Papers on the rat sensorimotor thalamus


Possible Papers for JFL Journal Club 2011

Mechanisms of deep brain stimulation: an intracellular study in rat thalamus
Anderson, T.; Hu, B.; Pittman, Q. & Kiss, Z.
JOURNAL OF PHYSIOLOGY-LONDON
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Vol. {559}
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pp. {301-313}
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{2004}
{High-frequency deep brain stimulation (DBS) in the thalamus alleviates most kinds of tremor, yet its mechanism of action is unknown. Studies in subthalamic nucleus and other brain sites have emphasized non-synaptic factors. To explore the mechanism underlying thalamic DBS, we simulated DBS in vitro by applying high-frequency (125 Hz) electrical stimulation directly into the sensorimotor thalamus of adult rat brain slices. Intracellular recordings revealed two distinct types of membrane responses, both of which were initiated with a depolarization and rapid spike firing. However, type 1 responses repolarized quickly and returned to quiescent baseline during simulated DBS whereas type 2 responses maintained the level of membrane depolarization, with or without spike firing. Individual thalamic neurones exhibited either type 1 or type 2 response but not both. In all neurones tested, simulated DBS-evoked membrane depolarization was reversibly eliminated by tetrodotoxin, glutamate receptor antagonists, and the Ca2+ channel antagonist Cd2+. Simulated DBS also increased the excitability of thalamic cells in the presence of glutamate receptor blockade, although this non-synaptic effect induced no spontaneous firing such as that found in subthalamic nucleus neurones. Our data suggest that high-frequency stimulation when applied in the ventral thalamus can rapidly disrupt local synaptic function and neuronal firing thereby leading to a `functional deafferentation' and/or `functional inactivation: These mechanisms, driven primarily by synaptic activation, help to explain the paradox that lesions, muscimol and DBS in thalamus all effectively stop tremor.}
Arborisation and termination of single motor thalamocortical axons in the rat
Aumann, T.; Ivanusic, J. & Horne, M.
JOURNAL OF COMPARATIVE NEUROLOGY
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Vol. {396}
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pp. {121-130}
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{1998}
{The aim of this study was to examine the arborisations and terminations of individual thalamocortical axons in the motor system of the rat. Small, extracellular injections of an anterograde tracer (dextran-biotin) were made into the ventrolateral (VL) or ventral posterolateral (VPL) thalamic nuclei to label thalamocortical projections. Eleven motor axons and one somatosensory axon were reconstructed through serial sections just rostral from the injection site to their terminations in sensorimotor cortex. The smallest arbor arising from a single motor axon extended approximately 0.9 mm rostrocaudal and 0.9 mm mediolateral, the largest extended 3.9 mm rostrocaudal and 1.0 mm mediolateral. In some cases, two distinct plexuses of terminals were formed by an axon. In addition, motor axons formed terminals in cortical layer V only or in layers I, III, and V. By contrast land in keeping with previous reports), the somatosensory axon formed a single plexus of terminals in layer IV of the cortex that extended approximately 0.3 mm rostrocaudal and 0.4 mm mediolateral. It is concluded that individual motor thalamocortical neurones are in a position to influence much more widespread cortical regions than somatosensory thalamocortical neurones. (C) 1998 Wiley-Liss, Inc.}
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Reversible and irreversible knockout of the ventroposterolateral thalamic nucleus measured by intracerebral SEP recordings in the rat brain - An aid to neuronavigation in small nuclei
Blunk, J. A.; Burke, M.; Maarouf, M. & Buehrle, C. P.
JOURNAL OF NEUROSCIENCE METHODS
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Vol. {162}
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pp. {19-25}
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{2007}
{Centrally active drugs are often hard to administer because of the blood brain barrier, and frequently high systemic doses are required to reach sufficient brain parenchyma concentrations, since these drugs are, additionally, diluted in the total blood volume. Moreover, topical administration via the systemic route is not possible. We here propose a technique for the local, quantitative deposition of active substances at defined intracerebral targets, e.g. the thalamic nuclei. We used a long micropipette and stereotactically advanced it to the desired coordinates under electrophysiological control. The pipette acted as both an electrode for intracerebral recordings and as a transportation means for the drug. The amplitude of intracerebral evoked potentials relayed by the thalamic nucleus to the sensorimotor cortex indicated the distance between the pipette tip and the neurons of the targeted nucleus. Data were obtained from anesthetized rats, where the micropipette was advanced towards the nucleus ventralis posterolateralis (VPL) during contralateral electrical forepaw stimulation and intracerebral recording of somatosensory evoked potentials. Within the VPL we either injected lidocaine or kainic acid, both resulting in an attenuation of the intracerebral as well as the cortical evoked potentials. This proposed tool may be useful for functional investigations of deep brain structures. (C) 2006 Elsevier B.V. All rights reserved.}
STUDY ON CONNECTIONS IN THE POSTERIOR REGION OF THE RAT THALAMUS
CADUSSEAU, J. & ROGER, M.
