Slow Bursts Research Articles

FC07-04 - Electrophysiological neuroimaging reveals re-set, re-activation and re-processing of procedural and declarative memory traces during post-training sleep

ObjectivesExperience-dependent cortical plasticity observed during post-training sleep has been hypothesized to be part of the global process of memory consolidation. Combining the temporal resolution of microstructure detectors and the spatial resolution of low-resolution brain electromagnetic tomography (LORETA) makes it possible to investigate when and where the experience-dependent reactivation occurs under normal (undisturbed) sleeping conditions.MethodsAfter an adaptation night, in the 2nd and 3rd night 48 young healthy volunteers were randomly assigned either to a control condition or to an experimental condition (declarative memory task: paired-associate word list or procedural memory task: mirror tracing). Sleep stages and sleep microstructures (slow waves, spindles and theta bursts) were detected automatically by means of the Somnolyzer 24x7. Changes in LORETA sources (experimental minus control night) were correlated with changes in memory performance (morning minus evening recall).ResultsOvernight improvements in the mirror tracing task were correlated with increased slow-wave sources in the right posterior parietal cortex (r = .70,p < 0.01) during NREM sleep and with desynchronized (r = −.76,p < 0.01) and synchronized (r = .62,p < 0.01) rolandic mu rhythm sources during periods with theta bursts in REM sleep. Overnight improvements in the declarative memory task were significantly correlated with increased spindle sources (r = .52, p < .01) in frontal, temporal and cingulate brain regions.ConclusionsThe present study supports the hypotheses of (1) a use-dependent reset of synaptic plasticity during slow-wave sleep (restorative function), (2) an experience-dependent reactivation during spindle episodes (stabilizing function) and (3) an off-line neuronal reprocessing during REM sleep (improvement without further training for novel tasks).

Mini-Review: Synaptic Integration in the Cerebellar Nuclei—Perspectives From Dynamic Clamp and Computer Simulation Studies

The cerebellar nuclei (CN) process inhibition from Purkinje cells (PC) and excitation from mossy and climbing fiber collaterals. CN neurons in slices show intrinsic pacemaking activity, which is easily modulated by synaptic inputs. Our work using dynamic clamping and computer modeling shows that synchronicity between PC inputs is an important factor in determining spike rate and spike timing of CN neurons and that brief pauses in PC inputs provide a potent stimulus to trigger CN spikes. Excitatory input can equally control spike rate, but, due to a large slow, NMDA component also amplifies responses to inhibitory inputs. Intrinsic properties of CN neurons are well suited to provide prolonged responses to strong input transients and could be involved in motor pattern generation. One such specific mechanism is given by fast and slow rebound bursting. Nevertheless, we are just beginning to unravel synaptic integration in the CN, and the outcome of the work to date is best characterized by the generation of new specific questions that lend themselves to a combined experimental and computer modeling approach in future studies.

