Central core modulation of spontaneous oscillations and sensory transmission in thalamocortical systems
Current Opinion in NeurobiologyPublished 1 August 1993
Mircea Steriade
Citations120
SJR quartileQ1
SJR score2.54
SNIP1.27
Generate an AI Snapshot to get a quick, structured summary of this paper.
Study Snapshot
ObjectiveStudy objective
MethodsResearch methodology
PopulationPopulation studied
Sample sizeSample sizes
OutcomesStudy outcomes here
ResultsStudy results comes here
LimitationsResearch study limitations comes here
A concise AI-generated summary of the paper will appear here once you click Generate AI Snapshot.
TL;DR
Central core (brainstem, diencephalic and basal forebrain) systems influence the functional modes of thalamic and cortical neurons during behavioral states of vigilance and the fine inhibitory sculpturing of afferent signals.
Abstract
Central core (brainstem, diencephalic and basal forebrain) systems influence the functional modes of thalamic and cortical neurons during behavioral states of vigilance. Recent studies in vivo and in vitro have focused on the cellular properties of central core systems and their modulation of slow sleep oscillations, fast rhythms during arousal and dreaming state, and the fine inhibitory sculpturing of afferent signals.
Keywords
Neuroscience
PubMedA novel slow (< 1 Hz) oscillation of neocortical neurons in vivo: depolarizing and hyperpolarizing components.
1,703 Citations1993Mircea Steriade, Ángel Núñez +1 more
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 is described and synchronous inhibitory periods in both neurons are demonstrated.
Journal of NeuroscienceA novel slow (< 1 Hz) oscillation of neocortical neurons in vivo: depolarizing and hyperpolarizing components
1,628 Citations1993Mircea Steriade, A Nunez +1 more
Brainstem Control of Wakefulness and Sleep
1,176 Citations1990Mircea Steriade, Robert W. McCarley
A monograph communicating the current realities and future possibilities of unifying basic studies on anatomy and cellular physiology with investigations of the behavioral and physiological events of waking and sleep.
The Journal of PhysiologyProperties of a hyperpolarization‐activated cation current and its role in rhythmic oscillation in thalamic relay neurones.
1,147 Citations1990David A. McCormick, Hans‐Christian Pape
Results indicate that Ih is carried by both Na+ and K+ ions, which is consistent with the extrapolated reversal potential of ‐43 mV, and contributes substantially to the resting and active membrane properties of thalamocortical relay neurones.
Proceedings of the National Academy of SciencesCoherent 25- to 35-Hz oscillations in the sensorimotor cortex of awake behaving monkeys.
1,013 Citations1992Venkatesh N. Murthy, Eberhard E. Fetz
Synchronous 25- to 35-Hz oscillations were observed in local field potentials and unit activity in sensorimotor cortex of awake rhesus monkeys, suggesting that such oscillations may facilitate interactions between cells during exploratory and manipulative movements, requiring attention to sensorsimotor integration.
Proceedings of the National Academy of SciencesCoherent 40-Hz oscillation characterizes dream state in humans.
958 Citations1993R. Llinás, Urs Ribary
It is proposed that the specific loops give the content of cognition, and a nonspecific loop gives the temporal binding required for the unity of cognitive experience.
ScienceInterhemispheric Synchronization of Oscillatory Neuronal Responses in Cat Visual Cortex
938 Citations1991Andreas K. Engel, Peter König +2 more
Response synchronization has now been shown to occur also between neurons in area 17 of the right and left cerebral hemispheres, and this synchronization is mediated by corticocortical connections, compatible with the hypothesis that temporal synchrony of neuronal discharges serves to bind features within and between the visual hemifields.
Journal of NeuroscienceIntracellular analysis of relations between the slow (< 1 Hz) neocortical oscillation and other sleep rhythms of the electroencephalogram
907 Citations1993Mircea Steriade, A Nunez +1 more
The data indicate that the thalamus is not essentially implicated in the genesis of the slow rhythm, and through the contralateral thalamocortical systems and callosal projections, also transected the corpus callosum in thalamically lesioned animals, and still recorded theslow rhythm in cortical neurons.
Journal of NeuroscienceNeuronal activities in brain-stem cholinergic nuclei related to tonic activation processes in thalamocortical systems
771 Citations1990Mircea Steriade, Subimal Datta +3 more
Dynamic analyses of sequential firing rates throughout the waking-sleep cycle showed that none of the full-blown states of vigilance is associated with a uniform level of spontaneous firing rate.