JOURNAL FUR HIRNFORSCHUNG
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Vol. {33}
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pp. {19-35}
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{1992}
{Using retograde and anterograde tracing methods we have studied in the posterior region of the thalamus of the rat the distribution of: (1) the terminal fields of the main afferents arising from somatosensory centers (dorsal column nuclei, interpolar trigeminal subnucleus, somatosensory cortex), motor centers (red nucleus, motor cortex) and multimodal structures (deep layers of the superior colliculus, zona incerta, cingular cortex) and of (2) the neurons giving rise to the main efferents towards the sensorimotor cortex, the red nucleus, the deep layers of the superior colliculus and the zone incerta. The overlap of the retrograde and anterograde labeling reveals a relatively homogeneous region. Considering however the cortical connections, three different subdivisions can be distinguished: a caudal pole completely devoid of cortical connecions, a medial subdivision receiving cortical afferents from the sensorimotor and cingulate cortices and a rostral pole reciprocally connected with the sensorimorot cortex. Therefore the rostral pole would be the only part of this region which should be included in the thalamus.}
Spatiotemporal properties of short-term plasticity in sensorimotor thalamocortical pathways of the rat
CastroAlamancos, M. & Connors, B.
JOURNAL OF NEUROSCIENCE
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Vol. {16}
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pp. {2767-2779}
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{1996}
{Each region of neocortex receives synaptic input from several thalamic nuclei, but the response properties of thalamocortical pathways may differ. We have studied the frontoparietal (motor and somatosensory) neocortex of the rat and have examined the responses induced by stimulating two convergent thalamocortical projections originating in the ventrolateral (VL) nucleus and ventroposterior lateral (VPL) nucleus. Depth recordings and current-source density (CSD) analysis revealed two primary responses with different laminar and temporal patterns when VL and VPL were stimulated. Single shocks to VL produced a characteristic small current sink in layer V, which strongly enhanced in response to a second pulse delivered within a 50-200 msec interval (i.e., the augmenting response). In contrast, a shock to VPL evoked a large current sink that originated in layer IV, spread strongly into the supragranular layers, and was almost abolished in response to a second pulse at intervals of <200 msec (i.e., the decremental response). Control experiments determined that these responses could not be attributed to the antidromic firing of corticothalamic cells, intrathalamic mechanisms, or anesthesia. Topographic response maps were obtained from a grid of 30 sites across frontoparietal cortex. One shock to VL excited a very limited cortical region, but an augmenting response evoked 50-200 msec later spread at similar to 1 m/sec to synchronize the activity across an area up to 25 times larger. In contrast, a single shock to VPL activated a relatively large area, but the area activated by a second shock delivered within 200 msec was much smaller. We conclude that overlapping thalamocortical projections, originating in different thalamic nuclei, have distinct spatiotemporal response characteristics that may serve the functional specializations of these pathways.}
Cellular mechanisms of the augmenting response: Short-term plasticity in a thalamocortical pathway
CastroAlamancos, M. & Connors, B.
JOURNAL OF NEUROSCIENCE
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Vol. {16}
,
pp. {7742-7756}
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{1996}
{Some thalamocortical pathways display an `'augmenting response'' when stimuli are delivered at frequencies between 7 and 14 Hz. Cortical responses to the first three stimuli of a series increase progressively in amplitude and are relatively stable thereafter. We have investigated the cellular mechanisms of the augmenting response using extracellular and intracellular recordings in vivo and in slices of the sensorimotor neocortex of the rat. Single stimuli to the ventrolateral (VL) nucleus of the thalamus generate EPSPs followed by feedforward IPSPs that hyperpolarize cells in layer V. A long-latency depolarization interrupts the IPSP with a peak at similar to 200 msec. A second VL stimulus delivered during the hyperpolarization and before the peak of the long-latency depolarization yields an augmenting response. The shortest latency for augmenting responses occurs in cells of layer V, and they appear in dendrites and somata recorded in upper layers similar to 5 msec later. Recordings in vitro show that some layer V cells have hyperpolarization-activated and deinactivated conductances that may serve to increase their excitability after IPSPs. Also in vitro, cells from layer V, but not from layer III, generated augmenting responses at the same stimulation frequencies that were effective in vivo. Control experiments indicated that neither paired-pulse depression of IPSPs nor presynaptically mediated facilitation can account for the augmenting response. Active dendritic conductances contribute to the spread of augmenting responses into upper layers by way of back-propagating fast spikes, which attenuate with repetition, and long-lasting spikes, which enhance in parallel with the augmenting response. In conclusion, we propose that the initiation of augmenting responses depends on an interaction between inhibition, intrinsic membrane properties, and synaptic interconnections of layer V pyramidal neurons.}
Regulation of thalamic neurite outgrowth by the Eph ligand ephrin-A5: Implications in the development of thalamocortical projections
Gao, P.; Yue, Y.; Zhang, J.; Cerretti, D.; Levitt, P. & Zhou, R.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
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Vol. {95}
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pp. {5329-5334}
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{1998}
{The cerebral cortex is parcellated into different functional domains that receive distinct inputs from other cortical and subcortical regions. The molecular mechanisms underlying the specificity of connections of cortical afferents remain unclear. We report here that the Eph family tyrosine kinase receptor EphA5 and the ligand ephrin-A5 may play a key role in the exclusion of the limbic thalamic afferents from the sensorimotor cortex by mediating repulsive interactions. In situ hybridization shows that the EphA5 transcript is expressed at high levels in both cortical and subcortical limbic regions, including the frontal cortex, the subiculum, and the medial thalamic nuclei. In contrast, ephrin-A5 is transcribed abundantly in the sensorimotor cortex. Consistent with the complementary expression, the ligand inhibited dramatically the growth of neurites from neurons isolated from the medial thalamus but was permissive for the growth of neurites from lateral thalamic neurons, which is primarily nonlimbic, Similarly, the growth of neurites from Eph-A5-expressing neurons isolated from the subiculum was inhibited by ephrin-A5. Our studies suggest that the Eph family ligand ephrin-A5 serves as a general inhibitor of axonal growth from limbic neurons, which may serve to prevent innervation of inappropriate primary sensorimotor regions, thus contributing to the generation of specificity of thalamic cortical afferents.}
High responsiveness and direction sensitivity of neurons in the rat thalamic reticular nucleus to vibrissa deflections
Hartings, J.; Temereanca, S. & Simons, D.