Local spindling in thalamus during cortical slow oscillation

Event Abstract Back to Event Local spindling in thalamus during cortical slow oscillation P. Barthó1, A. Slézia1, F. Mátyás1, I. Ulbert2 and L. Acsády1* 1 Hung. Acad. Sci.,, Institute of Experimental Medicine, Hungary 2 Hung. Acad. Sci.,, Institute of Psychology, Hungary Despite being the main input and output of the neocortex, the relationship of thalamus during cortical oscillations is not yet fully explored. To investigate this, we performed simultaneous multiple single-unit recordings in rats under urethane anesthesia in the ventral posteromedial nucleus (VPM) and the S1 cortex with four-shank silicon probes. In the VPM two types of spikes were recorded. Wide spikes showed the characteristic burst pattern of relay cells, while narrow spikes fired longer and slower bursts and displayed asymmetric cross-correlograms with wide spikes. During thalamic spindle episodes the two types of spikes fired at different phases, wide spikes preceding narrow spikes by ~25 ms. Most of the VPM multiunit activity was organized into spindle episodes, which only occasionally coincided with cortical spindles. These thalamic spindles were usually restricted to one or two electrode shanks. Both types of units were phase locked to spindles. Considering that VPM contains only relay cells, we propose that narrow spikes belong to axon terminals originating in the nRt. To prove this, we performed simultaneous juxtacell recording of the nRt soma, and axon terminal in VPM. Our data show that network activity in VPM is organized into spatially restricted spindle episodes, indicating that cortical control over VPM is not very, and VMP-nRt interaction dominates instead. Keywords: Neurophysiology, Neuroscience Conference: 13th Conference of the Hungarian Neuroscience Society (MITT), Budapest, Hungary, 20 Jan - 22 Jan, 2011. Presentation Type: Abstract Topic: Neurophysiology Citation: Barthó P, Slézia A, Mátyás F, Ulbert I and Acsády L (2011). Local spindling in thalamus during cortical slow oscillation. Front. Neurosci. Conference Abstract: 13th Conference of the Hungarian Neuroscience Society (MITT). doi: 10.3389/conf.fnins.2011.84.00093 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Mar 2011; Published Online: 23 Mar 2011. * Correspondence: Dr. L. Acsády, Hung. Acad. Sci.,, Institute of Experimental Medicine, Budapest, Hungary, acsady@koki.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers P. Barthó A. Slézia F. Mátyás I. Ulbert L. Acsády Google P. Barthó A. Slézia F. Mátyás I. Ulbert L. Acsády Google Scholar P. Barthó A. Slézia F. Mátyás I. Ulbert L. Acsády PubMed P. Barthó A. Slézia F. Mátyás I. Ulbert L. Acsády Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Synchronization of slow-fast systems

We describe different patterns of synchronization of two systems, each possessing oscillations on two very different time scales. Synchronization of slow and fast oscillations are characterized separately, leading to a possibility to observe partially synchronized states where, e.g., the slow motions are synchronous while the fast are desynchronized. As a first example we study two diffusively coupled Hindmarsh-Rose oscillators in the regime of regular or chaotic bursting and describe different synchronous states like phase synchronization of slow variables, burst and spike synchronization of fast variables, and complete synchronization. Next, we study two coupled four-dimensional model systems with chaotic slow dynamics and find phase synchronization of slow motion, complete and partially complete synchrony.

P24-21 Automatic detection of photic evoked EEG spikes with slow burst

P24-21 Automatic detection of photic evoked EEG spikes with slow burst

Transient left temporal lobe lesion in Menkes disease may influence the generation of tonic spasms

We report a 7-month-old boy with Menkes disease who presented West syndrome. Magnetic resonance imaging (MRI) revealed atrophy of the frontal and parietal lobes, subdural hematoma on the right side, and left temporal lobe lesion (low intensity in T1-weighted imaging (T1-WI), high intensity in T2-weighted imaging (T2-WI) and low intensity in diffusion-weighted imaging (DW-I)) at 7 months of age. The apparent diffusion coefficient (ADC) was 1.68 × 10 −3 mm 2/s in the left temporal lobe lesion and 1.15 × 10 −3 mm 2/s on the contralateral side. 1H-magnetic resonance spectroscopy ( 1H-MRS) revealed a decrease in N-acetylaspartate/(creatine + phosphocreatine) (NAA/Cr) (0.71) and a lactate peak in the left temporal lobe lesion. At 8 months of age, the left temporal lobe lesion disappeared, the ADC of this lesion was within the normal range (1.10 × 10 −3 mm 2/s), and 1H-MRS revealed a slight increase in NAA/Cr (1.12) and disappearance of the lactate peak. We suspected that the transient temporal lobe lesion in Menkes disease was mainly vasogenic edema. Electroencephalography (EEG) revealed left hemisphere dominant hypsarrhythmia and slowing in the left hemisphere. Ictal EEG revealed generalized slow wave burst with P3, T3 spike antecedence and the antecedent spike was consistent with left temporal lobe lesion. After disappearance of the left temporal lobe lesion, tonic spasms disappeared and EEG findings improved. In this case, the clinical course and ictal EEG suggested that epileptic activity from the left temporal lobe lesion may have given rise to tonic spasms.