Journal of NeuroscienceThe slow (< 1 Hz) oscillation in reticular thalamic and thalamocortical neurons: scenario of sleep rhythm generation in interacting thalamic and neocortical networks
662 Citations1993Mircea Steriade, Diego Contreras +2 more
A unified scenario of the genesis of the three major sleep rhythms: slow, delta, and spindle oscillations is proposed.
NeuroscienceOf dreaming and wakefulness
637 Citations1991Rodolfó R. Llinás, Denis Paré
It is argued that consciousness is fundamentally a closed-loop property, in which the ability of cells to be intrinsically active plays a central role, and the importance of spatial and temporal mapping in the elaboration of cognitive and perceptual constructs is discussed.
The Slow (4 Hz) Oscillation in Reticular Thalamic and Thalamocortical Neurons: Scenario of Sleep Rhythm Generation in Interacting Thalamic and Neocortical Networks
600 Citations1993Mircea Steriade, Diego Contreras +1 more
Journal of NeuroscienceCellular bases of neocortical activation: modulation of neural oscillations by the nucleus basalis and endogenous acetylcholine
590 Citations1992Raju Metherate, Charles L. Cox +1 more
In vivo and in vitro observations suggest that neocortical activation results from muscarinic modulation of intrinsic neural oscillations and firing modes, and NB cholinergic neurons may play a critical role in producing different states of neocorticals function.
Journal of NeuroscienceA novel T-type current underlies prolonged Ca(2+)-dependent burst firing in GABAergic neurons of rat thalamic reticular nucleus
566 Citations1992JR Huguenard, DA Prince
It is demonstrated that subtypes of transient Ca2+ current are present in two different classes of thalamic neurons, including steady-state inactivation and sensitivities to blockade by divalent cations, amiloride, and antiepileptic drugs.
Proceedings of the National Academy of SciencesIn vitro neurons in mammalian cortical layer 4 exhibit intrinsic oscillatory activity in the 10- to 50-Hz frequency range.
547 Citations1991Rodolfó R. Llinás, Anthony A. Grace +1 more
The presence of fast subthreshold oscillatory potentials recorded in vitro from neurons within layer 4 of the guinea pig frontal cortex is reported, indicating that this neuron has extensive local axonal collaterals that ramify in layers 3 and 4 such that they may contribute to the columnar synchronization of activity in the 40- to 50-Hz range.
Proceedings of the National Academy of SciencesMagnetic field tomography of coherent thalamocortical 40-Hz oscillations in humans.
539 Citations1991Urs Ribary, A.A. Ioannides +6 more
The use of magnetic field tomography (MFT), a noninvasive technique based on distributed source analysis of magnetoencephalography data, which makes possible the three-dimensional reconstruction of dynamic brain activity in humans, is introduced.
Proceedings of the National Academy of SciencesCorticothalamic activation modulates thalamic firing through glutamate "metabotropic" receptors.
504 Citations1992David A. McCormick, M. von Krosigk
It is reported that activation of corticothalamic fibers causes a prolonged excitatory postsynaptic potential in guinea pig dorsal lateral geniculate relay neurons resulting from the reduction of a potassium conductance, consistent with the activation of glutamatergic "metabotropic" receptors.
Journal of NeuroscienceNetwork modulation of a slow intrinsic oscillation of cat thalamocortical neurons implicated in sleep delta waves: cortically induced synchronization and brainstem cholinergic suppression
480 Citations1991Mircea Steriade, RC Curro Dossi +1 more
This study proposes that the potentiating influence of the corticothalamic input results from the engagement of two GABAergic thalamic cell classes, reticular and local-circuit neurons, and proposes a progressive hyperpolarization of thalamocortical neurons with the deepening of the behavioral state of EEG-synchronized sleep.
Proceedings of the National Academy of SciencesFast oscillations (20-40 Hz) in thalamocortical systems and their potentiation by mesopontine cholinergic nuclei in the cat.
451 Citations1991Mircea Steriade, Roberto Curró Dossi +2 more
The possibility that stimulation of these brainstem nuclei potentiates the 40-Hz waves on the background of the cortical electroencephalogram was tested and the phenomenon was confirmed by persistence of the phenomenon after large excitotoxic lesions of the nucleus basalis of Meynert.