JOURNAL OF NEUROPHYSIOLOGY
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Vol. {83}
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pp. {2791-2801}
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{2000}
{The thalamic reticular nucleus (Rt) is strategically positioned to integrate descending and ascending signals in the control of sensorimotor and other thalamocortical activity. Its prominent role in the generation of sleep spindles notwithstanding, relatively little is known of Rt function in regulating interactions with the sensory environment. We recorded and compared the responses of individual lit and thalamocortical neurons in the ventroposterior medial (VPm) nucleus of the rat to controlled deflections of mystacial vibrissae. Transient Rt responses to the onset (ON) and offset (OFF) of vibrissa deflection are larger and longer in duration than those of VPm and of all other populations studied in the whisker/barrel pathway. Magnitudes of ON and om responses in Rt were negatively correlated with immediately preceding activities, suggesting a contribution of low-threshold T-type Ca2+ channels. Rt neurons also respond with high tonic firing rates during sustained vibrissa deflections. By comparison, VPm neurons are less likely to respond tonically and are more likely to exhibit tonic suppression. Rt and VPm populations are similar to each other, however, in that they retain properties of directional sensitivity established in primary afferent neurons. In both populations neurons are selective for deflection angle and exhibit directional consistency, responding best to a particular direction of movement regardless of the starting position of the vibrissal hair. These findings suggest a role for Rt in the processing of detailed sensory information. Temporally, Rt may function to limit the duration of stimulus-evoked VPm responses and to focus them on rapid vibrissa perturbations. Moreover, by regulating the baseline activity of VPm neurons, Rt may indirectly enhance the response selectivity of layer IV barrel neurons to synchronous VPm firing.}
Secondary Brain Injuries in Thalamus and Hippocampus after Focal Ischemia Caused by Mild, Transient Extradural Compression of the Somatosensori Cortex in the Rat
Holmberg, P.; Liljequist, S. & Wagner, A.
CURRENT NEUROVASCULAR RESEARCH
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Vol. {6}
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pp. {1-11}
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{2009}
{The development and distribution of secondary brain lesions, subsequent to ischemic stroke, are of considerable clinical interest but so far only a limited number of studies have investigated the distribution and development of these secondary lesions in detail. In this study, we used an animal model of focal ischemia caused by extradural compression of the sensorimotor cortex. This paradigm of focal ischemia was shown to produce a consistent pattern of secondary lesions located distally from the primary lesion. Functionally the primary brain lesion produced a transient neurological deficit, which was evaluated by daily beam walking tests. Morphological changes were assessed in parallel after the ischemic event using Fluoro-Jade (FJ) staining as a marker of neuronal cell death. Secondary brain lesions were observed in the thalamus as well as in the hippocampus. The first sign of the slowly developing secondary brain lesions was present on day 3 with subsequent lesions being identified until day 16 after the primary ischemia. In addition to the identification of neuronal cell death by the FJ assays, immunostaining for parvalbumin ( PA), a marker of GABAergic interneurons, revealed a loss of PA-staining in the pyramidal layer of CA1 on day 3, thus showing a similar time pattern for loss of PA-staining as for the loss of FJ stained cells. Based upon our present results, we suggest that the current animal model of focal ischemia represents a valuable tool for studies concerning the development of secondary remote brain lesions and their association to impaired motor and cognitive functions.}
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Neuronal response to local electrical stimulation in rat thalamus: Physiological implications for mechanisms of deep brain stimulation
Kiss, Z.; Mooney, D.; Renaud, L. & Hu, B.
