Thalamus

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Sarah L Pallas - One of the best experts on this subject based on the ideXlab platform.

  • visual behaviour mediated by retinal projections directed to the auditory pathway
    Nature, 2000
    Co-Authors: Laurie Von Melchner, Sarah L Pallas
    Abstract:

    An unresolved issue in cortical development concerns the relative contributions of intrinsic and extrinsic factors to the functional specification of different cortical areas1,2,3,4. Ferrets in which retinal projections are redirected neonatally to the auditory Thalamus5 have visually responsive cells in auditory Thalamus and cortex, form a retinotopic map in auditory cortex and have visual receptive field properties in auditory cortex that are typical of cells in visual cortex5,6,7,8. Here we report that this cross-modal projection and its representation in auditory cortex can mediate visual behaviour. When light stimuli are presented in the portion of the visual field that is ‘seen’ only by this projection, ‘rewired’ ferrets respond as though they perceive the stimuli to be visual rather than auditory. Thus the perceptual modality of a neocortical region is instructed to a significant extent by its extrinsic inputs. In addition, gratings of different spatial frequencies can be discriminated by the rewired pathway, although the grating acuity is lower than that of the normal visual pathway.

Radhouane Dallel - One of the best experts on this subject based on the ideXlab platform.

  • nociceptive stimulation activates locus coeruleus neurones projecting to the somatosensory Thalamus in the rat
    The Journal of Physiology, 2005
    Co-Authors: Daniel L Voisin, Michal Chalus, Radhouane Dallel
    Abstract:

    In the Thalamus, noradrenergic output from the pontine nucleus locus coeruleus (LC) may actively shape the response properties of various sensory networks en route to the cortex. Little is known, however, about the involvement of ascending noradrenergic innervation of the somatosensory Thalamus in the processing of nociceptive information. To address this question, we combined the study of Fos expression upon nociceptive tooth pulp stimulation in the anaesthetized rat, with the detection of retrogradely traced neurones from the somatosensory Thalamus. Cell bodies labelled retrogradely from the left Thalamus were observed on both sides of the LC, with an ipsilateral predominance (n= 8). Electrical stimulation of the right incisor pulp (n= 4) provoked a significantly stronger Fos expression (around twice) than sham surgery (n= 4), in both the ipsi- and contralateral LC. Significantly larger numbers of double labelled neurones were counted in the LC of tooth-pulp-stimulated animals (representing around 30% of retrogradely labelled cells in LC) than in the LC of sham animals. They were found bilaterally, but with a clear, significant, ipsilateral (i.e. left) predominance. The present data offer an anatomical framework to understand how the LC is involved in the sensory processing of nociceptive information in the Thalamus. For the first time, it is shown that nociceptive stimulation activates LC neurones projecting to the somatosensory Thalamus. This suggests a new role for LC in modulating nociception within the Thalamus.

Giulio Tononi - One of the best experts on this subject based on the ideXlab platform.

  • the thalamic reticular nucleus and schizophrenia
    Schizophrenia Bulletin, 2011
    Co-Authors: Fabio Ferrarelli, Giulio Tononi
    Abstract:

    Background: The thalamic reticular nucleus (TRN) is a shell-shaped gamma amino butyric acid (GABA)ergic nucleus, which is uniquely placed between the Thalamus and the cortex, because it receives excitatory afferents from both cortical and thalamic neurons and sends inhibitory projections to all nuclei of the dorsal Thalamus. Method: A review of the evidence suggesting that the TRN is implicated in the neurobiology of schizophrenia. Results: TRN-Thalamus circuits are implicated in bottom-up as well as top-down processing. TRN projections to nonspecific nuclei of the dorsal Thalamus mediate top-down processes, including attentional modulation, which are initiated by cortical afferents to the TRN. TRN-Thalamus circuits are also involved in bottom-up activities, including sensory gating and the transfer to the cortex of sleep spindles. Intriguingly, deficits in attention and sensory gating have been consistently found in schizophrenics, including first-break and chronic patients. Furthermore, high-density electroencephalographic studies have revealed a marked reduction in sleep spindles in schizophrenics. Conclusion: On the basis of our current knowledge on the molecular and anatomo-functional properties of the TRN, we suggest that this thalamic GABAergic nucleus may be involved in the neurobiology of schizophrenia.

Laurie Von Melchner - One of the best experts on this subject based on the ideXlab platform.

  • visual behaviour mediated by retinal projections directed to the auditory pathway
    Nature, 2000
    Co-Authors: Laurie Von Melchner, Sarah L Pallas
    Abstract:

    An unresolved issue in cortical development concerns the relative contributions of intrinsic and extrinsic factors to the functional specification of different cortical areas1,2,3,4. Ferrets in which retinal projections are redirected neonatally to the auditory Thalamus5 have visually responsive cells in auditory Thalamus and cortex, form a retinotopic map in auditory cortex and have visual receptive field properties in auditory cortex that are typical of cells in visual cortex5,6,7,8. Here we report that this cross-modal projection and its representation in auditory cortex can mediate visual behaviour. When light stimuli are presented in the portion of the visual field that is ‘seen’ only by this projection, ‘rewired’ ferrets respond as though they perceive the stimuli to be visual rather than auditory. Thus the perceptual modality of a neocortical region is instructed to a significant extent by its extrinsic inputs. In addition, gratings of different spatial frequencies can be discriminated by the rewired pathway, although the grating acuity is lower than that of the normal visual pathway.

Kamen G. Usunoff - One of the best experts on this subject based on the ideXlab platform.

  • Neurons in the dorsal column nuclei of the rat emit a moderate projection to the ipsilateral ventrobasal Thalamus
    Anatomy and Embryology, 2005
    Co-Authors: Andreas Wree, D. E. Itzev, O. Schmitt, Kamen G. Usunoff
    Abstract:

    The dorsal column nuclei (DCN; gracile and cuneate nuclei) give rise to the medial lemniscus, the fibre system that provides an organised somatosensory input to the Thalamus. Unlike the spinothalamic and trigeminothalamic tracts that project, also to the ipsilateral Thalamus, the medial lemniscus system is believed to be entirely crossed. We demonstrate that DCN emit a small number of axons that reach the ipsilateral Thalamus. As retrograde fluorescent neuronal tracer Fluoro-gold was stereotaxically injected in the ventrobasal Thalamus of nine young adult Wistar rats. The injection foci were voluminous and encroached upon adjacent nuclei, but the periphery of the injection halo never spilled over to the contralateral Thalamus. All sections of the contralateral gracile and cuneate nuclei and the midline nucleus of Bischoff contained abundant retrogradely labelled neurons. The comparison with the Nissl-stained parallel sections suggests that approximately 70–80% of the DCN neurons project to the contralateral Thalamus. Counting of retrogradely labelled neurons in two cases revealed 4,809 and 4,222 neurons in the contralateral and 265 and 214 in the ipsilateral DCN, respectively. Thus, although less prominent than the ipsilateral spinothalamic tract, the lemniscal system also emits an ipsilateral projection that accounts for about 5% of the neuronal population in DCN that innervates the ventrobasal Thalamus.