Dataset Information

Synaptic organization of the tectorecipient zone of the rat lateral posterior nucleus.

ABSTRACT: Dorsal thalamic nuclei have been categorized as either "first-order" nuclei that gate the transfer of relatively unaltered signals from the periphery to the cortex or "higher order" nuclei that transfer signals from one cortical area to another. To classify the tectorecipient lateral posterior (LPN), we examined the synaptic organization of tracer-labeled cortical and tectal terminals and terminals labeled with antibodies against the type 1 and type 2 vesicular glutamate transporters (vGLUT1 and vGLUT2) within the caudal/lateral LPN of the rat. For this zone, we found that all tracer-labeled cortical terminals, as well as vGLUT1 antibody-labeled terminals, are small profiles with round vesicles (RS profiles) that innervate small-caliber dendrites. Tracer-labeled tecto-LPN terminals, as well as vGLUT2 antibody-labeled terminals, were medium-sized profiles with round vesicles (RM profiles). Tecto-LPN terminals were significantly larger than cortico-LPN terminals and contacted significantly larger dendrites. These results indicate that, within the tectorecipient zone of the rat LPN, cortical terminals are located distal to tectal terminals and that vGLUT1 and vGLUT2 antibodies may be used as markers for cortical and tectal terminals, respectively. Finally, comparisons of the synaptic patterns formed by tracer-labeled terminals with those of vGLUT antibody-labeled terminals suggest that individual LPN neurons receive input from multiple cortical and tectal axons. We suggest that the tectorecipient LPN constitutes a third category of thalamic nucleus ("second-order") that integrates convergent tectal and cortical inputs. This organization may function to signal the movement of novel or threatening objects moving across the visual field.

SUBMITTER: Masterson SP

PROVIDER: S-EPMC4412189 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Synaptic organization of the tectorecipient zone of the rat lateral posterior nucleus.

Masterson Sean P SP Li Jianli J Bickford Martha E ME

The Journal of comparative neurology 20090801 6

Dorsal thalamic nuclei have been categorized as either "first-order" nuclei that gate the transfer of relatively unaltered signals from the periphery to the cortex or "higher order" nuclei that transfer signals from one cortical area to another. To classify the tectorecipient lateral posterior (LPN), we examined the synaptic organization of tracer-labeled cortical and tectal terminals and terminals labeled with antibodies against the type 1 and type 2 vesicular glutamate transporters (vGLUT1 and ...[more]

PMID: 19496169

Similar Datasets

Project description:In both dichromats and trichromats, cone opsin signals are maintained independently in cones and combined at the bipolar and retinal ganglion cell level, creating parallel color opponent pathways to the central visual system. Like other dichromats, the mouse retina expresses a short-wavelength (S) and a medium-wavelength (M) opsin, with the S-opsin shifted to peak sensitivity in the ultraviolet (UV) range. Unlike in primates, nonuniform opsin expression across the retina and coexpression in single cones creates a mostly mixed chromatic signal. Here, we describe the visuotopic and chromatic organization of spiking responses in the dorsal lateral geniculate and of the local field potentials in their recipient zone in primary visual cortex (V1). We used an immersive visual stimulus dome that allowed us to present spatiotemporally modulated UV and green luminance in any region of the visual field of an awake, head-fixed mouse. Consistent with retinal expression of opsins, we observed graded UV-to-green dominated responses from the upper to lower visual fields, with a smaller difference across azimuth. In addition, we identified a subpopulation of cells (<10%) that exhibited spectrally opponent responses along the S-M axis. Luminance signals of each wavelength and color signals project to the middle layers of V1.Significance statementIn natural environments, color information is useful for guiding behavior. How small terrestrial mammals such as mice use graded expression of cone opsins to extract visual information from their environments is not clear, even as the use of mice for studying visually guided behavior grows. In this study, we examined the color signals that the retina sends to the visual cortex via the lateral geniculate nucleus of the thalamus. We found that green dominated responses in the lower and nasal visual field and ultraviolet dominated responses in the upper visual field. We describe a subset of cells that exhibit color opponent responses.

Project description:The thalamic reticular nucleus (TRN) is a shell-like structure comprised of GABAergic neurons that surrounds the dorsal thalamus. While playing a key role in modulating thalamocortical interactions, TRN inhibition of thalamic activity is often thought of as having an all-or-none impact. Although TRN neurons have a dynamic firing range, it remains unclear how variable rates of TRN activity gate thalamocortical transmission. To address this, we examined the ultrastructural features and functional synaptic properties of the feedback connections in the mouse thalamus between TRN and the dorsal lateral geniculate nucleus (dLGN), the principal relay of retinal signals to visual cortex. Using electron microscopy to identify TRN input to dLGN, we found that TRN terminals formed synapses with non-GABAergic postsynaptic profiles. Compared with other nonretinal terminals in dLGN, those from TRN were relatively large and tended to contact proximal regions of relay cell dendrites. To evoke TRN activity in dLGN, we adopted an optogenetic approach by expressing ChR2, or a variant (ChIEF) in TRN terminals. Both in vitro and in vivo recordings revealed that repetitive stimulation of TRN terminals led to a frequency-dependent inhibition of dLGN activity, with higher rates of stimulation resulting in increasing levels of membrane hyperpolarization and corresponding decreases in spike firing. This relationship suggests that alterations in TRN activity lead to graded changes in relay cell spike firing.NEW & NOTEWORTHY The thalamic reticular nucleus (TRN) modulates thalamocortical transmission through inhibition. In mouse, TRN terminals in the dorsal lateral geniculate nucleus (dLGN) form synapses with relay neurons but not interneurons. Stimulation of TRN terminals in dLGN leads to a frequency-dependent form of inhibition, with higher rates of stimulation leading to a greater suppression of spike firing. Thus, TRN inhibition appears more dynamic than previously recognized, having a graded rather than an all-or-none impact on thalamocortical transmission.