NEUROSCIENCE
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Vol. {113}
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pp. {137-143}
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{2002}
{High-frequency deep brain stimulation (DBS) of sensorimotor thalamus containing `tremor cells' leads to tremor arrest in humans with parkinsonian and essential tremor. To examine the possible underlying mechanism(s), we recorded in vitro intracellular responses of rat thalamic neurons to local intrathalamic stimulation. Such simulated DBS (sDBS) induced a sustained membrane depolarization accompanied by an increase in apparent membrane conductance in both motor and sensory neurons. With stimulation frequency above approximately 100 Hz, the sDBS-induced depolarization most typically led to repetitive neuronal firing or less frequently resulted in a complete blockade of action potential genesis. When regular intracellular current pulses were injected into cells to mimic `tremor' activity, such rhythmic discharges were invariably disrupted or abolished by the random spike firing induced during high-frequency sDBS. Low-frequency sDBS left rhythmicity unaffected. We conclude that clinical thalamic DBS may lead to a neuronal de-rhythmicity and tremor stoppage through masking and/or blocking rhythmic firing of tremor cells. (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.}
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Active sensation: insights from the rodent vibrissa sensorimotor system
Kleinfeld, D.; Ahissar, E. & Diamond, M. E.
CURRENT OPINION IN NEUROBIOLOGY
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Vol. {16}
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pp. {435-444}
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{2006}
{Rats sweep their vibrissae through space to locate objects in their immediate environment. In essence, their view of the proximal world is generated through pliable hairs that tap and palpate objects. The texture and shape of those objects must be discerned for the rat to assess the value of the object. Furthermore, the location of those objects must be specified with reference to the position of the rat's head for the rat to plan its movements. Recent in vivo and in vitro electrophysiological measurements provide insight into the algorithms and mechanisms that underlie these behavioral-based computations.}
The thalamic reticular nucleus: More than a sensory nucleus?
Mc Alonan, K. & Brown, V.
NEUROSCIENTIST
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Vol. {8}
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pp. {302-305}
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{2002}
{Sensory information is routed to the cortex via the thalamus, but despite this sensory bombardment, animals must attend selectively to stimuli that signal danger or opportunity. Sensory input must be filtered, allowing only behaviorally relevant information to capture limited attentional resources. Located between the thalamus and cortex is a thin lamina of neurons called the thalamic reticular nucleus (Rt). The thalamic reticular nucleus projects exclusively to thalamus, thus forming an essential component of the circuitry mediating sensory transmission. This article presents evidence supporting a role for Rt beyond the mere relay of sensory information. Rather than operating as a component of the sensory relay, the authors suggest that Rt represents an inhibitory interface or ``attentional gate,{''} which regulates the flow of information between the thalamus and cortex. Recent findings have also implicated Rt in higher cognitive functions, including learning, memory, and spatial cognition. Drawing from recent insights into the dynamic nature of the thalamic relay in awake, behaving animals, the authors present a speculative account of how Rt might regulate thalamocortical transmission and ultimately the contents of consciousness.}
INPUT-OUTPUT ORGANIZATION OF THE RAT VIBRISSAL MOTOR CORTEX
MIYASHITA, E.; KELLER, A. & ASANUMA, H.
EXPERIMENTAL BRAIN RESEARCH
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Vol. {99}
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pp. {223-232}
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{1994}
{The afferent and efferent connections of the vibrissal area of the rat motor cortex (VMCx) were investigated by injecting Phaseolus vulgaris leucoagglutinin (PHA-L) or wheat germ agglutinin-horseradish peroxidase into the physiologically defined VMCx. The VMCx formed reciprocal connections with the primary and secondary somatosensory cortex, lateral and ventrolateral orbital cortex, retrosplenial cortex, and perirhinal cortex. These corticocortical afferents originated from cell bodies in layers II-III and V, and some afferents originated from cell bodies in layer VI of the primary sensory cortex. All of the VMCx efferents terminated in layers I and V or layers I-III and V. The VMCx also formed reciprocal connections with the ventrolateral, ventromedial and centrolateral nucleus, the lateral portion of the mediodorsal nucleus and the posterior complex of the thalamus. It projected bilaterally to the caudate putamen, primarily ipsilaterally to the superior colliculus, anterior pretectal nucleus, and pontine nucleus, and mainly contralaterally to the oral part of the spinotrigeminal nucleus and the reticular formation around the facial nerve nucleus. Finally, injections of PHA-L into the superior colliculus demonstrated that this structure projected contralaterally to the lateral part of the facial nerve nucleus. These data suggest that the VMCx plays a key role in sensorimotor integration, through its extensive interconnectivity with numerous brain structures, and may modulate orientation behaviors by relaying processed information to the superior colliculus.}
SENSORIMOTOR ENCODING BY SYNCHRONOUS NEURAL ENSEMBLE ACTIVITY AT MULTIPLE LEVELS OF THE SOMATOSENSORY SYSTEM
NICOLELIS, M.; BACCALA, L.; LIN, R. & CHAPIN, J.
