Fewer driver synapses in higher order than in first order thalamic relays

Horn, Susan C. Van; Sherman, S. Murray

doi:10.1016/j.neuroscience.2007.01.026

Cited by 26 publications

(23 citation statements)

References 36 publications

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“…Because the thalamic reticular nucleus is involved in the corticothalamic feedback, our data would also suggest information processing in the higher-order relays is under more extensive (disynaptic, inhibitory) control from the cortex. This notion is consistent with recent evidence that higher-order thalamic relays generally have a greater preponderance of modulatory inputs (Van Horn and Sherman 2007;Wang et al 2002) and are relatively selectively innervated by GABAergic inputs from the zona incerta and anterior pretectal nucleus (Bartho et al 2007;Bokor et al 2005;Trageser and Keller 2004) and by dopaminergic inputs (Sanchez-Gonzalez et al 2005).…”

Section: Functional Significancesupporting

confidence: 91%

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

Lam

Sherman²

2007

Journal of Neurophysiology

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Lam YW, Sherman SM. Different topography of the reticulothalmic inputs to first-and higher-order somatosensory thalamic relays revealed using photostimulation. J Neurophysiol 98: 2903-2909. First published September 19, 2007 doi:10.1152/jn.00782.2007. 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. I N T R O D U C T I O NThe thalamic reticular nucleus is a thin layer of GABAergic cells adjacent to the relay nuclei of the (dorsal) thalamus. Most axons connecting the thalamus and cortex in either direction pass through the thalamic reticular nucleus and innervate neurons there with collaterals; reticular neurons, in turn, provide strong inhibition to thalamic relay cells. Due to its strategic location between the thalamus and cortex, the thalamic reticular nucleus is often suggested as a key player in regulating the relay of information through the thalamus to cortex (Crick 1984;Guillery and Sherman 2002;Guillery et al. 1998;McAlonan et al. 2006;Pinault 2004;Sherman and Koch 1986;Yingling and Skinner 2007). Understanding the functional organization of inputs from the thalamic reticular nucleus to thalamic relay nuclei, and how it varies among these nuclei, is of obvious importance.Thalamic nuclei have been classified into first-and higher-order relays: the first-order relays receive their driver inputs, which represent the main information to be relayed, from subcortical sources, whereas the higher-order relays receive their driver inputs from layer 5 of the cortex as part of a cortico-thalamo-cortical route (Guillery and Sherman 2002). The somatosensory thalamic examples of these different rel...

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Section: Functional Significancesupporting

confidence: 91%

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

Lam

Sherman²

2007

Journal of Neurophysiology

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“…Earlier studies for the cat and rat showed that the ratio of drivers (RL) to modulators (RS and F) is higher in the first than the higher-order thalamic relays [9][10][11][12]. Most strikingly, the present study of GAERS shows an abnormality of this relationship.…”

Section: Discussioncontrasting

confidence: 54%

“…Earlier studies on the thalamus of normal rats and cats have shown that the ratios of different terminal types vary between thalamic nuclei [9][10][11][12]. Three major terminal types, RL (round vesicles and large terminals), RS (round vesicles and small terminals) and F (flattened vesicles) terminals, have been described in the thalamus [13,14].…”

Section: Introductionmentioning

confidence: 99%

Do the quantitative relationships of synaptic junctions and terminals in the thalamus of genetic absence epilepsy rats from Strasbourg (GAERS) differ from those in normal control Wistar rats

et al. 2011

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Abnormal functional properties of the thalamocortical connections were reported in the absence of epilepsy. The present study compares the ratios of terminals ('RL'-round vesicles, large terminals, 'RS'-round vesicles, small terminals and 'F'-flattened vesicles) and synapse in three first-order (ventrobasal, lateral geniculate and anteroventral) and in three higher-order (posterior, lateral posterior and mediodorsal) thalamic nuclei of genetic absence epilepsy rats from Strasbourg (GAERS) with our earlier quantitative studies of normal Wistar rats to show whether quantitative differences were present in GAERS as compared to Wistar rat. Rats were perfused transcardially, the brains were removed and cut as 300 μm coronal sections. Parts of the six thalamic nuclei were removed for routine electron microscopy and GABA immunocytochemistry. Twenty photographs from each section at 20,000× magnification were taken, and the terminals were identified as RL, RS or F. (1) In normal Wistar rats (as in cats), the proportion of driver terminals (RL) and synapses is lower in higher-order than in first-order thalamic nuclei, but this difference is not present in GAERS animals. (2) The proportions of RS terminals and synapses for each thalamic nucleus showed no significant differences between GAERS and Wistar rats for any of the thalamic nuclei. (3) In GAERS, the proportion of inhibitory F terminals and synapses was significantly high in the VB and low in the LP thalamic nucleus. These abnormal ratios in the GAERS may be the cause of the spike-and-wave discharges of absence seizures or may represent a compensatory response of the thalamocortical circuitry to the absence seizures.

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“…r The relative percentage of driver versus other synapses is significantly lower in higher order relays at roughly 2% versus 5% (168,169,180), suggesting that there is relatively more modulation of higher order relay cells.…”

Section: First and Higher Order Relaysmentioning

confidence: 99%

Functioning of Circuits Connecting Thalamus and Cortex

Sherman¹

2017

Comprehensive Physiology

131

108

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Glutamatergic pathways in thalamus and cortex are divided into two distinct classes: driver, which carries the main information between cells, and modulator, which modifies how driver inputs function. Identifying driver inputs helps to reveal functional computational circuits, and one set of such circuits identified by this approach are cortico-thalamo-cortical (or transthalamic corticocortical) circuits. This, in turn, leads to the conclusion that there are two types of thalamic relay: first order nuclei (such as the lateral geniculate nucleus) that relay driver input from a subcortical source (i.e., retina), and higher order nuclei (such as the pulvinar) which are involved in these transthalamic pathways by relaying driver input from layer 5 of one cortical area to another. This thalamic division is also seen in other sensory pathways and beyond these so that most of thalamus by volume consists of higher-order relays. Many, and perhaps all, direct driver connections between cortical areas are paralleled by an indirect cortico-thalamo-cortical (transthalamic) driver route involving higher order thalamic relays. Such thalamic relays represent a heretofore unappreciated role in cortical functioning, and this assessment challenges and extends conventional views regarding both the role of thalamus and mechanisms of corticocortical communication. Finally, many and perhaps the vast majority of driver inputs relayed through thalamus arrive via branching axons, with extrathalamic targets often being subcortical motor centers. This raises the possibility that inputs relayed by thalamus to cortex also serve as efference copies, and this may represent an important feature of information relayed up the cortical hierarchy via transthalamic circuits. © 2017 American Physiological Society. Compr Physiol 7:713-739, 2017.

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Fewer driver synapses in higher order than in first order thalamic relays

Cited by 26 publications

References 36 publications

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

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

Do the quantitative relationships of synaptic junctions and terminals in the thalamus of genetic absence epilepsy rats from Strasbourg (GAERS) differ from those in normal control Wistar rats

Functioning of Circuits Connecting Thalamus and Cortex

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