Multiunit Recordings Research Articles

Circadian oscillators in the epithalamus

The habenula complex is implicated in a range of cognitive, emotional and reproductive behaviors, and recently this epithalamic structure was suggested to be a component of the brain's circadian system. Circadian timekeeping is driven in cells by the cyclical activity of core clock genes and proteins such as per2/PER2. There are currently no reports of rhythmic clock gene/protein expression in the habenula and therefore the question of whether this structure has an intrinsic molecular clock remains unresolved. Here, using videomicroscopy imaging and photon-counting of a PER2::luciferase (LUC) fusion protein together with multiunit electrophysiological recordings, we tested the endogenous circadian properties of the mouse habenula in vitro. We show that a circadian oscillator is localized primarily to the medial portion of the lateral habenula. Rhythms in PER2:: LUC bioluminescence here are visualized in single cells and oscillations continue in the presence of the sodium channel blocker, tetrodotoxin, indicating that individual cells have intrinsic timekeeping properties. Ependymal cells lining the dorsal third ventricle also express circadian oscillations of PER2. These findings establish that neurons and non-neuronal cells in the epithalamus express rhythms in cellular and molecular activities, indicating a role for circadian oscillators in the temporal regulation of habenula controlled processes and behavior.

Relating Information, Encoding and Adaptation: Decoding the Population Firing Rate in Visual Areas 17/18 in Response to a Stimulus Transition

Neurons in the primary visual cortex typically reach their highest firing rate after an abrupt image transition. Since the mutual information between the firing rate and the currently presented image is largest during this early firing period it is tempting to conclude this early firing encodes the current image. This view is, however, made more complicated by the fact that the response to the current image is dependent on the preceding image. Therefore we hypothesize that neurons encode a combination of current and previous images, and that the strength of the current image relative to the previous image changes over time. The temporal encoding is interesting, first, because neurons are, at different time points, sensitive to different features such as luminance, edges and textures; second, because the temporal evolution provides temporal constraints for deciphering the instantaneous population activity. To study the temporal evolution of the encoding we presented a sequence of 250 ms stimulus patterns during multiunit recordings in areas 17 and 18 of the anaesthetized ferret. Using a novel method we decoded the pattern given the instantaneous population-firing rate. Following a stimulus transition from stimulus A to B the decoded stimulus during the first 90ms was more correlated with the difference between A and B (B-A) than with B alone. After 90ms the decoded stimulus was more correlated with stimulus B than with B-A. Finally we related our results to information measures of previous (B) and current stimulus (A). Despite that the initial transient conveys the majority of the stimulus-related information; we show that it actually encodes a difference image which can be independent of the stimulus. Only later on, spikes gradually encode the stimulus more exclusively.

Privileged Processing of the Straight-Ahead Direction in Primate Area V1

Gaze direction modulates the gain of neurons in most of the visual cortex, including the primary visual (V1) area. These gain modulations are thought to support a mechanism involved in the spatial localization of objects. In the present study, we show that part of them may reflect an additional function: enhancing the visual processing of the objects located straight ahead. Using single- and multiunit recordings in behaving macaques, we found that in peripheral V1, the gain of most neurons increases as their receptive fields (RF) are brought closer to the straight-ahead direction by changing the direction of gaze. No such tendency was observed in central V1, although the influence of gaze direction is similar in term of strength. This previously unknown organization of the gaze-related gain modulations might insure that objects located straight ahead still receive a privileged processing during eccentric fixation, reflecting the ecological importance of this particular egocentric direction.

Visual Targeting of Motor Actions in Climbing Drosophila

Drosophila melanogaster flies cross surmountable gaps in their walkway of widths exceeding their body length with an astounding maneuver but avoid attempts at insurmountable gaps by visual width estimation. Different mutant lines affect specific aspects of this maneuver, indicating a high complexity and modularity of the underlying motor control. Here we report on two mutants, ocelliless(1) and tay bridge(1), that, although making a correct decision to climb, fail dramatically in aiming at the right direction. Both mutants show structural defects in the protocerebral bridge, a central complex neuropil formed like a handlebar spanning the brain hemispheres. The bridge has been implicated in step-length control in walking flies and celestial E-vector orientation in locusts. In rescue experiments using tay bridge(1) flies, the integrity of the bridge was reestablished, concomitantly leading to a significant improvement of their orientation at the gap. Although producing directional scatter, their attempts were clearly aimed at the landing site. However, this partial rescue was lost in these flies at a reduced-visibility landing site. We therefore conclude that the protocerebral bridge is an essential part of a visual targeting network that transmits directional clues to the motor output via a known projection system.