SCIENCE
,
Vol. {268}
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pp. {1353-1358}
,
{1995}
{Neural ensemble processing of sensorimotor information during behavior was investigated by simultaneously recording up to 48 single neurons at multiple relays of the rat trigeminal somatosensory system. Cortical, thalamic, and brainstem neurons exhibited widespread 7- to 12-hertz synchronous oscillations, which began during attentive immobility and reliably predicted the imminent onset of rhythmic whisker twitching. Each oscillatory cycle began as a traveling wave of neural activity in the cortex that then spread to the thalamus. Just before the onset of rhythmic whisker twitching, the oscillations spread to the spinal trigeminal brainstem complex. Thereafter, the oscillations at all levels were synchronous with whisker protraction. Neural structures manifesting these rhythms also exhibited distributed spatiotemporal patterns of neuronal ensemble activity in response to tactile stimulation, thus, multilevel synchronous activity in this system may encode not only sensory information but also the onset and temporal domain of tactile exploratory movements.}
Rhythmic neuronal interactions and synchronization in the rat dorsal column nuclei
Nunez, A.; Panetsos, F. & Avendano, C.
NEUROSCIENCE
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Vol. {100}
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pp. {599-609}
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{2000}
{Single-unit and multiunit activities were recorded from dorsal column nuclei of anesthetized rats in order to study the characteristics of the oscillatory activity expressed by these cells and their neuronal interactions. On the basis of their firing rate characteristics in spontaneous conditions, two types of dorsal column nuclei cell have been identified. Low-frequency cells (74\%) were silent or displayed a low firing rate (1.9 +/- 0.48 spikes/s), and were identified as thalamic-projecting neurons because they were activated antidromically by medial lemniscus stimulation. High-frequency cells (26\%) were characterized by higher discharge rates (27.2 +/- 5.1 spikes/s). None of them was antidromically activated by medial lemniscus stimulation. Low-frequency neurons showed a non-rhythmic discharge pattern spontaneously which became rhythmic under sensory stimulation of their receptive fields (48\% of cases; 4.8 +/- 0.23 Hz). All high-frequency neurons showed a rhythmic discharge pattern at 13.8 +/- 0.68 Hz either spontaneously or during sensory stimulation of their receptive fields. The shift predictor analysis indicated that oscillatory activity is not phase-locked to the stimulus onset in either type of cell, although the stimulus can reset the phase of the rhythmic activity of high-frequency cells. Cross-correlograms between pairs of low-frequency neurons typically revealed synchronized rhythmic activity when the overlapping receptive fields were stimulated. Rhythmic synchronization of high-frequency discharges was rarely observed spontaneously or under sensory stimulation. High-frequency neuronal firing could be correlated with the low-frequency neuronal activity or more often with the multiunit activity during sensory stimulation. Moreover, the presence of oscillatory activity modulated the sensory responses of dorsal column nuclei cells, favoring their responses. These findings indicate that thalamic-projecting and non-projecting neurons in dorsal column nuclei exhibited distinct oscillatory characteristics. However, both types of neuron may be entrained into an oscillatory rhythmic pattern when their overlapping receptive fields are stimulated, suggesting that in those conditions the dorsal column nuclei generate a populational oscillatory output to the somatosensory thalamus which could modulate and amplify the effectiveness of the somatosensory transmission. (C) 2000 IBRO. Published by Elsevier Science Ltd. All rights reserved.}
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SINGLE UNIT OSCILLATIONS IN RAT TRIGEMINAL NUCLEI AND THEIR CONTROL BY THE SENSORIMOTOR CORTEX
Panetsos, F. & Sanchez-Jimenez, A.
NEUROSCIENCE
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Vol. {169}
,
pp. {893-905}
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{2010}
{Oscillatory activity at both the single and multiunit levels has been reported in most central nervous system structures, and is postulated as a key factor in information processing and coding. Rats provide an excellent model for oscillation-based information processing, since tactile perception of the environment is achieved by rhythmic movements of their whiskers and information-related rhythmic activity has been identified in the thalamus and cortex. However, rhythmic activity related to information processing has never been reported in the sensory trigeminal complex (STC), the first brain stem relay station for whisker-related tactile information. In the present work, we demonstrate the existence of neural oscillations in the vibrissae-related neurons of the nuclei principalis (Pr5), oralis (Sp5o), interpolaris (Sp5i) and caudalis (Sp5c). Rhythmic activity was associated with the main task of each nucleus, prominent in nuclei responsible for tactile vibrissae information processing (up to 17\% oscillating neurons in Pr5 and 26\% in Sp5i) and less conspicuous in those concerned with pain (8\% oscillating neurons in Sp5o and in Sp5c). The higher percentage of oscillating neurons and higher frequencies in Sp5i than in Pr5 suggests an active role for rhythmic activity in integrating multivibrissa inputs. Oscillations are generated within the brainstem; data obtained from decorticated animals suggest the existence of a differential cortical control of the rhythmic processes in STC nuclei. Corticofugal activity modifies oscillation frequency and synchronization strength of the rhythmic activity mainly during tactile stimulation of the vibrissae. (C) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.}
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Resting-state functional connectivity of the rat brain
Pawela, C. P.; Biswal, B. B.; Cho, Y. R.; Kao, D. S.; Li, R.; Jones, S. R.; Schulte, M. L.; Matloub, H. S.; Hudetz, A. G. & Hyde, J. S.