The Journal of PhysiologyNoradrenergic and serotonergic modulation of a hyperpolarization‐activated cation current in thalamic relay neurones.
421 Citations1990David A. McCormick, Hans‐Christian Pape
Modulation of the hyperpolarization‐activated cation current, Ih, by noradrenaline (NA) and serotonin (5‐HT) was examined in guinea‐pig and cat medial and lateral geniculate relay neurones using the in vitro slice technique, revealing a voltage‐dependent inward shift at membrane potentials negative to approximately ‐60 mV.
The Journal of Comparative NeurologyEfferent connections of the centromedian and parafascicular thalamic nuclei in the squirrel monkey: A PHA‐L study of subcortical projections
346 Citations1992Abbas F. Sadikot, André Parent +1 more
The complementary nature of CM and Pf projections to the striatum and other basal ganglia components suggests that this thalamic complex participates in a highly ordered manner in the parallel processing of the information that flows through the basal gangilia.
Cold Spring Harbor Symposia on Quantitative BiologySome Reflections on Visual Awareness
334 Citations1990Francis Crick, Christof Koch
Brain ResearchAgonists of cholinergic and noradrenergic receptors facilitate synergistically the induction of long-term potentiation in slices of rat visual cortex
275 Citations1992S. Bröcher, Alain Artola +1 more
It is suggested that the agonists of both receptor systems enhanced the depolarizing response to the tetanus and increased NMDA receptor-gated conductances during this response also accounts for the facilitatory effects which ACh and NA have on use-dependent synaptic plasticity in the developing visual cortex.
The Journal of PhysiologyTwo inward currents and the transformation of low‐frequency oscillations of rat and cat thalamocortical cells.
275 Citations1991Iván Soltész, Sean Lightowler +4 more
In cells showing the pacemaker oscillations it was found that the current developing from the most hyperpolarized potential of an oscillation cycle was an inward relaxation whose time course differed from that of Ih evoked at the same potential.
NeuroscienceSpindle rhythmicity in the reticularis thalami nucleus: Synchronization among mutually inhibitory neurons
271 Citations1993X.-J. Wang, John Rinzel
It is suggested that if GABAB receptors exist postsynaptically in the reticularis, they may play a critical role in the rhythmic synchronization among reticular neurons, hence in the thalamocortical system.
NeuroscienceInvolvement of intrathalamic GABAb neurotransmission in the control of absence seizures in the rat
255 Citations1992Z. Liu, Marguerite Vergnes +2 more
The results suggest that GABAB receptors in the ventrolateral thalamus and in the reticular nuclei are involved in an oscillatory activity which underlies the rhythmic spike and wave discharges recorded during spontaneous generalized non-convulsive seizures.
The Journal of PhysiologyElectrophysiology of a slow (0.5‐4 Hz) intrinsic oscillation of cat thalamocortical neurones in vivo.
246 Citations1992Roberto Curró Dossi, Ángel Núñez +1 more
The results demonstrate that the majority of thalamocortical neurones are endowed with electrophysiological properties allowing them to oscillate at 0.5‐4 Hz, if they have a membrane potential more negative than ‐65 mV and a high input resistance.
NeuroscienceElectrophysiological properties of intralaminar thalamocortical cells discharging rhythmic (≈40 HZ) spike-bursts at ≈1000 HZ during waking and rapid eye movement sleep
238 Citations1993Mircea Steriade, Roberto Curro ́Dossi +1 more
Intracellular recordings under barbiturate anesthesia showed that, during spindle oscillations, the spike-bursts of intralaminar neurons are generated by brief low-threshold spikes with a much shorter refractory phase than in other thalamocortical cells.
Proceedings of the National Academy of SciencesSerotonin hyperpolarizes cholinergic low-threshold burst neurons in the rat laterodorsal tegmental nucleus in vitro.
226 Citations1992Jennifer I. Luebke, Robert Greene +4 more
Analysis of intrinsic electrophysiological properties and response to serotonin (5-HT) of identified cholinergic rat laterodorsal tegmental nucleus neurons in vitro provides a cellular and molecular basis for the hypothesis that 5-HT modulates rapid eye movement sleep phenomenology by altering the firing pattern of bursting cholinerg neurons.