Origin of Active States in Local Neocortical Networks during Slow Sleep Oscillation

Slow-wave sleep is characterized by spontaneous alternations of activity and silence in corticothalamic networks, but the causes of transition from silence to activity remain unknown. We investigated local mechanisms underlying initiation of activity, using simultaneous multisite field potential, multiunit recordings, and intracellular recordings from 2 to 4 nearby neurons in naturally sleeping or anesthetized cats. We demonstrate that activity may start in any neuron or recording location, with tens of milliseconds delay in other cells and sites. Typically, however, activity originated at deep locations, then involved some superficial cells, but appeared later in the middle of the cortex. Neuronal firing was also found to begin, after the onset of active states, at depths that correspond to cortical layer V. These results support the hypothesis that switch from silence to activity is mediated by spontaneous synaptic events, whereby any neuron may become active first. Due to probabilistic nature of activity onset, the large pyramidal cells from deep cortical layers, which are equipped with the most numerous synaptic inputs and large projection fields, are best suited for switching the whole network into active state.

Discharge Patterns of Human Genioglossus Motor Units during Arousal from Sleep

Single motor unit recordings of the human genioglossus muscle reveal motor units with a variety of discharge patterns. Integrated multiunit electromyographic recordings of genioglossus have demonstrated an abrupt increase in the muscle's activity at arousal from sleep. The aim of the present study was to determine the effect of arousal from sleep on the activity of individual motor units as a function of their particular discharge pattern. Genioglossus activity was measured using intramuscular fine-wire electrodes inserted via a percutaneous approach. Arousals from sleep were identified using the ASDA criterion and the genioglossus electromyogram recordings analyzed for single motor unit activity. Sleep research laboratory. Sleep and respiratory data were collected in 8 healthy subjects (6 men). 138 motor units were identified during prearousalarousal sleep: 25% inspiratory phasic, 33% inspiratory tonic, 4% expiratory phasic, 3% expiratory tonic, and 35% tonic. At arousal from sleep inspiratory phasic units significantly increased the proportion of a breath over which they were active, but did not appreciably increase their rate of firing. 80 new units were identified at arousals, 75% were inspiratory, many of which were active for only 1 or 2 breaths. 22% of units active before arousal, particularly expiratory and tonic units, stopped at the arousal. Increased genioglossus muscle activity at arousal from sleep is primarily due to recruitment of inspiratory phasic motor units. Further, activity within the genioglossus motoneuron pool is reorganized at arousal as, in addition to recruitment, approximately 20% of units active before arousals stopped firing.

Multichannel Intraneural and Intramuscular Techniques for Multiunit Recording and Use in Active Prostheses

During the last decade there has been a renewed interest in the development of advanced, active hand prosthetic devices for amputees. In contrast to passive prostheses, active devices can be controlled by the user's intention. Active prosthetic devices have been substantially improved by integrating robot technology to achieve more functionalities and lifelike movements. Despite important progress in the technological development of prosthetics, their clinical application is still limited by the quantity and quality of biological signals that can be used for understanding the user's intention, and by the relatively poor performance of the algorithms that translate the user's intention into a desired movement. In this review we describe a solution to some of these limitations, i.e., the flexible, multichannel, implantable intraneural and intramuscular electrodes to interface the body's peripheral nerves or muscles. We aim to review the historic development, the underlying technology, and the design concepts of these electrodes. Moreover, the signal processing methods applied to these recordings and their use for the control of prosthetic devices will be discussed. Although the focus is on hand prostheses, the interface approach described is general.

Dual Somatic Recordings from Gonadotropin-Releasing Hormone (GnRH) Neurons Identified by Green Fluorescent Protein (GFP) in Hypothalamic Slices

Gonadotropin-Releasing Hormone (GnRH) is a small neuropeptide that regulates pituitary release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropins are essential for the regulation of reproductive function. The GnRH-containing neurons are distributed diffusely throughout the hypothalamus and project to the median eminence where they release GnRH from their axon terminals into the hypophysiotropic portal system (1). In the portal capillaries, GnRH travels to the anterior pituitary gland to stimulate release of gonadotropins into systemic circulation. GnRH release is not continuous but rather occurs in episodic pulses. It is well established that the intermittent manner of GnRH release is essential for reproduction (2, 3).Coordination of activity of multiple GnRH neurons probably underlies GnRH pulses. Total peptide content in GnRH neurons is approximately 1.0 pg/cell (4), of which 30% likely comprises the releasable pool. Levels of GnRH during a pulse (5, 6), suggest multiple GnRH neurons are probably involved in neurosecretion. Likewise, single unit activity extracted from hypothalamic multi-unit recordings during LH release indicates changes in activity of multiple neurons (7). The electrodes with recorded activity during LH pulses are associated with either GnRH somata or fibers (8). Therefore, at least some of this activity arises from GnRH neurons.The mechanisms that result in synchronized firing in hypothalamic GnRH neurons are unknown. Elucidating the mechanisms that coordinate firing in GnRH neurons is a complex problem. First, the GnRH neurons are relatively few in number. In rodents, there are 800-2500 GnRH neurons. It is not clear that all GnRH neurons are involved in episodic GnRH release. Moreover, GnRH neurons are diffusely distributed (1). This has complicated our understanding of coordination of firing and has made many technical approaches intractable. We have optimized loose cell-attached recordings in current-clamp mode for the direct detection of action potentials and developed a recording approach that allows for simultaneous recordings from pairs of GnRH neurons.

Dual Somatic Recordings from Gonadotropin-Releasing Hormone (GnRH) Neurons Identified by Green Fluorescent Protein (GFP) in Hypothalamic Slices

Gonadotropin-Releasing Hormone (GnRH) is a small neuropeptide that regulates pituitary release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropins are essential for the regulation of reproductive function. The GnRH-containing neurons are distributed diffusely throughout the hypothalamus and project to the median eminence where they release GnRH from their axon terminals into the hypophysiotropic portal system (1). In the portal capillaries, GnRH travels to the anterior pituitary gland to stimulate release of gonadotropins into systemic circulation. GnRH release is not continuous but rather occurs in episodic pulses. It is well established that the intermittent manner of GnRH release is essential for reproduction (2, 3). Coordination of activity of multiple GnRH neurons probably underlies GnRH pulses. Total peptide content in GnRH neurons is approximately 1.0 pg/cell (4), of which 30% likely comprises the releasable pool. Levels of GnRH during a pulse (5, 6), suggest multiple GnRH neurons are probably involved in neurosecretion. Likewise, single unit activity extracted from hypothalamic multi-unit recordings during LH release indicates changes in activity of multiple neurons (7). The electrodes with recorded activity during LH pulses are associated with either GnRH somata or fibers (8). Therefore, at least some of this activity arises from GnRH neurons. The mechanisms that result in synchronized firing in hypothalamic GnRH neurons are unknown. Elucidating the mechanisms that coordinate firing in GnRH neurons is a complex problem. First, the GnRH neurons are relatively few in number. In rodents, there are 800-2500 GnRH neurons. It is not clear that all GnRH neurons are involved in episodic GnRH release. Moreover, GnRH neurons are diffusely distributed (1). This has complicated our understanding of coordination of firing and has made many technical approaches intractable. We have optimized loose cell-attached recordings in current-clamp mode for the direct detection of action potentials and developed a recording approach that allows for simultaneous recordings from pairs of GnRH neurons.

Synaptic placement and distribution of feed-back input on cortical neurons combined with intrinsic signal optical imaging and multiunit recording