MAGNETIC RESONANCE IN MEDICINE
,
Vol. {59}
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pp. {1021-1029}
,
{2008}
{ations in blood oxygen level dependent (BOLD) MRI contrast at 9.4T in lightly anesthetized resting rat brain are formed, and correlation coefficients between time course pairs are interpreted as measures of connectivity. A hierarchy of regional pairwise correlation coefficients (RPCCs) is observed, with the highest values found in the thalamus and cortex, both intra- and interhemisphere, and lower values between the cortex and thalamus. Independent sensory networks are distinguished by two methods: data driven, where task activation defines regions of interest (ROI), and hypothesis driven, where regions are defined by the rat histological atlas. Success in these studies is attributed in part to the use of medetomidine hydrochloride (Domitor) for anesthesia. Consistent results in two different rat-brain systems, the sensorimotor and visual, strongly support the hypothesis that resting-state BOLD fluctuations are conserved across mammalian species and can be used to map brain systems.}
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A two-dimensional force sensor in the millinewton range for measuring vibrissal contacts
Quist, B. W. & Hartmann, M. J. Z.
JOURNAL OF NEUROSCIENCE METHODS
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Vol. {172}
,
pp. {158-167}
,
{2008}
{The rat vibrissal (whisker) array is a common model system in neuroscience used to study sensorimotor integration. Recent work has suggested that during object contact, the forces and moments at the whisker base may serve as important perceptual cues to the rat. To date, however, the force/moment profile that results from a whisker sweeping against an object has yet to be characterized, because it requires the simultaneous measurement of two-dimensional forces on the order of millinewtons. Current technology for these measurements typically involves prohibitively bulky, expensive equipment with complicated fabrication techniques. We have developed a simple, yet effective two-dimensional force sensor with +/- 0.02 mN resolution; it is extremely compact, has a highly linear static response with low-noise output, and is inexpensive to build. We demonstrate the advantages and limitations of the sensor in three different experimental protocols, ranging from the precise quantification of forces on isolated (plucked) whiskers, to the detection of whisker-contact times in the awake behaving animal. Given the high fidelity of the sensor, it could have utility in a broad range of applications in which measuring contact/detach occurrence and/or small magnitude forces are important. (c) 2008 Published by Elsevier B.V.}
COMPARISON OF THE CONNECTIONAL PROPERTIES OF THE 2 FORELIMB AREAS OF THE RAT SENSORIMOTOR CORTEX - SUPPORT FOR THE PRESENCE OF A PREMOTOR OR SUPPLEMENTARY MOTOR CORTICAL AREA
ROUILLER, E.; MORET, V. & LIANG, F.
SOMATOSENSORY AND MOTOR RESEARCH
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Vol. {10}
,
pp. {269-289}
,
{1993}
{The existence of multiple motor cortical are as that differ in some of their ProPerties is well known in primates, but is less clear in the rat. The present study addressed this question from the point of view of connectional properties by comparing the afferent and efferent projections of the caudal forelimb area (CFA), considered to be the equivalent of the forelimb area of the primary motor cortex (MI), and a second forelimb motor representation, the rostral forelimb area (RFA). As a result of various tracing experiments (including double labeling), it was observed that CFA and RFA had reciprocal corticocortical connections characterized by preferential, asymmetrical, laminar distribution, indicating that RFA may occupy a different hierarchical level than CFA, according to criteria previously discussed in the visual cortex of primates. Furthermore, it was found that RFA, but not CFA, exhibited dense reciprocal connections with the insular cortex. With respect to their efferent projection to the basal ganglia, it was observed that CFA projected very densely to the lateral portion of the ipsilateral caudate putamen, whereas the contralateral projection was sparse and more restricted. The ipsilateral projection originating from RFA was slightly less dense than that from CFA, but it covered a larger portion of the caudate putamen (in the medial direction); the contralateral projection from RFA to the caudate putamen was of the same density and extent as the ipsilateral projection. The reciprocal thalamocortical and corticothalamic connections of RFA and CFA differed from each other in the sense that CFA was mainly interconnected with the ventrolateral thalamic nucleus, while RFA was mainly connected with the ventromedial thalamic nucleus. Altogether, these connectional differences, compared with the pattern of organization of the motor cortical areas in primates, suggest that RFA in the rat may well be an equivalent of the premotor or supplementary motor area. In contrast to the corticocortical, corticostriatal, and thalamocortical connections, RFA and CFA showed similar efferent projections to the subthalamic nucleus, substantia nigra, red nucleus, tectum, pontine nuclei, inferior olive, and spinal cord.}
A NOVEL SLOW (LESS-THAN-1 HZ) OSCILLATION OF NEOCORTICAL NEURONS IN-VIVO - DEPOLARIZING AND HYPERPOLARIZING COMPONENTS
STERIADE, M.; NUNEZ, A. & AMZICA, F.