Na/K ATPase activity is coordinated with the persistent sodium current amplitude

It is known that the Na+/K+ ATPase may control the frequency of slow action potential bursts that can be found in motor patterns generating neurons. Thus, Na+/K+ ATPase can participate in the formation of firing patterns in neurons and it is likely that the ATPase activity is coordinated with the expression of ionic channels. However, so far, there is no such evidence. Here it is shown that, in pyramidal neurons of the rat prefrontal cortex, the density of electrogenic sodium-potassium ATPase current was correlated with the density of the persistent sodium current (R2=0.62, P<0.002). It is speculated that such coordination may improve the control of the firing patterns in prefrontal cortex pyramidal neurons.

M-type channels selectively control bursting in rat dopaminergic neurons.

Midbrain dopaminergic neurons in the substantia nigra, pars compacta and ventral tegmental area are critically important in many physiological functions. These neurons exhibit firing patterns that include tonic slow pacemaking, irregular firing and bursting, and the amount of dopamine that is present in the synaptic cleft is much increased during bursting. The mechanisms responsible for the switch between these spiking patterns remain unclear. Using both in-vivo recordings combined with microiontophoretic or intraperitoneal drug applications and in-vitro experiments, we have found that M-type channels, which are present in midbrain dopaminergic cells, modulate the firing during bursting without affecting the background low-frequency pacemaker firing. Thus, a selective blocker of these channels, 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride, specifically potentiated burst firing. Computer modeling of the dopamine neuron confirmed the possibility of a differential influence of M-type channels on excitability during various firing patterns. Therefore, these channels may provide a novel target for the treatment of dopamine-related diseases, including Parkinson’s disease and drug addiction. Moreover, our results demonstrate that the influence of M-type channels on the excitability of these slow pacemaker neurons is conditional upon their firing pattern.

Remembering the lost neuroscience of pharmaco‐EEG

To the electrophysiologist accustomed, in his animal experiments, to probing with his electrode into the nervous system and even into the nerve cell itself, it remains a matter of astonishment that so many of the brain's secrets escape across the wall of the skull to electrodes fixed to the scalp of man. That they indeed do so is testimony to the fact that the brain's electrical activity is a most sensitive indicator of its function. In this fact lies the attraction of electroencephalography for its devotees.

The Fate of Spontaneous Synchronous Rhythms on the Cerebrocerebellar Loop

How does the cerebellum participate in neocortical rhythms? Neocortical signals destined for the cerebellum are integrated in the pontine nuclei (PN) with cerebellar output signals via a direct, reciprocal feedback loop with the cerebellar nuclei (CN). The present study investigated the fate of two spontaneously occurring rhythms in rat neocortex under ketamine anesthesia-slow wave activity at around 1 Hz and gamma oscillations-within this pontonuclear feedback loop. Coordinated oscillatory neuronal activity was studied using simultaneous multineuron recordings in primary motor cortex (M1), PN, and lateral CN. It was revealed that slow burst firing-known in neocortex as "up and down states"-is readily conveyed within the pontonuclear feedback loop and thus engages the entire cerebropontocerebellothalamic loop. In contrast, gamma band synchronous oscillations reached only the PN under the present experimental conditions. Surprisingly, many CN single units were actually found to oscillate in the gamma range, but they completely failed to synchronize with other units in either CN or PN. These results show firstly that slow concerted activity can readily engage the entire cerebrocerebellar loop. Secondly, they raise the possibility that fast gamma oscillations may be incompatible with cerebellar processing and get blocked out. Future studies in behaving animals are needed to answer the question whether signals coded in gamma band frequency are converted to another carrier code using the feedback control exerted by the pontonuclear loop.

35. Automatic detection and feature extraction of evoked spikes and slow bursts during photostimulations

35. Automatic detection and feature extraction of evoked spikes and slow bursts during photostimulations

Successful Treatment of Acute Autoimmune Limbic Encephalitis With Negative VGKC and NMDAR Antibodies

To describe a case of acute nonherpetic limbic encephalitis (LE) with negative testing for antibodies directed against onconeuronal and cell membrane antigens, including voltage-gated potassium channels and N-methyl-D-aspartate receptor, that showed a dramatic response to immune therapy. A 30-year-old woman manifested generalized seizures, altered consciousness, and memory impairment shortly after a prodromal viral illness. Few days later the patient developed a drug-resistant epileptic status. Electroencephalograph showed bitemporal slowing and paroxysmal slow wave bursts. Brain magnetic resonance imaging showed bilateral swelling in the medial temporal lobes. Cerebrospinal fluid analysis ruled out viral etiologies. A diagnostic search for cancer, including serum testing for known onconeuronal antibodies proved negative. Screening for cell membrane antigen antibodies, including voltage-gated potassium channels and N-methyl-D-aspartate receptor, was also negative. Suspecting an autoimmune etiology, we started an immunomodulatory treatment with intravenous immunoglobulin followed by a short course of oral prednisone, obtaining a full clinical recovery. Our report confirms previous observations of "seronegative" autoimmune LE, suggesting the presence of other, still unknown central nervous system antigens representing a target of a postinfectious, autoimmune response in these patients. Moreover, it emphasizes the importance of early recognition and treatment of acute autoimmune LE, to reduce the risk of intensive care unit-related complications and the occurrence of permanent cognitive or behavioral defects.

Application of Microwave Technique for Dehydration of Sludge Generated in a Stainless Steel Plant

In ironmaking and steelmaking processes, dehydration technology is often recognized to be a key process for the successful operation. That is not an exception in recycling process of valuable elements such as Fe, Ni, Cr and so on by reducing the wasted materials including dust, scales and sludge, generated in each steel works. This investigation basically focused on the availability of microwave technique for dehydration stage of sludge generated in a stainless steel mill. Actually sludge is well-known as a wasted resource difficult to be dehydrated. Unless dehydration of such resource is successful, some problems with slow heating and/or burst of briquettes may arise.In this study, prior to the industrial studies, dehydration experiments of goethite were performed. The results showed that the microwave treatment could heat up the specimen directly from inside of specimen while being heated from the outside by the electric furnace. Thus the dehydration ratio resulted higher in the microwave irradiation, indicating the benefit of the microwave treatment.Thereafter the microwave technique was tried for dehydration of industrial sludge. Consequently, the effectiveness of microwave treatment was confirmed because 34 mass% weight-loss after the microwave treatment corresponded to the complete dehydration while 7 mass% weight-loss after heating in a conventional electric furnace. If application to industrial practice is realized, it is expected that the problems brought by the conventional way will be hopefully solved to prevent burst of agglomerations.

Dopamine induced switch in the subthreshold dynamics of the striatal cholinergic interneurons: A numerical study

The striatum is a part of the basal ganglia, which are a group of nuclei in the brain associated with motor control, cognition and learning. Striatal cholinergic interneurons (AchNs) play a crucial role in these functions. AchNs are tonically active in vivo and in vitro, and are able to fire in the absence of synaptic inputs. AchNs respond to sensory stimuli and sensorimotor learning by transiently suppressing their firing activity. This pause is dopamine signal sensitive, but the neurophysiological mechanism of the dopaminergic influence is under debate. Both the regular spiking response as well as the pause response are influenced by the inwardly rectifying outward G kir , a slow hyperpolarization activated noninactivating G h , and calcium and calcium-dependent potassium conductances [Wilson, C., Goldberg, J., 2006. Origin of the slow afterhyperpolarization and slow rhythmic bursting in striatal cholinergic interneurons. J. Neurophysiol. 95(1), 196–204; Wilson, C., 2005. The mechanism of intrinsic amplification of hyperpolarizations and spontaneous bursting in striatal cholinergic interneurons. Neuron 45(4), 575–585]. Recent experimental evidence has shown that dopaminergic modulations on G h , G kir and calcium conductances influence the AchN's excitability [Deng, P., Zhang, Y., Xu, Z., 2007. Involvement of I( h) in dopamine modulation of tonic firing in striatal cholinergic interneurons. J. Neurosci. 27(12), 3148–3156; Aosaki, T., Kiuchi, K., Kawaguchi, Y., 1998. Dopamine D 1 -like receptor activation excites rat striatal large aspiny neurons in vitro. J. Neurosci. 18(14), 5180–5190]. We employed computational models of the AchN to analyze the conductance based dopaminergic changes. We analyzed the robustness of these subthreshold oscillations and how they are affected by dopaminergic modulation. Our results predict that these conductances allow the dopamine to switch the AchN between stable oscillatory and fixed-point behaviors. The present approach and results show that dopamine receptors ( D 1 and D 2 ) mediate opposing effects on this switch and therefore on the suprathreshold excitability as well. The switching effect of the dopaminergic signal is the major qualitative feature that can serve as a building block for higher network-level descriptions. To our knowledge this is the first paper that synthesizes the growing body of experimental literature about the dopaminergic modulation of the AchNs into a modelling framework.

Genetic Ablation of V2a Ipsilateral Interneurons Disrupts Left-Right Locomotor Coordination in Mammalian Spinal Cord

The initiation and coordination of activity in limb muscles are the main functions of neural circuits that control locomotion. Commissural neurons connect locomotor circuits on the two sides of the spinal cord, and represent the known neural substrate for left-right coordination. Here we demonstrate that a group of ipsilateral interneurons, V2a interneurons, plays an essential role in the control of left-right alternation. In the absence of V2a interneurons, the spinal cord fails to exhibit consistent left-right alternation. Locomotor burst activity shows increased variability, but flexor-extensor coordination is unaffected. Anatomical tracing studies reveal a direct excitatory input of V2a interneurons onto commissural interneurons, including a set of molecularly defined V0 neurons that drive left-right alternation. Our findings imply that the neural substrate for left-right coordination consists of at least two components; commissural neurons and a class of ipsilateral interneurons that activate commissural pathways.

A Phantom Bursting Mechanism for Episodic Bursting

We describe a novel dynamic mechanism for episodic or compound bursting oscillations, in which bursts of electrical impulses are clustered together into episodes, separated by long silent phases. We demonstrate the mechanism for episodic bursting using a minimal mathematical model for "phantom bursting." Depending on the location in parameter space, this model can produce fast, medium, or slow bursting, or in the present case, fast, slow, and episodic bursting. The episodic bursting is modestly robust to noise and to parameter variation, and the effect that noise has on the episodic bursting pattern is quite different from that of an alternate episodic burst mechanism in which the slow envelope is produced by metabolic oscillations. This mechanism could account for episodic bursting produced in endocrine cells or neurons, such as pancreatic islets or gonadotropin releasing neurons of the hypothalamus.

Focal Activities and Re-Entrant Propagations as Mechanisms of Gastric Tachyarrhythmias

Gastric arrhythmias occur in humans and experimental animals either spontaneously or induced by drugs or diseases. However, there is no information regarding the origin or the propagation patterns of the slow waves that underlie such arrhythmias. To elucidate this, simultaneous recordings were made on the antrum and the distal corpus during tachygastrias in open abdominal anesthetized dogs using a 240 extracellular electrode assembly. After the recordings, the signals were analyzed, and the origin and path of slow wave propagations were reconstructed. Several types of arrhythmias could be distinguished, including (1) premature slow waves (25% of the arrhythmias), (2) single aberrant slow waves (4%), (3) bursts (18%), (4) regular tachygastria (11%), and (5) irregular tachygastria (10%). During regular tachygastria, rapid, regular slow waves emerged from the distal antrum or the greater curvature, whereas, during irregular tachygastria, numerous variations occurred in the direction of propagation, conduction blocks, focal activity, and re-entry. In 12 cases, the arrhythmia was initiated in the recorded area. In each case, after a normal propagating slow wave, a local premature slow wave occurred in the antrum. These premature slow waves propagated in various directions, often describing a single or a double loop that re-entered several times, thereby initiating additional slow waves. Gastric arrhythmias resemble those in the heart and share many common features such as focal origin, re-entry, circular propagation, conduction blocks, and fibrillation-like behavior.