Event Abstract Back to Event Synaptic placement and distribution of feed-back input on cortical neurons combined with intrinsic signal optical imaging and multiunit recording Katalin Sári1*, Fuyuki Karube1, Zsanett E-Sólyom1 and Zoltán Kisvárday1 1 University of Debrecen, Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, Hungary In the cat visual cortex area 17 (A17) projects to and receives input from numerous cortical areas of which area 18 (A18) provides the heaviest exchange of connections with A17 Indeed feed-back from A18 to A17 represents a substantial proportion of all input to A17 although the functional significance and termination pattern of synapses at the single cell level is not known. Here we used brain imaging, electrophysiological recording and morphological tools to reveal the contribution and significance of connections between A17 and A18. The border zone between A17 and A18 was visualised using activity maps obtained with intrinsic signal optical imaging based on the different spatial and temporal frequency preferences between A17 and A18 neurons. Next, multi unit activity was recorded at several locations in both areas in order to determine preferred orientation, direction and retinotopic position. Finally, extracellular microinjection of BDA was carried out at each electrode penetration. Anterogradely labelled axons running across the the border between A17/A18 and retrogradely labelled cell bodies were reconstructed in three-dimension using the Neurolucida reconstruction system. We expect to reveal corticocortical feed-back connections between the two early visual areas and determine the location of feed-back connections on the target cells. Combination of brain imaging and multiunit recordings will enable us to compare the functional characteristics of feed-back connections with the synaptic placement and distribution on visual cortical neurons. Supported by the European Consortium, FACETS (FP6-2004-IST-FETPI) and the Hungarian Academy of Sciences (TKI-242) to Z.K. Conference: IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010. Presentation Type: Poster Presentation Topic: Abstracts Citation: Sári K, Karube F, E-Sólyom Z and Kisvárday Z (2010). Synaptic placement and distribution of feed-back input on cortical neurons combined with intrinsic signal optical imaging and multiunit recording. Front. Neurosci. Conference Abstract: IBRO International Workshop 2010. doi: 10.3389/conf.fnins.2010.10.00259 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: 05 May 2010; Published Online: 05 May 2010. * Correspondence: Katalin Sári, University of Debrecen, Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, Debrecen, Hungary, sari.katalin@gmail.com 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 Katalin Sári Fuyuki Karube Zsanett E-Sólyom Zoltán Kisvárday Google Katalin Sári Fuyuki Karube Zsanett E-Sólyom Zoltán Kisvárday Google Scholar Katalin Sári Fuyuki Karube Zsanett E-Sólyom Zoltán Kisvárday PubMed Katalin Sári Fuyuki Karube Zsanett E-Sólyom Zoltán Kisvárday 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.

Differential degree of learning induced plasticity in primate lateral prefrontal cortex (lPFC) during auditory working

Event Abstract Back to Event Differential degree of learning induced plasticity in primate lateral prefrontal cortex (lPFC) during auditory working Hyun S. Kang1*, Christos Constantinidis2, Elsie Spingath1, Thane K. Plummer1, Jon Isaac1, Jonathan M. Crawford1 and David T. Blake1 1 Van der Veer Institute for Parkinson's and Brain Research, Brain and Behavior Discovery Institute, United States 2 Wake Forest University School of Medicine, Department of Neurobiology and Anatomy, United States The sensory cortex has shown that learning causes a non-transient increase in cortical response strength to the target stimulus, and differential degrees of cortical strength have been observed throughout learning progression. The current study investigates the learning-induced plasticity in the primate lateral prefrontal cortex (lPFC) in response to various task demands. We studied these issues using chronic cortical implants, allowing continued recordings over a period of months. The implants have 64 electrodes, each of which can be vertically positioned independently. The cortical implant was surgically placed lateral to the principal sulcus, sampling a 4x4-mm surface area. Single unit & multiunit recordings were sampled from more than 40 electrodes daily. As a control plasticity study, broad responses to acoustic stimuli were first collected before any behavioral training. We observed few responses to tone stimuli and macaque vocal calls during passive listening and before training. Animals were subsequently trained to hold a lever for 2 to 3 seconds while task-irrelevant tone stimuli were added at random times during the trial. Still, no tone-evoked action potential responses were observed, although task-evoked activity related to the press & release of the lever was observed. Then, shaping was initiated in a working memory task requiring the comparison of two stimuli presented in sequence with an intervening delay period. The animals then trained to perform the working memory task with a variety of intervening delays (1600ms, 800ms, 400ms). When the tonal stimuli became task-contingent and were delivered at predictable times during the lever-hold, lPFC neuronal responses were greatly elevated during the presentation of acoustic sound stimuli on some sessions, but not on others. The same sites could show acoustically-driven responses or not on the following days, with no apparent change in the recording quality. We also observed a degree of lPFC response strength where the high variance of firing rate correlated with a longer delay between the stimuli. Our results demonstrate that learning induced-plasticity is evident by the presence of tone-evoked responses only after behavioral training, and differential recruitment of the lPFC is dependant on the level of cognitive procedure. Conference: 2010 South East Nerve Net (SENN) and Georgia/South Carolina Neuroscience Consortium (GASCNC) conferences, Atlanta , United States, 5 Mar - 7 Mar, 2010. Presentation Type: Oral Presentation Topic: Talks Citation: Kang HS, Constantinidis C, Spingath E, Plummer TK, Isaac J, Crawford JM and Blake DT (2010). Differential degree of learning induced plasticity in primate lateral prefrontal cortex (lPFC) during auditory working. Front. Neurosci. Conference Abstract: 2010 South East Nerve Net (SENN) and Georgia/South Carolina Neuroscience Consortium (GASCNC) conferences. doi: 10.3389/conf.fnins.2010.04.00012 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: 15 Mar 2010; Published Online: 15 Mar 2010. * Correspondence: Hyun S Kang, Van der Veer Institute for Parkinson's and Brain Research, Brain and Behavior Discovery Institute, Christchurch, United States, hkang@students.mcg.edu 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 Hyun S Kang Christos Constantinidis Elsie Spingath Thane K Plummer Jon Isaac Jonathan M Crawford David T Blake Google Hyun S Kang Christos Constantinidis Elsie Spingath Thane K Plummer Jon Isaac Jonathan M Crawford David T Blake Google Scholar Hyun S Kang Christos Constantinidis Elsie Spingath Thane K Plummer Jon Isaac Jonathan M Crawford David T Blake PubMed Hyun S Kang Christos Constantinidis Elsie Spingath Thane K Plummer Jon Isaac Jonathan M Crawford David T Blake 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.

A novel multisite silicon probe fabricated by using an economical wet etching process for high quality laminar neural recordings

Event Abstract Back to Event A novel multisite silicon probe fabricated by using an economical wet etching process for high quality laminar neural recordings László Grand1, 2*, Anita Pongrácz3, Éva Vázsonyi3, Gergely Márton3, Dorottya Gubán3, Gábor Battistig3, György Karmos1, 2 and István Ulbert1, 2 1 Institute for Psychology of the Hungarian Academy of Sciences, Hungary 2 Pázmány Péter Catholic University, Faculty of Information Technology, Hungary 3 Research Institute for Technical Physics and Materials Science, Hungary For the construction of multiple site silicon based neural interface a novel process has been carried out. The applied economical wet etching method for the formation of the body of the probe ensures a wide variety of thickness and length dimensions for this neural interface. The probe contains 24 evenly spaced (100μm) recording sites, with shaft dimensions of: 280μm wide, 80μm thickness and 12mm length. It can easily penetrate both the dura and pia mater and exhibit excellent performance in Local Field Potential (LFP), Multiunit (MUA) and Single Unit Activity (SUA) recordings. In addition, the used special wet etching process form rounded edges while keeping the tip of the probe sharp, which makes it minimally invasive. Standard 3 inch diameter, <100> oriented, p-type Si wafer with 200μm thickness, polished on both sides was used for the probe fabrication that proceeded in several technological steps. The initial phase consisted of various thin-film depositions to form the bottom insulating layers, the Pt electrode contacts and leads, the passivation layer, the contact holes and bonding pads. The subsequent two phases consisted of different types of wet chemical etching processes for the probe shaping in order to obtain sharp tip with rounded edge. The final phase of the probe fabrication process series is the removal of protecting and masking layers and packaging of the probe. The probe was implanted into the caudate putamen nucleus of a ketamine/xylazine anesthetized rat. We recorded wide bandwidth neural data, good quality MUA was apparent on several channels, some of the sites that located closest to tip, recorded clearly distinguishable SUA as well. LFP recordings were also of satisfactory quality. Here we have reported on the production technology and electrophysiology results of the first working, purely Hungarian origin silicone probe prototype. Our preliminary results are encouraging for the further technological refinement and experimental utilization. Conference: IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010. Presentation Type: Poster Presentation Topic: Abstracts Citation: Grand L, Pongrácz A, Vázsonyi É, Márton G, Gubán D, Battistig G, Karmos G and Ulbert I (2010). A novel multisite silicon probe fabricated by using an economical wet etching process for high quality laminar neural recordings. Front. Neurosci. Conference Abstract: IBRO International Workshop 2010. doi: 10.3389/conf.fnins.2010.10.00231 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: 04 May 2010; Published Online: 04 May 2010. * Correspondence: László Grand, Institute for Psychology of the Hungarian Academy of Sciences, Budapest, Hungary, grand@cogpsyphy.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 László Grand Anita Pongrácz Éva Vázsonyi Gergely Márton Dorottya Gubán Gábor Battistig György Karmos István Ulbert Google László Grand Anita Pongrácz Éva Vázsonyi Gergely Márton Dorottya Gubán Gábor Battistig György Karmos István Ulbert Google Scholar László Grand Anita Pongrácz Éva Vázsonyi Gergely Márton Dorottya Gubán Gábor Battistig György Karmos István Ulbert PubMed László Grand Anita Pongrácz Éva Vázsonyi Gergely Márton Dorottya Gubán Gábor Battistig György Karmos István Ulbert 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.

Multiunit Recording of the Cerebellar Cortex, Inferior Olive, and Fastigial Nucleus During Copulation in Naive and Sexually Experienced Male Rats

The sexual behavior of male rats constitutes a natural model to study learning of motor skills at the level of the central nervous system. We previously showed that sexual behavior increases Fos expression in granule cells at lobules 6 to 9 of the vermis cerebellum. Herein, we obtained multiunit recordings of lobules 6a and 7 during the training period of naive subjects, and during consecutive ejaculations of expert males. Recordings from both lobules and the inferior olive showed that the maximum amplitude of mount, intromission, and ejaculation signals were similar, but sexual behavior during training tests produced a decrease in the amplitude for mount and intromission signals. The fastigial nucleus showed an inverse mirror-like response. Thus, the cerebellum is involved in the neural basis of sexual behavior and the learning of appropriate behavioral displays during copulation, with a wiring that involves the cerebellar cortex, inferior olive, and fastigial nucleus.

The 2009 Carl Ludwig Lecture: pathophysiology of the human sympathetic nervous system in cardiovascular diseases: the transition from mechanisms to medical management

Sympathetic nervous system responses typically are regionally differentiated, with activation in one outflow sometimes accompanying no change or sympathetic inhibition in another. Regional sympathetic activity is best studied in humans by recording from postganglionic sympathetic efferents (multiunit or single fiber recording) and by isotope dilution-derived measurement of organ-specific norepinephrine release to plasma (regional "norepinephrine spillover"). Evidence assembled in this review indicates that sympathetic nervous system abnormalities are crucial in the development of cardiovascular disorders, notably heart failure, essential hypertension, disorders of postural circulatory control causing syncope, and "psychogenic heart disease," heart disease attributable to mental stress and psychiatric illness. These abnormalities involve persistent, adverse activation of sympathetic outflows to the heart and kidneys in heart failure and hypertension, episodic or ongoing cardiac sympathetic activation in psychogenic heart disease, and defective sympathetic circulatory reflexes in disorders of postural circulatory control. An important goal for clinical scientists is translation of knowledge of pathophysiology, such as this, into better treatment for patients. The achievement of this "mechanisms-to-management" transition is at differing stages of development with the different conditions. Clinical translation is mature in cardiac failure, knowledge of cardiac neural pathophysiology having led to introduction of beta-adrenergic blockers, an effective therapy. With essential hypertension, perhaps we are on the cusp of effective translation, with recent successful testing of selective catheter-based renal sympathetic nerve ablation in patients with resistant hypertension, an intervention firmly based on demonstration of activation of the renal sympathetic outflow. With psychogenic heart disease and postural syncope syndromes, knowledge of the neural pathophysiology is emerging, but clinical translation remains for the future.

