dynamics on neurobiological coordination and control has provided valuable insights from studies of single joint movements in humans, researchers have shown increasing interest in coordination of multi-articular actions. Multi-articular movement models have provided valuable insights on neurobiological systems conceptualised as degenerate, adaptive complex systems satisfying the constraints of dynamic environments. In this paper, we overview empirical evidence illustrating the dynamics of adaptive movement behavior in a range of multi-articular actions including kicking, throwing, hitting and balancing. We model the emergence of creativity and the diversity of neurobiological action in the meta-stable region of self organising criticality. We examine the influence on multi-articular actions of decaying and emerging constraints in the context of skill acquisition. We demonstrate how, in this context, transitions between preferred movement patterns exemplify the search for and adaptation of attractor states within the perceptual motor workspace as a function of practice. We conclude by showing how empirical analyses of neurobiological coordination and control have been used to establish a nonlinear pedagogical framework for enhancing acquisition of multi-articular actions.
Collapse
Affiliation(s)
- Jia Yi Chow
- Physical Education & Sports Science, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore, 637616, Singapore.
| | | | | | | | | | | |
Collapse
|
44
|
Yüzgeç U, Türker M, Hocalar A. On-line evolutionary optimization of an industrial fed-batch yeast fermentation process. ISA Trans 2009; 48:79-92. [PMID: 18849027 DOI: 10.1016/j.isatra.2008.09.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Revised: 07/17/2008] [Accepted: 09/15/2008] [Indexed: 05/26/2023]
Abstract
This paper presents two genetic algorithms based on optimization methods to maximize biomass concentration, and to minimize ethanol formation. The objective function is maximized according to the values of feed flow rate, using genetic search approaches. Five case studies were carried out for different initial conditions, which strongly influence the optimal profiles of feed flow rate for the fermentation process. The ethanol and glucose disturbance effects were examined to stress the effectiveness of proposed approaches. The proposed genetic approaches were implemented for an industrial scale baker's yeast fermentor which produces Saccharomyces cerevisiae known as baker's yeast. The results show that optimal feed flow rate was obtained in a satisfactory and successful way for fed-batch fermentation process.
Collapse
Affiliation(s)
- Uğur Yüzgeç
- Department of Electronic and Telecommunication Engineering, Kocaeli University, 41040, Kocaeli, Turkey.
| | | | | |
Collapse
|
45
|
Abstract
Studies of developing and self-renewing tissues have shown that differentiated cell types are typically specified through the actions of multistage cell lineages. Such lineages commonly include a stem cell and multiple progenitor (transit amplifying; TA) cell stages, which ultimately give rise to terminally differentiated (TD) cells. In several cases, self-renewal and differentiation of stem and progenitor cells within such lineages have been shown to be under feedback regulation. Together, the existence of multiple cell stages within a lineage and complex feedback regulation are thought to confer upon a tissue the ability to autoregulate development and regeneration, in terms of both cell number (total tissue volume) and cell identity (the proportions of different cell types, especially TD cells, within the tissue). In this paper, we model neurogenesis in the olfactory epithelium (OE) of the mouse, a system in which the lineage stages and mediators of feedback regulation that govern the generation of terminally differentiated olfactory receptor neurons (ORNs) have been the subject of much experimental work. Here we report on the existence and uniqueness of steady states in this system, as well as local and global stability of these steady states. In particular, we identify parameter conditions for the stability of the system when negative feedback loops are represented either as Hill functions, or in more general terms. Our results suggest that two factors -- autoregulation of the proliferation of transit amplifying (TA) progenitor cells, and a low death rate of TD cells -- enhance the stability of this system.
Collapse
Affiliation(s)
- Wing-Cheong Lo
- Departments of Mathematics, University of California, Irvine, CA, United States
| | | | | | | | | | | | | |
Collapse
|
46
|
Färber M, Dahmke T, Bohn CA, Handels H. Needle bending in a VR-puncture training system using a 6DOF haptic device. Stud Health Technol Inform 2009; 142:91-93. [PMID: 19377121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The use of virtual reality techniques opens up new perspectives to support and improve the puncture training in medical education. In this work a 3D VR-Simulator for the training of lumbar and ascites punctures has been extended to support the bending of the puncture needle. For this purpose the needle is designed as an angular spring model. The forces that restrict the user from bending the needle are calculated using a multiproxy technique and given to the user via a 6DOF haptic device (Sensable Phantom Premium 1.5). Proxy based haptic volume rendering is used to calculate the proxy movement. This way it is possible to integrate original CT-patient data into the rendering process and generate forces from structures that have not been segmented. The bending technique has been integrated in a VR-training system for puncture interventions and shows good results concerning update rate and user acceptance.