Magnetic Source Imaging of Cortical Dysfunction in Amyotrophic Lateral Sclerosis

The goal was to determine whether magnetic source imaging could identify a signature for cortical involvement in patients with amyotrophic lateral sclerosis (ALS), and to determine whether the method might provide insight into functional abnormalities associated with the disease process. Spontaneous brain activity recordings from whole-head 148-channel magnetoencephalography (MEG) were employed to look for localized dipolar sources of focal delta-theta (1-7 Hz) discharges in patients with ALS without dementia. Localized slow wave dipoles were mapped and counted by anatomic brain region, defined by MRI, and correlated against the revised ALS functional rating scale (a functional measure of ALS disability). In a substudy, defects in cortical activations mediating purposeful movement were investigated in an ALS patient with probable motor apraxia of an upper limb. MEG revealed localized slow wave dipole sources in 7/7 ALS patients, including two recently diagnosed patients (0/8 age-similar controls). Systematic brain mapping of dipole source generators was possible in all seven ALS patients. The slow wave bursts were being generated from frontal, temporal, and parietal cortices, but not from occipital areas. The density of slow wave dipoles in cingulate gyrus correlated with the severity of upper-extremity disability as judged by the functional ALS measure. Further magnetic source imaging in the substudy patient with unilateral limb apraxia revealed abnormal central processing of purposeful movement with absent M2 in the contralateral secondary motor areas generating slow waves. This exploratory study documents widespread cortical dysfunction in patients with ALS, including those with recent onset of their disease. MEG is likely to be a powerful new tool for researching the contribution of cortical dysfunction to the motor disability that characterizes the disease process.

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

At birth, thoracosacral spinal cord networks in mouse can produce a coordinated locomotor-like pattern. In contrast, less is known about the cervicothoracic networks that generate forelimb locomotion. Here we show that cervical networks can produce coordinated rhythmic patterns in the brain stem-spinal cord preparation of the mouse. Segmentally the C5 and C8 neurograms were each found to be alternating left-right, and the ipsilateral C5 and C8 neurograms also alternated. Collectively these patterns were suggestive of locomotor-like activity. This pattern was not dependent on the presence of thoracosacral segments because they could be evoked following a complete transection of the spinal cord at T5. We next demonstrated that activation of thoracosacral networks either pharmacologically or by stimulation of sacrocaudal afferents could produce rhythmic activity within the C5 and C8 neurograms. On the other hand, pharmacological activation of cervical networks did not evoke alternating cervical rhythmic activity either in isolated cervicothoracic or -sacral preparations. Under these conditions, we found that activation of cervicothoracic networks could alter the timing of thoracosacral locomotor-like patterns. When thoracosacral networks were not activated pharmacologically but received rhythmic drive from cervicothoracic networks, a pattern of slow bursts with superimposed fast synchronous oscillations became the dominant lumbar neurogram pattern. Our data suggest that in neonatal mice the cervical CPG is capable of producing coordinated rhythmic patterns in the absence of input from lumbar segments, but caudorostral drive contributes to cervical patterns and rhythm stability.

Dopamine Activates the Motor Pattern for Crawling in the Medicinal Leech

Locomotion in segmented animals is thought to be based on the coupling of "unit burst generators," but the biological nature of the unit burst generator has been revealed in only a few animal systems. We determined that dopamine (DA), a universal modulator of motor activity, is sufficient to activate fictive crawling in the medicinal leech, and can exert its actions within the smallest division of the animal's CNS, the segmental ganglion. In the entire isolated nerve cord or in the single ganglion, DA induced slow antiphasic bursting (approximately 15 s period) of motoneurons known to participate in the two-step elongation-contraction cycle underlying crawling behavior. During each cycle, the dorsal (DE-3) and ventral (VE-4) longitudinal excitor motoneurons fired approximately 180 degrees out of phase from the ventrolateral circular excitor motoneuron (CV), which marks the elongation phase. In many isolated whole nerve cords, DE-3 bursting progressed in an anterior to posterior direction with intersegmental phase delays appropriate for crawling. In the single ganglion, the dorsal (DI-1) and ventral (VI-2) inhibitory longitudinal motoneurons fired out of phase with each DE-3 burst, further confirming that the crawl unit burst generator exists in the single ganglion. All isolated ganglia of the CNS were competent to produce DA-induced robust fictive crawling, which typically lasted uninterrupted for 5-15 min. A quantitative analysis indicated that DA-induced crawling was not significantly different from electrically evoked or spontaneous crawling. We conclude that DA is sufficient to activate the full crawl motor program and that the kernel for crawling resides within each segmental ganglion.