NeuronNitric oxide controls oscillatory activity in thalamocortical neurons
223 Citations1992Hans‐Christian Pape, Ralph Mager
Evidence is reported indicating that the release of NO onto thalamocortical neurons results in an alteration in voltage dependence of the hyperpolarization-activated cation conductance, probably mediated via the cGMP system.
Journal of NeurophysiologyOscillatory discharge in the visual system: does it have a functional role?
196 Citations1992Geoffrey M. Ghose, Ralph D. Freeman
The potential role of neuronal maturation in the generation of oscillatory activity was investigated by studying neuronal responses from kittens at 4 wk postnatal and the dependence of oscillations on different stimulus parameters was investigated.
Journal of NeurophysiologyShort-lasting nicotinic and long-lasting muscarinic depolarizing responses of thalamocortical neurons to stimulation of mesopontine cholinergic nuclei
184 Citations1991Roberto Curró Dossi, Denis Paré +1 more
These data demonstrate that, in addition to an initial nicotinic excitation, brain stem cholinergic stimulation elicits a late, long-lasting muscarinic depolarization of thalamocortical neurons, and suggest that the prolongeddepolarization plays an important role in cortical activation.
The Journal of PhysiologyElectrophysiological properties of cat reticular thalamic neurones in vivo.
160 Citations1993Diego Contreras, Roberto Curró Dossi +1 more
Results, showing that RE cells are endowed with an excitable dendritic tree and a graded bursting behaviour, support the proposed role of RE nucleus as the generator and synchronizer of spindle rhythmicity.
NeuroscienceIntracellular evidence for incompatibility between spindle and delta oscillations in thalamocortical neurons of cat
148 Citations1992A. Nún ̃ez, R. CurróDossi +2 more
A certain degree of incompatibility between spindles and delta rhythms in thalamocortical cells may explain the prevalence of these two types of oscillations during different stages of sleep with synchronization of the electroencephalogram.
NeuroscienceVoltage-dependent 40-Hz oscillations in rat reticular thalamic neurons in vivo
147 Citations1992Didier Pinault, Martin Deschênes
The present results indicate that the reticular thalamic nucleus might play a pacemaker function in the genesis of 40-Hz oscillations in the thalamus and cortex during states of focused arousal.
Journal of NeurophysiologyThalamic VPM nucleus in the behaving monkey. I. Multimodal and discriminative properties of thermosensitive neurons
123 Citations1993M. Catherine Bushnell, Gary H. Duncan +1 more
There was a high correlation between the monkey's success in detecting the stimulus changes and the magnitude of the neuronal responses to those changes, and further studies are needed to determine whether VPM neurons respond to the smallest detectable changes in skin cooling.
NeuroscienceVoltage-dependent fast (20–40 Hz) oscillations in long-axoned neocortical neurons
122 Citations1992Ángel Núñez, Florin Amzica +1 more
Depolarization-dependent 40-Hz oscillations in cat's motor and association neocortical neurons with identified projections to contralateral homotopic cortical area and thalamus are reported and indicate that this fast rhythm may be synchronized through intracortical and corticothalamic linkages.
Brain ResearchContralateral pallidothalamic and pallidotegmental projections in primates: an anterograde and retrograde labeling study
111 Citations1991Lili‐Naz Hazrati, André Parent
The results of these anterograde and retrograde investigations indicate that the contralateral pallidothalamic projection involves a relatively small population of GPi neurons, but that these neurons arborize extensively in theircontralateral thalamic targets.
Cerebral cortexAlertness, Quiet Sleep, Dreaming
103 Citations1991Mircea Steriade
The fluctuation in the electrical activity of the cerebrum during various behavioral conditions, as reflected in EEG waves, evoked potentials, and activities of different types of thalamic and cortical neurons is discussed.
Journal of NeurophysiologyMembrane properties of mesopontine cholinergic neurons studied with the whole-cell patch-clamp technique: implications for behavioral state control
103 Citations1992Anita Kamondi, Julie A. Williams +2 more
Delineation of the intrinsic membrane properties of identified mesopontine cholinergic neurons, in concert with recent results regarding the responses of these neurons to neurotransmitter agents, has led us to present a unifying and mechanistic hypothesis of brain stem Cholinergic function in the control of behavioral states.