JOURNAL OF NEUROSCIENCE
,
Vol. {13}
,
pp. {3252-3265}
,
{1993}
{We describe a novel slow oscillation in intracellular recordings from cortical association areas 5 and 7, motor areas 4 and 6, and visual areas 17 and 18 of cats under various anesthetics. The recorded neurons (n = 254) were antidromically and orthodromically identified as corticothalamic or callosal elements receiving projections from appropriate thalamic nuclei as well as from homotopic foci in the contralateral cortex. Two major types of cells were recorded: regular-spiking (mainly slow-adapting, but also fast-adapting) neurons and intrinsically bursting cells. A group of slowly oscillating neurons (n = 21) were intracellularly stained and found to be pyramidal-shaped cells in layers III-VI, with luxuriant basal dendritic arbors. The slow rhythm appeared in 88\% of recorded neurons. It consisted of slow depolarizing envelopes (lasting for 0.81. 5 sec) with superimposed full action potentials or presumed dendritic spikes, followed by long-lasting hyperpolarizations. Such sequences recurred rhythmically at less than 1 Hz, with a prevailing oscillation between 0.3 and 0.4 Hz in 67\% of urethane-anesthetized animals. While in most neurons (almost-equal-to 70\%) the repetitive spikes superimposed on the slow depolarization were completely blocked by slight DC hyperpolarization, 30\% of cells were found to display relatively small (3-12 mV), rapid, all-or-none potentials after obliteration of full action potentials. These fast spikes were suppressed in an all-or-none fashion at V(m) more negative than -90 mV. The depolarizing envelope of the slow rhythm was reduced or suppressed at a V(m) of -90 to -100 mV and its duration was greatly reduced by administration of the NMDA blocker ketamine. In keeping with this action, most (56\%) neurons recorded in animals under ketamine and nitrous oxide or ketamine and xylazine anesthesia displayed the slow oscillation at higher frequencies (0.6-1 Hz) than under urethane anesthesia (0.3-0.4 Hz). In 18\% of the oscillating cells, the slow rhythm mainly consisted of repetitive (15-30 Hz), relatively short-lasting (15-25 msec) IPSPs that could be revealed by bringing the V(m) at more positive values than -70 mV. The long-lasting (almost-equal-to 1 sec) hyperpolarizing phase of the slow oscillation was best observed at the resting V(m) and was reduced at about -100 mV. Simultaneous recording of another cell across the membrane demonstrated synchronous inhibitory periods in both neurons. Intracellular diffusion of Cl- or Cs+ reduced the amplitude and/or duration of cyclic long-lasting hyperpolarizations. Thus, the newly described oscillation is present in all investigated (sensory, motor, and associational) cortical areas, is displayed by morphologically and physiologically identified pyramidal cells, but does also seemingly involve local-circuit inhibitory cells as inferred from the rhythmic (0.3 Hz) sequences of repetitive IPSPs in pyramidal-type neurons. We then deal with a massive population event, as also indicated by the close correlation between the slow cellular and EEG oscillation. As shown in the following two companion articles (Steriade et al., 1993a,b), the slow cortical oscillation survives total lesions of thalamic perikarya projecting to the recorded cortical neurons and plays a pivotal role in grouping within the 0.3 Hz rhythm other sleep oscillations, such as spindle (7-14 Hz) and delta (1-4 Hz) waves. A new view of sleep oscillations emerges, with various cerebral rhythms generated by intrinsic electrophysiological properties of thalamic and cortical neurons and by synaptic interactions in complex corticothalamocortical networks.}
MAPPING OF THE MOTOR PATHWAYS IN RATS - C-FOS INDUCTION BY INTRACORTICAL MICROSTIMULATION OF THE MOTOR CORTEX CORRELATED WITH EFFERENT CONNECTIVITY OF THE SITE OF CORTICAL STIMULATION
WAN, X.; LIANG, F.; MORET, V.; WIESENDANGER, M. & ROUILLER, E.
NEUROSCIENCE
,
Vol. {49}
,
pp. {749-761}
,
{1992}
{The general goal of the present study was to investigate structural components of a neural system anatomically as well as functionally. The rat motor system, which is reasonably well understood, was selected and a new procedure was developed to combine a functional marker with axonal tracing methods (in the same animal). This was achieved by mapping c-fos induction immunocytochemically as a result of intracortical microstimulation in the distal forelimb area of the motor cortex. The anterograde tracers Phaseolus vulgaris-leucoagglutinin or biocytin were deposited at the site of intracortical microstimulation, the former three weeks and the latter two to three days before stimulation. Neuronal nuclei, labeled for the expressed c-fos protein, were present and mapped in the following structures: motor cortex; basal ganglia (caudate-putamen, globus pallidus); thalamus (reticular, ventromedial and posterior nuclei); subthalamic nucleus; substantia nigra; tectum; red nucleus; pontine nuclei; inferior olive; external cuneate nucleus; cerebellar cortex; deep cerebellar nuclei. Labeling was often bilateral but generally more substantial ipsilaterally, except in the cerebellum where it was mainly contralateral. Axonal labeling, including terminal branches and boutons, was also found in most of the above structures with the exception of the globus pallidus, deep cerebellar nuclei, cerebellar cortex and external cuneate nucleus. These expected exceptions demonstrate that activity changes in these latter structures, as revealed by c-fos labeled neurons, were induced over more than one synapse. This combined procedure might, therefore, be useful in deciding whether two structures in a given system are linked directly (monosynaptically) or indirectly (polysynaptically) to each other. In contrast to the 2-deoxyglucose technique, functional mapping by means of c-fos induction provides cellular resolution, making it possible to establish fine details of axonal contacts with target neurons: boutons in close apposition to c-fos labeled neurons were clearly observed here, for instance, in the cerebral cortex, caudate-putamen, thalamus, subthalamic nucleus and pontine nuclei. Surprisingly, the ventrolateral and ventrobasalis nuclei of the thalamus contained numerous and dense axon terminals labeled with Phaseolus vulgaris-leucoagglutinin or biocytin, but the contacted neurons in the ventrolateral and ventrobasalis nuclei were not marked with c-fos. However, with respect to directly connected structures, there was, in general, a good correlation between structures with axonal labeling and those with c-fos labeled neurons.}
doi
Induction of long-term potentiation leads to increased reliability of evoked neocortical spindles in vivo
Werk, C.; Harbour, V. & Chapman, C.
NEUROSCIENCE
,
Vol. {131}
,
pp. {793-800}
,
{2005}
{Large amplitude electroencephalographic spindle waves (7-14 Hz) occur spontaneously in the neocortex during both sleep and awake immobility, and it has been proposed that synchronous neuronal activation during spindles may contribute to learning-related synaptic plasticity. Spindles can also be evoked in the sensorimotor cortex by electrical stimulation of cortical or thalamic inputs in the rat. To determine if strengthening cortical synapses can affect the initiation and maintenance of electrically evoked spindles, stimulation pulses were delivered at a range of intensities to the corpus callosum or ventrolateral thalamus in the awake rat before and after the induction of long-term potentiation (LTP) by tetanization of the corpus callosum. The morphology of evoked spindles was similar to that of naturally occurring spindles. Spindles were evoked less reliably during slow-wave sleep than during waking, and this was correlated with smaller synaptic responses during slow-wave sleep. Similar to previous findings, daily tetanization of the corpus callosum for 15 days decreased the early component and increased the late component of synaptic responses evoked by corpus callosum stimulation, but did not significantly affect synaptic responses evoked by thalamic stimulation. Similarly, LTP induction increased the reliability with which low-intensity corpus callosum stimulation evoked spindles, but increases in spindles evoked by thalamic stimulation were not significant. Synaptic potentiation and the increased reliability of spindles developed with a similar time-course over the 15-day LTP induction period. These results reflect strong correlations between the strength of cortical layer V activation and the initiation of spindles in the sensorimotor cortex, and support the idea that monosynaptic and polysynaptic horizontal collaterals of layer V neurons can play a significant role in the initiation of spindles. (c) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.}
doi
Long-term depression in the sensorimotor cortex induced by repeated delivery of 10 Hz trains in vivo
Werk, C.; Klein, H.; Nesbitt, C. & Chapman, C.
NEUROSCIENCE
,
Vol. {140}
,
pp. {13-20}
,
{2006}
{Memory consolidation in the neocortex is thought to be mediated in part by bi-directional modifications of synaptic strength. The sensorimotor cortex shows marked spontaneous activity near 10 Hz during both waking and sleep in the form of electroencephalographic spindle waves, and is also sensitive to electrical activation of inputs at 10 Hz. Induction of long-term synaptic depression in corpus callosum inputs to layer V of the sensorimotor cortex of the awake, adult rat requires repeated low-frequency stimulation over many days. To determine if 10 Hz stimulation may facilitate the induction of long-term depression, we compared the amounts of long-term depression induced by conventional 1 Hz trains, repeated delivery of 450 pairs of stimulation pulses using a 100 ms interpulse interval, and 45 short, 2 s, 10 Hz trains. Each pattern was delivered daily for 10 days and was matched for total duration and number of pulses. Changes in synaptic responses were assessed by monitoring field potentials evoked by stimulation of the corpus callosum. A facilitation of synaptic responses in layer V was observed during delivery of both paired-pulse trains and 10 Hz trains. There was no significant difference in long-term depression induced by 1 Hz stimulation and repeated paired-pulse stimulation, but 10 Hz trains induced significantly greater longterm depression than 1 Hz trains in both the early monosynaptic and late polysynaptic field potential components. The effectiveness of short 10 Hz trains for the induction of longterm depression suggests that synchronous population activity at frequencies near 10 Hz such as spindle waves may contribute to endogenous synaptic depression in sensorimotor cortex. (c) 2006 Published by Elsevier Ltd on behalf of IBRO.}



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