Neural correlates of behavior in the mothManduca sextain response to complex odors

WithManduca sextaas a model system, we analyzed how natural odor mixtures that are most effective in eliciting flight and foraging behaviors are encoded in the primary olfactory center in the brain, the antennal lobe. We used gas chromatography coupled with multiunit neural-ensemble recording to identify key odorants from flowers of two important nectar resources, the desert plantsDatura wrightiiandAgave palmeri, that elicited responses from individual antennal-lobe neurons. Neural-ensemble responses to theA. palmerifloral scent, comprising &gt;60 odorants, could be reproduced by stimulation with a mixture of six of its constituents that had behavioral effectiveness equivalent to that of the complete scent. Likewise, a mixture of three floral volatiles fromD. wrightiielicited normal flight and feeding behaviors. By recording responses of neural ensembles to mixtures of varying behavioral effectiveness, we analyzed the coding of behaviorally “meaningful” odors. We considered four possible ensemble-coding mechanisms—mean firing rate, mean instantaneous firing rate, pattern of synchronous ensemble firing, and total net synchrony of firing—and found that mean firing rate and the pattern of ensemble synchrony were best correlated with behavior (R= 41% and 43%, respectively). Stepwise regression analysis showed that net synchrony and mean instantaneous firing rate contributed little to the variation in the behavioral results. We conclude that a combination of mean-rate coding and synchrony of firing of antennal-lobe neurons underlies generalization among related, behaviorally effective floral mixtures while maintaining sufficient contrast for discrimination of distinct scents.

Microcircuitry coordination of cortical motor information in self-initiation of voluntary movements

Motor cortex neurons are activated at different times during self-initiated voluntary movement. However, the manner in which excitatory and inhibitory neurons in distinct cortical layers help to organize voluntary movement is poorly understood. We carried out juxtacellular and multiunit recordings from actively behaving rats and found temporally and functionally distinct activations of excitatory pyramidal cells and inhibitory fast-spiking interneurons. Across cortical layers, pyramidal cells were activated diversely for sequential motor phases (for example, preparation, initiation and execution). In contrast, fast-spiking interneurons, including parvalbumin-positive basket cells, were recruited predominantly for motor execution, with pyramidal cells producing a command-like activity. Thus, fast-spiking interneurons may underlie command shaping by balanced inhibition or recurrent inhibition, rather than command gating by temporally alternating excitation and inhibition. Furthermore, initiation-associated pyramidal cells excited similar and different functional classes of neurons through putative monosynaptic connections. This suggests that these cells may temporally integrate information to initiate and coordinate voluntary movement.

Endocannabinoid Signaling Is Required for Development and Critical Period Plasticity of the Whisker Map in Somatosensory Cortex

Type 1 cannabinoid (CB1) receptors mediate widespread synaptic plasticity, but how this contributes to systems-level plasticity and development in vivo is unclear. We tested whether CB1 signaling is required for development and plasticity of the whisker map in rat somatosensory cortex. Treatment with the CB1 antagonist AM251 during an early critical period for layer (L) 2/3 development (beginning postnatal day [P] 12-16) disrupted whisker map development, leading to inappropriate whisker tuning in L2/3 column edges and a blurred map. Early AM251 treatment also prevented experience-dependent plasticity in L2/3, including deprivation-induced synapse weakening and weakening of deprived whisker responses. CB1 blockade after P25 did not disrupt map development or plasticity. AM251 had no acute effect on sensory-evoked spiking and only modestly affected field potentials, suggesting that plasticity effects were not secondary to gross activity changes. These findings implicate CB1-dependent plasticity in systems-level development and early postnatal plasticity of the whisker map.

Influence of Saccade Efference Copy on the Spatiotemporal Properties of Remapping: A Neural Network Study

Remapping of gaze-centered target-position signals across saccades has been observed in the superior colliculus and several cortical areas. It is generally assumed that this remapping is driven by saccade-related signals. What is not known is how the different potential forms of this signal (i.e., visual, visuomotor, or motor) might influence this remapping. We trained a three-layer recurrent neural network to update target position (represented as a "hill" of activity in a gaze-centered topographic map) across saccades, using discrete time steps and backpropagation-through-time algorithm. Updating was driven by an efference copy of one of three saccade-related signals: a transient visual response to the saccade-target in two-dimensional (2-D) topographic coordinates (Vtop), a temporally extended motor burst in 2-D topographic coordinates (Mtop), or a 3-D eye velocity signal in brain stem coordinates (EV). The Vtop model produced presaccadic remapping in the output layer, with a "jumping hill" of activity and intrasaccadic suppression. The Mtop model also produced presaccadic remapping with a dispersed moving hill of activity that closely reproduced the quantitative results of Sommer and Wurtz. The EV model produced a coherent moving hill of activity but failed to produce presaccadic remapping. When eye velocity and a topographic (Vtop or Mtop) updater signal were used together, the remapping relied primarily on the topographic signal. An analysis of the hidden layer activity revealed that the transient remapping was highly dispersed across hidden-layer units in both Vtop and Mtop models but tightly clustered in the EV model. These results show that the nature of the updater signal influences both the mechanism and final dynamics of remapping. Taken together with the currently known physiology, our simulations suggest that different brain areas might rely on different signals and mechanisms for updating that should be further distinguishable through currently available single- and multiunit recording paradigms.

Dopamine D3 Receptor Antagonist SB-277011A Influences Cell Firing in the Rat Ventral Tegmental Area, Parallel Role with the Cannabinoid System in Addiction and Neuropsychiatry Disorders?

SB-277011A is a compound entering the brain with high affinity and selectivity for the dopamine (DA) D3 receptor. Recent electrophysiological study has shown that acute oral administration of SB-277011A significantly alters the spontaneous activity of DA neurons in the ventral tegmental area (VTA) but that intravenous administration has no effects. In that electrophysiological study hypotheses to explain this discrepancy involved either administration route- dependent timing for the compound to reach its active site or the formation of an active metabolite following oral administration that would sustain the activity of SB-277011A on DA cell firing. In an attempt to assess whether formation of a metabolite may account for the activity of the parent compound we conducted electrophysiological multi-unit field recordings of DA neurons in the VTA of anaesthetised rats following treatment with SB-277011A either systemically or locally in the VTA. The local dose (2.5� g) was selected based on brain exposure achieved following systemic i.p. administration of 10mg/kg. Results show that both administrations increased VTA neurons firing compared to vehicle administration. However, local injection of SB-277011A in the VTA induced a more rapid and higher increase of neuronal activity than systemic treatment. These results suggest that the increased VTA cell firing occurring following systemic administration of SB-277011A is likely due to the compound itself and not to a putative metabolite. Finally, since the growing evidence that cannabinoids (CBs) modulate DA release in the brain and in view of the fact that CB1 receptors are widely distributed over DA neurons, the interplay between these two systems in the context of the current findings is discussed.

Extrinsic afferent nerve sensitivity and enteric neurotransmission in murine jejunum in vitro

Enteric and extrinsic sensory neurons respond to similar stimuli. Thus they may be activated in series or in parallel. Because signal transmission via synapses or mediator release would depend on calcium, we investigated its role for extrinsic afferent sensitivity to chemical and mechanical stimulation. Extracellular multiunit afferent recordings were made in vitro from paravascular nerve bundles supplying the mouse jejunum. Intraluminal pressure and afferent nerve responses were recorded under control conditions and under four conditions designed to interfere with enteric neurotransmission. We found that phasic intestinal contractions ceased after switching perfusion to Ca(2+)-free buffer with or without a purinergic P2 receptor antagonist, pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS) or cadmium (blocking all Ca(2+)-channels) but not following omega-conotoxin GVIA (N-type Ca(2+)-channel blocker). Luminal HCl (pH 2) and 5-HT (500 microM) evoked peak firing of 17 +/- 4 impulses per second (imp/s) (n = 10) and 21 +/- 4 imp/s (n = 13) under control conditions. These responses were reduced to 4 +/- 2 imp/s and 5 +/- 2 imp/s by cadmium (n = 7, P < 0.05), to 7 +/- 2 imp/s and 6 +/- 1 imp/s by Ca(2+)-free perfusion (n = 6, P < 0.05), and to 3 +/- 1 imp/s and 4 +/- 1 imp/s by Ca(2+)-free perfusion with PPADS (n = 6, P < 0.05). Responses were unchanged by omega-conotoxin GVIA. Mechanical ramp distension of the intestinal segment to 60 cmH(2)O was not altered by any of the experimental conditions. We concluded that HCl and 5-HT activate extrinsic afferents via a calcium-dependent mechanism, which is unlikely to involve enteric neurons carrying N-type calcium channels. Extrinsic mechanosensitivity is independent of enteric neurotransmission. It appears that cross talk from the enteric to the extrinsic nervous system does not mediate extrinsic afferent sensitivity.