Keyla Garcia - Academia.edu (original) (raw)
Papers by Keyla Garcia
Journal of Neuroscience Methods, 2009
Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synapt... more Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synaptic potentials, muscle contractions-are built up of discrete, elementary responses to each spike. However, the spikes occur in trains of arbitrary temporal complexity, and each elementary response not only sums with previous ones, but can itself be modified by the previous history of the activity. A basic goal in system identification is to characterize the spike-response transform in terms of a small number of functions-the elementary response kernel and additional kernels or functions that describe the dependence on previous history-that will predict the response to any arbitrary spike train. Here we do this by developing further and generalizing the "synaptic decoding" approach of Sen et al. (J Neurosci 16:6307-6318, 1996). Given the spike times in a train and the observed overall response, we use least-squares minimization to construct the best estimated response and at the same time best estimates of the elementary response kernel and the other functions that characterize the spike-response transform. We avoid the need for any specific initial assumptions about these functions by using techniques of mathematical analysis and linear algebra that allow us to solve simultaneously for all of the numerical function values treated as independent parameters. The functions are such that they may be interpreted mechanistically. We examine the performance of the method as applied to synthetic data. We then use the method to decode real synaptic and muscle contraction transforms.
Journal of Neurophysiology, 2009
The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central patte... more The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central pattern generator (CPG)-effector system. The CPG, the nine-neuron cardiac ganglion (CG), is embedded in the myocardium itself; it generates bursts of spikes that are transmitted by the CG's five motor neurons to the periphery of the system, the myocardium, to produce its contractions. Considerable evidence suggests that a CPG-peripheral loop is completed by a return feedback pathway through which the contractions modify, in turn, the CG motor pattern. One likely pathway is provided by dendrites, presumably mechanosensitive, that the CG neurons project into the adjacent myocardial muscle. Here we have tested the role of this pathway in the heart of the blue crab, Callinectes sapidus . We performed “de-efferentation” experiments in which we cut the motor neuron axons to the myocardium and “de-afferentation” experiments in which we cut or ligated the dendrites. In the isolated CG, these mani...
Journal of Neurophysiology, 2007
In regulating neurophysiological systems, neuromodulators exert multiple actions at multiple site... more In regulating neurophysiological systems, neuromodulators exert multiple actions at multiple sites in such a way as to control the activity in an integrated manner. We are studying how this happens in a simple central pattern generator (CPG)–effector system, the heart of the blue crab Callinectes sapidus. The rhythmic contractions of this heart are neurogenic, driven by rhythmic motor patterns generated by the cardiac ganglion (CG). In this study, we used anatomical and physiological methods to examine the sources and actions on the system of crustacean cardioactive peptide (CCAP). Immunohistochemical localization revealed a plexus of CCAP-immunoreactive fibers in the pericardial organs (POs), neurohemal structures from which blood-borne neurohormones reach the heart. Combined backfill and immunohistochemical experiments indicated that the CCAP in the POs originated from a large contralateral neuron in each thoracic neuromere. In physiological experiments, we examined the actions of...
BMC Neuroscience, 2008
Welcome and Acknowledgements Welcome to CNS*2008! The international Computational Neuroscience me... more Welcome and Acknowledgements Welcome to CNS*2008! The international Computational Neuroscience meeting (CNS) has been a premier forum for presenting experimental and theoretical results exploring the biology of computation in the nervous system for the last 17 years. The meeting is organized by the Organization for Computational Neurosciences (OCNS), a non-profit organization governed by an international executive committee and board of directors. A separate program committee is responsible for the scientific program of the meeting. Participants at the meeting are from academia and industry. The meeting not only provides a venue for research presentation and discussion by senior scientists but actively offers a forum for promoting and supporting young scientists and students from around the world. Welcome to Portland. We particularly want to acknowledge the contributions of the many individuals who made this meeting possible, particularly Patrick Roberts, the local organizer, and the administrative and computing staff at the Oregon Health and Sciences University. We are also very much indebted to the members of the program committee and the people who reviewed papers for this meeting.
Journal of Neurophysiology, 2011
The neurogenic heartbeat of crustaceans is controlled by the cardiac ganglion (CG), a central pat... more The neurogenic heartbeat of crustaceans is controlled by the cardiac ganglion (CG), a central pattern generator (CPG) microcircuit composed of nine neurons. In most decapods, five “large” motor neurons (MNs) project from the CG to the myocardium, where their excitatory synaptic signals generate the rhythmic heartbeat. The processes of four “small” premotor neurons (PMNs) are confined to the CG, where they provide excitatory drive to the MNs via impulse-mediated chemical signals and electrotonic coupling. This study explored feedforward and feedback interactions between the PMNs and the MNs in the CG of the blue crab ( Callinectes sapidus). Three methods were used to compare the activity of the MNs and the PMNs in the integrated CG to their autonomous firing patterns: 1) ligatures were tightened on the ganglion trunk that connects the PMNs and MNs; 2) TTX was applied focally to suppress selectively PMN or MN activity; and 3) sucrose pools were devised to block reversibly PMN or MN im...
Journal of Neuroscience Methods, 2009
Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synapt... more Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synaptic potentials, muscle contractions-are built up of discrete, elementary responses to each spike. However, the spikes occur in trains of arbitrary temporal complexity, and each elementary response not only sums with previous ones, but can itself be modified by the previous history of the activity. A basic goal in system identification is to characterize the spike-response transform in terms of a small number of functions-the elementary response kernel and additional kernels or functions that describe the dependence on previous history-that will predict the response to any arbitrary spike train. Here we do this by developing further and generalizing the "synaptic decoding" approach of Sen et al. (J Neurosci 16:6307-6318, 1996). Given the spike times in a train and the observed overall response, we use least-squares minimization to construct the best estimated response and at the same time best estimates of the elementary response kernel and the other functions that characterize the spike-response transform. We avoid the need for any specific initial assumptions about these functions by using techniques of mathematical analysis and linear algebra that allow us to solve simultaneously for all of the numerical function values treated as independent parameters. The functions are such that they may be interpreted mechanistically. We examine the performance of the method as applied to synthetic data. We then use the method to decode real synaptic and muscle contraction transforms.
Journal of Neurophysiology, 2009
The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central patte... more The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central pattern generator (CPG)-effector system. The CPG, the nine-neuron cardiac ganglion (CG), is embedded in the myocardium itself; it generates bursts of spikes that are transmitted by the CG's five motor neurons to the periphery of the system, the myocardium, to produce its contractions. Considerable evidence suggests that a CPG-peripheral loop is completed by a return feedback pathway through which the contractions modify, in turn, the CG motor pattern. One likely pathway is provided by dendrites, presumably mechanosensitive, that the CG neurons project into the adjacent myocardial muscle. Here we have tested the role of this pathway in the heart of the blue crab, Callinectes sapidus . We performed “de-efferentation” experiments in which we cut the motor neuron axons to the myocardium and “de-afferentation” experiments in which we cut or ligated the dendrites. In the isolated CG, these mani...
Journal of Neurophysiology, 2007
In regulating neurophysiological systems, neuromodulators exert multiple actions at multiple site... more In regulating neurophysiological systems, neuromodulators exert multiple actions at multiple sites in such a way as to control the activity in an integrated manner. We are studying how this happens in a simple central pattern generator (CPG)–effector system, the heart of the blue crab Callinectes sapidus. The rhythmic contractions of this heart are neurogenic, driven by rhythmic motor patterns generated by the cardiac ganglion (CG). In this study, we used anatomical and physiological methods to examine the sources and actions on the system of crustacean cardioactive peptide (CCAP). Immunohistochemical localization revealed a plexus of CCAP-immunoreactive fibers in the pericardial organs (POs), neurohemal structures from which blood-borne neurohormones reach the heart. Combined backfill and immunohistochemical experiments indicated that the CCAP in the POs originated from a large contralateral neuron in each thoracic neuromere. In physiological experiments, we examined the actions of...
BMC Neuroscience, 2008
Welcome and Acknowledgements Welcome to CNS*2008! The international Computational Neuroscience me... more Welcome and Acknowledgements Welcome to CNS*2008! The international Computational Neuroscience meeting (CNS) has been a premier forum for presenting experimental and theoretical results exploring the biology of computation in the nervous system for the last 17 years. The meeting is organized by the Organization for Computational Neurosciences (OCNS), a non-profit organization governed by an international executive committee and board of directors. A separate program committee is responsible for the scientific program of the meeting. Participants at the meeting are from academia and industry. The meeting not only provides a venue for research presentation and discussion by senior scientists but actively offers a forum for promoting and supporting young scientists and students from around the world. Welcome to Portland. We particularly want to acknowledge the contributions of the many individuals who made this meeting possible, particularly Patrick Roberts, the local organizer, and the administrative and computing staff at the Oregon Health and Sciences University. We are also very much indebted to the members of the program committee and the people who reviewed papers for this meeting.
Journal of Neurophysiology, 2011
The neurogenic heartbeat of crustaceans is controlled by the cardiac ganglion (CG), a central pat... more The neurogenic heartbeat of crustaceans is controlled by the cardiac ganglion (CG), a central pattern generator (CPG) microcircuit composed of nine neurons. In most decapods, five “large” motor neurons (MNs) project from the CG to the myocardium, where their excitatory synaptic signals generate the rhythmic heartbeat. The processes of four “small” premotor neurons (PMNs) are confined to the CG, where they provide excitatory drive to the MNs via impulse-mediated chemical signals and electrotonic coupling. This study explored feedforward and feedback interactions between the PMNs and the MNs in the CG of the blue crab ( Callinectes sapidus). Three methods were used to compare the activity of the MNs and the PMNs in the integrated CG to their autonomous firing patterns: 1) ligatures were tightened on the ganglion trunk that connects the PMNs and MNs; 2) TTX was applied focally to suppress selectively PMN or MN activity; and 3) sucrose pools were devised to block reversibly PMN or MN im...