NeuroscienceCholinergic nucleus basalis neurons display the capacity for rhythmic bursting activity mediated by low-threshold calcium spikes
101 Citations1992Asaid Khateb, Michel Mühlethaler +4 more
By virtue of these different modes, cholinergic basalis neurons may accordingly deter or facilitate the cortical response to sensory input and may furthermore modulate the major frequencies of cortical activity across the different states of the sleep-waking cycle.
Journal of NeurophysiologyBursting and tonic discharges in two classes of reticular thalamic neurons
88 Citations1992Diego Contreras, Roberto Curró Dossi +1 more
The presence of two cell classes in the RE nucleus challenges the common view that this nucleus consists of a single neuronal class, and suggests that a different set of conductances is present in type II RE neurons, thus preventing the low-threshold Ca2+ current from dominating the behavior of these cells.
Journal of NeurophysiologyThree types of inhibitory postsynaptic potentials generated by interneurons in the anterior thalamic complex of cat
85 Citations1991Denis Paré, Roberto Curró Dossi +1 more
To study how thalamic interneurons generate inhibitory postsynaptic potentials (IPSPs) in relay cells, the differential mode of termination of cortical and MB afferents on interneuron roles was taken to infer the respective roles of the axons and PSDs of interneuran in the genesis of the IPSPs recorded from relay cells.
NeuroscienceIntrinsic and synaptically generated delta (1–4 Hz) rhythms in dorsal lateral geniculate neurons and their modulation by light-induced fast (30–70 Hz) events
78 Citations1992A. Nún ̃ez, Florin Amzica +1 more
Different types of sleep delta oscillations in visual thalamic neurons are demonstrated and show that they are modulated not only by brainstem regulatory systems, but also by specific drives along the visual channel.
The Journal of Comparative NeurologyCrosstalk between the two sides of the thalamus through the reticular nucleus: A retrograde and anterograde tracing study in the rat
76 Citations1993Vassilis Raos, Marina Bentivoglio
The connections of the reticular nucleus (RT), the major component of the ventral thalamus, with contralateral dorsal thalamic nuclei were systematically investigated in the adult rat with several tract‐tracing techniques.
NeuroscienceControl of 40-Hz firing of reticular thalamic cells by neurotransmitters
75 Citations1992Didier Pinault, Martin Deschênes
It is proposed that the 40-Hz firing frequency reflects a point of equilibrium in the reticular thalamic network when the leaky K conductance is fully deactivated by the metabotropic effects of monoamines and/or excitatory amino acids.
Progress in brain researchChapter 8 GABAA and pre- and post-synaptic GABAB receptor-mediated responses in the lateral geniculate nucleus
63 Citations1992Iván Soltész, Vincenzo Crunelli
This chapter reviews the results that have emerged in past years from the electrophysiological studies concerning the action of gamma-aminobutyric acid in in vitro slices of the ventral-lateral geniculate nucleus of cats and rats and the effects of pre- and post-synaptic GABA B receptor activation help to appreciate the variety of responses that GABA can generate in the visual thalamus.
Brain ResearchEEG-dependent modulation of response dynamics of cat dLGN relay cells and the contribution of corticogeniculate feedback
58 Citations1992Klaus Funke, Ulf T. Eysel
The results indicate that state-dependent changes in CNS activity modulate dL'GN responsiveness in part via the corticogeniculate feedback, and that predominantly the tonic response component is modulated.
Brain ResearchThe time course of σ activity and slow-wave activity during NREMS in cortical and thalamic EEG of the cat during baseline and after 12 hours of wakefulness
58 Citations1992Marike Lancel, Henk van Riezen +1 more
The present data show that, in the thalamic EEG, an inverse relation exists between spindle and slow-wave activity during baseline NREMS, and this relation is preserved after sleep deprivation.
The Journal of PhysiologyA role for low‐frequency, rhythmic synaptic potentials in the synchronization of cat thalamocortical cells.
51 Citations1992Iván Soltész, Vincenzo Crunelli
Low‐frequency, rhythmic synaptic potentials recorded in TC cells of the dLGN are capable of driving other TC cells to oscillate rhythmically, or of modulating the frequency of pacemaker oscillations, and provide a means by which oscillatory activities of TC cells can be synchronized in the absence of sensory, cortical and reticular thalamic inputs.
NeuroscienceDelta frequency (1–4 Hz) oscillations of perigeniculate thalamic neurons and their modulation by light
49 Citations1992Florin Amzica, A. Nún ̃ez +1 more
The results suggest that the two types of delta rhythmicity result from intrinsic and network properties of visual thalamic neurons and that perigeniculate cells may synchronize, through backward connections, the activity of dorsal lateral geniculates cells during deep stages of resting sleep.
Journal of NeurophysiologyState-related modulation of thalamic somatosensory responses in the awake monkey
48 Citations1992Thomas Morrow, K. L. Casey
88 neurons were tested for changes in activity as the monkey's state of arousal shifted between quiet waking, waking movement, and drowsy states as defined by behavioral and electroencephalographic criteria and showed arousal-related response modulation (ARM).
NeuroscienceSerotonin1 and serotonin2 receptors hyperpolarize and depolarize separate populations of medial pontine reticular formation neurons in vitro
47 Citations1992David R. Stevens, Robert W. McCarley +1 more
The excitability of medial pontine reticular formation neurons is influenced by serotonin acting to increase or decrease potassium conductance(s) in a manner consistent with a conductance increase primarily to this ion.
NeuroscienceVarious types of inhibitory postsynaptic potentials in anterior thalamic cells are differentially altered by stimulation of laterodorsal tegmental cholinergic nucleus
44 Citations1992Roberto Curro ́Dossi, Denis Paré +1 more
It is suggested that mesopontine cholinergic depressive actions on A and B inhibitory postsynaptic potentials may be due to an increased conductance in thalamocortical cells during the short-lasting nicotinic action combined with a somatic hyperpolarization of local-circuit cells, whereas the enhancement of the earliest inhibitorship reflects a concomitant potentiating action at the level of intraglomerular presynaptic dendrites.
Journal of NeurophysiologyAction of brain stem reticular afferents on lagged and nonlagged cells in the cat lateral geniculate nucleus
33 Citations1992Allen L. Humphrey, Alan Saul
The peribrachial region of the pontine reticular formation was stimulated electrically with the use of 1,100-ms-long pulse trains that were paired with flashing spot stimuli to investigate whether the inhibitory dip and sluggish response of lagged cells could be reversed during brain stem activation and the cells induced to respond like nonlagged cells.
NeurosciencePreferential innervation of immunoreactive choline acetyltransferase synapses on relay cells of the cat's lateral geniculate nucleus: A double-labelling study
31 Citations1992Catherine Beaulieu, M. Cynader
Cholinergic inputs show a preference to target geniculate relay neurons without a strong innervation of GABA-immunoreactive interneurons, however, cholinergic synapses provide a powerful input to GABAergic cells in the perigeniculate nucleus.
Journal of NeuroscienceExcitatory amino acid-mediated responses and synaptic potentials in medial pontine reticular formation neurons of the rat in vitro
31 Citations1992David R. Stevens, Robert W. McCarley +1 more
Results suggest that excitatory reticulo-reticular neurotransmission is mediated by an EAA, and both non-NMDA and NMDA receptors contribute to EAA neurotransmission in the mPRF formation and play an integral role in reticular formation function.
Journal of NeurophysiologyThalamic VPM nucleus in the behaving monkey. II. Response to air-puff stimulation during discrimination and attention tasks
30 Citations1993Nicole Tremblay, M. Catherine Bushnell +1 more
Any or all of RA, SA, and MM neurons could play a role in the discrimination of air-puff intensities, and data suggest that the excitatory tactile afferent input to MM neurons is different from that to low-threshold neurons.
NeurosciencePotentiation of electroencephalographic spindles by ibotenate microinjections into nucleus reticularis thalami of cats
26 Citations1992Gabriella Marini, G Macchi +1 more
It is found that, in cats, spindle density was dramatically increased following infusion of ibotenic acid into the rostral pole of the nucleus, supporting the role of this sector in spindle-related rhythmicity.
Neuroscience LettersThe reticular thalamic nucleus projects to the contralateral dorsal thalamus in macaque monkey
24 Citations1993Denis Paré, Mircea Steriade
This study demonstrates, using the retrograde transport of horseradish peroxidase conjugated to the lectin wheat germ-agglutinin (WGA-HRP), that the reticular thalamic nucleus (RE) projects to the contralateral dorsal thalamus in macaque monkeys.