Functional organization of receptive fields in thalamic ventrobasal neurons examined by neuronal response to iterative electrical stimulation of skin.

Iwamura, Yoshiaki; Inubushi, S

doi:10.1152/jn.1974.37.5.920

Cited by 15 publications

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“…These lemniscal terminals form glutamatergic synaptic contacts with the soma and proximal dendrites of neurons in the ventroposterior medial (VPM) thalamus (Spacek & Lieberman, 1974; Feldman & Kruger, 1980; Chiaia et al 1991 a ; Liu et al 1995; Williams et al 1994 b ; Diamond, 1995; Veinante & Deschenes, 1999). Electrophysiological and pharmacological studies in vivo have shown that stimulation of the lemniscal pathway produces a glutamatergic short latency EPSP followed by a longer latency GABergic IPSP (Andersen et al 1966; Iwamura & Inubushi, 1974; Tsumoto & Nakamura, 1974; Baldissera & Margnelli, 1979; Salt, 1987; Salt & Eaton, 1990; Chiaia et al 1991 b ; Mishima, 1992). In rodent VPM the long latency IPSP is generated by feedback inhibition from the nucleus reticularis thalami (nRt), because there are no inhibitory interneurons within the ventrobasal thalamus of rodents (Spacek & Lieberman, 1974; Barbaresi et al 1986; Harris & Hendrickson, 1987; Ohara & Lieberman, 1993).…”

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Different temporal processing of sensory inputs in the rat thalamus during quiescent and information processing states in vivo

Castro‐Alamancos

2002

The Journal of Physiology

123

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Sensory inputs from the whiskers reach the primary somatosensory thalamus through the medial lemniscus tract. The main role of the thalamus is to relay these sensory inputs to the neocortex according to the regulations dictated by behavioural state. Intracellular recordings in urethaneanaesthetized rats show that whisker stimulation evokes EPSP-IPSP sequences in thalamic neurons. Both EPSPs and IPSPs depress with repetitive whisker stimulation at frequencies above 2 Hz. Single-unit recordings reveal that during quiescent states thalamic responses to repetitive whisker stimulation are suppressed at frequencies above 2 Hz, so that only low-frequency sensory stimulation is relayed to the neocortex. In contrast, during activated states, induced by stimulation of the brainstem reticular formation or application of acetylcholine in the thalamus, high-frequency whisker stimulation at up to 40 Hz is relayed to the neocortex. Sensory suppression is caused by the depression of lemniscal EPSPs in relatively hyperpolarized thalamocortical neurons. Sensory suppression is abolished during activated states because thalamocortical neurons depolarize and the depressed lemniscal EPSPs are able to reach firing threshold. Strong IPSPs may also contribute to sensory suppression by hyperpolarizing thalamocortical neurons, but during activated states IPSPs are strongly reduced altogether. The results indicate that the synaptic depression of lemniscal EPSPs and the level of depolarization of thalamocortical neurons work together in thalamic primary sensory pathways to suppress high-frequency sensory inputs during non-activated (quiescent) states while permitting the faithful relay of high-frequency sensory information during activated (processing) states.

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confidence: 99%

Different temporal processing of sensory inputs in the rat thalamus during quiescent and information processing states in vivo

Castro‐Alamancos

2002

The Journal of Physiology

123

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The efferent connections of the feline nucleus cuneatus

Hand

Winkle

1977

J of Comparative Neurology

170

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Nucleus cuneatus projections to nucleus ventralis posterolarteralis pars medialis (VPLm) and other thalamic as well as midbrain and medullary nuclei were studied in cats using the Fink-Heimer I silver technique. Single electrolytic lesions of very small size were made stereotaxically in different zones of nucleus cuneatus under electrophysiological control. All zones studied projected to contralateral VPLm in a pattern of discrete terminal arborizations or clusters, which were organized in onionskin-like dorso-ventral laminae. The clusters of degeneration varied in size and density according to their dorsoventral location within VPLm. Those in dorsal areas were smaller in diameter (50-125 mu) and contained less dense amounts of degeneration than clusters (150-300 mu) in more ventral regions. The clustered terminal arborizations mirrored the organization of the VPLm neuronal clusters, themselves. Terminations within VPLm were topographically organized, but were completely inverted, i.e. dorsal nucleus cuneatus projected to ventral VPLm and ventral to dorsal, lateral to medial, and medial to lateral VPLm. A ventral zone of nucleus cuneatus, which contained "deep" units, projected to a separate dorsal zone of VPLm. In addition to its classical connection with VPLm, nucleus cuneatus projected to the following contralateral brainstem or thalamic nuclei: medial and dorsal accessory olives, external nucleus of the inferior colliculus, ventrolateral part of the superior colliculus, nucleus ruber, medial geniculate nucleus pars magnocellularis, suprageniculatus, medial and lateral divisions of the posterior thalamic nuclear group, zona incerta, and Fields of Forel. Very sparse amounts of degeneration were also present within nuclei ventralis posteromedialis (caudal pole) and ventralis posterolateralis pars lateralis. The brain-stem and thalamic projections of the dorsocaudal part (cell nest region) of the cuneate nucleus were more restricted than those of its rostral and ventral regions. The clusters of both the VPLm neurons and cuneate terminations within VPLm provides an anatomical basis for the functional characteristics of synaptic security, fine grain somatotopia and modality specificity so prominent in the dorsal column nuclei-medial lemniscal system.

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Central Nervous Mechanisms in Mechanoreceptive Sensibility

Mountcastle

1984

Comprehensive Physiology

149

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Functional organization of receptive fields in thalamic ventrobasal neurons examined by neuronal response to iterative electrical stimulation of skin.

Cited by 15 publications

References 0 publications

Different temporal processing of sensory inputs in the rat thalamus during quiescent and information processing states in vivo

Different temporal processing of sensory inputs in the rat thalamus during quiescent and information processing states in vivo

The efferent connections of the feline nucleus cuneatus

Central Nervous Mechanisms in Mechanoreceptive Sensibility

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