Project description:Neurons in the mouse primary visual cortex (V1) exhibit characteristic response selectivity to visual stimuli, such as orientation, direction and spatial frequency selectivity. Since V1 receives thalamic visual inputs from the lateral geniculate nucleus (LGN) and lateral posterior nucleus (LPN), the response selectivity of the V1 neurons could be influenced mostly by these inputs. However, it remains unclear how these two thalamic inputs contribute to the response selectivity of the V1 neurons. In this study, we examined the orientation, direction and spatial frequency selectivity of the LPN axons projecting to V1 and compared their response selectivity with our previous results of the LGN axons in mice. For this purpose, the genetically encoded calcium indicator, GCaMP6s, was locally expressed in the LPN using the adeno-associated virus (AAV) infection method. Visual stimulations were presented, and axonal imaging was conducted in V1 by two-photon calcium imaging in vivo. We found that LPN axons primarily terminate in layers 1 and 5 and, to a lesser extent, in layers 2/3 and 4 of V1, while LGN axons mainly terminate in layer 4 and, to a lesser extent, in layers 1 and 2/3 of V1. LPN axons send highly orientation- and direction-selective inputs to all the examined layers in V1, whereas LGN axons send highly orientation- and direction-selective inputs to layers 1 and 2/3 but low orientation and direction selective inputs to layer 4 in V1. The distribution of preferred orientation and direction was strongly biased toward specific orientations and directions in LPN axons, while weakly biased to cardinal orientations and directions in LGN axons. In spatial frequency tuning, both the LPN and LGN axons send selective inputs to V1. The distribution of preferred spatial frequency was more diverse in the LPN axons than in the LGN axons. In conclusion, LPN inputs to V1 are functionally different from LGN inputs and may have different roles in the orientation, direction and spatial frequency tuning of the V1 neurons.

Project description:Dopamine is known to differentially modulate the impact of cortical input to the striatum between the direct and indirect pathways of the basal ganglia (BG). However, the role of extrastriatal dopamine receptors (DRs) in BG information processing is less clear. To investigate the role of extrastriatal DRs, we studied their distribution and function in one of the output nuclei of the BG of the rodent, the entopeduncular nucleus (EP). qRT-PCR indicated that all DR subtypes were expressed by EP neurons, suggesting that both D1-like receptors (D1LRs) and D2-like receptors (D2LRs) were likely to affect information processing in the EP. Whole-cell recordings revealed that striatal inputs to the EP were potentiated by D1LRs whereas pallidal inputs to the EP were depressed by D2LRs. Changes to the paired-pulse ratio of inputs to the EP suggested that dopaminergic modulation of striatal inputs is mediated by postsynaptic receptors, and that of globus pallidus-evoked inputs is mediated by presynaptic receptors. We show that these changes in synaptic efficacy changed the information content of EP neuron firing. Overall, the findings suggest that the dopaminergic system affects the passage of feedforward information through the BG by modulating input divergence in the striatum and output convergence in the EP.SIGNIFICANCE STATEMENT The entopeduncular nucleus (EP), one of the basal ganglia (BG) output nuclei, is an important station in information processing in BG. However, it remains unclear how EP neurons encode information and how dopamine affects this process. This contrasts with the well established role of dopamine in the striatum, which is known to redistribute cortical input between the direct and indirect pathways. Here we show that, in symmetry with the striatum, dopamine controls the rebalancing of information flow between the two pathways in the EP. Specifically, we demonstrate that dopamine regulates EP activity by differentially modulating striatal and pallidal GABAergic inputs. These results call for a reassessment of current perspectives on BG information processing by highlighting the functional role of extrastriatal dopamine receptors.

Project description:Rodents move rhythmically their facial whiskers and compute differences between signals predicted and those resulting from the movement to infer information about objects near their head. These computations are carried out by a large network of forebrain structures that includes the thalamus and the primary somatosensory (S1BF) and motor (M1wk) cortices. Spatially and temporally precise mechanorreceptive whisker information reaches the S1BF cortex via the ventroposterior medial thalamic nucleus (VPM). Other whisker-related information may reach both M1wk and S1BF via the axons from the posterior thalamic nucleus (Po). However, Po axons may convey, in addition to direct sensory signals, the dynamic output of computations between whisker signals and descending motor commands. It has been proposed that this input may be relevant for adjusting cortical responses to predicted vs. unpredicted whisker signals, but the effects of Po input on M1wk and S1BF function have not been directly tested or compared in vivo. Here, using electrophysiology, optogenetics and pharmacological tools, we compared in adult rats M1wk and S1BF in vivo responses in the whisker areas of the motor and primary somatosensory cortices to passive multi-whisker deflection, their dependence on Po activity, and their changes after a brief intense activation of Po axons. We report that the latencies of the first component of tactile-evoked local field potentials in M1wk and S1BF are similar. The evoked potentials decrease markedly in M1wk, but not in S1BF, by injection in Po of the GABAA agonist muscimol. A brief high-frequency electrical stimulation of Po decreases the responsivity of M1wk and S1BF cells to subsequent whisker stimulation. This effect is prevented by the local application of omega-agatoxin, suggesting that it may in part depend on GABA release by fast-spiking parvalbumin (PV)-expressing cortical interneurons. Local optogenetic activation of Po synapses in different cortical layers also diminishes M1wk and S1BF responses. This effect is most pronounced in the superficial layers of both areas, known to be the main source and target of their reciprocal cortico-cortical connections.

Dataset Information

Synaptic organization of the tectorecipient zone of the rat lateral posterior nucleus.

Publications

Synaptic organization of the tectorecipient zone of the rat lateral posterior nucleus.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets