scholarly journals Different Topography of the Reticulothalmic Inputs to First- and Higher-Order Somatosensory Thalamic Relays Revealed Using Photostimulation

2007 ◽  
Vol 98 (5) ◽  
pp. 2903-2909 ◽  
Author(s):  
Ying-Wan Lam ◽  
S. Murray Sherman
Keyword(s):  
Laser Scanning ◽  
Higher Order ◽  
Gabaergic Neurons ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Local Inhibition ◽  
Strategic Position ◽  
Almost All ◽  
Laser Scanning Photostimulation ◽  
Lateral Nucleus

The thalamic reticular nucleus is a layer of GABAergic neurons that occupy a strategic position between the thalamus and cortex. Here we used laser scanning photostimulation to compare in young mice (9–12 days old) the organization of the reticular inputs to first- and higher-order somatosensory relays, namely, the ventral posterior lateral nucleus and posterior nucleus, respectively. The reticulothalamic input footprints to the ventral posterior lateral nucleus neurons consisted of small, single, topographically organized elliptical regions in a tier away from the reticulothalamic border. In contrast, those to the posterior nucleus were complicated and varied considerably among neurons: although almost all contained a single elliptical region near the reticulothalamic border, in most cases, they consisted of additional discontinuous regions or relatively diffuse regions throughout the thickness of the thalamic reticular nucleus. Our results suggest two sources of reticular inputs to the posterior nucleus neurons: one that is relatively topographic from regions near the reticulothalamic border and one that is relatively diffuse and convergent from most or all of the thickness of the thalamic reticular nucleus. We propose that the more topographic reticular input is the basis of local inhibition seen in posterior nucleus neurons and that the more diffuse and convergent input may represent circuitry through which the ventral posterior lateral and posterior nuclei interact.

Mapping by Laser Photostimulation of Connections Between the Thalamic Reticular and Ventral Posterior Lateral Nuclei in the Rat

2005 ◽  
Vol 94 (4) ◽  
pp. 2472-2483 ◽  
Author(s):  
Ying-Wan Lam ◽  
S. Murray Sherman
Keyword(s):  
Laser Scanning ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Relay Cell ◽  
Reticular Neurons ◽  
Caged Glutamate ◽  
Tracing Techniques ◽  
Laser Scanning Photostimulation ◽  
Lateral Nucleus

We used laser scanning photostimulation through a focused UV laser of caged glutamate in an in vitro slice preparation through the rat’s somatosensory thalamus to study topography and connectivity between the thalamic reticular nucleus and ventral posterior lateral nucleus. This enabled us to focally stimulate the soma or dendrites of reticular neurons. We were thus able to confirm and extend previous observations based mainly on neuroanatomical pathway tracing techniques: the projections from the thalamic reticular nucleus to the ventral posterior lateral nucleus have precise topography. The reticular zone, which we refer to as a “footprint,” within which photostimulation evoked inhibitory postsynaptic currents (IPSCs) in relay cells, was relatively small and oval, with the long axis being parallel to the border between the thalamic reticular nucleus and ventral posterior lateral nucleus. These evoked IPSCs were large, and by using appropriate GABA antagonists, we were able to show both GABAA and GABAB components. This suggests that photostimulation strongly activated reticular neurons. Finally, we were able to activate a disynaptic relay cell-to-reticular-to- relay cell pathway by evoking IPSCs in relay cells from photostimulation of the region surrounding a recorded relay cell. This, too, suggests strong responses of relay cells, responses strong enough to evoke spiking in their postsynaptic reticular targets. The regions of photostimulation for these disynaptic responses were much larger than the above-mentioned reticular footprints, and this suggests that reticulothalamic axon arbors are less widespread than thalamoreticular arbors, that there is more convergence in thalamoreticular connections than in reticulothalamic connections, or both.

scholarly journals Functional topographic organization of the motor reticulothalamic pathway

2015 ◽  
Vol 113 (9) ◽  
pp. 3090-3097 ◽  
Author(s):  
Ying-Wan Lam ◽  
S. Murray Sherman
Keyword(s):  
Laser Scanning ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Thalamic Nuclei ◽  
Dorsal Thalamus ◽  
Thalamic Relay ◽  
Thalamocortical Projections ◽  
Motor Information ◽  
Laser Scanning Photostimulation ◽  
Similar Organization

The thalamic reticular nucleus (TRN) is a thin layer of GABAergic cells lying rostral and lateral to the dorsal thalamus, and its projection to thalamic relay cells (i.e., the reticulothalamic pathway) strongly inhibits these cells. In an attempt to extend earlier studies of reticulothalamic connections to sensory thalamic nuclei, we used laser-scanning photostimulation to study the reticulothalamic projections to the main motor thalamic relays, the ventral anterior and lateral (VA and VL) nuclei, as well as to the nearby central lateral (CL) thalamic nucleus. VA/VL and the earlier studied somatosensory thalamic nuclei are considered “core” nuclei with topographic thalamocortical projections, whereas CL is thought to be a “matrix” nucleus with diffuse thalamocortical projections. We found that the TRN input footprints to VA/VL and CL are spatially localized and topographic and generally conform to the patterns established earlier for the TRN projections to sensory thalamic relays. These remarkable similarities suggest similar organization of reticulothalamic pathways and TRN regulation of thalamocortical communication for motor and sensory systems and perhaps also for core and matrix thalamus. Furthermore, we found that VA/VL and CL shared overlapping TRN input regions, suggesting that CL may also be involved in the relay of motor information.

First order connections of the visual sector of the thalamic reticular nucleus in marmoset monkeys (Callithrix jacchus)

2007 ◽  
Vol 24 (6) ◽  
pp. 857-874 ◽  
Author(s):  
THOMAS FITZGIBBON ◽  
BRETT A. SZMAJDA ◽  
PAUL R. MARTIN
Keyword(s):  
Visual Field ◽  
Callithrix Jacchus ◽  
Higher Order ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Lower Visual Field ◽  
First Order ◽  
Cortical Areas ◽  
Visual Areas

The thalamic reticular nucleus (TRN) supplies an important inhibitory input to the dorsal thalamus. Previous studies in non-primate mammals have suggested that the visual sector of the TRN has a lateral division, which has connections with first-order (primary) sensory thalamic and cortical areas, and a medial division, which has connections with higher-order (association) thalamic and cortical areas. However, the question whether the primate TRN is segregated in the same manner is controversial. Here, we investigated the connections of the TRN in a New World primate, the marmoset (Callithrix jacchus). The topography of labeled cells and terminals was analyzed following iontophoretic injections of tracers into the primary visual cortex (V1) or the dorsal lateral geniculate nucleus (LGNd). The results show that rostroventral TRN, adjacent to the LGNd, is primarily connected with primary visual areas, while the most caudal parts of the TRN are associated with higher order visual thalamic areas. A small region of the TRN near the caudal pole of the LGNd (foveal representation) contains connections where first (lateral TRN) and higher order visual areas (medial TRN) overlap. Reciprocal connections between LGNd and TRN are topographically organized, so that a series of rostrocaudal injections within the LGNd labeled cells and terminals in the TRN in a pattern shaped like rostrocaudal overlapping “fish scales.” We propose that the dorsal areas of the TRN, adjacent to the top of the LGNd, represent the lower visual field (connected with medial LGNd), and the more ventral parts of the TRN contain a map representing the upper visual field (connected with lateral LGNd).

Mapping of the Functional Interconnections Between Thalamic Reticular Neurons Using Photostimulation

2006 ◽  
Vol 96 (5) ◽  
pp. 2593-2600 ◽  
Author(s):  
Ying-Wan Lam ◽  
Christopher S. Nelson ◽  
S. Murray Sherman
Keyword(s):  
Laser Scanning ◽  
Spatial Extent ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Reticular Cell ◽  
Relay Cell ◽  
Dominant Form ◽  
Electrical Synapses ◽  
Reticular Neurons ◽  
Reticular Cells

The thalamic reticular nucleus is strategically located in the axonal pathways between thalamus and cortex, and reticular cells exert strong, topographic inhibition on thalamic relay cells. Although evidence exists that reticular neurons are interconnected through conventional and electrical synapses, the spatial extent and relative strength of these synapses are unclear. To address these issues, we used uncaging of glutamate by laser-scanning photostimulation to provide precisely localized and consistent activation of reticular cell bodies and dendrites in an in vitro slice preparation from the rat as a means to study reticulo-reticular connections. Among the 47 recorded reticular neurons, 29 (62%) received GABAergic axodendritic input from an area immediately surrounding each of the recorded cell bodies, and 8 (17%) responded with depolarizing spikelets, suggesting inputs through electrical synapses. We also found that TTX completely blocked all evoked IPSCs, implying that any dendrodendritic synapses between reticular cells either are relatively weak, have no nearby glutamatergic receptors, or are dependent on back-propagation of action potentials. Finally, we showed that the GABAergic connections between reticular cells are weaker than those from reticular cells to relay cells. Our results suggest that the GABAergic axodendritic synapse is the dominant form of reticulo-reticular connectivity, and because they are much weaker than the reticulo-relay cell synapses, their functional purpose may be to regulate the spatial extent of the reticular inhibition on relay cells.

scholarly journals Significance of the Thalamic Reticular Nucleus GABAergic Neurons in Normal and Pathological Activity of the Brain

2012 ◽  
Vol 02 (04) ◽  
pp. 436-444 ◽  
Author(s):  
Zakaria I. Nanobashvili ◽  
Arkadi G. Surmava ◽  
Irine G. Bilanishvili ◽  
Maia G. Barbaqadze ◽  
Magda D. Mariamidze ◽  
...  
Keyword(s):  
Gabaergic Neurons ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
The Brain

scholarly journals Two dynamically distinct circuits driving inhibition in sensory thalamus

2020 ◽  
Author(s):  
Rosa I. Martinez-Garcia ◽  
Bettina Voelcker ◽  
Julia B. Zaltsman ◽  
Saundra L. Patrick ◽  
Tanya R. Stevens ◽  
...  
Keyword(s):  
Sensory Information ◽  
Cell Types ◽  
Higher Order ◽  
Inhibitory Neurons ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Order Structure ◽  
Multiple Sources ◽  
Cell Groups ◽  
And Function

AbstractMost sensory information destined for the neocortex is relayed through the thalamus, where considerable transformation occurs1,2. One powerful means of transformation involves interactions between excitatory thalamocortical neurons that carry data to cortex and inhibitory neurons of the thalamic reticular nucleus (TRN) that regulate flow of those data3-6. Despite enduring recognition of its importance7-9, understanding of TRN cell types, their organization, and their functional properties has lagged that of the thalamocortical systems they control.Here we address this, investigating somatosensory and visual circuits of the TRN. In the somatosensory TRN we observed two groups of genetically defined neurons that are topographically segregated, physiologically distinct, and connect reciprocally with independent thalamocortical nuclei via dynamically divergent synapses. Calbindin-expressing cells, located in the central core, connect with the ventral posterior nucleus (VP), the primary somatosensory thalamocortical relay. In contrast, somatostatin-expressing cells, residing along the surrounding edges of TRN, synapse with the posterior medial thalamic nucleus (POM), a higher-order structure that carries both top-down and bottom-up information10-12. The two TRN cell groups process their inputs in pathway-specific ways. Synapses from VP to central TRN cells transmit rapid excitatory currents that depress deeply during repetitive activity, driving phasic spike output. Synapses from POM to edge TRN cells evoke slower, less depressing excitatory currents that drive more persistent spiking. Differences in intrinsic physiology of TRN cell types, including state-dependent bursting, contribute to these output dynamics. Thus, processing specializations of two somatosensory TRN subcircuits appear to be tuned to the signals they carry—a primary central subcircuit to discrete sensory events, and a higher-order edge subcircuit to temporally distributed signals integrated from multiple sources. The structure and function of visual TRN subcircuits closely resemble those of the somatosensory TRN. These results provide fundamental insights about how subnetworks of TRN neurons may differentially process distinct classes of thalamic information.

scholarly journals Rebound Bursts in GABAergic Neurons of the Thalamic Reticular Nucleus in Postnatal Mice

2010 ◽  
pp. 273-280
Author(s):  
X Wang ◽  
G Yu ◽  
X Hou ◽  
J Zhou ◽  
B Yang ◽  
...  
Keyword(s):  
Patch Clamp ◽  
Receptor Antagonist ◽  
Channel Blocker ◽  
Gabaergic Neurons ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
K Channel ◽  
Whole Cell Patch Clamp ◽  
Gabaa Receptor Antagonist ◽  
Inactive Analog

Whole cell patch-clamp recordings from GABAergic cells of thalamic reticular nucleus (RTN) in thalamocortical slices made from postnatal day 6 (P6) to 10 (P10) were used to investigate the pattern of rebound bursts (RBs) triggered by an injection of hyperpolarizing current into RTN cells. The number of RBs in the RTN and the overlying Na+/K+ spikes changed in an agedependent manner. The generation of RBs depended largely on the amplitude of the after-hyperpolarizations (AHPs). RB patterns in response to hyperpolarizing current injection into relay cells were markedly different from RB patterns in RTN cells with an after-depolarization. GABAA receptor antagonist bicuculline methiodide (BMI) changed burst firing patterns, increasing the duration of RB and decreasing the amplitude of AHP in RTN cells. Furthermore, local puffs of NMDA in the presence of BMI induced RBs. K+ channel blocker 4-aminopyridine partially mimicked the effect of BMI on AHPs. The shapes of RBs were altered by a selective CaMKII inhibitor KN-62, but not by an inactive analog KN-04.

scholarly journals Selectively driving cholinergic fibers optically in the thalamic reticular nucleus promotes sleep

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Kun-Ming Ni ◽  
Xiao-Jun Hou ◽  
Ci-Hang Yang ◽  
Ping Dong ◽  
Yue Li ◽  
...  
Keyword(s):  
Eye Movement ◽  
Nicotinic Acetylcholine Receptors ◽  
Rem Sleep ◽  
Sleep Onset ◽  
Cholinergic Neurons ◽  
Nrem Sleep ◽  
Gabaergic Neurons ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Rapid Eye Movement

Cholinergic projections from the basal forebrain and brainstem are thought to play important roles in rapid eye movement (REM) sleep and arousal. Using transgenic mice in which channelrhdopsin-2 is selectively expressed in cholinergic neurons, we show that optical stimulation of cholinergic inputs to the thalamic reticular nucleus (TRN) activates local GABAergic neurons to promote sleep and protect non-rapid eye movement (NREM) sleep. It does not affect REM sleep. Instead, direct activation of cholinergic input to the TRN shortens the time to sleep onset and generates spindle oscillations that correlate with NREM sleep. It does so by evoking excitatory postsynaptic currents via α7-containing nicotinic acetylcholine receptors and inducing bursts of action potentials in local GABAergic neurons. These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal. Our results provide new insight into the mechanisms controlling sleep.

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