Collapse
Affiliation(s)
- Matthias Färber
- Department of Medical Informatics, University Medical Center, Hamburg-Eppendorf, Germany.
| | | | | | | |
Collapse
|
47
|
Mochizuki G, Sibley KM, Cheung HJ, Camilleri JM, McIlroy WE. Generalizability of perturbation-evoked cortical potentials: Independence from sensory, motor and overall postural state. Neurosci Lett 2008; 451:40-4. [PMID: 19110034 DOI: 10.1016/j.neulet.2008.12.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 11/10/2008] [Accepted: 12/11/2008] [Indexed: 11/16/2022]
Abstract
Following disturbances to postural stability, balance recovery reactions are evoked by numerous sensory inputs and characterized by motor reactions involving different patterns of activity, depending on postural task conditions. It remains unknown whether well-documented cortical responses to instability share common spatio-temporal characteristics, despite variations in the sensory, motor, and postural components of the reactions. The objective was to explore the spatio-temporal profile of cortical potentials evoked by instability requiring either upper- or lower-limb compensatory responses. The hypothesis that upper- and lower-limb balance-correcting reactions are associated with evoked cortical potentials (N1, P2) featuring similar spatio-temporal characteristics was tested by inducing postural perturbations in seated (SIT) or standing (STAND) positions. For both conditions, N1 amplitude was greatest at FCz, with no significant differences in the timing of N1 peak (SIT: 142.4+/-7.95ms; STAND: 148.4+/-4.10ms) or N1 amplitude (SIT: 37.16+/-6.99microV; STAND: 39.08+/-4.51microV). The amplitude of the P2 potential (measured at CPz) was significantly larger in the STAND condition (37.87+/-6.14microV) than in the SIT (23.66+/-6.21microV) condition. Significant differences in P2 peak time between tasks were absent (SIT: 319.9+/-11.45ms; STAND: 322.7+/-7.61ms). Though differences in the amplitude of components of evoked potentials may reflect the extent of cortical involvement in different aspects of postural control, similarities in the spatio-temporal components of cortical potentials between tasks reflects generalizable cortical processing of unexpected stimuli independent of the sensory, motor, or postural aspects of the response.
Collapse
Affiliation(s)
- George Mochizuki
- Mobility Team, Toronto Rehabilitation Institute, University Centre, Toronto, Canada.
| | | | | | | | | |
Collapse
|
48
|
Abstract
Although the lateral geniculate nucleus (LGN) is one of the most thoroughly characterized thalamic nuclei, its functional role remains controversial. Traditionally, the LGN in primates has been viewed as the lowest level of a set of feedforward parallel visual pathways to cortex. These feedforward pathways are pictured as connected hierarchies of areas designed to construct the visual image gradually - adding more complex features as one marches through successive levels of the hierarchy. In terms of synapse number and circuitry, the anatomy suggests that the LGN can be viewed also as the ultimate terminus in a series of feedback pathways that originate at the highest cortical levels. Since the visual system is dynamic, a more accurate picture of image construction might be one in which information flows bidirectionally, through both the feedforward and feedback pathways constantly and simultaneously. Based upon evidence from anatomy, physiology, and imaging, we argue that the LGN is more than a simple gate for retinal information. Here, we review evidence that suggests that one function of the LGN is to enhance relevant visual signals through circuits related to both motor planning and attention. Specifically, we argue that major extraretinal inputs to the LGN may provide: (1) eye movement information to enhance and bind visual signals related to new saccade targets and (2) top-down and bottom-up information about target relevance to selectively enhance visual signals through spatial attention.
Collapse
Affiliation(s)
- Vivien A Casagrande
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA.
| | | | | | | |
Collapse
|
49
|
Hiraoka K, Kamata N, Iwata A, Minamida F, Abe K. Finger movement improves ankle control for gait initiation in patients with Parkinson's disease. Electromyogr Clin Neurophysiol 2008; 48:343-349. [PMID: 19097474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The purpose of this study was to investigate the effect of finger movement on ankle control for gait initiation in patients with Parkinson's disease (PD patients). The subjects were 13 PD patients and 6 age-matched healthy adults. The subjects moved fingers before or after gait initiation, or initiated gait without finger movement. Ankle joint movement in the stance leg was recorded to estimate the duration of ankle dorsiflexion (DIF duration), which reflects the degree of disturbance in ankle control for gait initiation in PD patients. In the PD patients with prolonged D/F duration, finger movement that preceded gait initiation shortened the D/F duration, but in the PD patients without prolonged D/F duration and in healthy subjects, the effect was not found. Accordingly, finger movement that precedes gait initiation improves ankle control for gait initiation in PD patients who suffer disturbance in ankle control for gait initiation.
Collapse
Affiliation(s)
- K Hiraoka
- School of Comprehensive Rehabilitation, Osaka Prefecure University, Japan.
| | | | | | | | | |
Collapse
|
50
|
Berret B, Darlot C, Jean F, Pozzo T, Papaxanthis C, Gauthier JP. The inactivation principle: mathematical solutions minimizing the absolute work and biological implications for the planning of arm movements. PLoS Comput Biol 2008; 4:e1000194. [PMID: 18949023 PMCID: PMC2561290 DOI: 10.1371/journal.pcbi.1000194] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 08/30/2008] [Indexed: 11/18/2022] Open
Abstract
An important question in the literature focusing on motor control is to determine
which laws drive biological limb movements. This question has prompted numerous
investigations analyzing arm movements in both humans and monkeys. Many theories
assume that among all possible movements the one actually performed satisfies an
optimality criterion. In the framework of optimal control theory, a first
approach is to choose a cost function and test whether the proposed model fits
with experimental data. A second approach (generally considered as the more
difficult) is to infer the cost function from behavioral data. The cost proposed
here includes a term called the absolute work of forces, reflecting the
mechanical energy expenditure. Contrary to most investigations studying
optimality principles of arm movements, this model has the particularity of
using a cost function that is not smooth. First, a mathematical theory related
to both direct and inverse optimal control approaches is presented. The first
theoretical result is the Inactivation Principle, according to which minimizing
a term similar to the absolute work implies simultaneous inactivation of
agonistic and antagonistic muscles acting on a single joint, near the time of
peak velocity. The second theoretical result is that, conversely, the presence
of non-smoothness in the cost function is a necessary condition for the
existence of such inactivation. Second, during an experimental study,
participants were asked to perform fast vertical arm movements with one, two,
and three degrees of freedom. Observed trajectories, velocity profiles, and
final postures were accurately simulated by the model. In accordance,
electromyographic signals showed brief simultaneous inactivation of opposing
muscles during movements. Thus, assuming that human movements are optimal with
respect to a certain integral cost, the minimization of an absolute-work-like
cost is supported by experimental observations. Such types of optimality
criteria may be applied to a large range of biological movements. When performing reaching and grasping movements, the brain has to choose one
trajectory among an infinite set of possibilities. Nevertheless, because human
and animal movements provide highly stereotyped features, motor strategies used
by the brain were assumed to be optimal according to certain optimality
criteria. In this study, we propose a theoretical model for motor planning of
arm movements that minimizes a compromise between the absolute work exerted by
the muscles and the integral of the squared acceleration. We demonstrate that
under these assumptions agonistic and antagonistic muscles are inactivated
during overlapping periods of time for quick enough movements. Moreover, it is
shown that only this type of criterion can predict these inactivation periods.
Finally, experimental evidence is in agreement with the predictions of the
model. Indeed, we report the existence of simultaneous inactivation of opposing
muscles during fast vertical arm movements. Therefore, this study suggests that
biological movements partly optimize the energy expenditure, integrating both
inertial and gravitational forces during the motor planning process.
Collapse
Affiliation(s)
- Bastien Berret
- Université de Bourgogne, INSERM U887 Motricité-Plasticité, Dijon, France.
| | | | | | | | | | | |
Collapse
|